Comments made by johnriley - Page 1511

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Mechanically compensated fixed aperture zooms have a slight stopping down applied at the wider end of the range. This opens up as the lens is zoomed.

This fits in with the usual slight reduction of resolution at the telephoto end of a zoom. At the long end the lens is literally wide open, but at the wide end it is slightly stopped down to maintain the same f number.

Some zooms are optically compensated, but I think this is expensive and quite rare.

Comment by johnriley posted on How do constant aperture zooms work? at 12/03/2010 - 16:24

Anvh wrote:
Indeed John but it's never a sin to have something you like.
I'm sure you could appreciate the build quality of the WR lens.

I'm sure I could and if I were to be buying new at this moment then that's the one I would go for.

Comment by johnriley posted on DFA100 WR good or not? at 12/03/2010 - 16:18

We have the FA and D-FA 100mm macro lenses, and in terms of quality there's nothing to choose between them. The limiting factor is our technique.

Comment by johnriley posted on DFA100 WR good or not? at 12/03/2010 - 15:07

Royal Mail Air Mail delivers to Italy, but best to send insured....

Comment by johnriley posted on Wanted: Pentax 12-24mm at 12/03/2010 - 08:16

I thought the WR lens had a rounder diaphragm. This would affect the rendering of the out of focus areas.

Comment by johnriley posted on DFA100 WR good or not? at 12/03/2010 - 08:14

No idea, Stefan. Perhaps there is a critical modification in it?

Comment by johnriley posted on 645D Press Release at 12/03/2010 - 00:10

Someone mentioned that Jacobs were selling them at £399 at the NEC. Worth checking out?

Comment by johnriley posted on Wanted: Pentax 12-24mm at 11/03/2010 - 23:48

Quote:
It seems btw that Pentax is using a new viewfinder or not?

It looks the same as the original 645 viewfinder. It is an unusual design, very low profile with a long telescopic eyepiece.

Comment by johnriley posted on 645D Press Release at 11/03/2010 - 23:47

Other members please start a new thread rather than hijacking this one. Thanks.

Comment by johnriley posted on FS: Sigma 18-50mm & 55-200mm at 11/03/2010 - 22:37

Perhaps the CCD is too large for SR to be effective. For medium format, we've managed without SR and the cameras are inherently more stable.

Comment by johnriley posted on 645D Press Release at 11/03/2010 - 22:34

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johnriley

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