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Old Oct 29, 2005, 9:18 AM   #1
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Hello

I have been searching the net, to find the precise and priciple diffrence between the Pentax SMC F and FA series of lenses - so far without luck.

Could some of you please enlighten me?

Yours

Lars K. Christensen
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Old Oct 29, 2005, 11:22 AM   #2
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I believe that the FA lenses are able to transmit their MTF data to cameras that are capable of using it in full auto mode to generate the optimal focus and exposure settings for the scene. I think that this is the major difference, BICBW.

Lou
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Old Oct 29, 2005, 2:49 PM   #3
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Lars

You might find something to help here

http://kmp.bdimitrov.de/lenses/


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Old Oct 29, 2005, 7:09 PM   #4
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st-ronan wrote:
Quote:
Lars

You might find something to help here

http://kmp.bdimitrov.de/lenses/


I have already been there several times before, and you are right: its an interesting site. But I didn't manage to get the answers for my question in the first place.

The part of the site you point to lists a great number (all?) of the SMC lenses ever produced. But when comparing F and FA versions of lenses with the same lenght/aperture, its hard to deduct any principal differences from the list.

However, following Lou's hint, I re-read the pages on the same site with detailed infoabout different versions of the K-mount, and found confirmation that the FA lenses uses a K-mount that is updated (Kaf2) in relation to the one used by the F lenses (Kaf). One of the differences is, as Lou says, the ability to transmit MTF-data from lens to camera. As I understand, this means that the camera will be able to take into consideration whichF-stops will give the highest resolution, when in program mode.

But since I rarely use program mode,this not of much practical concern for me.

Another difference seems to be, that (at least som of) the FA zooms have a feature called Power-zoom, which means that the zoom can be controlled electronically from the camera. However, my istDS doesnt support this feature (and I wouldn't want it anyway), so this is of even less concern.

But I still wonder: are there any other reasons for preferring an FA version to an F version?
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Old Oct 29, 2005, 8:24 PM   #5
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I know the istDS doesn't support power zoom, but it is a wonderful feature, giving fast smooth zooms and if you could use it you would really like it. You can also do some interesting special effects with power zoom, which cameras that can use the feature (PZ-1P) can do automatically.

I believe optically the F and FA lenses are the same, altough on some sites the F rates higher than the FA in tests.

Tom
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