I'll be honest, the first 20 or so patents relating to diffractive optics lenses had me excited about what was coming down the pipeline. However, the last bunch of patents for DO optical formulas hasn't really given me a lot of hope that we're going to see new and exciting super telephoto lenses from Canon.
Below are three embodiments that show 400mm, 600mm, and 800mm DO optical formulas.
Japan Patent Application 2019-028317
Canon 600mm f/4 DO IS
- Focal distance: 582.00mm
- F number: 4.12
- Half field angle: 2.13°
- Image height: 21.64mm
- Whole length of the lens: 394.25mm
- BF: 62.79mm
Canon 400mm f/4 DO IS
- Focal distance: 405.00mm
- F number: 4.12
- Half field angle: 3.06°
- Image height: 21.64mm
- Whole length of the lens: 330.16mm
- BF: 50.46mm
Canon 800mm f/5.6 DO IS
- Focal distance: 795.00mm
- F number: 5.60
- Half field angle: 1.56°
- Image height: 21.64mm
- Whole length of the lens: 490.24mm
- BF: 105.13mm
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.
I do have it and it is exceptional! Why should I be so stupid to update it with a model 50% longer???
And the 600mm f/4 IS DO prototype was 31cm long not 39!
Unless the mentioned numbers are not really length but the distance from the sensor. The text mentions "whole length" which I have never seen before. Normally "length" is enough. I guess these are patents in addition to ... other patents so we will not see anything in the near future anyway.
Perhaps these are new not-so-drastic DO like lenses that are meant to replace the current 400/600 EF lens without the optical quality difference between the versions?
I'm much more interested in the 3rd party vendor news.
"In the optical system containing a diffraction optical element, the object of this invention is small-diameter-izing a diffraction optical element, correcting several aberrations including a chromatic aberration satisfactorily."
The front diffraction grating is a Blaze type Grating, the second is just referred to a diffraction grating.
BTW, lengths are specified as whole length, every lens patent is specified like this, its nothing new. But, they still tell you this in the patent. Its the length from the front optical element to the sensor plane. BF is the length from the last lens element to the sensor plane, it is not the flange distance.
From what I see, the most likely lens to appear is the 600mm f/4 DO. Its a lot shorter while there appears to be no length advantage to the 800mm, and the 400mm is longer than the existing DO lens.
In the first example, we have a 600mm f/4 with a 394mm whole length and a back focus of 63mm, the back focus being the distance from the rear optical element to the sensor plane.
The existing 600mm f/4 is 448mm (457mm fully extended), so the new design is a lot shorter once you add the 44mm flange distance.
Various data
Focal distance 582.00
F number 4.12
Half field angle (degree) 2.13
Image height 21.64
Whole length of the lens 394.25
BF 62.79
In the second example, we have a 400mm f/4 with a 330mm whole length and a back focus of 50mm, the back focus being the distance from the rear optical element to the sensor plane.
The existing 400mm D) II f/4 is 233mm (240mm fully extended), so the new design is longer once you add the 44mm flange distance. Its pretty certain that it won't appear unless its lighter and cheaper.
Various data
Focal distance 405.00
F number 4.12
Half field angle (degree) 3.06
Image height 21.64
Whole length of the lens 330.16
BF 50.46
In the third example, we have a 800mm f/5.6 with a 490mm whole length and a back focus of 105.13mm, the back focus being the distance from the rear optical element to the sensor plane.
The existing 800mm f/5.6 is 461mm (472 mm fully extended), so the new design is only slightly shorter once you add the 44mm flange distance. I doubt we'd see it either unless its a lot lighter and cheaper.
Various data
Focal distance 795.00
F number 5.60
Half field angle (degree) 1.56
Image height 21.64
Whole length of the lens 490.24
BF 105.13
RF.
All depends on your perspective. RF is an immature system that will take years to fill out. I'm not willing to play the waiting game. RF has some really great stuff and has a really bright future but I highly doubt it will play any role in my future. There are lots of companies out there creating great new products/services that I'll never use so they just don't excite me.
At 57, and a hobbyist, I'm only interested in what Canon is doing for me now. I waited for years to upgrade my kit when opportunity finally knocked this last fall. Since then I've bought a 5D IV, 100-400 II, 400 DO II, 24-105 II, 600 EX II RT, Pixma Pro 100, Tamron 24-70 G2 and Tamron 15-30 G2. I already had the Canon 70-200 f/2.8 II, 100mm Macro and the Canon III TCs. The only things I'm really interested in are an affordable/useable (for me) 600mm and a second body (7D III?). A new 180mm macro might get me to bite and if I get a GAS attack maybe a TS lens. The ND filter revolution is also exciting.
Certainly, what I'm using exceeds my creative capabilities but that's just me and as much as I'm interested in exciting developments I just can't jump on any half baked bandwagon.
I love to see photos that demonstrate what's stated in words. Repeatedly we here testimonies that it's not possible to discern which camera has produced which properly exposed photo and yet folk are bemoaning there fate as if the difference is huge.
Jack
Would you get it all the same if it was 33cm instead of 22cm long (and most probably much heavier due to excess length)? This was what my protest was about!
I include myself in saying this. Having a ton of great gear doesn't make one a better photographer unless you're fully capable of extracting the maximum from it and the same goes for lusting after every new highly rated arrival. Comments about a new arrival obsoleting a perfectly good previous generation camera or lens are utter nonsense!:) That's how you explode GAS - remind yourself of the previous sentence.;)
Jack
Keep in mind that in the volume of a cylinder, the radius factors in squared. Assuming a lens would be a solid chunk of material throughout, doubling the length doubles the weight, but cutting the radius in half reduces the weight to a quarter.
Just for fun, a rough comparision between the EF 300mm 2.8 IS II and the 300mm 4.0 IS. The difference in diameter is 128/90 = 1.42, which squared is 2. And that's pretty exactly the weight difference between them (2400g / 1190g). Those number are from the wikipage for the 300mm Canon lenses.
But lenses aren't solid. The length should have basically nothing to do with the weight, it just influences the center of mass maybe. So reducing diameter at the cost of length makes a ton of sense for reducing weight and maybe using a smaller volume in glass, which could even help with cost.
The point remains, it might be a good deal lighter or maybe optically better than current models, or cheaper. Any of those could be a good tradeoff for a bit of extra length.
The minimum diameter of a lens is determined by its f-number and its focal length. A 400mm f/4 has to have a diameter of at least 100mm at some point, plus some more to allow for the thickness of the mount. The current 400mm f/4 DO II has an overall diameter of 128mm and the diameter of the front element is just under 100mm, i.e. it is at the minimum diameter already.
Jack