# understanding lens on dx bodies.



## Nubster

***EDIT***

I thought I knew, I read something just to confirm and now I'm confused too...lol


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## Patriot

It's been confusing me for some time now. You would think that those lens would be made to compensate like you said. Does this mean that the minimum focus distance also increases meaning that you have to step further back from your subject?


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## Ulupica

The "crop factor" has no effect on the actual focal length of the lens. A 35mm lens is a 35mm lens no matter what body it's used on. Same goes for the fstop value. A sensor that's less than "full frame" simply captures a smaller part of the scene.


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## Nubster

But that image is "cropped" thus it is magnified x1.5...right? Just like taking an image and cropping it in PS?


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## Patriot

Ulupica said:


> The "crop factor" has no effect on the actual focal length of the lens. A 35mm lens is a 35mm lens no matter what body it's used on. Same goes for the fstop value. A sensor that's less than "full frame" simply captures a smaller part of the scene.


I don't thinks that's the case because everywhere I go I hear that a 50mm on a DX body is 75mm. 

It even explains it here:
http://www.digital-photography-school.com/crop-factor-explained


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## fishykid1

Patriot100% said:


> I don't thinks that's the case because everywhere I go I hear that a 50mm on a DX body is 75mm.
> 
> It even explains it here:
> http://www.digital-photography-school.com/crop-factor-explained



It's the equivalent to that on a 1.5x crop frame. Basically what it does is narrow the angle of view. On a full frame camera a 50mm is 50mm. But on a 1.6x (such as the canon 40D), a 50mm lens has the effect of a 80mm focal length. 

So your right about it not changing the lens, a 50 mm length is 50mm. But due to the sensor being a crop factor, it increases the 'focal length', or narrows the angle of view. An example here: 

Notice that the lens on the Crop and Full Frame did not move in the room, but rather the crop sensor essentially "cut out" the extra space by narrowing the field of view where was the full frame shot was able to capture a wider portion of the room


FX vs DX and 35mm vs 50mm by fluud7, on Flickr


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## Ibn

The difference is in the perspective vs. the actual lenses changing itself. 

Stick to non-DX lenses if you plan to upgrade to FF cameras in the future, unless what you shoot is on the telephoto side of thing. You'll want the increase crop factor for times like those.


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## fishykid1

Ibn said:


> The difference is in the perspective vs. the actual lenses changing itself.
> 
> Stick to non-DX lenses if you plan to upgrade to FF cameras in the future, unless what you shoot is on the telephoto side of thing. You'll want the increase crop factor for times like those.


well yes, but the majority of users "consumer" lenses are dx and bodies. For canon L lenses are usually best on full-frames.


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## GraphicGr8s

fishykid1 said:


> It's the equivalent to that on a 1.5x crop frame. Basically what it does is narrow the angle of view. On a full frame camera a 50mm is 50mm. But on a 1.6x (such as the canon 40D), a 50mm lens has the effect of a 80mm focal length.
> 
> So your right about it not changing the lens, a 50 mm length is 50mm. But due to the sensor being a crop factor, it increases the 'focal length', or narrows the angle of view. An example here:
> 
> Notice that the lens on the Crop and Full Frame did not move in the room, but rather the crop sensor essentially "cut out" the extra space by narrowing the field of view where was the full frame shot was able to capture a wider portion of the room
> 
> 
> FX vs DX and 35mm vs 50mm by fluud7, on Flickr


Your example is not quite right. The objects in the cropped frame would be the same size in all four shots. However the size of the frame itself would be smaller for the "cropped" sensor.


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## fishykid1

GraphicGr8s said:


> Your example is not quite right. The objects in the cropped frame would be the same size in all four shots. However the size of the frame itself would be smaller for the "cropped" sensor.



Note they are comparisons with 2 different focal length lenses.

On the d80 with the 35mm, it's effectively making it a ~52.5mm 'lens'. It doesn't change the lens, but rather the angle of view.

Comparing the full frame 50mm and the crop frame with 35mm you see what I'm talking about. I believe the user in that instance wanted to compare shots that were exactly same width and height.


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## GraphicGr8s

fishykid1 said:


> Note they are comparisons with 2 different focal length lenses.
> 
> On the d80 with the 35mm, it's effectively making it a ~52.5mm 'lens'. It doesn't change the lens, but rather the angle of view.
> 
> Comparing the full frame 50mm and the crop frame with 35mm you see what I'm talking about. I believe the user in that instance wanted to compare shots that were exactly same width and height.


I realize that. I was looking at each lens on a full frame and a cropped sensor. A cropped sensor is physically smaller than a full frame sensor. To get the same size object in the frame you must enlarge the cropped sensor to get the same frame size. If you were to imagine that instead of a sensor you had film for each size of sensor and looked at the developed negatives the image size would be identical. The film size however is different.
Your example gives the impression that the image is larger on a cropped sensor. It's not. It's the same size.


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## fishykid1

GraphicGr8s said:


> I realize that. I was looking at each lens on a full frame and a cropped sensor. A cropped sensor is physically smaller than a full frame sensor. To get the same size object in the frame you must enlarge the cropped sensor to get the same frame size. If you were to imagine that instead of a sensor you had film for each size of sensor and looked at the developed negatives the image size would be identical. The film size however is different.


well yeah, that's true. I can't disagree there. 

Some people wouldn't make that comparison or the math. I like the example you showed. I was looking for that, but couldn't find it. :angryfire good job roud:


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## GraphicGr8s

Yeah, thanks. You have to realize that this is my living. Anything to do with graphic arts. From shooting the photos to designing the collateral to printing it to PP other photographers photos. Then add in teaching it. Want to see something interesting? Look at the exif data. Next month of course it will be irrelevant.


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## fishykid1

GraphicGr8s said:


> Yeah, thanks. You have to realize that this is my living. Anything to do with graphic arts. From shooting the photos to designing the collateral to printing it to PP other photographers photos. Then add in teaching it. Want to see something interesting? Look at the exif data. Look at the program used to do that jpeg.



For the example I saw? I will. Just not tonight! darn eastern time zone >.<

I've been into photography quite a while now, but until recently didn't really give a hoot about the differences in full-frame and crop bodies. I feel that full frame (lens and body) would have a HUGE advantage with landscape shots over crop bodies...


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## GraphicGr8s

fishykid1 said:


> For the example I saw? I will. Just not tonight! darn eastern time zone >.<
> 
> I've been into photography quite a while now, but until recently didn't really give a hoot about the differences in full-frame and crop bodies. I feel that full frame (lens and body) would have a HUGE advantage with landscape shots over crop bodies...


Hey I'm in the same TZ. I've still got the original camera I bought with my very first paycheck. Still use it too. Pentax K1000 I got in 75 or 76. Now I've got about 4 Pentaxes a couple of Mamiyas a Minolta a minox that all still work. I'd hate to add up all the money in 3 systems though. Heck I still have the first PS I started with PS4

For landscapes with a cropped I just shoot a pano. Works great.


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## fishykid1

GraphicGr8s said:


> Hey I'm in the same TZ. I've still got the original camera I bought with my very first paycheck. Still use it too. Pentax K1000 I got in 75 or 76. Now I've got about 4 Pentaxes a couple of Mamiyas a Minolta a minox that all still work. I'd hate to add up all the money in 3 systems though. Heck I still have the first PS I started with PS4
> 
> For landscapes with a cropped I just shoot a pano. Works great.



Pano's seem to always be hard to get the photos to mesh perfectly. :/ It can be done, but with rapidly changing views like the beach it's always hard to get them to match. 

My parents - notably my mother - has a an old pentax slr from when they lived in Alaska. Neat little camera


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