500mm FOV native vs cropped

What do you think would render the sharpest image?

The subject is a small bird, 25 feet away, which needs cropping in post to fill the frame.

Here are the options:
Canon 100-400 ver2 at 400mm, image cropped/zoomed to match the 500mm FOV
Canon 100-400 ver2 with the Canon 1.4x ver3, shot at 500mm with no crop
Sig/Tam 150-600 shot at 500mm, again no crop required

I don't have a 150-600 to test against but maybe someone here has both lenses.

chuckmiller wrote in post #19278824
What do you think would render the sharpest image?

The subject is a small bird, 25 feet away, which needs cropping in post to fill the frame.

Here are the options:
Canon 100-400 ver2 at 400mm, image cropped/zoomed to match the 500mm FOV
Canon 100-400 ver2 with the Canon 1.4x ver3, shot at 500mm with no crop
Sig/Tam 150-600 shot at 500mm, again no crop required

I don't have a 150-600 to test against but maybe someone here has both lenses.

Depending on the lens and/teleconverter quality-
Sig/Tam 500 followed by the canon 100-400 with teleconverter, and cropping a distant third.

I can test with my Sigma 150-600 C.

After trying it some this morning I can say that an image from the 400mm (at max zoom-400mm) cropped/zoomed to match the FOV of 560mm (400mm + 1.4x and max zoom) is sharper than the same lens using the 1.4x shot at 560mm. Using the lens without the 1.4x TC wins out. I should use it only when I REALLY need more than 400mm to peep at something.

Disclaimer: I am shooting a subject with great contrast and detail about 18 feet from the camera. A distant wide spread landscape scene probably wouldn't have enough detail to see a difference and using the TC wouldn't hurt.

I need to go one step more and recheck the AFMA when the TC is mounted to see if that is hurting those images. I should have done that before I posted any of this.

gossamer88 wrote in post #19278835
I can test with my Sigma 150-600 C.

I see both lenses are listed in your gear list!! Please be my guest and post your results.

chuckmiller wrote in post #19278824
What do you think would render the sharpest image?

The subject is a small bird, 25 feet away, which needs cropping in post to fill the frame.

Here are the options:
Canon 100-400 ver2 at 400mm, image cropped/zoomed to match the 500mm FOV
Canon 100-400 ver2 with the Canon 1.4x ver3, shot at 500mm with no crop
Sig/Tam 150-600 shot at 500mm, again no crop required

I don't have a 150-600 to test against but maybe someone here has both lenses.

Let us start with assumption that you shoot with a Canon R5 with 8192 x 5464 pixels just for discussion.

• If you crop the original image to match 500mm lens FOV, you end up with about 6550 x 4370 pixels left after the crop...you have -20% of the len's delivered resolution to the sensor
  
• In the past, the Canon 70-200mm lenses of various vintages used with Canon 1.4x telconvertors were tested and confirmed to have lost a relatively small amount of resolution delivered to the sensor. only about -10%
  

After a recheck the AFMA (with the 1.4x) at Wide stayed the same at -2 and Tele bumped 2 clicks from -3 to -1. So my earlier images at 400mm and 560mm were a smidge off. Using the 1.4x TC drops the image quality but by only a very small amount but it's there, as everyone knows.

The daily rain has begun so I cannot reshoot the the same high contrast high detail image as before but for now I'm going to stay with the belief that shooting at 400mm and then cropping to fill the frame yields a tad better image than using the TC.

Maybe tomorrow before the rain comes I will test the now dialed in viewfinder setup against using Live View.

chuckmiller wrote in post #19278824
What do you think would render the sharpest image?

The subject is a small bird, 25 feet away, which needs cropping in post to fill the frame.

Here are the options:
Canon 100-400 ver2 at 400mm, image cropped/zoomed to match the 500mm FOV
Canon 100-400 ver2 with the Canon 1.4x ver3, shot at 500mm with no crop
Sig/Tam 150-600 shot at 500mm, again no crop required

I don't have a 150-600 to test against but maybe someone here has both lenses.

Unfortunately this test is just going to show optical design variation and various forms of aberration as the difference. It doesn't account for the control of chromatic and spherical aberration as you change up the optics, add optics, or switch glass, etc. Even if you keep the pixels on the sensor constant and the ambient light and subject constant. So when it comes to sampling (recording angular resolution) it won't be comparing the same things going on, since the optics involved are different.

The nerd stuff, if you care (ignore if you don't):

If the glass was the same and you were simply testing variables that influence resolution (ie, recording angular resolution at critical sampling, differentiating the airy disc), you would find that all of these setups are undersampling for the wavelengths of light and the pixel size for these fast focal-ratios and so lots of resolution is actually lost on these setups. The saving grace is that you're actually close to the subject (a few feet) and have lots of signal (light) so you can stand to loose massive amounts of angular resolution to unoptimized imaging setups, like fast camera lenses and big pixel sensors. For example, a 4.0um pixel pitch will critically sample visible spectrum light (ie, BGR, so around 400nm to 700nm roughly) with a focal ratio F25 (for the blue), F18 (for the green) and F14 (for the red), so F25 to critically sample all the visible spectrum wavelengths in one exposure on that pixel size. Just as an example. Shooting at F8 or F11 is losing resolution due to being undersampled. This is of course again acceptable in terrestrial photograph when you're imaging a large subject that is a few feet away with lots of signal (light) where even a single hair covers many pixels, so its not a challenge to differentiate the airy disc when its light source is covering many pixels already.

Even if you did this test with those three arrangements, the results would be different on different bodies with different pixel sizes and if you had different sample copies of each optic, it would change a bit too.

TL;DR:

So anecdotally, I will assume the 100-400 MK II and the Sig 150-600 native glass will have less aberrations than the 100-400 Mk II + TC, on any modern pixel size sensor from APS-C to 35mm. But without testing it, your copies, you can't be positive either way.

Very best,

I had both the Sigma 150-600 and 100-400II. I used the 1.4xIII on the Canon and after many test runs and a couple game shots, I decided that the Canon and 1.4xIII delivered very nearly the same results at what feels like a smaller overall package, so I sold off my Sigma. As to a digital zoom into a 560mm view vs the lens and TC, I am not sure. I would be surprised to hear the digital zoom was better, but you also then have to contend with the loss of resolution by doing that, should you want to use the files for more large and close visual reproductions.