Review: Canon RF 16mm f/2.8 STM by Christopher Frost

LogicExtremist

Lux pictor
Sep 26, 2021
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I just sold my EF 16-35/4L IS.

The degree of cropping are reported for the 16/2.8 seems excessive, and given that it was an unsubstantiated comment on a review I take it with a large grain of salt. Regardless, to deliver the camera’s full resolution, the cropped images must be upscaled.

I also don’t find a comparison between two corrected profiles (Canon 14-35 vs Samyang 14) to be especially compelling. Distortion correction changes framing, and the degree to which distortion is corrected may differ between the profiles.

I am pretty sure that if Canon labels a lens 16mm or 14mm, the FoV delivered in the final images will be that. Keep in mind that focal length is specified at infinity focus. Since people testing for lens distortion aren’t using charts or walls large enough to fill the frame with the lenses focused at infinity, focus breathing must be considered. For example, the EF-S 18-200mm at the long end frames at ~150mm equivalent with a close subject, the EF 100/2.8L Macro frames like ~67mm at 1:1. The 16/2.8 probably has a fair bit of breathing, the 14-35 less so.

For me, an additional factor is the small size of the 14-35, compared to the 16-35/4 (with adapter). Also, the relevant comparison to me is both lenses at the wide end, so even if the 14-35 isn’t quite 14mm, it’s wider than 16mm, and smaller and lighter in my bag.

I ordered the RF 14-35, once it arrives I’ll run some comparisons, including vs my EF 11-24 for FoV.
When you test your RF 14-35mm f/4, can you please compare the uncorrected and software corrected images to confirm the extent of cropping that occurs? Thanks :)
 
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BBarn

EOS 90D
Nov 2, 2020
113
113
Here's a quick shot with an RP using the RF 16mm (processed in DPP).

IMG_2783s.jpg

I'm just getting started with PS Elements so I could easily be doing something wrong, but below are two lower right corner areas from the same pic. The first is a JPG from Canon DPP (which automatically applies distortion correction). The second is of the approximately the same area from Photoshop Elements (which was uncorrected). I assume the brightness/contrast/color differences are from the different JPG engines. I don't see much difference in sharpness, but I'll leave that to others.

DPP (corrected)
IMG_2783 corner 600 sq.JPG

Photoshop Elements (uncorrected)
IMG_2783pse no dist comp corner.jpg

Even though the 100% crops are of the same area, the DPP crop is 600x600 pixels, and the PSE crop is 433x433 pixels.
 
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Frodo

EOS RP
Nov 3, 2012
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A DPReview subscriber (crusliq) posted some images taken with the RF 16mm on an EOS R. Although not shot at infinity they give a sense of the degree of correction undertaken to remove barrel distortion. All @ f/2.8.
The first is the uncorrected image 6720 x 4480 pixels
In the second I applied +100 distortion correction in Lightroom.
The third is cropped such that the full vertical image is retained. This is 4994 x 3329 pixels or 16.6 MP, compared to 30.1 MP for the uncorrected image.
While this may be okay for an R5, the R6 is left with a little more than 11MP before the image is upscaled. I presume that this also applies for in-Camera corrections.

eosr_rf16mm_f2.8.jpg eosr_rf16mm_f2.8-2.jpg eosr_rf16mm_f2.8-3.jpg
 
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HMC11

Travel
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Sep 5, 2020
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There's another review (https://admiringlight.com/blog/review-canon-rf-14-35mm-f-4l-is-usm/) which indicated that the distortion became mild to moderate by 16mm. Here's his take:

"Thankfully, the distortion is really only truly severe at the 14mm setting. By 15mm, there is still a lot of barrel distortion, and the image circle is just barely not large enough, but by 16mm, the distortion is only mild to moderate and there are no truly dark corners. The mild barrel distortion persists through about 20mm, but by 24mm, the lens is essentially distortion free, before exhibiting a slight pincushion distortion at 35mm. Despite the absolutely severe distortion shown at 14mm, for most of the range, distortion control is pretty good."

Treating this as essentially a ligher & smaller RF 16-35 f4 with the added bonus of fairly usable 14-15mm FoV images might make it easier to go for this lens.

Eagerly awaiting your test results.
 
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LogicExtremist

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Sep 26, 2021
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A DPReview subscriber (crusliq) posted some images taken with the RF 16mm on an EOS R. Although not shot at infinity they give a sense of the degree of correction undertaken to remove barrel distortion. All @ f/2.8.
The first is the uncorrected image 6720 x 4480 pixels
In the second I applied +100 distortion correction in Lightroom.
The third is cropped such that the full vertical image is retained. This is 4994 x 3329 pixels or 16.6 MP, compared to 30.1 MP for the uncorrected image.
While this may be okay for an R5, the R6 is left with a little more than 11MP before the image is upscaled. I presume that this also applies for in-Camera corrections.

View attachment 201054 View attachment 201055 View attachment 201056
It looks like theres a definite crop, warping and upscaling required to deliver a usable software-corrected image on the RF 16mm f/2.8.
 
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LogicExtremist

Lux pictor
Sep 26, 2021
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I think I found the RF 16mm f/2.8 lens equivalent EF lens in terms of specs and performance, but it's an EF-S lens...

Canon RF 16mm F2.8 STM @ f/8 on an R5 vs Canon EF-S 10-18mm f/4.5-5.6 IS STM @ 10mm f/4.5 on a 7D Mark II

Equivalent focal length and aperture comparison, with a some very major advantages in favour of the RF lens - RF prime on 2020 release 45MP full-frame sensor vs EF-S zoomon 2014 release 20.2MP APSC sensor.


Even with this test skewed heavily in favour of the RF 16mm, can anybody spot a difference in image quality?
The centre sharpness is hard to call, may be sharper on the RF 16mm, mid-frame is a close call, but the EF-S lens appears to be sharper and have better contrast in the periphery to me. :oops:
 
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gruhl28

Canon 70D
Jul 26, 2013
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A DPReview subscriber (crusliq) posted some images taken with the RF 16mm on an EOS R. Although not shot at infinity they give a sense of the degree of correction undertaken to remove barrel distortion. All @ f/2.8.
The first is the uncorrected image 6720 x 4480 pixels
In the second I applied +100 distortion correction in Lightroom.
The third is cropped such that the full vertical image is retained. This is 4994 x 3329 pixels or 16.6 MP, compared to 30.1 MP for the uncorrected image.
While this may be okay for an R5, the R6 is left with a little more than 11MP before the image is upscaled. I presume that this also applies for in-Camera corrections.

View attachment 201054 View attachment 201055 View attachment 201056
Wow, that's even more being cropped out than previously reported.
 
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Czardoom

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Jan 27, 2020
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Wow, we probably have never seen such amazing analysis and page long essays regarding the auto-correction of a lens!

Thank goodness, as a photographer, all I care about is the final image. If the Digital Picture's Image comparison tool is reasonably accurate, and the corners are indeed considerably better than the EF 17-40L and not too much worse than the EF 16-35L, then that is good enough for me.

Just curious, but to all those that are despairing about the auto-correction, do you not do any distortion correction in post-processing? Keystone or perspective corrections? Do you ever use the new image enlarging programs (such as GigaPixel) or comands in Photoshop or any other software? Those enlargement programs or commands create a great deal of new pixels, does that mean you won't use them? Or does doing the same thing the camera does on your computer make you forget all about your concerns?
 
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RexxReviews

EOS M6 Mark II
  • Sep 3, 2021
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    Wasn't the RF mount supposed to allow easier engineering of better designs without these optical weaknesses? Watching this review, the way the focus sounds like the original nifty fifty... It feels like they just slapped this together for lowest possible cost.

    Meanwhile, I'm kicking myself. Two years ago I had a chance to purchase a 24-70 F/4 for $550, and I thought... meh, that's kinda pricey. Now it's going for $1200 on ebay from reputable places. The 16-35 F/4 is also skyrocketing. Maybe supply disruptions are a part of this, but there's still so much demand in good EF lenses, and they're optically no worse than the RF versions. Is Canon leaving money on the table?
    What do you consider "sky rocketing"? I just picked up another 16-34 f4 about a month ago for around $700 in mint condition, new its still at the same retail price of around 1099. I have purchased many of this lens in the last few years as its what we use on our real estate training cameras and the only time I've seen them under $600 were usually very heavily used lenses and every blue moon a good shaped one that someone was selling far lower than they realized on FB marketplace.
     
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    RexxReviews

    EOS M6 Mark II
  • Sep 3, 2021
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    Wow, that's even more being cropped out than previously reported.
    People are not taking in consideration that the lens is shooting much wider than 16mm so that the corrected version is at around 16mm. I have tested this against my 16-35 f4. The corrected RF16mm is even a tad wider than the 16mm of the 16-35
     
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    neuroanatomist

    I post too Much on Here!!
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    Jul 21, 2010
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    People are not taking in consideration that the lens is shooting much wider than 16mm so that the corrected version is at around 16mm. I have tested this against my 16-35 f4. The corrected RF16mm is even a tad wider than the 16mm of the 16-35
    But if the RF 16/2.8 is giving you a much lower MP image that is then being upscaled, to me that's a concern.
     
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    Frodo

    EOS RP
    Nov 3, 2012
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    Just curious, but to all those that are despairing about the auto-correction, do you not do any distortion correction in post-processing? Keystone or perspective corrections? Do you ever use the new image enlarging programs (such as GigaPixel) or comands in Photoshop or any other software? Those enlargement programs or commands create a great deal of new pixels, does that mean you won't use them? Or does doing the same thing the camera does on your computer make you forget all about your concerns?
    That is the entire point. Take astro photography. This involves a lot of image manipulation, stacking, compositing. If I start with a 20 or 30 MP file that is "clean" out of the camera, I have much more scope for subsequent processing than one which has had such heavy preprocessing.
    It is clear that I am asking more than this relatively cheap lens (its still USD500 in New Zealand) can deliver. Probably fine for lots of other photographers.
     
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    LogicExtremist

    Lux pictor
    Sep 26, 2021
    501
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    Wow, we probably have never seen such amazing analysis and page long essays regarding the auto-correction of a lens!

    Thank goodness, as a photographer, all I care about is the final image. If the Digital Picture's Image comparison tool is reasonably accurate, and the corners are indeed considerably better than the EF 17-40L and not too much worse than the EF 16-35L, then that is good enough for me.

    Just curious, but to all those that are despairing about the auto-correction, do you not do any distortion correction in post-processing? Keystone or perspective corrections? Do you ever use the new image enlarging programs (such as GigaPixel) or comands in Photoshop or any other software? Those enlargement programs or commands create a great deal of new pixels, does that mean you won't use them? Or does doing the same thing the camera does on your computer make you forget all about your concerns?
    As far as I know all lenses use distortion correction, that's not the issue. What is catching peoples attention here is the crazy amount of distortion of this lens that is only possible because it's being used on a mirrorless system, which can hide it because it does on-the-fly image correction when looking through the EVF and makes the same corrections in camera when shooting JPEG images. This level of distortion would never be seen on a DSLR with an OVF, as it would produce a severely warped image viewing through the lens.

    The are three main problems:
    1. The lens has heavy vignetting, the corners of the uncorrected image are pure black, so no amount of shadow recovery will bring those details back. As such, they need to be cropped away, which by most estimates is thought to remove around 30% of the pixels! Rather than create a smaller cropped image, the software then upscales the image digitally back to full size, so 1/3 of the pixels are just made up. This is like digital zoom on a smartphone and on point-and-shoot cameras.
    2. The uncorrected image is extremely warped, that it requires extreme correction, so in some places, pixels need to be squeezed closer together (are multiple pixels averages and then thrown out?), and in other places, like the corners, they need to be stretched further apart to create a rectilinear shape. Pixels don't stretch, so the spaces need to be filled in with extra pixels of fake computer-generated data, which the computer can't possibly predict, so it uses a formula to guess what they might be from surrounding pixels, so the detail in the corners will look soft and mushy.
    3. When the cropped image with fake pixels in the corners is upscaled, it is filled with computer generated pixels right through the image. The corners which are already degraded and soft from being filled with fake data pixels are then also digitally enlarged and filled a second time with more fake data, degrading them even further.

    Simply put, the reason why photographers are advised not to go too heavy handed with post-processing is because image quality can start to fall apart, and detail can be lost. To produce usable images, two post-processing operations need to be performed at an extreme level with this lens just to get a usable image that we can start working on.

    Earlier in this thread, I compared the Rf 16mm to the equivalent APSC lens, the EF-S 10-18mm, and this old crop sensor lens has very little distortion by comparison, as shown here:


    115897_can10-18_dys10.jpg


    Here's the lens distortion of the RF 16mm f/2.8 for the Christopher Frost video:

    1635791418828.png

    One important point that everyone has probably missed here is that test charts shot in RAW don't have any post processing applied to them other than lens corrections. Real images will have additional post-processing applied, sometimes a bit, sometimes quite a lot, and when they're applied over really extreme previous post-processing changes, the images simply don't hold up.

    Comparing test charts and using image test tools like I've posted in this thread don't give an objective and accurate picture of how the software corrections affect real world images. It would be interesting to see a comparison of two identical landscape images, one taken on the RF 16mm f/2.8, and one on another 16mm (that doesn't use the radical software corrections), both taken through the complete workflow to produce the final photo, to see how the end result looks!
     
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    RexxReviews

    EOS M6 Mark II
  • Sep 3, 2021
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    Here are some samples I have been playing with. These have been shot on the R5

    The first is from my 16-35 f4. This is with the LR profile.

    JCM-9220.jpg

    This is with the RF 16mm. This is a .jpg directly from camera using the built in camera corrections. The built in camera crop is Pretty much the same as the 16-35 @16mm

    JCM-9221-2.jpg

    This is the RAW of the same photo directly above with my manual corrections in LR. RF 24-240mm Profile . 130 Distortion. +100 Vignetting and 11 Midpoint in the manual tab.

    JCM-9221.jpg
     
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    gruhl28

    Canon 70D
    Jul 26, 2013
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    Here are some samples I have been playing with. These have been shot on the R5

    The first is from my 16-35 f4. This is with the LR profile.

    View attachment 201070

    This is with the RF 16mm. This is a .jpg directly from camera using the built in camera corrections. The built in camera crop is Pretty much the same as the 16-35 @16mm

    View attachment 201071

    This is the RAW of the same photo directly above with my manual corrections in LR. RF 24-240mm Profile . 130 Distortion. +100 Vignetting and 11 Midpoint in the manual tab.

    View attachment 201072
    Thanks for the samples! The 16-35 seems to show a slightly wider FOV than the 16 mm jpg (see the right side of the image; the left side lines up identically but there is more visible on the right), and the Raw image with the correction from the 24-240 shows a much wider FOV than either of the two previous images.
     
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    LogicExtremist

    Lux pictor
    Sep 26, 2021
    501
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    One interesting thing about the 16mm, which I think someone earlier made reference to, is that stopping down seems to have virtually no effect on image quality other than vignetting. See https://www.the-digital-picture.com...eraComp=1508&SampleComp=0&FLIComp=0&APIComp=4
    That was me! :) Yes, that's correct, corner sharpness doesn't improve when stopping down like regular lenses do because the corners are streched out and digitally filled with fake pixels to make up what the optics never captured in the first place! :(
     
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    RexxReviews

    EOS M6 Mark II
  • Sep 3, 2021
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    Its really starting to feel like this is going to turn into more of a "YouTuber" "Vlogger" lens than anything else as the video seems decent on it for the price. I think those of us hoping to do more with it from a photog point of view are just going to be out of luck. We were REALLY hoping to be able to use this lens for real estate on our training camera due to the size and weight vs the 16-35's.
     
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