Patent: Canon EF 85mm f/1.8 & EF 100mm f/1.8

[Cory]

I would pre-order an 85 1.8 replacement right now.

...even if it was a plastic fantastic STM lens like the 50 f/1.8 STM?

- A

Good point, but assuming that it's like the current one without the occasional purple. I wonder if the smallest possible/highest quality optics in an 85 2.8 is something that would have a market.

 

[mb66energy]

Obligatory reminder that patents =/= lenses being made.

That said, it'll be interesting to see how Canon handles 100mm going forward. Originally, they made the 100mm f/2 first and the 85mm f/1.8 was a kind of "might as well" afterthought, reusing some of the same parts. It's no surprise that the 100mm turned out to be the better performer (everything was designed for it first), but 85mm ended up becoming a much more popular focal length (as people moved to 35mm stock for magazines, which required cropping) so that one 'won' anyway. So I'm interested to see—in the hypothetical situation where the lower-end 85mm and 100mm lenses are refreshed—which one Canon works on first. From a design point of view it would make more sense to make the 100mm first again as it's a technically simpler focal length to design; there's no questioning how much more popular 85mm still is, though.

There's also the issue of the AF. The 100mm f/2 has Canon's fastest* and most confident AF motor and the 85mm f/1.8 is just a hair slower (though noticeably less confident) and the other lenses of that series—the 50mm f/1.4, 28mm f/1.8, and 20mm f/2.8—also have not been improved upon in terms of AF speed by either their replacements (28mm) or their betters (50mm f/1.2L; the 20mm has no comparable model, period). So, again in the hypothetical situation where these two lenses are remade, there's a very healthy chance that any new versions of the 100mm and 85mm might have worse AF than the existing models.

All that said, it'd sure be nice to have a short-telephoto lens which matches the 35mm f/2 IS. Throwing IS on the 85 and 100, without pushing the aperture so far they compete with the 'L' lenses, would be a solid move. That 35mm is lonely in it's weird midpoint, where it's not been given the L badge but it's clearly far better than any other primes Canon makes; giving it a short-tele friend would be swell.

*When lenses are tested in absolute optimal conditions. In average conditions it's the joint-second fastest.

Why would 100 mm be "a technically simpler focal length to design"?

The longer the focal length the larger the distance of the last lens before the mirror box / sensor if you compare one lens design class.

If you have additional space between last lens element and mirror box / sensor you have more variability to place the lenses / add lenses to improve the image quality.

For shorter wavelengths you have to make workarounds: a simple 16mm lens with a 30mm deep mirror box is simply impossible - additional lens elements bend the light to shift the lens elements out of the 30mm deep mirror box but "simulate" a lens with 16mm focal length. This explains the ~15 lens elements of typical ultrawides and the aspherical elements to correct for spherical aberrations.
Longer focal lengths may suffer from dispersion, the different focal lengths for different colors. Here you need special glasses with low dispersion (= nearly same focal length for different colors) and/or combination of two lenses (=lens groups) with different dispersion types which reduce dispersion effectively (achromatic , apochromatic correction).

This explains why 135mm lenses are among the best corrected lenses for a long time e.g. the ca. 1975 FD 3.5 / 135 and FD 2.5 / 135 designs and the comparable products of other companies. The FD 3.5 / 135 sports just 4 lens elements in 4 groups but sports a near perfect IQ.

 

[aceflibble]

^Basically all that, and also because production is already well versed for a few common focal lengths. The reason 50mm became the 'standard' focal length, despite a mathematical standard being more like 43mm, is simply because Leica and Zeiss both set up production for 50mm (they already had lenses around the 40mm mark, and 50mm for them was intended to be a 'secondary' standard, much like 35mm is) and it just so happened that workers, machines, and whole production line which were used to make those 50mms ended up being moved to/used by other companies, too, and it was cheaper for those companies to keep the 50mm lenses coming than to reconfigure for a more proper standard. Thus 50mm completely took over as the standard focal length.

For 100mm, it's much the same story. 100-110mm was often adapted to 35mm from medium format (where it was more like a 35-50mm equivalent, depending on the MF in question), and 100mm (or thereabouts) was the portrait length for decades. It wasn't really until the late 70s that 85mm started to pick up steam, and it wasn't until the late 80s that it equalled 100mm in popularity. As 35mm format was used more and more for magazine shoots, which required cropping, the slightly wider 85mm picked up in popularity and by the mid-90s 85mm was 'the' portrait length... but production was still set up for 100mm. It takes a long time to get factories to move on and to get designers used to prioritising new focal lengths. That's why even in the early 90s, when it was starting to look like 85mm would take over from 100mm in popularity, Canon still designed and released the 100mm f/2 before the 85mm f/1.8, and based the 85 on the 100's design. It was becoming clear 85mm would be the bigger deal, but it was cheaper and quicker for them to get 100mm sorted and out the door, first, and then use that to kickstart the 85mm afterward.

These days it's less about physical production and more about the ease of design (as mb66energy says, lenses around this length are often the easiest and best-corrected designs) as well as the designer's familiarity with the lengths. That will change as the older generation of designers retire and younger engineers come up.