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05-05-2010, 04:30 AM   #1
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LS A 645 75 and 135 lenses

Hello,

as I am right now trying to score some 645N and a few lenses. As I would like to use the camera also with my studio flashes I would be interested to head a bit about the LS lenses.

In particular - at first glance the FA 75/2.8 and and LS 75/2.8 look rather similar (save for the close focusing) - how do they compare optically? What would be the advantage to use the FA over the LS in normal (non flash) shooting - apart from the AF? I guess with the LS lens once can still use the focal plane shutter of the 645N when not synchronizing with flash above 1/60 s or?

Also - any general comments from the users about the LS 75 and 135 lenses would be great.

05-05-2010, 06:13 AM   #2
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the FA is generally considered to be superior to the LS in optical terms, to the best of my knowledge the the LS is exclusively a manual focus lens and cocking the leaf shutter is a bit cumbersome.
05-05-2010, 05:37 PM   #3
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QuoteOriginally posted by Digitalis Quote
the FA is generally considered to be superior to the LS in optical terms, to the best of my knowledge the the LS is exclusively a manual focus lens and cocking the leaf shutter is a bit cumbersome.
Is it really? The optical design would seem very similar - the A and FA are identical, I think, but I do not believe the LS version is very different either—apart from minimum focus distance and the leaf shutter.
I actually recall reading someone somewhere here saying his LS version outperformed his FA one.
The main question is, why Pentax Lens Review and Specification Database - SMC Pentax-A 645 75mm F2.8 states that the LS lenses are not suited to the 645D, as discussed here: https://www.pentaxforums.com/forums/pentax-medium-format-645-6x7-645d/99669-p...ls-lenses.html
05-06-2010, 06:33 AM   #4
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this question has come up before(try doing a search before you ask a question especially if you want to find out if the FA31 is better than the FA35 - save us the trouble of that debate) and the answer is simple:

The LS lens doesn't have an automatic aperture coupling ergo, it will not be usable in the AE modes plus it isn't an AF lens either it's really a one trick dog, fast flash sync that's basically the only advantage it has over other 645 lenses. the FA is regarded as being better because it has AF, it is fully compatible with the AE system, and it has updated lens coatings and as you pointed out it focuses closer.

*I'm actually in the process of compiling my family lens collection of lens tests and putting the results into a report. I have access to most of the 645 and 67 (Including the 800mm f/6.7 ED [IF]) lenses pentax produced and I'm compiling the test data( which has been done on film) for submission for the lens reviews section of this site.


Last edited by Digitalis; 05-06-2010 at 06:42 AM.
05-06-2010, 10:28 AM   #5
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QuoteOriginally posted by Digitalis Quote
The LS lens doesn't have an automatic aperture coupling ergo, it will not be usable in the AE modes plus it isn't an AF lens either it's really a one trick dog, fast flash sync that's basically the only advantage it has over other 645 lenses.
The question was whether it performs better or worse in an optical sense.
I'd still like to know, but maybe I'll just give it a try with my 75 A and LS versions when i find the time. I would do that digitally when my 645 to K lens adapter arrives (assuming that the results would apply mutatis mutandis to film).

Last edited by Smolk; 05-06-2010 at 02:27 PM. Reason: less fire
05-06-2010, 11:57 AM   #6
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No need for fire - thank for all your replies - all are helpful.

Digitalis - I am really looking forward to see your reviews. Great to hear they are all film-based.
05-06-2010, 02:27 PM   #7
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Point taken, previous post edited.
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