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03-31-2009, 01:49 PM   #1
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K vs. M vs. A vs. FA.....

I was wondering what the main difference(s) is/are between the K, M, A & FA series lenses? Is it mostly one major change (I.e. "We've improved the coating on the "M" series, so now it will be the "A" series), or maybe a series of smaller changes and so every 6-8-10 years they change the series designation?

It's time to start looking into some primes to supplement my kit lens & 55 - 300 for my K20D, and I'm trying to narrow the list down a bit. I've got my M50mm 1.7 that I got new with my ME Super back in the early to mid 80's and it works great, but I'd like to know - are M's better than K's, are A's better than M's, etc.? If so, why?

Do any of the series' work better or worse with a DSLR? If I was looking for, say a 100mm 2.8 macro, why would I pick one over another?

Thanks in advance for any insight........


03-31-2009, 01:56 PM   #2
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Here is a great page which you will find some of the info you are looking for:

Summary of the K-Mount Evolution, Names, and Features

As to which optical formulas are better than the others I will let others chime in as I have not used enough of the older lenses to formulate an opinion.
03-31-2009, 02:41 PM   #3
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M42 - pre K bayonet lenses (such as the venerable Takumars, Super Takumars)
K - first generation of K mount lenses (basicaly taken off M42 screw and slapped K bayonet on the lenses) being manufactured sometimes between 75-84 +/- mostly though 75-80 (note that the letter "K" is not official part of the name of the lens! f.e.: lens known as K400/5.6 is officialy SMC 400/5.6!)
M - 2nd generation of K mount, many were opticaly redesigned compared to Ks. As result they are smaller. I believe ED elements were introduced at this stage too. Lenses are still fully manual. years 79-84 +/- (from this point onwards the letters become official part of the name, f.e.: Pentax SMC-M 50/1.4)
A - A indicates A setting on apperture ring. So the lenses can be used in other than M mode (depends on the body). Opticaly I believe they are the same (most of them) as Ms. years 84-89 +/-
F - first generation of auto focus lenses (other functions as A), different looks too. (K,M,A are all metal and similarly looking). F series looks VERY 80ish. But contains some excellent glass nontheless! years 87-91 +/-
FA - development of Fs. Many have AL elements added compared to Fs. Used more plastics. Some featured power zoom function. years 91-2004 (only few vere manufactured until 04)
FA-J - first generation of lenses without apperture ring! Control of the lens totaly depends on the camera. (f.e.: lenses can't be used with some old bodies which don't have apperture control function! they remain stopped down all the times) only 3 zooms in this group! years 03-reportedly still in production
D-FA - only 50 & 100 macro lenses, added some coatings to make them more digital friendly, maybe slight redesign, but opticaly they are the same as FAs. Years 2004 - still in protuction
DA - current lens generation designed for the "crippled K mount". They don't have apperture ring. Opticaly they are mostly new designs with only APS-C coverage! years 04- still in production.

except these you'll commonly find two another things:
ltd - limited lenses. Top quality, all metal built. Regarded as some of the Pentax's finest. (there are 3 FA ltds, and 5 DA ltds)
* - going through most generations (certainly from M onwards). They are again some of the best lenses Pentax has made. they have exeptional optical qualities, perfect mechanical built, etc... current DA* have weather sealing too (older *lenses DON'T)

OK, this is as much as I know. Please if I made mistake anywhere, anybody feel free to correct me.



PS: ohter than that:
I'm not sure about coating, it may have changed it may have not, as previouse poster pointed out, the mount and it's compatibility/functions have changed. f.e.: no pre A lens will be recognised, A lenses will only transport apperture and related data to body, F lenses may be recognised (I have to verify this), FA and newer I believe will be recognized (In pentax browser you will see name of the lens) and will transfer additional data (such as MTF)...
03-31-2009, 03:46 PM   #4
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Thanks guys.
Now it's time to start scouring eBay, pawn shops, etc!



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