Re: Relationship between IR focal length adjustment and focal length.

[George L Smyth <GLSmyth@xxxxxxx>]

Rolland Rainbow Elliott wrote:
> 
[clip]
> 
> I agree with your comments George and I rechecked the instructions that came
> with my Sigma APO 70-210 f/2.8D Nikon Mount lens. However the instructions
> still state that no IR correction is needed at the longer focal length of
> 210mm, only at the 70mm end.  I find this very interesting.

I can only guess that this lens has APO correction into the infrared at the far end
of its focal expansion(?).

george

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