Canon News has uncovered a patent for a Canon RF 17-70mm f/4-5.6 BR optical formula. This is a pretty detailed patent, and kind of interesting with the inclusion of a BR lens element. A BR element can help in reducing the size required for such a lens.
One drawback as pointed out by Canon News is that this design requires image stretching from 17mm to about 28mm.
This sort of lens design would be a great kit lens for an APS-C RF mount camera that would also work on your full-frame RF mount camera. Which I think is the route Canon will go whenever they announce an APS-C RF mount camera body.
Canon RF 17-70mm F4-5.6 BR
- Focal length 17.50 28.00 58.00
- F value 4.10 4.50 5.70
- Angle of view (°) 51.50 38.16 20.77
- Maximum image height 22.00 22.00 22.00
- Real image height 19.47 20.98 21.94
- Total length 108.50 114.27 158.50
- BF 21.38 33.45 49.01
Some of our articles may include affiliate links. If you purchase through these links, we may earn an affiliate commission at no extra cost to you.
Though the IQ and performance of L lenses is great and impressing I suppose to keep the camera market alive Canon will have to address people more that don't want to spend too much money but want more than the EOS M system. And we haven't seen much news there.
More to come ....
But, of course, I have no idea what Canon is considering.
Hopefully they will include a remote cable release port on an entry level APS-C R body unlike the M50, in my opinion the good old fashioned wired cable is just easier to use.
I bought the EOS RP with the 1.8 35 IS MACRO two years ago and I must say, the this lens is a gorgeous package.
Hoped for a 1.4 (or 1.8) 50 IS MACRO but they gave us the non-IS non-MACRO ...
Hoped for a well corrected RF 2.8 16 but they gave us a fisheye lens defished in camera ...
I really like my (basic, simple) camera gear which gives me lots of options with all these great old(er) EF/EF-S lenses but I HATE, really HATE designing "bad" lenses and correct them in camera (that is JUST MY OWN OPINION).
For the 50mm IS MACRO lens: I use mainly my two M50s (maybe add a third one) and enjoy the 1.4 32 lens as "50mm replacement" without IS but with good close focus (60 x 90mm image field is close to 1:2 macro in FF).
For the 16mm 2.8 RF lens: I think strongly about buying an EF 4.0 16-35 IS for the 16mm option which is compatible to all my cameras. And it is open to video with maybe the EF-EOS R variable ND filter adapter or the focal reducer with the C70 if I need better video ...
Alas, after 25 years or so shooting Canon, I ended up switching back to Canon and did buy an R6 about a month ago. I came back for the Canon color. I know many folks don't notice, or don't care, or might even like the Nikon colors better, but I did not. But if that was not an issue, I would have had no problem saying bye to Canon and going with Nikon for the foreseeable future. They make excellent cameras and lenses as far as I can tell.
One advantage to sticking with Canon , however, would be that you don't need to buy any RF lenses. Since you don't seem to be satisfied with what is offered so far, just use the EF lenses you have now - or even buy additional EF lenses used for relatively inexpensive. If , as you say, you won't buy any lenses slower than f/4, however, I think you are going to find mirrorless lenses in that category are going to be in whatever systems "pro" category and expensive.
I think this would be a cool walk-around lens for cityscapes and such.
For APS-C I would have expected either 17-85mm (circa 28-135mm on FF), or 15-65mm (circa 24-105mm on FF).
So I think this formula is more likely to be a compact budget full frame lens, a contender for a new ultra-cheap FF model below the RP.
AFAIK, the only lenses so far with a BR elements are L (EF 35/1.4L II and both RF 85/1.2L).
However, the current trend with Canon is to expand their range of small aperture lower-cost lenses, as per 600/F11, 800/F11, 100-400/F5.6-8, and I expect further lenses in this category to be added, especially if they have a mind (as you've suggested in the past) to bang out a really cheap entry-level FF body.
One thing for sure, as demonstrated by the dual fish-eye, is that Canon are thinking outside the box and testing the market with non-traditional lens designs.
It's worth taking a look at their web page, which shows how effectively the BR lens reduces CA in the EF 35mm f/1.4L II USM compared to the EF 35mm f/1.4L USM
BR Lens
"This color fringing – called chromatic aberration – has long been the Achilles heel of lens performance. As part of ongoing efforts to correct chromatic aberration, Canon successively developed and implemented fluorite, UD, and Super UD lenses. Now, aiming to achieve ideal correction of chromatic aberration, Canon has developed BR (Blue Spectrum Refractive) optics, delivering anomalous dispersion characteristics equal to or surpassing fluorite."
"BR optics is based on a new organic optical material, developed by reexamining lens material from its molecular structure. This new lens material features unique anomalous dispersion characteristics that are capable of greatly refracting blue light (short wavelengths spectrum), which has traditionally been difficult to focus on a single point."
The second paragraph includes an interesting point "BR optics is based on a new organic optical material", which is a fancy way of saying that they're using an optical plastic lens element, that they've sandwiched between two glass elements.