Effects of diffraction and R5/R6 sensor on resolution of f/5.6, f/7.1 and f/11 lenses and TCs

LogicExtremist

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Sep 26, 2021
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There aren't much data out there, and I have never handled an RF 600mm f/11. So, here is my indirect opinion. Canon's own MTF values and the-digital-picture show clearly that the RF 100-500mm is significantly sharper and with better contrast at 500mm than the RF 600mm. My 100-400mm II + 1.4x TC at 560mm is pretty close to the Rf 100-500mm in sharpness and contrast. My very good copy of the Sigma 150-600mm C at 600mm had similar resolution but poorer contrast than my 100-400mm II at 560mm, and was definitely inferior to my RF 100-500mm - the RF cropped from 500 was better than the 150-600mm C at 600mm. I would guess that the weaker performance due to diffraction at f/11 of the RF 600mm is not far from the performance of the 150-600mm at f/6.3, which is n ot optimised for optical quality at the longest end. I found the AF and the IS of the Sigma much below those of the Canon lenses on the R5.
Thanks, that's quite helpful. I've been getting more interested in trying out bird photography, and I've put my EF 70-200 f/2.8 III or 55-250 STM on my 80D for more reach, but it's not really long enough.

I've been considering purchasing a longer telephoto but I can't decide whether to go with the RF 600 f/11, Rf 800 f/11 or wait for the RF 100-400 f/8 when that comes out, to use on my RF mount camera, or to go with something like the Sigma 100-400 or 150-600 on the crop body. The images I've seen from the RF f/11 lenses always look dark to me, like they're shot through a ND filter, guessing that's due to the narrow aperture. I've only ever shot that aperture for macro from an inch or two away!

The prices of the Canon EF 100-400 ($3500) or RF 100-500 ($5000) in my part of the world are hard to justify, even though the exchange rate isn't double, Canon likes doubling the prices here, an R5 with an RF 100-500 is a $10,500 setup! :(
 

AlanF

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Aug 16, 2012
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Thanks, that's quite helpful. I've been getting more interested in trying out bird photography, and I've put my EF 70-200 f/2.8 III or 55-250 STM on my 80D for more reach, but it's not really long enough.

I've been considering purchasing a longer telephoto but I can't decide whether to go with the RF 600 f/11, Rf 800 f/11 or wait for the RF 100-400 f/8 when that comes out, to use on my RF mount camera, or to go with something like the Sigma 100-400 or 150-600 on the crop body. The images I've seen from the RF f/11 lenses always look dark to me, like they're shot through a ND filter, guessing that's due to the narrow aperture. I've only ever shot that aperture for macro from an inch or two away!

The prices of the Canon EF 100-400 ($3500) or RF 100-500 ($5000) in my part of the world are hard to justify, even though the exchange rate isn't double, Canon likes doubling the prices here, an R5 with an RF 100-500 is a $10,500 setup! :(
The brightness of images depends on whether you expose or underexpose or on your post processing settings. The RF f/11 lenses are no exception to this, as are any images from any other lens at f/11. (Strictly speaking T-stops are more accurate for absolute transmittance, but the difference between T and f is corrected by your exposure metering or you.)
 
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LogicExtremist

Lux pictor
Sep 26, 2021
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The brightness of images depends on whether you expose or underexpose or on your post processing settings. The RF f/11 lenses are no exception to this, as are any images from any other lens at f/11. (Strictly speaking T-stops are more accurate for absolute transmittance, but the difference between T and f is corrected by your exposure metering or you.)
That's what I would have thought, you'd just just adjust the exposure meter to the centre, and brighten the images in post if necessary. I've seen this 'image darkness' for lack of a better expression in most 600 and 800 f/11 image I've seen posted on the internet, and that put me off. I can't imagine they're all shooting jpegs SOOC. I'm at loss to explain it, though you might have some ideas of why this might be the case.

Not sure if I'm allowed to link to the dpreview image gallery:
https://www.dpreview.com/sample-gal...f-800mm-f-11-is-stm-sample-gallery/2421245585

To me many of these images seem to have a grey cast, does it seem that way to you? Thanks :)
 

koenkooi

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Feb 25, 2015
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That's what I would have thought, you'd just just adjust the exposure meter to the centre, and brighten the images in post if necessary. I've seen this 'image darkness' for lack of a better expression in most 600 and 800 f/11 image I've seen posted on the internet, and that put me off. I can't imagine they're all shooting jpegs SOOC. I'm at loss to explain it, though you might have some ideas of why this might be the case.

Not sure if I'm allowed to link to the dpreview image gallery:
https://www.dpreview.com/sample-gal...f-800mm-f-11-is-stm-sample-gallery/2421245585

To me many of these images seem to have a grey cast, does it seem that way to you? Thanks :)
You can download the RAW files and see if it's due to how DPReview processed them or present in the picture itself, the gallery states "Edited in Adobe Camera Raw 12.2 with Adobe Standard profile and sharpening set to 25. Adjustments limited to exposure, shadows, highlights and white balance."

DPReview complained about the R pictures having a green cast and took a long time to admit that they manually set the camera to green+1, which was recorded in the EXIF. Since then I download the RAWs they provide and check how they look in both LR and DPP4 instead of relying on the JPEGs in their gallery.

Adobe produces horrible colours of R series out of the box, so check the RAW in DPP4 to see what Canon thinks the picture should look like. The RF24-240 RAWs DPReview provided showed how much work DPP4 did for corrections and how well it did.
 
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LogicExtremist

Lux pictor
Sep 26, 2021
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You can download the RAW files and see if it's due to how DPReview processed them or present in the picture itself, the gallery states "Edited in Adobe Camera Raw 12.2 with Adobe Standard profile and sharpening set to 25. Adjustments limited to exposure, shadows, highlights and white balance."

DPReview complained about the R pictures having a green cast and took a long time to admit that they manually set the camera to green+1, which was recorded in the EXIF. Since them I download the RAWs they provide and check how they look in both LR and DPP4 instead of relying on the JPEGs in their gallery.

Adobe produces horrible colours of R series out of the box, so check the RAW in DPP4 to see what Canon thinks the picture should look like. The RF24-240 RAWs DPReview provided showed how much work DPP4 did for corrections and how well it did.
Thanks, that great advice,, I'll download the raw files and post process them to see if I can get them to look any better. Much appreciated! :)
 

AlanF

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Aug 16, 2012
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That's what I would have thought, you'd just just adjust the exposure meter to the centre, and brighten the images in post if necessary. I've seen this 'image darkness' for lack of a better expression in most 600 and 800 f/11 image I've seen posted on the internet, and that put me off. I can't imagine they're all shooting jpegs SOOC. I'm at loss to explain it, though you might have some ideas of why this might be the case.

Not sure if I'm allowed to link to the dpreview image gallery:
https://www.dpreview.com/sample-gal...f-800mm-f-11-is-stm-sample-gallery/2421245585

To me many of these images seem to have a grey cast, does it seem that way to you? Thanks :)
I occasionally use the RF 800 f/11 and find no problems with it regarding image exposure. There are others like @usern4cr who have posted nice bright images with it in the birds thread.
 

HenryL

EOS R5
CR Pro
Apr 1, 2020
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That's what I would have thought, you'd just just adjust the exposure meter to the centre, and brighten the images in post if necessary. I've seen this 'image darkness' for lack of a better expression in most 600 and 800 f/11 image I've seen posted on the internet, and that put me off. I can't imagine they're all shooting jpegs SOOC. I'm at loss to explain it, though you might have some ideas of why this might be the case.

Not sure if I'm allowed to link to the dpreview image gallery:
https://www.dpreview.com/sample-gal...f-800mm-f-11-is-stm-sample-gallery/2421245585

To me many of these images seem to have a grey cast, does it seem that way to you? Thanks :)
Those images are just underexposed. The worst offenders seem to be examples where the intent might have been to protect the highlights (ie the kingfishers, geese and osprey, even Space Needle). Clearly still underexposed, bumping +1 on some of them and still no blown highlights. I'd say it's the photographer not the lens in those examples.
 
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LogicExtremist

Lux pictor
Sep 26, 2021
74
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I occasionally use the RF 800 f/11 and find no problems with it regarding image exposure. There are others like @usern4cr who have posted nice bright images with it in the birds thread.
Thanks, I'll check those out too! Great to know you have this lens, I've been considering it.

How would you rate the 800mm f/11 against the EF 100-400 without any extender. Does the 800mm focal length resolve way more than the bare zoom at 400? How does the contrast compare in your opinion?

From your graphs, the theoretical performance at the lens centre (if I'm reading the graphs correctly) is as follows:
  • 400mm @ f/5.6 resolves around 225 lp/mm (R5) and 150 lp/mm (R6)
  • 600mm @ f/11 resolves around 275 lp/mm (R5) and 225 lp/mm (R6)
  • 800mm @ f/11 resolves around 370 lp/mm (R5) and 300 lp/mm (R6)
This shows the 800mm f/11 resolving twice the detail of the bare 100-400 @ 400mm on the R6 (150 vs 300 lp/mm). Does this really reflect real world experience?
 

AlanF

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Aug 16, 2012
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Thanks, I'll check those out too! Great to know you have this lens, I've been considering it.

How would you rate the 800mm f/11 against the EF 100-400 without any extender. Does the 800mm focal length resolve way more than the bare zoom at 400? How does the contrast compare in your opinion?

From your graphs, the theoretical performance at the lens centre (if I'm reading the graphs correctly) is as follows:
  • 400mm @ f/5.6 resolves around 225 lp/mm (R5) and 150 lp/mm (R6)
  • 600mm @ f/11 resolves around 275 lp/mm (R5) and 225 lp/mm (R6)
  • 800mm @ f/11 resolves around 370 lp/mm (R5) and 300 lp/mm (R6)
This shows the 800mm f/11 resolving twice the detail of the bare 100-400 @ 400mm on the R6 (150 vs 300 lp/mm). Does this really reflect real world experience?
On the R5, the RF 800mm f/11 resolves about 1.6x the EF 100-400mm II at 400mm (my copies of the lenses). The factor will be higher on the R6. The contrast of both lenses is good. If you want resolution, the 800mm f/11 will significantly outperform the 600mm f/11. They have similar MTF values but the 33% extra length of the 800 will increase its resolution by 1.33x. An 800mm f/11 although having the same f-number as the 600mm f/11, has effectively nearly an extra stop of iso (~0.8) in its favour as it projects 77% more photons per duck.
 
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