Toothwalker wrote:
A recent Canon patent showed a design with f = 97.5 mm and an f-number of 1.46. That would be a tight fit, but who knows.
Steve Spencer wrote:
If they are willing to round and truncate in that way, then if they alter that design a "smidge," and make it a 95.5mm and an f/number of 1.49, that ought to make the front element about 64mm and give them the room they need. It still won't solve that the T number of the lens might be a bit different from the other lenses in the series. You can truncate the aperture value, and leave a lot of vignetting, but once you start doing that you may affect the consistency of the look and I think that is a design goal too. It probably wouldn't even be a sixth of a stop, so maybe it is ok, and won't be noticeable. I suppose we will have to wait until the lens is produced to see....Show more →
There will probably be a lens code or something that will tell the camera to boost exposure by a certain amount to offset the slightly lower light transmission from it not being a true f/1.4 lens. I recall reading a long time ago that this is already anyway the case with fast lenses on digital because of the way the spread of light rays at wide apertures doesn't fill pixel wells the way light rays do when a lens is stopped down somewhat. Because of this, wider aperture files are automatically given an exposure boost at some point post capture.
rscheffler wrote:
There will probably be a lens code or something that will tell the camera to boost exposure by a certain amount to offset the slightly lower light transmission from it not being a true f/1.4 lens. I recall reading a long time ago that this is already anyway the case with fast lenses on digital because of the way the spread of light rays at wide apertures doesn't fill pixel wells the way light rays do when a lens is stopped down somewhat. Because of this, wider aperture files are automatically given an exposure boost at some point post capture....Show more →
I think the claim was they were boosting ISO, not the exposure. If you changed the shutter speed or aperture, that would have visible effects in some cases (e.g. photographing a screen).
Steve Spencer wrote:
If they are willing to round and truncate in that way, then if they alter that design a "smidge," and make it a 95.5mm and an f/number of 1.49, that ought to make the front element about 64mm and give them the room they need. It still won't solve that the T number of the lens might be a bit different from the other lenses in the series. You can truncate the aperture value, and leave a lot of vignetting, but once you start doing that you may affect the consistency of the look and I think that is a design goal too. It probably wouldn't even be a sixth of a stop, so maybe it is ok, and won't be noticeable. I suppose we will have to wait until the lens is produced to see....Show more →
As to the willingness of rounding and truncating in that way, they do it all the time - and not just Canon. The 20 and the 50 VCM are f/1.46 (I don't know about the other ones) so said design would not be an inconsistent addition. I am thoroughly enjoying my VCM lenses, but as a photographer. I don't care whether they have the exact same dimensions or T-number.
Yes, as we've seen from many patents from many camera companies, there is always some rounding to suit marketing or user familiarity. I believe until recently Leica was the only brand marking exact focal length of some of their M lenses with a code on each lens. I'd have to dig out my 50 Lux ASPH-M but I believe it's 51-something mm rather than 50mm. I'm not sure why it mattered with these M lenses other than maybe Leica wanting to be very precise. I don't think of that lens as a 51mm, rather a 50mm as it's generally described and marketed.
My RF 28-70/2 is noticeably wider at 70mm than my 70-200s at 70, the 24-105/2.8 at 70mm, etc. Yet Canon still calls it a 28-70 rather than 28-65. In practical use I don't feel like I'm being shortchanged though in side by side use with other 70mm lenses, it is a little puzzling.
My point to the concern expressed about maintaining light transmission consistency was that whatever minor transmission variations there might be across the VCM lenses, it can be addressed in-camera with lens-specific profiles/tables that automatically tweak image processing so that the end result is the desired consistency. Whether or not Canon does it with these lenses, I don't know. Maybe they're too low-end to bother doing so compared to a 'proper' family of cine lenses where for a lot more money, end users are likely a lot more demanding about consistency.
As an out-and-out partisan of the VCM line, I do wish Canon would roll some of this technology over into a line of smaller, slower, high quality primes. I would love a VCM 35 2.0, or a 40 2.5, 20 3.5, etc. L series optics, weather sealed, tiny, VCM/linear motors, but slower apertures. Sony and L mount come closest to addressing this niche right now but are still miles away from where I'd like them to be.
100% agree. I would also welcome such options from Canon. Unfortunately Canon currently appears to view such specifications as entry level aimed at a moderate price point, with the corresponding build quality and optical compromises.
I suspect it's also a tough ask from Canon for such lenses because slow and high price, high performance make it a difficult marketing proposition that requires a specific type of more educated, more experienced customer desiring those specifications. It's probably a lot easier to justify putting the best optical performance into fast lenses, that therefore also have to be expensive and likely have higher margins. From the consumer side, big, fast, high optical quality lenses can initially appear to be a matter of getting the most performance value for the money.
rscheffler wrote:
My RF 28-70/2 is noticeably wider at 70mm than my 70-200s at 70, the 24-105/2.8 at 70mm, etc. Yet Canon still calls it a 28-70 rather than 28-65. In practical use I don't feel like I'm being shortchanged though in side by side use with other 70mm lenses, it is a little puzzling.
The RF 28-70/2 is 29-68 mm, and the 70-200 is 72-194 mm (all three of them). So yes, there is a noticeable gap of 4 mm at 70 mm.
My point to the concern expressed about maintaining light transmission consistency was that whatever minor transmission variations there might be across the VCM lenses, it can be addressed in-camera with lens-specific profiles/tables that automatically tweak image processing so that the end result is the desired consistency. Whether or not Canon does it with these lenses, I don't know. Maybe they're too low-end to bother doing so compared to a 'proper' family of cine lenses where for a lot more money, end users are likely a lot more demanding about consistency.
Indeed, it can easily be addressed in-camera. F-numbers and T-numbers apply only to the image center, anyway. The illumination falloff away from the center is already addressed in-camera with the vignetting profile.
Toothwalker wrote:
Indeed, it can easily be addressed in-camera. F-numbers and T-numbers apply only to the image center, anyway. The illumination falloff away from the center is already addressed in-camera with the vignetting profile.
This is another way of altering the brightness level, by scaling the RGGB values after exposure, instead of increasing exposure or ISO.
If the lens protocol was not designed from the start to allow a nonzero falloff correction in the centre, Canon would need to issue firmware updates for every RF mount camera model ever made, in order that in-camera JPEGs and especially video is correctly exposed. (And if it was so designed, those two things would work straight away, since unlike EF lenses the RF lenses send this information to the body.)
Firmware updates they can do (although they often seem to be reluctant to). The larger problem is raw converters, even their own. If it doesn’t read the embedded lens profile, and can’t be updated, every image would appear underexposed, which far fewer customers are likely to accept than accept uncorrected vignetting. If it does read the profile, but needs to be updated for a nonzero value in the centre, some users may be left behind due to hardware support or licensing issues. That would break the previous behaviour that if your body was supported, you didn’t need to update your raw converter for new Canon RF lenses.