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A couple of optical formula patents from Sigma have appeared. There is no mention of mount types in these optical formulas, so we'll have to wait and see if either will ever make its way to the RF mount.
First up is a 50-140mm f/2.8 for APS-C equipped cameras. It would basically give you a 70-200 f/2.8 equivalent in APS-C terms (80-220).
The second is an external zoom 70-200mm f/2.8 for full-frame cameras. This sort of lens design makes some sense for size and balance with smaller mirrorless cameras, but there is a large number of shooters that much prefer an internal zoom 70-200 f/2.8.
Sigma 50-140mm f/2.8 DC (APS-C)
- Focal length: 50.50mm – 136.50mm
- F-number: 2.92
- Half angle of view: 30.62° – 11.40°
- Height: 14.20mm
- Length: 125.00mm – 145.00mm
Sigma 70-200mm f/2.8 (Full-Frame)
- Focal length: 72.00mm – 194.10mm
- F-number: 2.92
- Half angle of view: 32.92° – 12.12°
- Height: 21.63mm
- Length: 168.00mm – 203.60mm
This patent information was found at asobinet.
The issue with the RF 70-200 on the mirrorless mount is very shallow disctance between the rear element and the sensor. It requires some really complex aspherical last group lens elements that DSLR lenses didn't require. It also precludes the use of teleconverters and for me this is a massive reduciton in versatility and appeal to a 70-200mm f2.8 lens. The ability to use a 1.4x and have a 100-300mm f4 or a 2x and have a very capable 140-400mm lens is a massive camera bag saving bonus. It's not just the space betweenthe rear element, it's the fact that the rear elements bend the light rays specifically for a close proximity sensor. Even if upi could put a TC in there, it would dramatically reduce image quality and increase teleconverter lens design complexity, trying to retro mod these last elements of the 70-200. It's also why we aren't going to get any Canon RF extension tubes anytime soon.
As much as I adore the new RF version...the lack of teleconverter use is a deal breaker for me. I regularly use TC's on my ef 70-200 II LIS as well as a 12mm extension tube for flowers and floral close ups.
So for me, this lens design isn't a great fit. I aslo have a very low opinion of Sigma's ability to make a great 70-200 f2.8 mk1. They have pushed out so many designs over the years making marginal adjustments to something that should have been right 1st time. Talk about !measure once and cut twice".
I wouldn't be surprised to see a second 70-200 f/2.8 with an internal zoom and TC compatibility added to the line-up in the future. At one point the EF line-up had 4 70-200s in production.
At good light, the smallest f-stop I use usually is f/8, because I want to minimize bokeh. Others might make use of f/2.8 all the time.
I wonder how much Sigma will be asking for that lens. As the Canon version is around $2,800, imagine Sigma comes with a $1,500 version with a good image quality. Or will Canon demand very high fees from Sigma for the access to the RF mount?
I bought Meike tubes for 36€ on Amazon, and they work like a charm, both on RF lenses (especially on the 85 f2 Macro, even if I just sold it yesterday) and on EF lenses (installed before the RF to EF converter); so from that point of view I don't feel the need of Canon own tubes now.
Meike Cine-Standard Storytelling
I agree abut the TC on 70-200; even if I very rarely use the 2x extender on my EF 70-200 2.8 non-IS, I'm glad I've the option to do it if needed.
Either way, it's exciting to see new, innovative APS-C lens formulae being developed (at least patented, if nothing else). I'm skeptical of how soon we'll see third party AF lenses for Canon RF, if ever, but that's a subject for a different thread...
In the old Popular Photography magazine lens reviews, they would measure the actual focal length on an optical bench. As I recall, most zooms lenses differed from their rated ranges by 5-10 mm at each end anyway.
The upcoming 70-200mm f2.8 DG DN I expect to be excellent like their recent primes.
We all have our priorities. I absolutely LOVE the compact design of the RF 70-200 f/2.8. I probably would have settled for the f/4 version if not for the ability to squeeze my R6 and this lens into a small bag for taking action shots of my children doing dance and show choir. When I need more reach, I use a different lens. Packing both for trips is fine as the 70-200 is smaller than my Tamron 15-30 f/2.8.