# Patent - 400-600mm f/2.8-f/4 zoom lens



## x-vision (May 27, 2011)

Here's another interesting patent that Canon just received in the US.

It's for a 400-600mm f/2.8-f/4 zoom lens:
http://www.freepatentsonline.com/7948691.pdf

I'd say that this would be the new sports uber-telephoto - with a matching price tag, of course ;


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## Bob Howland (May 27, 2011)

I think the bird photographers would love this, assuming that they were strong enough to carry it into the field. The focal length range is a little short for my tastes although it is clearly a natural for a built-in 1.4X TC. 300-600mm or even 250-500mm would be better. To me, the most interesting aspect is that they are not holding the maximum aperture constant. Bravo!


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## IronMike (May 28, 2011)

Are you sure? My take on the patent is that it is actually a patent for 6 different lens designs. The first 4 are 400mm f2.8 lenses, the next is a 300mm f2.8 and the last is a 600mm f4, all have IS. If you examine the block diagrams they are obviously different optical designs...

Mike


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## x-vision (May 28, 2011)

Well, the abstract starts with:


> Provided is a zoom lens system including ...



So, I don't know. I assumed it's a zoom lens.


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## Admin US West (May 28, 2011)

x-vision said:


> Well, the abstract starts with:
> 
> 
> > Provided is a zoom lens system including ...
> ...



I think the abstract has a typo in it, nothing in the patent would allow the lens to zoom. The patent is for a design that allows a telephoto lens to be made shorter and still have low CA's. 

Examples are given of designs claimed by the patent.


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