Compression and crop frame v. full frame

[fjrabon]

So, with the D600 coming out, I'm trying to sort of 'get all the info' on crop frame v. full frame. I'll probably rent a D600 after it comes out, before I fully decide, but I have a question:

I tend to like the enhanced sense of depth that comes from shorter focal lengths. I almost never use telephotos for anything other than long distance sports shots. Almost always, if I can, I tend to choose a wider focal length and get closer, for the enhanced sense of depth. For my tastes, there's nothing like being able to almost feel like you could 'step inside' a photograph.

My question is this: For a given focal length, the compression is the same, regardless of whether or not it's full frame or crop frame? Correct? ie a 35mm lens on a crop frame has the same sense of depth as a 35mm on a full frame, even though the field of view is roughly equivalent to 50mm on a full frame for the 35mm on a crop frame? So, basically, for a given field of view, full frames will have more compression?

I guess I could always just zoom out if I wanted more sense of depth, and then crop the picture in post. But I'm mostly just wondering if the way I'm thinking about compression, and full frame v crop frame is correct?

 

[unpopular]

No. I can't give a full explanation now, but if that were the case then a 90mm lens on a 5x7 would have the same sense of compression as a 90mm on an APS-C, this isn't the case:

http://www.largeformatphotography.i...Water%92s-Edge&p=845866&viewfull=1#post845866

I'll give you a hint though: magnification

 

[fjrabon]

No. I can't give a full explanation now, but if that were the case then a 90mm lens on a 5x7 would have the same sense of compression as a 90mm on an APS-C, this isn't the case:

What did you compose at Water’s Edge? - Page 202

I'll give you a hint though: magnification

To get that field of view on a crop frame, you'd need like a 30mm? Which would have a very deep sense of depth. You'd have to compare just the middle 1/4 of that photo to compare the senses of depth for the same field of view. Sorry if I didn't make that clear in my original question that this was what I was asking.

The middle 1/4 of that photo doesn't have very much sense of depth. The sense of depth is coming from the edges.I guess let me try to make my question as clear as possible: "For a given field of view (not a given focal length), does a crop frame give more, less, or no different sense of depth?"

 

[Ysarex]

No different. Field of view is the determining factor not the size of the recording media. If you have a 72 degree field of view on a P&S digital camera you'll get the same image from the same position if you also use a 4x5 camera with a 72 degree field of view (same aspect ratio of course).

Joe

 

[fjrabon]

No different. Field of view is the determining factor not the size of the recording media. If you have a 72 degree field of view on a P&S digital camera you'll get the same image from the same position if you also use a 4x5 camera with a 72 degree field of view (same aspect ratio of course).

Joe

oh ok, yeah, that makes sense. I guess I was sort of conceptually thinking about it like the whole frame had the same sense of depth, but then I remembered that the central portion of the frame is more compressed, since it's a smaller angle to the lens. the sense of depth is most enhanced at the edges. And since angle of view decides sense of depth, as long as you have the same angle of view, you have the same sense of depth. hence format doesn't really change sense of depth if you use equivalent focal lengths.

Thanks.

 

[greybeard]

It is field of view or angle of view that determines compression and not focal length. These terms can get very confusing but every format has it's "normal" focal length that creates a normal perspective. For a full frame it is a 50mm, APS-C it is a 35mm for a 2 1/4 it is an 80mm, for a 4x5 it is 150mm. They will all create the same perspective when matched with the proper format. What IS different is Depth of field or what I like to call Depth of focus. When you compare a 50mm FF with a 150mm 4x5, the 150mm 4x5 is much shallower for every matching f/stop.

 

[unpopular]

Imagine FOV as rays extending from the edge of the sensor or film plane through the center of the lens and out to infinity. If you shrink the sensor, the angle becomes more oblique. So as a result, distant objects will consume more of the field, while expanding the sensor larger, the angle becomes more obtuse, and objects at the same distance as before will consume less of the field; however, the same is not true of near objects, and as you approach the lens the proportion which near objects consume the frame will become more and more similar.

Since spacial compression is created by the the relative size of foreground objects to background objects, the degree of the effect is determined by the format relative to the magnification, rather than the focal length of the lens.

----

ETA: This is completely wrong.

 

[Solarflare]

The main reason I would like to get the D600 is really for the enhanced availability of lenses. Many of the really cool ones really only make sense on a full frame sensor. The AF 105mm/135mm DC lenses for example wouldnt do the same thing on DX. We would need AF-S 70mm / 90mm DC for that.

I am already quite happy with my depth of field with my APS-C sensor and a 35mm f/1.8 DX lens. I dont need any more than that.

 

[unpopular]

^^ not what he was asking...

and derp.

 

[jaomul]

What's derp

 

[Solarflare]

Has his question not already been answered ?

I also have no clue what "derp" means.

 

[unpopular]

just your reasoning for not using APS-C is kind of derpy. If you're looking at using an APS-C camera, you're probably not going to have a $2000 lens anyway. I'd say anyone who is interested in a DC lens whilst still shooting APS-C, that they should consider buying a full frame camera first.

Nobody thinks to themselves "Am I ever going to put a high end lens on this camera, and will that high end lens' focal length be suitable given the crop factor" when settling for APS-C.

 

[jaomul]

just your reasoning for not using APS-C is kind of derpy. If you're looking at using an APS-C camera, you're probably not going to have a $2000 lens anyway. I'd say anyone who is interested in a DC lens whilst still shooting APS-C, that they should consider buying a full frame camera first.

Nobody thinks to themselves "Am I ever going to put a high end lens on this camera, and will that high end lens' focal length be suitable given the crop factor" when settling for APS-C.

wildlife shooters?

 

[Dao]

Compression between crop vs full frame. If the distance between the recording medium focal plane and the subject is unchanged, there is no difference regardless the recording medium size.

For example, there are 2 identical trees and they are 5 feet apart. You are standing about 100 feet from them and are almost inline with them (maybe at a angle about 15 degrees). So the tree which is closer to you is about 100 feet away while the other one is between 100 - 105feet. No big different in them as far as size concern since they both appear to be a tree 100 feet away (close to same distance). When you take a photo with a 200mm lens mounted on a crop camera or full frame camera, the trees should appear about the same size in the crop photo, or in the full frame photo.


Now, you walk towards the tree to a point you are 5 feet away from the first tree and the 2nd tree is between close to10 feet. Now, the 1st tree appears to be bigger because it is much closer than the 2nd one. The 2nd one now almost 2x the distance. And because of the size difference, the compression you see when you are 100 feet away is pretty gone. So if you take a photo (crop or full frame) with a focal length in which the first tree is about the same size, the 2nd tree will appear smaller when compare to the photos you take 100 feet away.


So the compression is pretty much the result of the distance between you and the subject, not the recording medium.

 

[Ysarex]

Compression between crop vs full frame. If the distance between the recording medium focal plane and the subject is unchanged, there is no difference regardless the recording medium size.

For example, there are 2 identical trees and they are 5 feet apart. You are standing about 100 feet from them and are almost inline with them (maybe at a angle about 15 degrees). So the tree which is closer to you is about 100 feet away while the other one is between 100 - 105feet. No big different in them as far as size concern since they both appear to be a tree 100 feet away (close to same distance). When you take a photo with a 200mm lens mounted on a crop camera or full frame camera, the trees should appear about the same size in the crop photo, or in the full frame photo.


Now, you walk towards the tree to a point you are 5 feet away from the first tree and the 2nd tree is between close to10 feet. Now, the 1st tree appears to be bigger because it is much closer than the 2nd one. The 2nd one now almost 2x the distance. And because of the size difference, the compression you see when you are 100 feet away is pretty gone. So if you take a photo (crop or full frame) with a focal length in which the first tree is about the same size, the 2nd tree will appear smaller when compare to the photos you take 100 feet away.


So the compression is pretty much the result of the distance between you and the subject, not the recording medium.

Yes! That's right. Perspective is not a function of lens focal length or the size of the recording medium. Perspective in a photo -- the apparent relationship of objects in 3D space -- is a direct function of only one factor: camera placement. Different lens focal lengths matched with different size film/sensors simply facilitate the desired crop from the chosen perspective position. Obviously you need that 300mm lens to get the photo from a distant location and likewise you need that 20mm lens to get in really close. Conversely, the 300mm isn't going to be the lens of choice when working in close to the subject. The problem here is that a transference of causality has taken place in the common jargon (i.e. telephoto/wideangle perspective) and the effects we see that are in fact due to camera placement get described as if they were caused by some property of the lens. Then people get confused.

Joe