It seems patent applications for diffractive optic super telephoto lenses is becoming a monthly thing. Canon News has uncovered another patent application showing both a 500mm f/4 DO IS and a 600mm f/4 DO IS example.
Canon showcased a 600mm f/4 DO IS at the Canon Expo back in 2015, and we haven't really heard anything else about it since. There seems to be a lot of resources being put into DO lenses and yet we only have one available from Canon in the EF 400mm f/4 DO IS II.
We predict that the RF mount will get some DO lenses in the future for the obvious reasons of size and weight reduction, which is especially important for a lot of super telephoto shooters.
Japan Patent Application 2019-008047
Canon 600mm f/4 DO IS
- Focal distance: 584.99mm
- F number: 4.12
- A half field angle: 2°
- Image height: 21.64
- Length of the lens: 474.74mm
- Backfocus: 109.42mm
Canon 500mm f/4 DO IS
- Focal distance: 487.49mm
- F number: 4.12
- A half field angle: 2.54°
- Image height: 21.64
- Length of the lens: 409.74mm
- Backfocus: 98.4mm
I am curious how much they can shrink and slim down those "big" whites.
Seems to be just about 2cm each:
They've made a big deal about "straighter paths of light" with the new system that don't really seem to apply as much to long lenses. But maybe the DO lenses have less elements for a clearer and lighter system? 60MM is not really a huge difference, but if it's better image quality and slightly lighter It'll still sell to all the professionals. Even then 2.3 inches adds up if every lens in a professional's bad is that much smaller and lighter too.
Sorry but I don't get your 60 mm.
As I said, the overall optical formula (first element to sensor plane) is just about 2 cm (=20 mm) shorter.
As the flange distance between EF and RF (44mm-20mm) deliver a 22 mm LONGER lens barrel (like using the adapter) the difference is about NULL.
Mechanically the lenses will have about the same length. :confused:
This might lead to the conclusion that the patented lens design can be substantially lighter than the current design - and maybe substantially cheaper.
If they can shave off 20% of the price they are close to Sigma's 500mm lens (7000 EUR for the Canon vs. 5900 for the Sigma) - but I think roughly 100% of Canon users would prefer the Canon in that case.
> and yet we only have one available from Canon in the EF 400mm f/4 DO IS II.
No, the horrid 70-300 DO is still in the catalogue, 15 years after introduction:
The lack of a mirror box offers little benefits with longer lenses. Anything over 50mm will have generally be the same size as it's SLR equivalent. SLR wide lenses generally have been employing a retro-focus design to allow the mirror box space in the lens design. A Mirror less camera doesn't have the requirement so the wide lenses (roughly anything under 50mm) don't require a retro-focus design so they can be a lot smaller, lighter and with less internal vignetting or light fall off. Mirror less formats aren't a magic bullet that make every lens shorter....it's not a crop format. I can see little benefits for a 400/500/600mm lens on a Mirror less format. So I wonder if Canon is very aware of this and will only release the "DO" range on the Eos R range...purely for marketing reasons. If you want a dedicated big while on an Eor R...you go DO, which will be lighter and smaller because of the DO design and not because of the mount it's attached too.
Thanks for pointing that out again. I was aware of that but maybe others not.
As I showed with my posts and calculations above in this case/these patents the DO does NOT make the lenses mechanically any smaller and the optical formula is only about 2 cm smaller. And this is used up by the shorter flange distance.
So in this case maybe the lenses will become lighter with DO but certainly NOT shorter.
"Then, as for the optical system L0 of the present invention, the aperture-diaphragm S twist is also using lens constitution in pre-group LF on the object side as the positive lens GFP and the cemented lens which forms the diffraction optical element Ldoe. A lens effective diameter is small-diameter-ized and the weight saving of lens weight is attained because this takes the sufficiently wide interval on the optic axis of both lenses. And the focus lens group Lfo which is a moving lens group for focuses is also arranging an aperture-diaphragm S twist to the image side, it small-diameter-izes a lens effective diameter, also miniaturizes a mechanism mechanism in connection with it, and is attaining the weight saving of the whole system."
Multiple resin molded diffraction lenses cemented to glass lenses are used, thats expensive, and probably not likely to be used, the yield may be too low to afford two or more diffraction lenses.
The patent also states that the design is only practical for lenses with 4.5 degree FOV or less (>455mm), which makes a 500mm lens near the lower limit of practicality. I read this to mean that there is more benefit in a 600mm or longer lens.
"The imaging device described in Claim 10, wherein the maximum imaging half field angle is 4.5 degree or less."
Canon has always been cagey about describing its Blue Goo stuff as plastic, probably fearing negative reaction to the term. It does beg the question about whether or not such a lens element will remain perfectly clear and in shape 2 or 3 decades after manufacture. That said, if I were given an opportunity to buy a 500mm DO f/4 with plastic elements at $6000 that would last only 15 years in prime optical quality, I'd do it over purchasing a $9000, heavier glass one.
But this size reduction is not part of THIS patent, as optical formula and therefore lens are much longer.