Canon 400mm f5.6 on a 5Ds 1.6 crop mode VS. on a 7DII

Which is better?

The 400mm f5.6 was left off Canon's list of recommended lenses for the 5Ds. Perhaps this means the 7DII combo is better?

IQ should be about same, but if you shoot any action or birds in flight, the 7DII shoots much faster.

texshooter wrote in post #17701142
The 400mm f5.6 was left off Canon's list of recommended lenses for the 5Ds. Perhaps this means the 7DII combo is better?

It probably just means that Canon would like you to buy more expensive lenses / those with a higher profit margin.

Personally I wouldn't bother with using the crop mode, unless you are really tight for space on your CF card, and it makes no difference to file size in RAW anyway. You still get the advantage of the pixel density, but you get 2.56× the area to frame in. handy for those times when you might otherwise miss a bit of a fast moving subject off the edge of the frame as you pan. You can still crop down in post for better framing anyway. Not only that but using a 400mm prime on the 5DS will actually give you the framing options of a 250-400mm zoom on a 1.6 cropper.

Alan

BigAl007 wrote in post #17701364
Personally I wouldn't bother with using the crop mode, unless you are really tight for space on your CF card, and it makes no difference to file size in RAW anyway. You still get the advantage of the pixel density, but you get 2.56× the area to frame in. handy for those times when you might otherwise miss a bit of a fast moving subject off the edge of the frame as you pan. You can still crop down in post for better framing anyway. Not only that but using a 400mm prime on the 5DS will actually give you the framing options of a 250-400mm zoom on a 1.6 cropper.

Alan

But if I crop in post (5Ds full frame mode), I won't get as much background blur as if I crop in camera (5Ds 1.6 crop mode). Yes?

texshooter wrote in post #17701472
But if I crop in post (5Ds full frame mode), I won't get as much background blur as if I crop in camera (5Ds 1.6 crop mode). Yes?

No. When and where you discard the edge of the frame makes no difference on the blur. The degree of blur and the DOF are function of the lens focal length, the aperture, and the enlargement from image to print. The enlargement is a factor of the cropped image file size (and by size, I mean the physical dimenstions of the part of the sensor that captured the image.....24x36mm for the full, un-cropped sensor in the 5D for example).

The resulting image quality would be about the same. The shooting experience favors the 7D II (faster shooting). But, as a great all-in-one solution the 5DS is terrific (handy for wildlife and a 400mm, while great for wider-angle lens for other types of photography.

JeffreyG wrote in post #17701486
No. The degree of blur and the DOF are function of the lens focal length, ).

This why I would expect the 5ds 1.6 crop mode to give more background blur because it increases the effective focal length by a factor of 1.60.

texshooter wrote in post #17701672
This why I would expect the 5ds 1.6 crop mode to give more background blur because it increases the effective focal length by a factor of 1.60.

It actually does not. The focal length stays the same, no matter what crop mode you use or not. What you get with a crop is the field of view of a longer lens (a smaller portion of your subject will fill the frame). But this effect has no impact on the DOF (background blur). For the DOF calculation, the actual focal length is used, so just 400mm.

texshooter wrote in post #17701672
This why I would expect the 5ds 1.6 crop mode to give more background blur because it increases the effective focal length by a factor of 1.60.

But shooting with a 24x36mm frame and cropping in camera via the crop mode to 14.9x22.3 mm image area results in the identical image presented by the same 400mm lens to the APS-C body!

DOF ends up identical for FF cropped vs. APS-C
Background blur ends up identical for FF-cropped vs. APS-C
AOV ends up identical for FF-cropped vs. APS-C

...no advantage.

I think we are all wrong. See below. Cropping in camera actually reduces background blur.

Read Jeffrey's post again, he has put it best:

Note that DOF depends on the enlargement! If you crop an image, you will get less DOF, due to the fact that you would be enlarging the image more (compared to printing the uncropped image to the same print size). So you will get more background blur by cropping, but this is not due to the focal length, and it is exactly the same no matter if you crop in camera or in post. Also, this change in DOF is much smaller compared to a real focal length change (i.e. swapping out the 400mm lens for a 600mm lens).

texshooter wrote in post #17701687
I think we are all wrong. See below. Cropping in camera actually reduces background blur.

Hosted photo: posted by texshooter in
./showthread.php?p=177​01687&i=i86081443
forum: Canon Lenses

That graph fails to take into consideration the cropping (in camera by the 5DS) of the image from 24x36mm to 14.9x22.3mm, it assumes use of the FULL frame area!

To do what happens in camera with the 5DS crop capability, you list that as crop 1.6, (which is identical to the APS-C camera) for the effective area of the image being used.

texshooter wrote in post #17701687
I think we are all wrong. See below. Cropping in camera actually reduces background blur.

Hosted photo: posted by texshooter in
./showthread.php?p=177​01687&i=i86081443
forum: Canon Lenses

The numbers in this chart are correct, but you may have interpreted it wrong. The "blur disk diameter", sometimes also called circle of confusion (CoC) is a measure what diameter the human eye will still see as a point, when looking at a given print form a certain viewing distance. Point of light sources that are in front or behind the focal plane are rendered as a circle by the optical system. So what we regard as DOF is not actually all perfectly in focus. It's just that the blur is so small that the eye cannot see it, so it still "looks" in focus. If you enlarge an image more (i.e. by starting from a crop), you are also enlarging those circles. That means a smaller original circle will be required for the eye to still see it as a point. Smaller circle = less DOF. So what this chart shows is that with 1.6x crop, you get a smaller CoC and therefore less DOF (more background blur).

If you want to read up more on it, check our this article: https://en.wikipedia.o​rg/wiki/Circle_of_conf​usion

For a more hands-on demonstration, try DOF calculation, i.e. with this calculator: http://www.dofmaster.c​om/dofjs.html
Try a few scenarios, i.e. keep everything the same (focal length, subject distance) and just replace a 5Ds with the 7DII (meaning you would crop the image). See how the DOF gets smaller (but not by much). Or try to change the lens from 400mm to 600mm, and see how the DOF gets much smaller.