Lens Patents

probably dummy question, but what is that DO. I’ve seen that these lens are bit shorter in physical size than non-DO lens, but what about picture quality?

I’m not so familiar with the technology, but is the plastic really as clear (see-through) as glass and gives similar performance and picture quality?

But good to see that new lens are coming!

DO stands for Diffractive Optics, you can google around to find more about it, but in essence the DO element inside a lens enables Canon to make the lens physically smaller & lighter, at the cost of loosing a bit of IQ (mainly contrast, I think).

There is nothing inherently wrong with using plastic for lens elements. Plastics like CR-39 resin have almost identical optical properties to crown glass, but only weight half as much. It is very commonly used for eyeglass lenses. Because plastics are easily moulded, there are probably applications where cost and weight savings can be made without compromising the image quality in camera lenses.

According to Wikipedia (so it must be true), uncured CR-39 resin was used to protect the fuel tanks in B-17 bombers from flak during WW2. With a pedigree like that, wouldn’t it be cool to have it in your camera lenses. You could use that fact to impress chicks at parties.

“You could use that fact to impress chicks at parties”

LOL!

“I think this would be a great fisheye solution. It wouldn’t cost a lot at first sight.”

Oh fisheye, the Lady Gaga of lenses, seemed like such a good idea when I saw it first but so over it in the next five minutes… Honestly, the 60s are over, just get a wide angle and if required distort it in PS.

Plastic and DO are not the same thing.

Patents do not necessarily mean that there will be a product at all.

Thinking a little about the 70-210(L?) IS, I agree that optically it is not one that needs updating. So the question then is why else would it be changed? A google translation of the linked blog suggests the plastic elements will replace the flourite elements, and probably the UD elements too. From my understanding, the flourite elements are very expensive to manufacture. If a cheaper but effective alternative is found, that could help reduce the costs, particularly so for bigger lenses.

Yeah maybe they can come out with a L-ite super teles. 500 f/4 L-ite for $3000. 300 f/2.8 L-ite for $2000. Etc. Longest shot for sure.

Wouldn’t all these DO lenses be way more expensive than the non-DO ones that are out now? If not, why is the current 400 DO so expensive?

Has it actually been proven that DO reduces weight?
the 70-300 DO vs 70-300 IS comparison: DO is heavier.

Unfortunately there’s no direct 400 DO vs non-DO to compare… but do we know for sure it would be lighter and not just more compact? FWIW, the 70-300 DO’s compactness advantage is only really noticeable in the amount of space it takes in the bag – when used, it can be the same size

Because you’re paying not to break your neck when accidentally hang your camera on your neck and forgot you had the 400L with it.

Canon did not invent DO, but how they solve problems can be protected in a patent.

The 70-210mm f/4 IS makes sense because as the megapixel count goes up you need lenses that can resolve much more lines, that´s why Nikon had to introduce their new lenses and Canon will have to catch up with their own sensors too, also the diffraction limit of the lenses will have to be pushed in order for it to behave better with those sensors crammed with megapixels.

:/

DO is meant to reduce the physical size and not the weight. :/ And what´s with the sissyness of light weight lenses you people are too used to the plastic fantastic crap…

My guess would be DO cost is a combination of low manufacturing quantity and the premium Canon can charge for its benefits. Both should subside as it becomes more commonplace (but the latter won’t really go away if Canon has the technology cornered in some way.)

I took a look at the source post, it is indeed plastic lenses. The main downside (according to the source) is that plastic lens performance can vary with temperature, and therefore the patents use two different types of plastic to cancel out the effects (highlighted in purple and green in the pics.)

what parties are you attending??? lol

well if they manage to make plastic elements perform as well as the fluorite then this is going to be a revolution (especially if they pass on the savings to the consumer). I’d love to see a 500/4 L IS plastic that at least matches the current lens… DO…meh, don’t mind the extra size as long as I get the bokeh and contrast of the traditional lens… if they can get DO lenses to match them then that could be cool though frankly if I had to choose between size and cost, Id go for cost as long as optical performance was identical (big hypothetical)

DO lenses are harder to make i believe, and if they have so much trouble with a 400 f/4 DO, i think they just keep the technology in production to develop, but don’t expect to sell many lenses with it (explaining the incredibly high price). If i am correct, DO lenses look like a Fresnel lens, so they are grooved. Doing something like that to a 800 mm lens might result in too much disfigurement, and doing it for a 100 mm lens may not yield enough results. (if i look at Canons own site, it looks like it’s a triple lens, with the middle being the DO part. Making that in a 15cm wide plate of glass might be too much at the moment)

So far their choices have been defensive at least (400/4 is right between the cheap, and light 5.6 and the expensive, razor sharp, but heavy 2.8), and until Nikon or Sigma produces DO stuff, i think it’ll stay that way.

I have the current 400mm F/4.0 DO IS lens and love it. It is (relatively) short and light, and I’ve had excellent results with it. Seems to me that the bokeh complaints are from people who haven’t used the lens. As you go up in the higher telephoto ranges, the background bokeh is affected at least as much by atmospheric conditions as lens character, as your subjects are typically farther away. I shot this photo of a grizzly bear in Alaska last year with the DO lens and am very happy with it. Check it out – http://www.flickr.com/photos/26317521@N00/3726024358/sizes/l/

Another rather nasty property of plastics is for it to darken with age and heat cycling. Some plastics last longer, but its always a tradeoff, you can’t have everything you want.

I have a large plastic lens from a B25, made in the 1940’s still in its original crate. Its absolutely beautiful, crystal clear with no darkening. As near as I can tell, searching parts lists and drawings, it was a test item and never went on production B25’s. It is a very interesting relic though. I hate to think what something like this cost in today’s dollars.

Yes, DO is just another name for a Fresnel lens – the same thing used in lighthouses since decades, but pushed to much better image quality. When you look at the cross section of a DO element (in the patents or in Canon’s description of the 400 f/4 DO), you see a sawtooth-like structure. The quality of the image will depend critically on the details of the “teeth”, in particular, on how sharp you can make the edge.

I would expect that DO elements are easier to make for long focal lengths – the shorter the focal length, the steeper the “teeth” become towards the outside of the lens. For the same reason, they are easier to make for moderate apertures, i.e. a 400 f/4 is much easer to make than a 400 f/2.8.

Or if you are physically disabled and can’t lift such heavy lenses…