Would love to see an RF 17-85 / 4L IS, actually. I think that would actually pair better with the RF 70-200 / 4L IS than an RF 20-70 / 2.8L IS. Of course, ¿Por qué no los dos?
garyvot wrote:
If it is anything like the VCM wides, the 14-35, or 24-105 Z, it will be fine.
What people forget is that in order to fully correct for distortion optically, you need additional elements which introduce their own aberrations, like coma and astigmatism.
Yes, but these downsides largely disappear stopped down, while stopping down doesn't improve anything for digital corrections. Stopped down corner sharpness in wide angle lenses is important for common use cases.
garyvot wrote:
Allowing for some distortion enables a simpler lens design with greater sharpness edge-to-edge. Even after corrections, not much is lost.
I consider the corrections to be part of the optical design, taking the place of several lens elements that would otherwise have to be present. This was not possible in DSLR lenses, due to the possibility that they could be used with film cameras.
I think most lens reviewers have not really caught up with the new thinking, as lenses that are designed with digital corrections in mind should not really be judged for distortion (though I recognize why they still do this)....Show more →
Apr 01, 2026 at 05:32 AM
Steve Spencer Offline • • • • • • • Upload & Sell: On
steamtrain wrote:
Yes, but these downsides largely disappear stopped down, while stopping down doesn't improve anything for digital corrections. Stopped down corner sharpness in wide angle lenses is important for common use cases.
For me the proof of the pudding is in the eating. Yes, digital corrections take their toll even stopped down, but how much? Optical correction require a bigger lens if more elements are required but how much? We all want a small lens with great performance, but there are tradeoffs. I think Canon's approach is sensible. Play both sides of the tradeoff. For ultra-wide angle zooms they make at least one premium lens that aims for low digital corrections but is large. For Canon that is the 15-35 f/2.8L, and make at least one lens that allows pretty extensive digital corrections but is small. For Canon that is the 16-28 f/2.8 IS STM. In between you have the 14-35 f/4L that still has a conderable amount of optical corrections but isn't as fast (but even wider than the premium f/2.8 lens) or quite as small as the IS STM. You get three lenses with different balances of the tradeoff. Personally, I am looking for the 16-28 IS STM for a travel lens. I am glad for the digital corrections which keep it small for that purpose, but at some point I may well get another lens with less digital corrections and bit better performance to use when I am not travelling and worried about size and weight.
What does that mean for this potential 20-70 VCM lens? I think we can expect that as a VCM lens it will take the approach of the VCM primes which is the middle road--something like 5% distortion corrected digitally to keep the lens smaller which is useful for video on a gimbal, but still allows really strong corrected performance. Not ultimately small size, but not ultimate performance either.
Steve Spencer wrote:
For me the proof of the pudding is in the eating. Yes, digital corrections take their toll even stopped down, but how much? Optical correction require a bigger lens if more elements are required but how much? We all want a small lens with great performance, but there are tradeoffs. I think Canon's approach is sensible. Play both sides of the tradeoff. Make at least one premium lens that aims for low digital corrections but is large. For Canon that is the 15-35 f/2.8L, and make at least one lens that allows pretty extensive digital corrections but is small. For Canon that is the 16-28 f/2.8 IS STM. In between you have the 14-35 f/4L that still has a conderable amount of optical corrections but isn't as fast (but even wider than the premium f/2.8 lens) or quite as small as the IS STM. You get three lenses with different balances of the tradeoff. Personally, I am looking for the 16-28 IS STM for a travel lens. I am glad for the digital corrections which keep it small for that purpose, but at some point I may well get another lens with less digital corrections and bit better performance to use when I am not travelling and worried about size and weight....Show more →
For zooms you can't blame Canon for not giving enough options.
But what if you want some focal lengths with no optical distortion for best stopped down corner performance you can run into problems ("problems"), 20mm and 24mm for instance.
Claims like optical corrections are necessarily making the IQ weaker doesn't hold true when looking at the performance of the (budget) Viltrox 16mm f/1.8. It's corners are quite good already wide open and stellar from f/2.8, while there's no need for digital distortion corrections. I prefer that over something needing digital corrections.
That said, looking at the final jpg output from the 20mm VCM, I have to say it's quite impressive how much detail there is even after digital corrections. The remaining question: Is this a true f/1.4 lens, considering the sensor surface wasted to make corrections possible and hence a considerable amount of collected light? There's something with the "T-stop after corrections" so to speak.
I will say it again. It's all a marketing ploy, they make a lens that is much cheaper to manufacture but the price doesn't reflect that. To me it's particle board vs plywood. I use that example because I am looking at kitchen cabinets.
I suspect none of us will "win" the philosophical argument over the use of digital corrections in lens design.
At the end of the day, it's the results that matter. If the lens produces quality images, then I don't really care how it is designed. By all accounts, all of the VCM lenses are quite good.
Extreme corners are almost never important in my images, so perhaps that why I am so copacetic about this approach (although evidence suggests that the corners are still fine in practical terms).
Perhaps Canon will someday produce monster f/1.2 lenses at 24mm and 35mm with no distortion to satisfy the optical purists.
steamtrain wrote:
Claims like optical corrections are necessarily making the IQ weaker doesn't hold true when looking at the performance of the (budget) Viltrox 16mm f/1.8. It's corners are quite good already wide open and stellar from f/2.8, while there's no need for digital distortion corrections. I prefer that over something needing digital corrections.
The VCM lenses are ridiculously sharp without corrections; it's resolution that makes the end image sharp. But they do have various optical compromises to keep the lenses relatively lightweight and working well as a set. But things like tolerating more vignetting, lateral CA, and distortion allow for that end product. The alternative would be lenses that provided inferior results overall before or after correction, or lenses that would be far larger and heavier.
steamtrain wrote:
That said, looking at the final jpg output from the 20mm VCM, I have to say it's quite impressive how much detail there is even after digital corrections. The remaining question: Is this a true f/1.4 lens, considering the sensor surface wasted to make corrections possible and hence a considerable amount of collected light? There's something with the "T-stop after corrections" so to speak.
This is a problem, but not much of one. It's still going to be faster than an f/1.8-class lens, and it's still going to provide the desired subject isolation if shot wide open (as much as can be at 20mm on full-frame).
johnctharp wrote:
The VCM lenses are ridiculously sharp without corrections; it's resolution that makes the end image sharp. But they do have various optical compromises to keep the lenses relatively lightweight and working well as a set. But things like tolerating more vignetting, lateral CA, and distortion allow for that end product. The alternative would be lenses that provided inferior results overall before
The Viltrox 16mm f/1.8 shows this doesn't have to be the case, that was my point. If Viltrox can do it in a 16mm, why can't Canon do it in a 20mm or 24mm. I know the VCM lenses are brighter, but the less wide focal length is less challenging.
steamtrain wrote:
or after correction, or lenses that would be far larger and heavier.
This is a problem, but not much of one. It's still going to be faster than an f/1.8-class lens, and it's still going to provide the desired subject isolation if shot wide open (as much as can be at 20mm on full-frame).
I don't know how to do the math, so I have to take your word for it.
garyvot wrote:
I suspect none of us will "win" the philosophical argument over the use of digital corrections in lens design.
At the end of the day, it's the results that matter. If the lens produces quality images, then I don't really care how it is designed. By all accounts, all of the VCM lenses are quite good.
Extreme corners are almost never important in my images, so perhaps that why I am so copacetic about this approach (although evidence suggests that the corners are still fine in practical terms).
Perhaps Canon will someday produce monster f/1.2 lenses at 24mm and 35mm with no distortion to satisfy the optical purists. ...Show more →
I think that the really distortion-free lens designs will remain with tilt-shift type lenses where being able to use different parts of the optical path and changing angles would dictate a more perfect lens design. To me, and I could be way off base here, if a design would lend itself to superior purely optical performance, such as lens would be the place to put it. And such a lens would definitely satisfy the optical purists, though the "it's too heavy" purists would balk. Still, in my opinion, that is an area where optical excellence across the frame needs to remain.
I'm not saying that digital correction couldn't and wouldn't be used with such a lens, but the movements of the lens truly complicate that option, perhaps to the point that it would be better to get it right optically in the first place.
johnctharp wrote:
The Viltrox has a 77mm filter thread vs. the Canon's 67mm - and keeping things to 67mm was a goal for the VCM lenses.
That is a good point.
Some have mentioned a low amount of focus breathing as a designers goal as well.
johnctharp wrote:
As I said above, size is a compromise Canon made by relaxing correctable aberrations like distortion, vignetting, and lateral CA.
For stills I stick with my 500 euro Viltrox for stopped down corner/border sharpness.
