07-12-2020, 01:26 AM
Off the top of my head, I'd say these lenses are brilliant! They lack versatility but give a huge telephoto length that is actually affordable. Centering should not be a big problem. Nor will aperture movement vibration. BTW, probably it has been discussed, but the new EF 600mm f/4L IS USM Mk-iii is rumored to have IS problems that are the result of the of the redesigned aperture. At $13,000 I would be pretty upset. At the price of the new RF 600mm F/11 STM, I think I could put up with what I expect to be really good performance.
As for DLA, this is a theoretical limit, and yet it doesn't seem to effect all lenses equally. I'm totally guessing, but with a very narrow field of view on a distant object the light rays are going to hit the front element which are very nearly parallel. The front two bonded defractive elements should bring them to the other elements after which they are even more parallel. We'll see, but I'm guessing the results will be such that many birders will have to have one. If nothing else, to be used as a spotting scope!
I haven't seen actual photos yet. BC's links did not work for me.
Lastly, I must have it wrong, but I thought Canon's MTF charts were done at F/8 (where possible?). I could be wrong. DLA was not a thing before high MP sensors, so maybe this has changed, if it ever was the case. But one would want a standard that could be applied to (almost) every lens!
This is exciting stuff!
As for DLA, this is a theoretical limit, and yet it doesn't seem to effect all lenses equally. I'm totally guessing, but with a very narrow field of view on a distant object the light rays are going to hit the front element which are very nearly parallel. The front two bonded defractive elements should bring them to the other elements after which they are even more parallel. We'll see, but I'm guessing the results will be such that many birders will have to have one. If nothing else, to be used as a spotting scope!
I haven't seen actual photos yet. BC's links did not work for me.
Lastly, I must have it wrong, but I thought Canon's MTF charts were done at F/8 (where possible?). I could be wrong. DLA was not a thing before high MP sensors, so maybe this has changed, if it ever was the case. But one would want a standard that could be applied to (almost) every lens!
This is exciting stuff!