[pentaxus]

I'm calling BS too. The rays coming out of the DSLR lens only look that way because that is the way canon chose to draw them. I have a friend with a Sony mirrorless outfit. He also has Leica RF equipment. He says that his Leica wide angles don't work very well with his M adapter because of the oblique angles the light hits the sensor toward the edges. His Nikkor SLR 20 and 24 work better because the rays come in straighter from farther away.

[clackers]

I'm calling BS too. The rays coming out of the DSLR lens only look that way because that is the way canon chose to draw them. I have a friend with a Sony mirrorless outfit. He also has Leica RF equipment. He says that his Leica wide angles don't work very well with his M adapter because of the oblique angles the light hits the sensor toward the edges. His Nikkor SLR 20 and 24 work better because the rays come in straighter from farther away.

A short registration distance is a much bigger problem for digital than on film. The sensor is perfectly flat and pixels on the edges are going to miss out on being struck and penetrated because of the wide angles, which are of course worse with an WA lens. The percentage of photons that set off a pixel is lower anyway than film grains.

Sony knew this and put a layer on the sensor of microlenses to try and address this, but they present problems of their own including colour artefacts. Forum member Pinholecam even paid someone to remove that layer from his A7's sensor.

Parallel rays are what you want for image quality, so that's a retrofocal group in a lens to help that, you resist the temptation to do without one when designing.

[Rondec]

The big thing is that many of the lens designs still in use on SLRs are ancient designs -- tweaked a bit and with new coatings, it is true, but still with their origins from 50 years ago and older. It is not surprising that the new Canon 50 f1.2 is a better lens than the old Canon 50 f1.2 L. I think the same will probably be true for the DFA *35 f1.4 (whenever it appears) when compared to the older FA 31 limited. And for all the talk about lighter lenses, the Canon 85mm f1.2 II is 1025 grams and the RF 85mm f1.2 is 1195 grams -- and 850 dollars more expensive on B and H.

Is it any wonder that Canon wants folks to buy RF lenses?

[Wheatfield]

A short registration distance is a much bigger problem for digital than on film. The sensor is perfectly flat and pixels on the edges are going to miss out on being struck and penetrated because of the wide angles, which are of course worse with an WA lens. The percentage of photons that set off a pixel is lower anyway than film grains.

Sony knew this and put a layer on the sensor of microlenses to try and address this, but they present problems of their own including colour artefacts. Forum member Pinholecam even paid someone to remove that layer from his A7's sensor.

Parallel rays are what you want for image quality, so that's a retrofocal group in a lens to help that, you resist the temptation to do without one when designing.

It seems to me that the shorter the registration distance, the larger the rear element needs to be.

[kaseki]

It seems to me that the shorter the registration distance, the larger the rear element needs to be.

Yes, in the limit of the glass nearly touching the focal plane, the diameter of the last piece of glass has to be slightly larger than the diagonal of the focal plane. At a one millimeter gap, the ray bundle leaving the glass would be a millimeter or less in diameter depending on f/number, and pretty well centered over its focus point.

[Wheatfield]

Yes, in the limit of the glass nearly touching the focal plane, the diameter of the last piece of glass has to be slightly larger than the diagonal of the focal plane. At a one millimeter gap, the ray bundle leaving the glass would be a millimeter or less in diameter depending on f/number, and pretty well centered over its focus point.

With this in mind, and glass being the most expensive part of a lens, I guess it's no surprise that lenses are getting more and more expensive, especially the ones for short registration full frame cameras.

[kaseki]

With this in mind, and glass being the most expensive part of a lens, I guess it's no surprise that lenses are getting more and more expensive, especially the ones for short registration full frame cameras.

With exotic glasses and aspherical shapes being potential candidates for IQ improvement, there are plenty of opportunities for price enhancement. And as Canon points out, more aggressive coating tech is needed to deal with lens surface reflections (the cause of Boys' points).

[Digitalis]

. At a one millimeter gap, the ray bundle leaving the glass would be a millimeter or less in diameter depending on f/number, and pretty well centered over its focus point.

Quite right, and the shorter the registration distance optical alignment is going to be even more of a headache. With SLR lenses here is be a degree of slop with optical alignment, you can't get away with that when the entire optical assembly is so close to the sensor, where perfectly centered delivery of each ray is critical. Also AR coating technologies are going to have to improve vastly to counter the problematic issue of flare that are common with short registration distances.

Canon wants folks to buy RF lenses?

There was a point where Canon Made RF lenses. As I recall, the Canon 50mm f/0.95 was in production before the famed Leica 50mm f/1.2 Noctilux ASPH