# LUX readings 10-1/2" brooder clamp-on light



## sowNreap (Jun 10, 2012)

Lux readings for a 10-1/2” Brooder clamp-on light fixture. First here's a few photos of the fixture:

Angled view - No flash - bulb lit 









Straight on view .. no flash ... bulb lit









Comparison .. regular 10-1/2 on left .. 10-1/2 brooder on right








Comparison .. regular 10-1/2 on left .. 10-1/2 brooder on right .. You can see the floodlight in the right one










Hoppy I know you said you only use the center number for your charts but I was curious to see the light spread on these round fixtures so took readings in several different spots. Once I get the initial measurements it goes quick. I spend more time trying to get the height just right then I do taking the actual readings. LOL 

Also, I never could get this fixture to hang straight no matter what I did. After tinkering for way too long I said the heck with it and just did the best I could. I could visibly see the light was usually brighter to the left/back until it got high enough then evened out. So I know that threw off the readings. Anyone using this light will probably have the same problem.

The nice things about this fixture compared to the regular 10-1/2” is there is a longer cord (8' vs 6'), it's sturdier, it's got a better clamp and there's a bracket rod (not the right words but can't think how to describe it LOL) that makes it easy to hang rather than using the cord or clamp. The biggest negative is there is NO SWITCH. You have to plug/unplug it .. not a problem if using a timer. 

For the measurements I used the distance to the actual bulb, not the reflector. The floodlight bulb I used hung approx. 3/4” below the reflector which could pose a problem for anyone setting it right on a tank. 

But I'm not sure if the floodlight bulb I used is the same size as say an outdoor floodlight. The one I have is for indoor track & recessed use and is dimmable. It's the only one I had. No where does it say what color temp the bulb is but it looked like warm white. Here's a pic of the bulb & package. 



















Enough of my rambling , here's the readings. Used 10x scale unless noted. 

*15 watt (60 equivalent) Daylight 6500k .. Home Depot brand * 

*Location ---- 8” Height ---- 10” Height ---- 15”height ---- 20”height ---- 25” height ---- 30” height * 
Center --------- 276=100x ------- 1710 ----------- 687 -------------- 350 ----------- 243 -------------- 158 
5” back -------- 316 --------------- 278 ----------- 276 -------------- 198 ----------- 185 -------------- 139
9” back -------- 138 --------------- 130 ----------- 137 ---------------118 ----------- 127 -------------- 111
5” front -------- 478 --------------- 551 ----------- 432 -------------- 292 ----------- 200 -------------- 138
9” front -------- 112 --------------- 128 ----------- 149 -------------- 161 ----------- 123 -------------- 100
5” right -------- 341 --------------- 336 ----------- 338 -------------- 229 ----------- 150 -------------- 121
5” left ---------- 444 --------------- 416 ----------- 369 -------------- 281 ----------- 237 -------------- 154


*23 watt (100 equivalent) Daylight 6500k .. Home Depot brand*

*Location ---- 8” Height ---- 10” Height ---- 15”height ---- 20”height ---- 25” height ---- 30” height * 
Center --------- 337=100x ------ 217=100x ----- 961 -------------- 516 ----------- 318 -------------- 229 
5” back -------- 610 --------------- 654 ----------- 531 -------------- 395 ----------- 280 -------------- 220
9” back -------- 268 --------------- 280 ----------- 284 ---------------264 ----------- 220 -------------- 192
5” front -------- 856 --------------- 852 ----------- 627 -------------- 422 ----------- 275 -------------- 205
9” front -------- 222 --------------- 233 ----------- 248 -------------- 241 ----------- 188 -------------- 153
5” right -------- 586 --------------- 606 ----------- 501 -------------- 384 ----------- 258 -------------- 197
5” left --------- 1072 -------------- 940 ------------706 -------------- 441 ----------- 308 -------------- 222


*26 watt (100 equivalent) Floodlight GE brand*

*Location ---- 8” Height ---- 10” Height ---- 15”height ---- 20”height ---- 25” height ---- 30” height * 
Center --------- 888=100x -------- 618 ----------- 282 -------------- 172 ----------- 107 -------------- 158 
5” back -------- 460 --------------- 381 ----------- 234 -------------- 169 ----------- 106 -------------- 139
9” back -------- 246 --------------- 256 ----------- 185 ---------------144 ----------- 955=1x --------- 111
5” front -------- 554 --------------- 443 ----------- 244 -------------- 155 ----------- 101 -------------- 138
9” front -------- 222 --------------- 234 ----------- 173 -------------- 124 ----------- 882=1x --------- 100
5” right -------- 536 --------------- 420 ----------- 250 -------------- 168 ----------- 103 -------------- 121
5” left ---------- 506 --------------- 403 ----------- 223 -------------- 158 ----------- 101 -------------- 154

Hoppy .. not to impose to much but hope you'll convert & chart this.  Hope this format is ok. Got it saved in OpenOffice.org now so will make it easy to just plug in new numbers.


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## Hoppy (Dec 24, 2005)

Compare this to:









This isn't at all like I expected. You got considerably higher PAR readings than I got, with 8.5 inch reflectors. So, either, one of us is wrong, or the larger diameter reflectors are more efficient in concentrating the available lumens, which is reasonable to believe. The larger reflector probably has the bulb well below the rim of the reflector, where the smaller reflector has the bulb almost flush with the rim of the reflector. For now, that is what I will assume to be the benefit of the larger reflector.

The flood light bulb you tested has an internal reflector, so the external dome reflector has little or no effect on the light intensity. So, that result is what I expected.

It seems like every time we test a light we get a surprise!


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## sowNreap (Jun 10, 2012)

Thanks Hoppy once again for the great charts!! I really do appreciate it. They show a big difference between them. 

I don't have the figures with me right now but I think the 23 watt was 1/2" inside the reflector and if I remember right the 15 watt was 1-1/4 inside the reflector. I wish I'd had more bulbs of different watts to check them but those 2 are about the only ones I use. 

I plan on replacing my 8-1/2" reflector and taking readings with it BUT the reflector is not shiny anymore .. it's pretty old. So will be interesting to see those numbers. 

Another thing is I'm using a Lux meter but you used a PAR meter so that could account for some of the difference as well. But yeah I could be off a bit. On the floodlight bulb the last reading at 8" height, the numbers started going crazy ... started at 1000+ using 10x scale but in a matter of a few seconds was down to 300+. Changed batteries twice and got steady readings but no where near the 1000+ reading. 

We really need more people to buy that Lux meter and do readings on their fixtures to get better data. The more we have the better the charts will be. At less than $20 it's a good investment.


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## Hoppy (Dec 24, 2005)

I used a modified lux meter for my PAR numbers for the CFL/dome reflector data. I first "calibrated" the lux meter by rechecking some other lights I had good data on, and adjusted the conversion to PAR constant based on that. I'm pretty sure my data are good to +/- 10% or, at worst, +/-20%. But, that wouldn't even begin to account for the difference between your 10.5 inch data and my 8.5 inch data. When you check the lux with your 8.5 inch dome we will have a much better way to determine why there is such a big difference. My 8.5 inch reflector isn't extremely shiny either, but it never was. And, my measurements this time aren't too far off the ones I did a year or more ago, using a PAR meter.

I found it to be a little tricky to measure PAR under one of those reflectors. First, it isn't always obvious where the center of the light is, so I always had to move the sensor around a bit to find it. This time I propped the sensor on boxes/books to change the distance, so each time I had to again locate the center of the light - the maximum reading. And, this time I noticed that the PAR tended to slowly increase as the bulb got hotter, so I had to make sure it was hot before each measurement. But, repeat measurements were the same, so I feel confident about that part.


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## sowNreap (Jun 10, 2012)

Hoppy … I'm an idiot. In all my previous readings I forgot one simple little thing. I forgot to allow for the thickness of the sensor itself. So all the heights are off about 1-3/16” .. at least the best I could measure it. But I didn't realize that until I was more than half way through the readings for the 8-1/2” clamp on light. So I kept doing what I've been doing. I just can't believe I did that! 

And to top if off … the threaded reflector holder that holds the reflector in place broke. Which meant the reflector no longer stayed where it should but rested on the bulb. The bulb was the only thing holding the reflector on. I put some duct tape around it to hold it in place but never could get it straight. So the readings may be off especially for the floodlight bulb since that bulb sticks out past the reflector by approx 1-7/8 … rather hard to measure when the reflector won't stay put. And then every time I moved the fixture the reflector would move. I almost didn't even do the floodlight. Definitely not lab quality work. 

Anyway, here's the readings for what they're worth for the 8-1/2” clamp-on. I was able to use a fixture that looks new and shiny not the dull one. But obviously cheap quality. 

Again, all readings are Lux x10 unless noted.

15 watt (60 equivalent) Daylight 6500k .. Home Depot brand (somehow missed one of my 30” height readings. From the numbers it looks like 9” back)

Location ------- 8” Height ---- 10” Height ---- 15”height -------- 20”height ----- 25” height ------ 30” height 
Center --------- 143=100x -------- 840 ----------- 350 -------------- 190 ----------- 120 ------------- 825=1x 
5” back -------- 371 ----------------355 ----------- 247 -------------- 154 ----------- 107 ------------- 788=1x
9” back -------- 148 --------------- 162 ----------- 159 ---------------119 ----------- 861=1x --------- missed
5” front -------- 343 --------------- 348 ----------- 242 -------------- 152 ----------- 105 -------------- 766=1x
9” front -------- 965=1x ---------- 116 ----------- 126 -------------- 107 ----------- 759=1x ---------- 606=1x
5” right -------- 323 --------------- 308 ----------- 223 -------------- 153 ----------- 107 -------------- 774=1x
5” left ---------- 420 --------------- 386 ----------- 260 -------------- 161 ----------- 106 -------------- 777=1x


23 watt (100 equivalent) Daylight 6500k .. Home Depot brand

Location ------- 8” Height ---- 10” Height ---- 15”height -------- 20”height ----- 25” height ------ 30” height 
Center --------- 226=x100 --------656 ----------- 705 -------------- 390 ----------- 247 -------------- 169 
5” back -------- 853 --------------- 440 ----------- 498 -------------- 328 ----------- 225 -------------- 168
9” back -------- 344 --------------- 293 ----------- 322 ---------------254 ----------- 188 -------------- 153
5” front -------- 568 --------------- 408 ----------- 462 -------------- 293 ----------- 209 -------------- 162
9” front -------- 196 --------------- 208 ----------- 220 -------------- 194 ----------- 156 -------------- 131
5” right -------- 725 --------------- 396 ----------- 479 -------------- 326 ----------- 223 -------------- 156
5” left ---------- 743 --------------- 348------------502 -------------- 327 ----------- 223 -------------- 151


26 watt (100 equivalent) Floodlight GE brand (again missed a reading not surprising all the trouble this fixture gave me) 

Location ------- 8” Height ---- 10” Height ---- 15”height -------- 20”height ----- 25” height ------ 30” height 
Center --------- 227=100x --------576 ------------227 -------------- 159 ----------- 105 ------------- 724=1x 
5” back -------- 460 --------------- 370 ----------- 241--------------- 155----------- 102 -------------- 720=1x
9” back -------- 154 --------------- 247 ----------- 190 ---------------135 ----------- 936=1x ---------685=1x
5” front -------- 730 --------------- 395 ----------- missed ---------- 141 ----------- 961=1x --------- 691=1x
9” front -------- 155 --------------- 206 ----------- 164 -------------- 113 ----------- 832=1x --------- 628=1x
5” right -------- 628 --------------- 369 ----------- 223 -------------- 150 ----------- 100 -------------- 706=1x
5” left ---------- 564 --------------- 425 ----------- 241 -------------- 142 ----------- 957=1x --------- 675=1x

Here's how I do my measurements for these lights. I have a rod stretched across the upper cabinets which always hangs the light in the same spot front to back but not side to side. I use several marks on the counter top to show where the center of bulb should be but I use the center at the top of the fixture for measuring. I have several marks front to back, side to side and use a wooden 3' ruler to give me a straight line to measure from the center out. I use a 3/4” board to give me a straight hard edge to which I butt against a microwave at one end and the back of the counter the other way. When I get up to about 20” the board is too short (need a longer board) but it's high enough to now use the cabinet on the other end. This is how I try to make sure the light is always centered over my mark. I measure after every height adjustment and use these 2 points. On the first reading, I measure to my center mark and take a reading. Then I move the sensor around a bit just to make sure the light really is centered over my mark and make adjustments as needed. Once I'm sure the light is centered over my mark the rest of the measurements go quickly. For height I use the reflector edge but first measure where the bulb is in relation to that edge, then make adjustment for that. For example, if the bulb is ½” inside the reflector I add an extra 1/2” to my height measurement. So if I'm using 15” height I would measure 15-1/2 at the reflector edge. Hope all this makes sense. Seems to work as long as I don't accidentally bump the fixture. If I do I have to re-measure to make sure I'm still centered once the light quits swinging.  And it seemed the easiest way to be able to get front/back readings so I could see how much the light spread at different heights. If only I hadn't forgotten that 1 parameter. 

So all in all I had a rough time doing this group. I'm not real confident of these numbers so I'm curious to see how they compare to your 8-1/2” readings. 

I feel really bad about doing to all this work & you making all the charts to find out now it's with inaccurate bulb to substrate numbers. I guess it does gives us a rough estimate which might be better than no estimate but I wanted them to be as close to perfect as possible so it bothers me.


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## Hoppy (Dec 24, 2005)

Don't worry about the distance error, it is easy to correct. And, when you do this type of testing as much as you now have, errors like that tend to creep in. I have had to repeat a lot of readings because of that or similar errors.

Your data with the floodlight bulb in the two reflectors is consistent - not identical but only a small difference from one reflector to the other. This means your measuring techniques are also consistent. 

Your data also shows that the 10.5 inch reflector gives a lot more light than the 8.5 inch reflector, which is also consistent with the comparison of your 10.5 inch reflector data to my 8.5 inch data. But, your 8.5 inch reflector data is almost twice my 8.5 inch reflector data for similar wattage bulbs. I think my data is suspect, so I need to repeat it. I may have to borrow a PAR meter and recalibrate my DIY PAR meter again, since that is the most likely source of the error. Until I can figure this out I won't make a chart of this data.


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## sowNreap (Jun 10, 2012)

Thanks Hoppy I feel a little bit better now. Especially since the floodlight bulb is consistent. 

I think I might try the "2 chair" method and retest only the center spot for the various fixtures. I may be taking the brooder fixture back and keep the regular 10-1/2 one. Finding items to be able to raise/lower the fixture or sensor will be the challenge though. 

Maybe I'll test the old non-shiny reflector too. I want to test the diamond plate t8 again with insect screen to see how much light is reduced.

Edit: Is is possible my unit gets "out of whack" from being exposed to too much light. I keep the sensor covered when not taking readings.


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## Hoppy (Dec 24, 2005)

The photodiode in the sensor will lose sensitivity proportional to the light intensity it is exposed to and the length of time it is exposed to it. I think the sensor will last for years with just occasional exposure to relatively weak light, like we do. Notice that none of your readings were anywhere near the maximum that can be measured on the meter.


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## sowNreap (Jun 10, 2012)

Ok ..Good to know. I'll try to get new readings on an 8-1/2" clamp-on using an alternate method for center reading only. Maybe I have another shiny one that's not broke.


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## sowNreap (Jun 10, 2012)

I tried hard to use an alternate method by using my camera tripod to hold the light and using books under the legs and/or sensor. I spent about as long trying to get 5 center readings for 1 bulb as I do all my other readings on 3 bulbs. And the worst thing is I'm not very confident of the numbers. In fact I couldn't get the exact heights needed, so for instance when trying to measure 15”, closest I could get was 14-3/4. When I tried to gauge where the center was and then move the sensor around from there I got highest readings in 2 places both of which appeared to be approx. 2”-2-1/2” from the “center”. Was consistent at heights 14-3/4 and above and reproducible. One was in the left front, the other right rear. Both read almost exact but higher than the guesstimated center. Not sure it might not have been re-strike or what ..it was just weird. 

Oh … before I ever started doing any readings I got the clue gun out and attach the reflector so it wouldn't move. That sucker ain't going anywhere! LOL I have much more confidence in these numbers. 

But here's those reading for what they're worth for only the 15 watt bulb in the 8-1/2” fixture. 

9-3/4 height ---- guesstimated center----957 .. was the highest reading
14-3/4 height----guesstimated center----362 was also the highest reading
20-1/4 height----guesstimated center----1749-------left front 2-2-1/2 from “center”----------1776
-----------------------------------------------------------right rear 2-1/2” from “center”-----------1775
25 height---------guesstimated center----1095 -------left front 2-1/2” from “center”-----------1105 ------------------------------------------------------------right rear 2-1/2” from “center”----------1104
30 height---------guesstimated center----767-1x -----left front didn't record " from center----774=1x ------------------------------------------------------------right rear 2-1/2” from “center”----------771=1x

I actually started with the 30” reading because I wanted to see if I could get that high and once I had it set up just did the reading and then worked my way down. I got frustrated with this method and gave up before I could do an 8” reading or change bulbs. 

So I went back to my old way with a couple changes. One, I measured to the bulb itself rather than the reflector (eliminated another variable). Not sure why I wasn't doing it this way already as it was much easier and more precise. I think I had trouble measuring to the bulb when doing the 10-1/2 reflector. ?? Also instead of measuring to the right cabinet I used the left one over the microwave now that I have that area cleared off .. much easier and again more precise. I also realized that I haven't been moving the sensor around to find the highest center reading. I guess I stopped doing that once I got all my marks and measurements setup. But I did it this time just to see how far off I was. I also eliminated the plant pulley and just used chains with an S hook to attach 2 together since I didn't have one long enough. They were hung from a short coat hangar that hung from the rod. The coat hangar makes it easier for small measurement adjustments like 1/8” or 3/16”.

Another thing I noticed I had been doing is maybe reading the sensor too quickly. I had been turning it on, taking off cover, then hit my mark/measured, then read it .. all this in probably less than 1 minute. This time I looked at the reading, then moved the sensor around and then came back to do the actual reading. I does drop a bit after a few minutes. My bulb has usually been on for a while while I set up my stuff so it's already hot. 

*15 watt bulb* where the highest reading was (in some cases was the same number) I guesstimated distance from my center which is noted

Location ----------8” Hght ------ 10” Hght ----- 15”hght ------20”hght ------ 25” hght ------ 30” hght 
My Center --------1425-----------856 ------------ 346 ----------189 ---------- 120 --------------811 
Highest reading---1474---------- 881=1-1/2”--- 350=1”-------189 2-1/2”----120=2-1/4”------817=1-3/4”


*23 watt bulb* – got a bit more precise 

Location -------------8” Hght ------- 10” Hght ----- 15”hght ------20”hght ---- 25” hght ------ 30” hght 
My Center ---------218=100x ------142=100x ------- 614 ---------339 ---------- 215--------------147 
Highest reading----218=100x ------142=100x--------615----------340-----------215--------------148=3”

Not really sure these readings can be compared to the previous ones since that reflector was messed up & I was using it for measuring. I was going to do 2nd reading but just didn't have time tonight. Maybe in a few days I'll do it again and see if they're consistent.

On another note, for my T8 Diamond Plate fixture, I got 2 bulb protectors rigged up 2 different ways with insect window screen to filter the light down a bit so I can hang my fixture lower. I will be measuring the effects of that and will have pictures showing what I did in case someone else might want to do it that way. I'll be measuring 1 lit bulb at a time. I'll post those in the T8 Lux reading thread.

I think I'm forgetting something but oh well, I've been long-winded enough for tonight. 

EDIT: I remembered what I wanted to say .. these readings are still off the height of the sensor. I didn't adjust for that yet because I wanted to see how they compared to previous readings.


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## Hoppy (Dec 24, 2005)

Yesterday I ordered another cheap luxmeter, a $11 one. When I get it I will do some more measuring too. Until then, our measurements, and your sets of measurements vary too much to know what the "right" answers are. It is really tricky to measure the light from one of those "brooder" lights, compared to that from a T8/T5 light.


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## sowNreap (Jun 10, 2012)

I just now realized that the readings using the alternate setup (camera tripod) for 20-1/4" & 25" height was 1x scale, not 10x. I didn't note that in post above. I wanted the higher number to more precisely find the "center".

Yeah ... it's not a lab setup so it's going to vary some. Just moving the fixture using the chain can spin the light and put the bulb in a different spot, but think I now have it more precise and hopefully more consistent. Once you measure again and I measure again we'll see if we can get it nailed down better. If we had a 3rd person measuring might help.


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## Hoppy (Dec 24, 2005)

My measurements are now compromised because I modified my luxmeter considerably. I'm finding that my calibration of the meter has changed enough since I first calibrated it that I don't trust it now. With the new meter I expect to get more reliable data, and, of course I will soon modify it too, but the way I will do it this time is different and should give a more reliable calibration.


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## sowNreap (Jun 10, 2012)

Ok .. good to know because I was really sure your data would be more accurate then mine. 

I'm hoping I've got my measurements down now and my readings will be more consistent.

Hey look a short post. LOL


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## Hoppy (Dec 24, 2005)

I used my new lux meter to measure the light from a 8.5 inch diameter "brooder" light, with 3 wattages of GE 6500K bulbs. Disappointing results, to say the least. I measured as accurately as I could, the distance from the end of the bulbs to the top of the sensor, carefully moved the sensor to the maximum reading, then visually verified that it was centered under the light. Here is what I got, in lux:

26 watt bulb:
17.25 inches------2400 lux (39 PAR)
15.25 inches------3120 lux (51 PAR)
10.25 inches------7250 lux (120 PAR)

20 watt bulb
17.75 inches------3450 lux (57 PAR)
15.75 inches------4540 lux (74 PAR)
10.75 inches------9800 lux (160 PAR)

10 watt bulb
18 inches----------2080 lux (34 PAR)
16 inches----------2700 lux (44 PAR)
11 inches----------6120 lux (100 PAR)

I plotted these data points on the chart I made from my data before. The HD bulbs are sowNreap's data, and the GE bulbs are my data.










This is confusing, to say the least, but the probable explanation is the physical sizes of the bulbs. The 26 watt bulb slightly extends outside the reflector, the 20 watt bulb is about a quarter inch below the rim of the reflector and the 10 watt bulb is 1/2 inch below the rim of the reflector. But, the outer half inch or so of the reflector is not effective as a reflector (on my reflectors) because it includes the rolled over rim, with a smooth transition to the rolled edge, which is not a continuation of the main reflector curvature. I think the reflector is simply more efficient with the short bulbs, and much less efficient with the bulb sticking out beyond the edge of the reflector.

We probably can't accurately say how much PAR a certain wattage CFL bulb will give with these reflectors without knowing a lot more about the shape of the bulb, and reflector. So, we can only crudely guess at the PAR. Probably the extra small versions of these bulbs would give considerably more PAR with this size reflector than these do.

One more generalization shot down. (for now.)


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## sowNreap (Jun 10, 2012)

I'm just not sure what to make of this. You're theory sounds good to me. But how to explain why my HD 23 watt is so much higher than your GE 26 watt which falls in line with both your GE 10 watt and my HD 15 watt.?? And why does my some of my 15 watts line up with my 23 watt but others line up along the 26 watt line? Are the ones that line up close to the 23 watt from the first measurements I took? And why does your 20 watt not line up with the first 20 watt line? Is that because of the new Lux meter?

I've got to buy some CFL's so while there I'm going to look around at the sizes and shapes and see what's available. 

Would it do any good for me to test my 23 watt again? Or any of them for that matter?


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## Hoppy (Dec 24, 2005)

Once you recognize that the bulb has to be below the usable rim of the reflector, the whole effort to get PAR vs wattage of CFL bulbs falls apart. Possibly it would be worth testing the extra compact CFL bulbs, but I don't see it doing much good for regular ones. I may be just a bit depressed though.


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## sowNreap (Jun 10, 2012)

Yeah .. I'm stunned about all this. I really thought we'd be able to get this nailed down.

I wonder how the circular lights might do? I have a circular light but think it's too big to even fit my 10-1/2" light. I haven't been able to find any at Lowe's or HD that can use a regular screw-in base .. not pins. But maybe I could "borrow" the base from the big one I have which does convert from pins to screw-in. I'll have to look at that more.


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## Hoppy (Dec 24, 2005)

I think as long as we use the 10.5 inch diameter reflector, the data behave good - all of the bulbs commonly available should be well below the rim of the reflector. But, I'm still puzzled about how to figure out what wattage bulb to use with the 8.5 inch reflector. For that one maybe something can be worked out using the very small new version. I just don't want to rush out and buy some of them to test, even though I can always use them around the house over a few years or less.

Looking back at the origination of this whole idea, http://www.plantedtank.net/forums/showpost.php?p=837592&postcount=21 it looks like the bulbs used then were much smaller, at least for the highest wattage one.


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## sowNreap (Jun 10, 2012)

I need to buy some bulbs .. want a couple 9watt (40 equiv) or maybe just get the 13watt (60 equiv). I can't remember the reason I wanted the smaller ones now. LOL I'll see if I can't find smaller sized one. Think I'll try a different brand also. 

And the circular one I have is too big to fit either dome fixture. I don't know if they make it any smaller but I'll look.


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## Hoppy (Dec 24, 2005)

It is only money! So, I bought a 26 watt GE "mini" fast start CFL bulb. Here is what 3 of my bulbs look like:









The bulb on the right is the standard GE 6500K bulb. The middle one is the mini fast start version of the same bulb. And, the one on the right is the 20 watt version. The lines below the bulbs are .25 inches apart.

I measured how far each bulbs last horizontal portion of the tube sticks above the usable portion of the dome reflector - that portion that follows the circular profile, not the flared out portion. The 20 watt and 26 watt mini bulbs both end the horizontal portion of the tube right at the end of the good portion of the reflector. The standard 26 watt bulb sticks up about 5/16 inch above the usable portion of the reflector. That is about 8+% of the length of the fluorescent tube portion of the bulb that extends outside of the reflector. If we assume that only the 92% of the bulb that is within the envelop of the reflector contributes fully to the PAR I get, then the PAR for the standard bulb should be about 92% of that for the mini version of the bulb. The PAR readings I just measured range from 87 to 90% lower for the standard bulb! Here is that data for those two bulbs, charted:









I'm now convinced that it is the inadequate reflector depth vs the bulb length that upset my data yesterday. Again, today convinced me that our PAR readings are never going to be super accurate, if we get within 5% of the right values we will be very lucky. It takes such a minor mistake to throw off the readings. It is still a worthwhile effort, but we just don't have the equipment to keep everything lined up, at exactly the right distance, not tilted at all, etc. needed for better accuracy.

SowNreap, I still don't know why our readings are not the same. I suspect it is that we have difficulty finding the center of the spot of light to measure at, our sensors may not be exactly normal to the light, and our distance measurements may be off a bit. Also, I am finding that my meter readings tend to drift slowly down as I wait, and due to the digital readout it looks like a bigger drift than it really is, but it makes me keep readjusting my sensor position, which can introduce errors too.


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## sowNreap (Jun 10, 2012)

I noticed it does drift down for the couple minutes so I've started taking the cap off and letting it sit for a just a bit before I start doing my center reading. I then move it around slightly to find the highest center Lux and note it. I finish taking my other readings, then come back to the center to see if it has changed. It's been working pretty good that way. I usually get the same number. 

But yeah ... I don't have a good "lab" quality setup. Not sure what I can do to make it more precise, have to think about that more. It doesn't seem to take much to throw off the readings. A measurement error of 1/8" throws it off. Reading 1/16"s is sometimes hard to see. LOL 

So the 10-1/2" dome light is probably better to use because the reflector is larger and the bulbs stay inside the reflector ... except the floodlight I noted was outside of the reflector. I didn't note whether the 23 watt did but since I didn't say anything about it I'm thinking it didn't. Plus the bigger reflector gives better light spread for only a few dollars more. I thought I posted comparison photo of it to the 8" but see I didn't. I'll try to post that later.

Edit: You beat me to the store.  I was going to see if the mini's weren't shorter. I still haven't got there, so thank for doing that.


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## wastewater (Apr 5, 2010)

Hoppy said:


> It is only money! So, I bought a 26 watt GE "mini" fast start CFL bulb... I measured how far each bulbs last horizontal portion of the tube sticks above the usable portion of the dome reflector...


*Major kudos *(and much respect) for taking one for the team!


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## Hoppy (Dec 24, 2005)

Maybe we are off track in trying to use the brooder lights, since their dome reflectors are not very deep. This one, http://www.petsmart.com/product/index.jsp?productId=3569157 might be a much better choice, and not much more costly. Plus it looks better, I think. It is obvious, now, that if you can see any part of the bulb from the side, you won't get the full effect of the reflector, which limits the brooder lights to 20 watt or less, or mini CFL bulbs. Without seeing one of the linked ones it is hard to say how much better they are - which suggests a visit to my local PetSmart to see what they look like in person.


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## sowNreap (Jun 10, 2012)

You'd either have to get the 10" or use a couple of the small 5.5" ones. But that dome does look deeper than the 10-1/2" one I've got. 

Here's the photo comparison of the 8-1/2" to the 10-1/2" dome light. I know you can't see the bulb depth very good in these photos but even the 23 watt is at least 1" contained within the reflector.

























edit: The reason I called it brooder light is because that's what the first 10-1/2 dome light was called as compared to the regular 10-1/2" light.


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## blt (Apr 1, 2012)

This thread has me very curious. I just rigged up a fixture that has 23watt Sylvania CFLs in 8.5" reflectors resting about 23" off the substrate. They're micros, so they sit completely inside the dome with a 1/2" to spare. With the wide discrepancy in the measurements you guys have been getting, I really I have no idea what PAR I may be getting. I guess time will tell if its adequate, or If I need to lower the fixture.


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## sowNreap (Jun 10, 2012)

Yeah .. I was hoping we'd get better handle on using these type fixtures with spiral bulbs. 

Hoppy ... I really messed up again I just looked at my fixture, took the bulb out to study it more and noticed the my 100 watt equivalent is actually a 27 watt bulb not 23 watt. So found the original package and yep .. it says 27 watt 1750 lumen Daylight bulb. I assumed Daylight meant 6500k because I couldn't find it on the packaging and that's what HD's other daylight bulbs equate to but. Well I finally found the fine print that says it's only 5000k. I had some 23 watt 6500k bulbs in a fixture I took out that I was going to use but when I bought the first 10-1/2 fixture they had these bulbs on markdown so got them & used it instead since they were brand new & my other has been in use for quite a while. So when I made up my "chart" before taking measurements I wrote the wrong bulb info down. So now that really messes things up and the charts will need to be corrected. Would it help to actually take some readings with my well-used 23 watt 6500k bulb?

After checking into that Petsmart Fluker fixture, I noticed reviewers on Amazon said the 10" only actually measured 8-1/2" in diameter. So it may be deeper but wonder if it's any deeper than my 10-1/2 fixture which does measure 10-1/2" diameter and is a lot cheaper .. yeah I just measured it again to make sure I didn't mess that up too. :icon_redf


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## Hoppy (Dec 24, 2005)

It might help to get some measurements of lux with the 23 watt bulb. Hopefully that will help explain part of the difference between our 8.5 inch dome measurements.

About the Fluke dome, I noticed that the size was listed as 8" x 8", which confused me completely. I may visit PetSmart soon hoping they have one and try to measure it. PetSmart isn't far from me.

A problem I keep having is just getting confused about what data goes with what bulb, then I sometimes plot the wrong data, so don't be concerned about missing the bulb wattage and color. This was all so much easier when I just had a simple AH Supply light and did measurements only on it.


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## sowNreap (Jun 10, 2012)

I'll get those 23 watt readings soon. 

Yeah, I saw that 8"x8" size which had me scratching my head. I decided to see if I could find something similar to maybe find it cheaper. That's when I saw the review on Amazon about the actual diameter. 

I tried hard to get my hanging setup right only to mess up writing wrong bulb info down. I prepare my list of heights and what readings I'll be doing on my notepad before I ever get started. That way I keep everything in the same order so I don't get confused when taking the readings and then again when typing them up. I tweak it a bit as I go but never did check the bulb again since I "thought" I had written the right info down.


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## sowNreap (Jun 10, 2012)

I see now why I got messed up on the bulbs. The 23 watt I was originally going to use, when I turned it on was not a daylight bulb so that's why I switched to the new 27 watt bulb but didn't write it down. My 23 watt looks to be soft white although I no longer have the packaging and there's nothing on the bulb to indicate the color temp. It's a Walmart brand. I guess I don't have any 23 watt daylight bulbs. Don't even know why I have soft white because I don't like the look of that color but they were probably cheap. LOL 

But if they do any good here's the readings for it. I DID allow 1" for the sensor thickness. Hoppy, can you measure your sensor thickness and tell me what you come up with so I know for sure what it is? It's kind of hard to measure with that rounded point. 

23 watt (soft white ???)
10" = 655
15" = 318
20" = 172
25" = 111

Oh ... And my bulb is fully within the fixture by about 1/4". 

I should have a 23 watt bright white 5000k somewhere in this house in a fixture. If that would work better I can hunt for it.


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## Hoppy (Dec 24, 2005)

I haven't had time to do anything with these last lux readings, but I hope to tomorrow. Today was a busy one for me.


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## Hoppy (Dec 24, 2005)

The 8.5 inch reflector readings still refuse to act like they should. After struggling with trying to force them to do so I think I might have an idea about why they dont. With T5HO lights we have learned that the ballast is very important in determining how much light you get from a bulb, at least as important as the reflector is. CFL bulbs have the ballast as part of the bulb, so there is no separate ballast and no specific CFL light fixture for manufacturers to cut corners on. But, CFL bulbs now have a wide range of prices, as much as 10-1 range of prices. That may be a result of manufacturers using ever cheaper, poorer quality ballasts. I do know from my experience that the CFL bulbs I buy today last nowhere near as long as they used to before quitting, so I don't doubt that ballast quality has deteriorated too.

So, the misbehaving data may be a result of using different manufacturers bulbs, different quality bulbs. Cheaper bulbs may be brighter, but with much shorter lives, or they may be dimmer. Maybe we need to just accept that, for this type of bulb, you can't make a good guess at how much light you get from any wattage bulb, so it takes a PAR or lux meter to actually measure the light you get, then adjust the height of the light or the wattage of the bulbs to adjust to the amount of light you want. For now I am assuming this is true, and I will probably remove the chart of PAR vs distance for that type of bulb from http://www.plantedtank.net/forums/showthread.php?t=184368


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## sowNreap (Jun 10, 2012)

I wondered if different brands of bulbs might behave differently so yeah your theory sounds good to me. I remember Consumer Reports rating CFL bulbs but don't really remember much about the article other than how quickly some light up to full brightness. I may try to find that article to see what else they had to say. 

That Walmart 23 watt bulb sure didn't perform anywhere close to either the GE or Home Depot brand. It's closer to the HD 15 watt bulb. 

Looking back over the readings in this thread it appears my 15 watt readings are more consistent than my 23 (actually 27watt) ones. And I see at least one possible measurement error for the 23(27) watt. I may do the 27 watt again to see if I can get consistent readings. That one set of readings is when the reflector holder broke so the reflector was being held on by the bulb. Which meant the bulb was well contained within the reflector and now realize that would have thrown those readings off. 

The only way to really use the chart would be to put a big caveat on it saying the chart is only for these specific bulbs similar to the t5 chart. *IF* I can get a consistent reading on the 27 watt. Otherwise even that won't work.


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## sowNreap (Jun 10, 2012)

I did 3 more readings using the 27 watt 5000k Daylight bulb. I measured from top of sensor to tip of bulb. Did NOT allow for sensor thickness since that messed me up from making comparison to previous readings. 

I used my plant pulley with a clamp to make it easier to make 1/16"-1/32" adjustments. Can't really get much closer than that. 1/32" is just too hard to see and adjust for. I did the best I could but could be off 1/16". But that's closer than the 1/8" I could have been off previously.

Here's exactly what I did. I measured height. Turned lux meter on and opened cover. Moved sensor around to find highest center reading. Removed hand (it will cause the reading to be higher if left on sensor grip), then let sit there for another couple minutes. I tried not to create any motion that would cause the fixture to sway or move at all. 

Moved up to next height did same as above. Worked all the way up to 25" height, then started over again at 10". Did this exact same thing 3 times. 

The reason for letting it sit so long is I discovered that the reading will go down after a short period but then after another short time it will go back up. Plus it's possible the fixture hadn't totally quit swaying after moving/measuring. This was mostly an issue only at the 10" height.

All readings in lux 10x scale.
*
Height ----1st -----2nd-----3rd*
10" -------1291-----1304----1320 
15"---------579------573------577
20"---------324------322------320
25"---------210------210------208

All except the 10" height is fairly consistent but not with my previous readings. However, I'm very confident these numbers are the most accurate I'm going to get, again except at the 10" height. 

Since the 10" height was giving me fits I tried an experiment 3 more times. I *never *moved the fixture at all just covered the sensor, turned off meter, waited a couple minutes. Then uncovered sensor, moved slightly to make sure still in correct spot, waited several minutes .. as long as 15 minutes in some cases and then took reading. So measurement error is NOT a factor in these readings but does show how being off just a small measurement error or taking the reading at wrong time can really effect the number. 

10" height
4th reading = 1327 .. final range varied between 1317-1340 .. original range I think was 1290's - 1320's. I changed it when it "stabilized" into this new range.
5th reading = 1333 .. final range varied between 1307-1336 
6th reading = 1328 .. final varied between 1315-1330

At 10" the Lux number would never stabilize. These last 3 readings I stood there for at least 10-15 minutes just watching the numbers move. I waited so long that I really didn't know what number to use because it never quit moving and almost never stayed in a small range for very long. So realizing it was never going to quit bouncing around I finally decided that if it bounced between 1-2 numbers for some undetermined number of seconds and stayed at 1 number longer than the other, that's the reading I used. At least the final 3 readings are fairly consistent and maybe I'm getting better at pinpointing when to take the actual reading considering the ranges it was bouncing around. ??? The first 3 readings I might have read to quickly or the height was off. 

For me, it seems unlikely I'll get a more accurate reading at 10". The higher the height the more quickly the reading stabilized at just 1 number, so 15" and up are much easier to read and much more accurate.

Edit: I forgot to mention this 27 watt bulb does stick out past the reflector. I forgot to measure that though.


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## Hoppy (Dec 24, 2005)

This only gets more confusing and more interesting! This set of data for a 27 watt bulb falls right on the line I have for a 15 watt bulb. Weird coincidence! But, then your last edit, about the bulb sticking out past the reflector.......that could be the explanation if the original 27 watt bulb data you got was with a bulb that didn't stick out.

I get the feeling that the best answer for determining how much light someone will get with one of these reflectors will come from them investing $20 in a lux meter and measuring the intensity at the distance they plan to use the light. That way the variations in bulbs will go away, and any variations in reflectors will also go away.

I keep thinking $20 isn't a lot to pay to be able to see how much light you have with any lighting system. I'm thinking about a DIY simple mod to make those cheap lux meters do the "divide by 61" step for us so they directly read in PAR units. I think it will cost less than $5 to do that.


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## sowNreap (Jun 10, 2012)

I can't really remember but I didn't note that it stick out past the reflector so I'm thinking the bulb was fully contained within it 

I think you're right when it comes to CFL bulbs & fixtures. If the fixture/bulbs are bought locally is easy enough to return if it doesn't perform as needed. 

I'm done testing these CFL's and dome lights. Just for curiosity I want to test my aluminum foil lined 48" t12 old grow light.


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## Hoppy (Dec 24, 2005)

We need more T8 data too.


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## sowNreap (Jun 10, 2012)

What other T8 data do we need that I can do? Or are you referring the the T12 fixture I plan on testing?

Can T8 bulbs be used in a T12 fixture? I found out it's not a good idea to use T12's in a T8 fixture but not sure of the other way around.


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## Hoppy (Dec 24, 2005)

T8 light fixtures can use magnetic ballasts or electronic ballasts. Obviously electronic ballasts are better, and I suspect they give more light than magnetic ballasts. You can use T8 bulbs in T12 fixtures, with either kind of ballast.

I have some data I took from a standard 4 bulb aquarium light, with only one bulb installed. It had no real reflectors, which was standard for fluorescent lights of that era. And, I have data from the Home Depot diamond plate shop light, with good reflectors. 

It would at least be interesting to get data on your T12 light with T8 bulbs, especially if you can do both one and two bulb testing. That would let me update my T8 PAR vs Distance chart.


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## sowNreap (Jun 10, 2012)

Ok .. good deal about using T8 bulbs in T12 fixture. I'll get some readings with the aluminum foil lined fixture and then I may take foil off and take some more readings. It's white painted .. just to see how it compares to yours. 

I also have an old 48" T12 single bulb hood that I got when I bought my second-hand 75 gal. The reflector is not great but with the smaller T8 bulb might be a tad bit better. I can do that one also.


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## sowNreap (Jun 10, 2012)

Hoppy ... my T8 bulbs don't work right in my T12 fixture. They just flicker and I can tell they're not very bright. This fixture is very, very old .. at least 10 yrs probably even more than that. I put the T12's back in and no flickering. So it just doesn't like the T8's. This fixture may have been made before there was t8's .. did I mention it's really old. LOL Just wasn't used much. Dang thing weighs a ton .. ok maybe only 5 lbs but when hanging it, feels heavier than that. 

I can do some testing with t12 bulbs if that would help at all.


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## Hoppy (Dec 24, 2005)

I doubt that we would get much from PAR results on T12 lights, especially since they aren't even made that way now.


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## sowNreap (Jun 10, 2012)

ok ..sorry about that. I'd tried. 

And I forgot to try the T8 bulb in my single T12 aquarium hood, so I try that. If it does work I'll put it in a new thread.

I'll look around the house and see if I have any other 2 bulb fixtures. Don't think I do .. I've got 4 bulb ceiling type ones but think that was the only 2 bulb I had.


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