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

Jan 27, 2020
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Trouble is: these electronic corrections come at a cost, namely decrease of sharpness due to "corner stretching". But I guess this is acceptable for a $300 lens, designed mostly for street and vlogging.
....
Yes, corner sharpness is less than the uncorrected lens, but...

Better than the EF 17-40mm f/4L lens.
Very close to the 16-35mm f/4L lens.

It seems more like the reality is that trying to get corner sharpness optically is not so easy to do and was rarely done to the extent that it can be done with digital correction without a high cost and much more weight due to much more glass.
 
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LogicExtremist

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Yes, corner sharpness is less than the uncorrected lens, but...

Better than the EF 17-40mm f/4L lens.
Very close to the 16-35mm f/4L lens.

It seems more like the reality is that trying to get corner sharpness optically is not so easy to do and was rarely done to the extent that it can be done with digital correction without a high cost and much more weight due to much more glass.
Hmmm, not really, there's no comparison between a budget lens and the EF 16-35mm f/4 L lens, which gets reviews like this:

"If you are looking for an extremely sharp ultra-wide angle zoom lens, the Canon EF 16-35mm f/4L IS USM Lens should be at the top of your consideration list. This lens delivers prime-grade image sharpness right into full frame corners and it has the overall performance to match, including AF speed and accuracy." (https://www.the-digital-picture.com/Reviews/Canon-EF-16-35mm-f-4-L-IS-USM-Lens.aspx)

There is no substitute for optical correction when it comes to corner sharpness on a wide lens, because the corrections must add in pixels that aren't really there. Of course, people will start arguing about accuracy of the software algorithms that guess what the pixels should be, but that's a moot point. Some post processing operations add data that was never there and also result in a loss of sharpness. Objectively, we can simply look at the images produced after software correction and clearly see that the corners are soft, end of story. :)

There is a bit of a strange rationalisation process going on with some comments. Not a criticism of any particular person here, I wish people can just let this little budget lens be what it is, and appreciate it for what it can do, rather than fuss over what it isn't and cant do. Denying or playing down its limitations isn't really helpful either in my opinion.

We basically have a compact, lightweight and cheap 16mm lens with a fast aperture, which is sharp in the centre and soft in the corners. That means it's not good for serious landscape photography, can't be used for astro unless stopped down to f/4, but makes an awesome carry around lens where a wide angle is needed but the corners don't matter. Casual landscape and group photos, vlogging and talking head videos come to mind. Any other applications?

One thing that baffles me is the questionable logic justifying software corrections on more expensive lenses. Like all engineering compromises, they come at a cost, and they can be made in Canon's favour, NOT the buyers! They can skimp on the lens formula, use software corrections to compensate, and sell the lens for the same price as an optically corrected one, but make a bigger profit. That's one possibility. Is that's what's happening? You guys tell me, are software corrected RF lenses selling at a cheaper price than optically corrected equivalents if such exist? Or is it not an apples for apples comparison because they're just trading a bit more sharpness for a lot more distortion?

Each lens has a specific use case, and where such compromises are fine, then so be it, if not, then it's necessary to use a lens with decent enough optics to captures all the data required for the necessary image quality. otherwise it's a pointless game of justification and self deception like this video:(!
 
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HMC11

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Hmmm, not really, there's no comparison between a budget lens and the EF 16-35mm f/4 L lens, which gets reviews like this:

"If you are looking for an extremely sharp ultra-wide angle zoom lens, the Canon EF 16-35mm f/4L IS USM Lens should be at the top of your consideration list. This lens delivers prime-grade image sharpness right into full frame corners and it has the overall performance to match, including AF speed and accuracy." (https://www.the-digital-picture.com/Reviews/Canon-EF-16-35mm-f-4-L-IS-USM-Lens.aspx)

There is no substitute for optical correction when it comes to corner sharpness on a wide lens, because the corrections must add in pixels that aren't really there. Of course, people will start arguing about accuracy of the software algorithms that guess what the pixels should be, but that's a moot point. Some post processing operations add data that was never there and also result in a loss of sharpness. Objectively, we can simply look at the images produced after software correction and clearly see that the corners are soft, end of story. :)

There is a bit of a strange rationalisation process going on with some comments. Not a criticism of any particular person here, I wish people can just let this little budget lens be what it is, and appreciate it for what it can do, rather than fuss over what it isn't and cant do. Denying or playing down its limitations isn't really helpful either in my opinion.

We basically have a compact, lightweight and cheap 16mm lens with a fast aperture, which is sharp in the centre and soft in the corners. That means it's not good for serious landscape photography, can't be used for astro unless stopped down to f/4, but makes an awesome carry around lens where a wide angle is needed but the corners don't matter. Casual landscape and group photos, vlogging and talking head videos come to mind. Any other applications?

One thing that baffles me is the questionable logic justifying software corrections on more expensive lenses. Like all engineering compromises, they come at a cost, and they can be made in Canon's favour, NOT the buyers! They can skimp on the lens formula, use software corrections to compensate, and sell the lens for the same price as an optically corrected one, but make a bigger profit. That's one possibility. Is that's what's happening? You guys tell me, are software corrected RF lenses selling at a cheaper price than optically corrected equivalents if such exist? Or is it not an apples for apples comparison because they're just trading a bit more sharpness for a lot more distortion?

Each lens has a specific use case, and where such compromises are fine, then so be it, if not, then it's necessary to use a lens with decent enough optics to captures all the data required for the necessary image quality. otherwise it's a pointless game of justification and self deception like this video:(!
Thank you for a clear-minded take. Dustin Abbott just released his review of the RF 14-35 f4. It seems that the lens follows a similar approach as the RF 16mm in that it relies on software to do some fairly major corrections, and that actual image is wider than 14mm but crops in to remove the 'physical' vignetting. Despite this, it seems that the 14-35 is still very sharp at almost the entire range (except at 35mm) when wide-open, which makes it a viable landscape lens. While psychologically it doesn't feel good to know at the back of the mind that the image is fairly heavily software corrected, the end results may well be more than satisfactory. Overall, had it been priced closer to the EF16-35, the 14-35 could be a fairly compelling purchase for me. Given the significant price difference, I am somewhat hesitant. I may just have to bite the bullet and get it if this is going to be the 'standard' approach in order to get a lighter and smaller lens with very good final image output.
 
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LogicExtremist

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Thank you for a clear-minded take. Dustin Abbott just released his review of the RF 14-35 f4. It seems that the lens follows a similar approach as the RF 16mm in that it relies on software to do some fairly major corrections, and that actual image is wider than 14mm but crops in to remove the 'physical' vignetting. Despite this, it seems that the 14-35 is still very sharp at almost the entire range (except at 35mm) when wide-open, which makes it a viable landscape lens. While psychologically it doesn't feel good to know at the back of the mind that the image is fairly heavily software corrected, the end results may well be more than satisfactory. Overall, had it been priced closer to the EF16-35, the 14-35 could be a fairly compelling purchase for me. Given the significant price difference, I am somewhat hesitant. I may just have to bite the bullet and get it if this is going to be the 'standard' approach in order to get a lighter and smaller lens with very good final image output.
Good point, it depends on which way Canon is planning to go with their RF lenses in terms of design strategy. The new mirrorless platform provides a convenient cover for the use of software correction, which can be used as a way of giving less and charging more for it.

I looked at thedigitalpicture.com review, where the author of the article points out the issue of AI generated fake detail in the corners, but then plays that down:

"Stretching the image out to the as-framed composition requires AI. Although today's image correction AI is very good, AI does not really know what the subject details were in the stretched areas, and calling the result fake detail does not seem untrue.

Does the strong distortion correction matter? Psychologically it does, and an image captured from a non-distorted lens can similarly be up-sized to even higher resolution using AI, potentially giving it an advantage. That said, did you notice any corner issues until this point in the review? Likely not substantial ones.

I need to get over the psychological issue of the geometric distortion correction, but otherwise, this lens is a stellar performer."


I'm not sure how he can reduce the issue of AI generated fake detail in the corners down to a psychological issue, when it's actually an image reproduction issue that is visible. Surely, some subjects won't be affected, and what's good enough might be subjective, but here we're talking about a crop of the full image and a smearing of details on an L-series pro-grade lens that is not cheap. I can accept that as a compromise on the handy little RF 16mm f/2.8 budget lens, but that's an entry level budget lens! :)

The Rf 14-35mm Ff/4 L should be usable for landscape like the EF 16-35 f/4 L, and no amount of arguments can justify missing corner details because the optics can't deliver them. What the review ignores is that images most likely will be post-processed, and with a combination of heavy vignetting and AI generated fake detail, the details might degrade further and start to fall apart with certain post-processing tasks.

The correction also crops the image, so for those who fuss over details and maximum pixels over the subject, the whole sensor is not used, and this might not be much of a pixel loss percentage-wise, but it's nevertheless there.

So what do we get for the more expensive Rf lens compared to its EF counterpart? Doesn't look like much in terms of image quality, even when the corner issue is ignored.

"In the image quality comparison, the two lenses show rather similar image quality overall. Both lenses have slight advantages in specific comparisons. For example, the RF lens produces sharper periphery image quality at 28mm, and the EF lens is sharper in the center of the frame at 35mm f/4. Performing similarly in this comparison reflects positively on the RF lens — this EF lens is a great performer. The RF lens has dramatically stronger geometric distortion and has stronger lateral CA. The EF lens shows stronger peripheral shading at 35mm f/4 and slightly less at narrower apertures in the wider half of the focal length range."

Lens image comparison tool for Rf 14-35 f/4 L and EF 16-34 f/4 L here.

(https://www.the-digital-picture.com/Reviews/Canon-RF-14-35mm-F4-L-IS-USM-Lens.aspx)

I'm kind of glad I got the EF 16-35mm f/4 almost new a while back, I can't see much benefit for me in upgrading. For others, if having the native RF mount, 175g less weight and 2mm extra at the wide end is important, then there isn't much choice, other than paying not that much more, relatively speaking, and stepping up to the 15-35mm f/2.8 which is a much better engineered lens.

We may be stepping into a whole new era of different compromises with the new RF range. We know they all have a heavy vignetting problem that's due to the RF mount design, and I can live with that. We've seen a molded plastic lens element included in the Rf 100-400, and some radical geometric distortion in a few lenses being rectified with software correction. Compromises imply that you give something to gain something else, and if we're not gaining much over the older EF lenses, but paying more, then we need to ask whether these are just cost cutting measures, or if we're gaining enough to offset what is being lost. Obviously, this will vary from lens to lens, and each needs to be considered against the buyers requirements. :oops:
 
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I may just have to bite the bullet and get it if this is going to be the 'standard' approach in order to get a lighter and smaller lens with very good final image output.
I think it is going to be the standard approach. Sony and Fuji have been doing this for years, even in high end lenses. Think about how many people on this forum have clamored for Canon to ‘keep up with the competition’. I guess they are.
 
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LogicExtremist

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I think it is going to be the standard approach. Sony and Fuji have been doing this for years, even in high end lenses. Think about how many people on this forum have clamored for Canon to ‘keep up with the competition’. I guess they are.
Reminds me of the old saying "be careful what you wish for!" :confused:
 
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Tom W

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Interesting lens, and a good price, but I'm a little concerned at the excessive use of software corrections to make up for large lens weaknesses. I suppose it's a tradeoff for getting an ultra-wide that is this small and inexpensive, but I'd prefer less correction and better lens capability. I suppose that for $300, what I'm asking for is not necessarily possible.
 
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gruhl28

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I'm not sure this talk of "adding pixels" and using AI and creating things that weren't there is accurate. Does distortion correction really need or even use AI? Distortion correction has been around for years in LR, Photoshop, etc., long before anyone was talking about AI in post-processing. Distortion correction crops out some pixels and moves others, and maybe it averages and interpolates some to create new ones, I'm not sure. But it doesn't add things to the side of the frame, it actually crops out the sides, and it doesn't require AI to average two adjacent pixels to create a new one. Sure, this can magnify other aberrations and soften the image, but it's the final image that counts. If the corners are sharp even after distortion correction, as they are with the 14-35, then what difference does it make? The lens must be really sharp in the corners in order for the final pic to still be sharp after the stretching. Even with the corners of the 16mm not being as sharp as we would like, would even this level of quality have been possible in a lens this size and price without using distortion correction?

The statement made earlier, "The Rf 14-35mm Ff/4 L should be usable for landscape like the EF 16-35 f/4 L, and no amount of arguments can justify missing corner details because the optics can't deliver them" is wrong in my opinion. The RF 14-35 is not missing corner details - the corner detail is extremely good, just look at the pictures. This detail wasn't just "made up", it is because the lens is so sharp that even after stretching the result is still excellent. The designers sacrificed some optical distortion correction for excellent sharpness and other benefits, knowing that the distortion could be easily corrected in software, whereas a lack of resolution cannot be corrected - to make up for lack of resolution really would require AI. If AI were "creating" this detail then the16mm would have "sharp" corners also.
 
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LSXPhotog

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It's a shame that Canon has taken so long to release lens profiles for new RF glass to Adobe because the cat's out of the bag on this lens now...it's a lens that requires a truly hilariously amount of correction to create a presentable image. I'm finding it to be a brilliant lens for video and I purchased it exclusively as a gimbal ultra-wide for real estate video - which I'm confident it will do very well in. However...this lens is not a very good photography lens in regards to corner performance even after correction. It may be better to just crop the image even further to an 18-20mm to actually get good results. Things deteriorate rapidly at the corners of the frame - not a problem for video. It's just very sad that I was hoping for a better performance in the corners. I'll take it out a bunch next week and see if my opinion on it changed in regards to photography.
 
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HMC11

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Good point, it depends on which way Canon is planning to go with their RF lenses in terms of design strategy. The new mirrorless platform provides a convenient cover for the use of software correction, which can be used as a way of giving less and charging more for it.

I looked at thedigitalpicture.com review, where the author of the article points out the issue of AI generated fake detail in the corners, but then plays that down:

"Stretching the image out to the as-framed composition requires AI. Although today's image correction AI is very good, AI does not really know what the subject details were in the stretched areas, and calling the result fake detail does not seem untrue.

Does the strong distortion correction matter? Psychologically it does, and an image captured from a non-distorted lens can similarly be up-sized to even higher resolution using AI, potentially giving it an advantage. That said, did you notice any corner issues until this point in the review? Likely not substantial ones.

I need to get over the psychological issue of the geometric distortion correction, but otherwise, this lens is a stellar performer."


I'm not sure how he can reduce the issue of AI generated fake detail in the corners down to a psychological issue, when it's actually an image reproduction issue that is visible. Surely, some subjects won't be affected, and what's good enough might be subjective, but here we're talking about a crop of the full image and a smearing of details on an L-series pro-grade lens that is not cheap. I can accept that as a compromise on the handy little RF 16mm f/2.8 budget lens, but that's an entry level budget lens! :)

The Rf 14-35mm Ff/4 L should be usable for landscape like the EF 16-35 f/4 L, and no amount of arguments can justify missing corner details because the optics can't deliver them. What the review ignores is that images most likely will be post-processed, and with a combination of heavy vignetting and AI generated fake detail, the details might degrade further and start to fall apart with certain post-processing tasks.

The correction also crops the image, so for those who fuss over details and maximum pixels over the subject, the whole sensor is not used, and this might not be much of a pixel loss percentage-wise, but it's nevertheless there.

So what do we get for the more expensive Rf lens compared to its EF counterpart? Doesn't look like much in terms of image quality, even when the corner issue is ignored.

"In the image quality comparison, the two lenses show rather similar image quality overall. Both lenses have slight advantages in specific comparisons. For example, the RF lens produces sharper periphery image quality at 28mm, and the EF lens is sharper in the center of the frame at 35mm f/4. Performing similarly in this comparison reflects positively on the RF lens — this EF lens is a great performer. The RF lens has dramatically stronger geometric distortion and has stronger lateral CA. The EF lens shows stronger peripheral shading at 35mm f/4 and slightly less at narrower apertures in the wider half of the focal length range."

Lens image comparison tool for Rf 14-35 f/4 L and EF 16-34 f/4 L here.

(https://www.the-digital-picture.com/Reviews/Canon-RF-14-35mm-F4-L-IS-USM-Lens.aspx)

I'm kind of glad I got the EF 16-35mm f/4 almost new a while back, I can't see much benefit for me in upgrading. For others, if having the native RF mount, 175g less weight and 2mm extra at the wide end is important, then there isn't much choice, other than paying not that much more, relatively speaking, and stepping up to the 15-35mm f/2.8 which is a much better engineered lens.

We may be stepping into a whole new era of different compromises with the new RF range. We know they all have a heavy vignetting problem that's due to the RF mount design, and I can live with that. We've seen a molded plastic lens element included in the Rf 100-400, and some radical geometric distortion in a few lenses being rectified with software correction. Compromises imply that you give something to gain something else, and if we're not gaining much over the older EF lenses, but paying more, then we need to ask whether these are just cost cutting measures, or if we're gaining enough to offset what is being lost. Obviously, this will vary from lens to lens, and each needs to be considered against the buyers requirements. :oops:
As I don’t have the EF 16-35, I may need to do some mental gymnastics to persuade myself that this is worth going for . From ‘The digital picture’ review you shared, the distortion at 16mm seems not too bad. If so, I could take this as a RF 16-35 f4 lens, and that the premium over the EF version is for it being lighter, smaller, a tad sharper, better IS, and the control ring. Besides, with the EF launch price at $1199 in 2014 being about $1390 today, the ‘actual’ premium would be about $300. That may be easier to swallow .
 
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The correction also crops the image, so for those who fuss over details and maximum pixels over the subject, the whole sensor is not used, and this might not be much of a pixel loss percentage-wise, but it's nevertheless there.
The issue there is that means it’s not just fake details in the corners after geometric corrections. The R3 outputs a 6000x4000 pixel RAW file. I presume that even though the wider-than-14mm image is cropped to a 14mm FoV without mechanical vignetting, the output will remain 6000x4000. That suggests that the cropped image must be up-scaled…fake pixels across the whole image.

I don’t know if that’s true, will be interesting to see if the RAW images at 14mm have larger pixel dimensions (i.e., use some of the non-effective pixels).

I'm kind of glad I got the EF 16-35mm f/4 almost new a while back, I can't see much benefit for me in upgrading. For others, if having the native RF mount, 175g less weight and 2mm extra at the wide end is important, then there isn't much more choice, other than paying not that much more relatively speaking and stepping up to the 15-35mm f/2.8 which is a much better engineered lens.
The RF is significantly shorter and lighter, for me that’s useful for travel. Although I sometimes travel with the 11-24/4 and the 17+24 TS-E, But sometimes I want a smaller and lighter kit and the 14-35 and 24-105 will make a nice kit for those occasions.
 
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You have to stop it with the goddamn AI fake detail BS. Go sit in a corner and breath deeply until you can talk rationally.
Take a chill pill, or better yet some real medication. AI is a hip term that people toss around indiscriminately, when what they really mean is simply the use of algorithms.

My Mac runs those algorithms on a ‘neural engine’…is that AI? I don’t think anyone really cares, except apparently you.
 
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HMC11

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The statement made earlier, "The Rf 14-35mm Ff/4 L should be usable for landscape like the EF 16-35 f/4 L, and no amount of arguments can justify missing corner details because the optics can't deliver them" is totally wrong. The RF 14-35 is not missing corner details - the corner detail is extremely good, just look at the pictures. This detail wasn't just "made up", it is because the lens is so sharp that even after stretching the result is still excellent. The designers sacrificed some optical distortion correction for excellent sharpness and other benefits, knowing that the distortion could be easily corrected in software, whereas a lack of resolution cannot be corrected - to make up for lack of resolution really would require AI. If AI were "creating" this detail then the16mm would have "sharp" corners also.
Kindly correct me if I got this wrong. My understanding of the statement is that the optics projects an image that is a little wider than 14mm, and the software crops that to give a 14mm field of view as part of the correction process. If so, there would be some loss of pixels compared with a lens that projects an image with a 14mm FoV that covers the entire sensor. Thus, the statement is not incorrect as the optical design 'can't deliver' a 14mm FoV that covers the whole sensor but has to resort to a wider FoV and cropping to correct the distortion. Having said this, I do agree that if the image corners are sharp, and that to all intent and purposes one can't tell whether there are 'fake' pixels added, then it would make little material difference to someone looking at the image in the size, viewing distance etc that it is intended for.
 
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LogicExtremist

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Kindly correct me if I got this wrong. My understanding of the statement is that the optics projects an image that is a little wider than 14mm, and the software crops that to give a 14mm field of view as part of the correction process. If so, there would be some loss of pixels compared with a lens that projects an image with a 14mm FoV that covers the entire sensor. Thus, the statement is not incorrect as the optical design 'can't deliver' a 14mm FoV that covers the whole sensor but has to resort to a wider FoV and cropping to correct the distortion. Having said this, I do agree that if the image corners are sharp, and that to all intent and purposes one can't tell whether there are 'fake' pixels added, then it would make little material difference to someone looking at the image in the size, viewing distance etc that it is intended for.
If you're saying that the lens projects a distorted image wider than 14mm across the whole sensor, then crops to a smaller size to create a 14mm FOV, then yes, that's what I believe is happening.

It looks like some people don't quite get that an image only contains the data that was captured when the photo was taken. If corners are really heavily vignetted, then the amount of detail recoverable from the shadows will be whatever the camera is capable of recovering if you underexposed by so many stops. If geometric distortion of a lens is so bad that extra pixels need to be generated to flatten an image, then we're looking at computational photography, much like what happens on a smartphone.

Is there a price to pay for adding computer generated pixels to create fake data for filling in corner details that were never actually captured in the first place? Well, of course, as the computer has no idea what the corners were meant to look like, and just uses a fancy mathematical formula, a computer algorithm, to guess what the pixels might be.

Seeing is believing, so I've created a very clear comparison to show this effect, by comparing the Canon RF 16mm F2.8 STM Lens vs Canon RF 50mm F1.8 STM Lens. Similar sized lenses, with comparable price and build quality, the difference being software correction.

Check out the comparison tool below, what happens when we stop down the lenses to f/8:


The RF 50mm gets sharper as we stop down, and by f/8 is VERY sharp in the corners. When we look at the RF 16mm, we see that stopping down has no effect on sharpness in the corners, because the corner data was never actually captured optically in the first place, and as a consequence, doesn't sharpen with a narrower aperture. The corners stay blurry right through the aperture range because they're being digitally filled. Feel free to set both lenses in the tool to f/2.8 then compare from there through the aperture range. Hope this helps people understand what's going on here, the goal is understanding to make better and more informed buying decisions, it's not a competition or an attack on anyone's values! :)
 
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LogicExtremist

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For the people that had questions about the software correction on the RF 14-35mm, Dustin Abbot has some great information - https://dustinabbott.net/tag/14-35mm/

See cut & paste below, which explains that the lens optics are actually wider than 14mm, but mechanical vignetting is so high that all data is lost under the pure black corners, so it has to be cropped away. After cropping the image is only equivalent to a 15mm FOV. If the sensor is capturing all the uncorrected data (20MP on an R6), but the final images are still the full sensor size of megapixels (20MP) after the in-camera cropping, then it probably means the image is being digitally enlarged too, because the extra pixels didn't appear from thin air.

This is what Dustin Abbot has to say in his review:

"Note those corners? That is actually mechanical vignetting, or a place where the lens actually doesn’t quite cover the full frame image circle. What you are are seeing is part of a lens’ circular opening iris that didn’t quite cover the rectangular sensor, so only the corners show dark. This isn’t lens vignetting in the traditional sense, as something physical is actually blocking light from reaching that portion of the sensor. Unlike typical vignette, this mechanical vignette will be there regardless of what aperture you choose; it is just as strong at F8 as it is at F4. I’ve seen this with superzoom or cheaper lenses, but I can’t recall seeing this on a professional grade zoom.


So let’s dive in a see what’s going on. Below is a sequence of three images, though this is actually all the same image. The first is the RAW file as it arrived in Lightroom (though with a white balance correction; the R5 is [for some reason] really terrible with the auto white balance on my test chart), the second is my attempt at manually correction the image, and the final is the JPEG image as it was corrected in camera.


25-14mm-Distortion
25-14mm-Distortion-2
25-14mm-Distortion-3


Of the three, the JPEG is clearly the cleanest, though if you compare it to the previous images, you will see just how much of the frame is lost to achieve that final correction. What you see in the JPEG was how I framed the chart in camera, but the resulting RAW file was very loose in the frame because of how much space Canon is leaving for correction of both the heavy distortion and the various vignette issues. The distortion is extremely heavy; it required a +34 to achieve this manual correction, and it is also is not linear, so that results in a “mustache” pattern left behind. The standard correction profile obviously does a much cleaner job on the JPEG, and will on RAW images as well when that profile arrives.


I said “various vignette issues” as there are actually two separate issues here. The mechanical vignette issue can only be solved via cropping, as there is no picture information under that pure black in the corners. The traditional distortion is also very heavy, however, requiring me to max out the vignette slider at +100 and sliding the midpoint to zero. We are talking at least 3 stops of vignette, perhaps a bit more.


The heavy need for corrections also plays a bit of havoc with the focal length. On paper, the 14-35L is actually bit wider than the Samyang AF 14mm F2.8 prime lens which I used for comparison as it is the only other RF mount 14mm lens I had on hand. I put both lenses on a tripod and shot a brick wall scene to test width. Sure enough, the uncorrected image from the RF 14-35L is wider, though with some major problems, as you can see.

26-Uncorrected-Framing


But I grabbed the corrected JPEGs from both lenses, and found, unsurprisingly, that now the Samyang’s image was actually wider. There are blocks showing on Samyang image (right) that are completely clipped off on the Canon’s image. I would say the corrected image from the Canon probably behaves more like a 15mm lens. "


To quote a poster on dpreview, "You should know the outsides of the image are going to be soft due to the amount of distortion correction. No amount of stopping down can fix squeezing 2 pixels worth of image into one pixel on the camera sensor." That, in a nutshell is the truth. If your photography is unaffected by this, then these lenses are an option for you, if not, then they're not the right tool for the job. :)
 
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LogicExtremist

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501
352
As I don’t have the EF 16-35, I may need to do some mental gymnastics to persuade myself that this is worth going for . From ‘The digital picture’ review you shared, the distortion at 16mm seems not too bad. If so, I could take this as a RF 16-35 f4 lens, and that the premium over the EF version is for it being lighter, smaller, a tad sharper, better IS, and the control ring. Besides, with the EF launch price at $1199 in 2014 being about $1390 today, the ‘actual’ premium would be about $300. That may be easier to swallow .
If I didn't have the EF lens, and I wanted the get a wide angle f/4 zoom, the 14-35mm is the only one available for the RF mount and I would consider it rather than invest in an old mount lens. The two considerations are value for money and image quality. If the IQ is suitable for your requirements, then it might be a matter of waiting till the Xmas or EOFY sales arrive!
 
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