FF vs 1.6x crop: The real world reach difference

OK, I have seen many, many threads where somebody states that the 1.6x crop cameras are better for birding etc, because they have much better reach because of the 1.6 crop factor.

This is absolute rubbish, the crop factor is irrelevant. It simply means that they only record the central part of the image projected onto the sensor, whereas the FF sensor records the whole image. As the lens projects the same image onto both, all else being equal you would simply need to crop the edges from the FF image to get an identical result.

Whilst there is a big difference when comparing an identical sized image (say a 12x8 print) produced from each, without cropping, once you have to crop the image (common in birding shots) the difference becomes much less marked, you just have to crop the 5D image more.

The key point here being the all else being equal part. The 5D uses larger pixels and so has a lower pixel density than the crop bodies, therefore the image will be recorded on less pixels and be smaller when viewed on a computer screen, or printed at xxxdpi.

So, yes, you do get more reach from a crop body than the 5D, but it is due to pixel density and not the crop factor. I have always wondered exactly how much difference this makes in 'the real world', after cropping has taken place to suit the subject, so I have done a comparison test to compare them.

This test was done between a 5D and a 20D with a 100-400L at full stretch, users of a 1DSII will find much less of a difference, because that camera has a higher pixel density than the 5D.

Yes, the image is crap - I was shooting in very dull conditions, waiting for the rain to stop, I was far too far away from the buzzard to get a decent shot but I thought it would be a good test of reach, when trying to shoot birds a bit less far away.

These images are very heavily cropped and have been reduced in size (identically) a little for posting, All the original production was done on (and the final measurement is based on) the originals at 100%.

I didn't use the actual buzzard for the measurements because he is more upright in one pic than the other, I therefore measured between two easily measured points on the rock wall - the small peak at position 1 and the notch at position 2 (20D) / 3 (5D).

First up, the image from the 20D:

Things are even more clear at sensors of 10MP like the new 400D.You have a 1.6 crop sensor and 10MP.

doc, the 10mp sensor will have no impact on the field of view difference over 8mp or even 6mp. Megapixels only governs the physical size of the image. Field of view is not changed by adding megapixels. At these websizes, you're looking at the equivalent of a half megapixel shot.

That's been discussed a million times before. The 20D (and the 400D even more) has an advantage over the 5D, a so called "better reach". The smaller photosites make up for a finer sampling of the subject.

The size of the 400D photosite is 5.7μm, that of the 5D is 8.2μm. That will give you a x1.44 magnification for the 400D image over the 5D with the same lens used. Bigger magnification means more fine detail visible.

I think the point of this post is to prove that you can use a 5D that costs twice as much to get the same quality photo that you can with a 20D. I am not certain that it actually proves the point, but it is a good attempt.

ScottE wrote in post #2381092
I think the point of this post is to prove that you can use a 5D that costs twice as much to get the same quality photo that you can with a 20D. I am not certain that it actually proves the point, but it is a good attempt.

And only at long focal lengths

Ronald S. Jr. wrote in post #2380074
doc, the 10mp sensor will have no impact on the field of view difference over 8mp or even 6mp. Megapixels only governs the physical size of the image. Field of view is not changed by adding megapixels. At these websizes, you're looking at the equivalent of a half megapixel shot.

Well I know that with 10MP sensors you could crop more and in general you have a bigger picture.Since at 8MP there is a difference in size,at 10 MP there is going to be a bigger difference(at 100% you will have a bigger pic,more "zoom").

Now blow up the 5D image so point 3 is in the same place as point 2 in the 20D image and compare them...

Ronald S. Jr. wrote in post #2380074
Megapixels only governs the physical size of the image. Field of view is not changed by adding megapixels. At these websizes, you're looking at the equivalent of a half megapixel shot.

I'd supplement this by saying that megapixels only govern the physical size of the shot when your ppi resolution is fixed. In print, where it really matters, the megapixels matter simply to determine the upper size limit at which one can print with acceptable resolution (from a non-interpolated image). In terms of enlargement factor, which I find more important than megapixels, the cropped FF is identical to the APS-C by definition.

sandpiper wrote in post #2379974
OK, I have seen many, many threads where somebody states that the 1.6x crop cameras are better for birding etc, because they have much better reach because of the 1.6 crop factor.

This is absolute rubbish, the crop factor is irrelevant. It simply means that they only record the central part of the image projected onto the sensor, whereas the FF sensor records the whole image. As the lens projects the same image onto both, all else being equal you would simply need to crop the edges from the FF image to get an identical result.

Whilst there is a big difference when comparing an identical sized image (say a 12x8 print) produced from each, without cropping, once you have to crop the image (common in birding shots) the difference becomes much less marked, you just have to crop the 5D image more.

The key point here being the all else being equal part. The 5D uses larger pixels and so has a lower pixel density than the crop bodies, therefore the image will be recorded on less pixels and be smaller when viewed on a computer screen, or printed at xxxdpi.

So, yes, you do get more reach from a crop body than the 5D, but it is due to pixel density and not the crop factor. I have always wondered exactly how much difference this makes in 'the real world', after cropping has taken place to suit the subject, so I have done a comparison test to compare them.

This test was done between a 5D and a 20D with a 100-400L at full stretch, users of a 1DSII will find much less of a difference, because that camera has a higher pixel density than the 5D.

Yes, the image is crap - I was shooting in very dull conditions, waiting for the rain to stop, I was far too far away from the buzzard to get a decent shot but I thought it would be a good test of reach, when trying to shoot birds a bit less far away.

These images are very heavily cropped and have been reduced in size (identically) a little for posting, All the original production was done on (and the final measurement is based on) the originals at 100%.

I didn't use the actual buzzard for the measurements because he is more upright in one pic than the other, I therefore measured between two easily measured points on the rock wall - the small peak at position 1 and the notch at position 2 (20D) / 3 (5D).

First up, the image from the 20D:

Now the image from the 5D:

Finally, the 5D superimposed over the 20D:

As you can see, the 20D image is significantly larger than the 5D, although not as great as some might think.

In pixel terms the distance between points 1 and 2 (the 20D shot) is 1011, the distance between points 1 and 3 (the 5D shot) is 791. In linear terms the 20D result is about 26.6% longer than the 5D image. More to the point, that appears to have resulted in a better image due to the extra pixels, although it should be noted that I haven't done much to these in post processing. Remember these figures were measured on the original 100% crops.

So, it does seem that the 1.6x crop factor cameras have a significant advantage when the subject requires heavy cropping. In this case of course the cropping needed would be too heavy (even at his full height, on the 20D image at 100%, the buzzard is only around 380 pixels tall) but the image serves to compare the two formats.

If you can get much nearer to the birds and fill a significant portion of the viewfinder, I would choose the 5D over the 20D in many cases for it's better AF with moving targets. I certainly won't be getting rid of my 20D for some time though, this is one situation where it can be the camera of choice.

So you got any of what your smoking for sale?.............that sh*t is deep

While the info in the first post is correct, I suggest that very few people think of their cameras in that way. I believe that, for most people, 'reach' (which is a hopelessly vague term, IMHO) refers to what you see in the whole image from the camera - i.e. the field of view. The number of megapixels defines the resolution of that image, and is usually thought of separately.

For example, someone moving from a Canon 300D to a 400D would most likely think of their lenses as still giving them the same 'reach', but they would have gained resolution.

The equivalent in the world of film would be to compare, say a decent ISO50 film with an ISO400 film. The ISO50 would give better resolution and lower noise, and therefore the ability to crop more while printing at the same size. But somehow I doubt that a film photographer would think their lenses had greater 'reach' when using a higher resolution film.

As I say, there's nothing wrong with viewing 'reach' in terms of pixel density - I just don't think most people would think about it in that way.

So in other words. the crop will give you better quality so you can print a larger picture with the same quality and a smaller one form a non-crop camera???