Patent: Canon EF 300mm f/4L IS & Others

[keithcooper]

Re: Patent: Canon EF 300mm f/4L IS & Others

... I think keithcooper has the key to the answer: this patent is not about individual lens designs, but about a new design concept using DO, and the 50/1.3 in that patent is only one example how to put that concept to use.

Sorry, I wasn't quite clear, its a 'new' technology, as in the way that DO is a 'new' feature to include in your optical designs. This one seems to involve resin layers (??)

From what I can see, it is a thin flat element in the 50 and 300 and a thin layer on the last but one element of the 24mm.

Having lenses that vary in refractive index in different places is not new, you are looking through them to read this...

 

[StudentOfLight]

Re: Patent: Canon EF 300mm f/4L IS & Others

Not familiar with all the numbers in this tab. What is BF?

Back Focus - the distance between the rear element and the focus plane (at infinity I beleive)

You beat me to it. Anyway, I wanted to also add that with 8x.xmm BF, all the listed 300mm options listed would be able to take a TC.

 

[Markus D]

Re: Patent: Canon EF 300mm f/4L IS & Others

Dear Canon, If you could change just one of those 300 F4 L IS to a 400 F4.5 or 5.6 L IS it would be greatly welcomed. A lighter to carry, fixed 400 to replace the solid but oldish current one with IS. thank you.

 

[Rudeofus]

Re: Patent: Canon EF 300mm f/4L IS & Others

Sorry, I wasn't quite clear, its a 'new' technology, as in the way that DO is a 'new' feature to include in your optical designs. This one seems to involve resin layers (??)

You are right, this has nothing to do with DO, in fact the blog even writes about the drawback of DO and specifically mentions Nikon's recently released 300 PF. The key claim of this patent seems to be lenses with prescribed distribution of diffractive index over the radius, made from special resins.

The blog also mentions that instead of going the Zeiss Otus / Sigma Art route, Canon may elect to stick with conventional design for fast 50mm lens, with performance improvements coming from this technology.

Having lenses that vary in refractive index in different places is not new, you are looking through them to read this...

And even Canon seems to have patented aspects of this technology over three years ago ...