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01-13-2008, 09:07 PM   #16
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QuoteOriginally posted by ankit Quote
So what is the difference between the K-, A-, and M- mount lenses (lenses that will mount without an adapter, but dont give AF if I understand correctly). Is there a database of these lenses somewhere?
Hold on! There are only "K" mount lenses. All lenses are K-mount, letters indicate variations and upgrades in functionality. All Pentax lenses have compatible "K" mount and ANY Pentax K-mount lens can be mounted on any Pentax K-mount camera. What functionality certain lens-body combination will offer is what differentiate between them. Here is the best resource:

Pentax K-Mount Lenses and Lens Accessories

Let me give you a brief summary: In 1975 Pentax introduced "K" mount lenses. The name engraved on those lenses was simply SMC PENTAX. We refer to those lenses as "K" to avoid confusion (for example take SMC PENTAX 1:1.4/50: there is no "K" in the name itself which indicated the very first K-mount generation but we would call this lens K50/1.4 anyway). Here is the example: K 50/1.4). All following generations do have additional letters after Pentax to indicate family as follows:

smc PENTAX-M: redesigned optics to provide same focal length and aperture in smaller mechanical package. Sometimes optics remained the same if original design was compact enough. "smc" lettering is lowercase, original was "SMC" uppercase. Example: M 50/1.4

smc PENTAX-A: added "A" position to the aperture ring to "surrender" control of the aperture to the body, and electrical contacts on the mount so that camera body can know aperture range. Example: A 50/1.4

smc PENTAX-F: added auto focus, first generation. Example: F 50/1.4

smc PENTAX-FA: second generation auto focus, mechanically compatible with "F" series. I believe there are some changes in the communications protocol, otherwise "F" and "FA" are functionally the same. Example: FA 50/1.4

smc PENTAX-FA J: no primes ever made in "FAJ" series only zooms. This is the first series without aperture ring: they operate the same way A, F and FA lenses do with aperture ring in "A" position where body controls aperture. Made in an attempt to reduce price and survive on the market. I believe FAJ series made Pentax look bad and actually loosing to other brands. Lenses in "FAJ" series are of very poor mechanical construction and not so good optically and even designed poorly (like toys) and are in general not recommended. Example: FAJ 28-80/3.5-5.6 AL

smc PENTAX-D FA: coating of the rear lens element optimized to reduce flare from the sensor, otherwise functionally the same as "FA" series. Only two were designed, both macro (DFA50/2.8 MACRO and DFA100/2.8 MACRO). Example: D FA 50/2.8 Macro

smc PENTAX-DA: designed for digital. No aperture ring and some lenses have reduced image circle to fit APS-C sensor and are not suitable for film bodies. "DA" lenses can be used with film bodies that support A, F, FA, FA J and D FA lenses with aperture ring in "A" position. Very old mechanical bodies can not control aperture on "DA" lenses although you can mount them. Example: DA 40/2.8 AL Limited

There are also "Limited" lenses, but apart from exceptional mechanical construction and optical qualities FA Limiteds are functionally identical to other FA lenses and DA Limiteds are functionally identical to other DA lenses.

So with your digital bodies you can use all lenses but here is what you will get:

K, M: no auto focus, limited shooting modes, limited metering modes, no P-TTL flash support.
A: no auto focus, all shooting modes, all metering modes, P-TTL flash support.
F, FA, FA J, D FA, DA: auto focus, all shooting modes, all metering modes, P-TTL flash support.

Easy! :-)

QuoteQuote:
hmm, the DA 40mm/2.8 looks very attractive with the $50 rebate. Maybe I'll just get that and the K100D for now!?
That is a good idea! Consider FA 50/1.4 as well if you like 50mm on digital bodies.

01-13-2008, 09:25 PM   #17
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Original Poster
Ivan, wow! That is exactly what I was looking for. Thanks a lot!

One more clarification: What exactly do you mean by "limited shooting modes, limited metering modes" for K and M? Does this imply stop-down metering, and the camera automatically sets the shutter speed? Also, what does the "AL" at the end of the lens name signify?

I think it is going to be a toss-up between the DA 40, FA 50, and the FA 43. Looking at picture samples to convince myself the FA 43mm is worth the extra money now
01-14-2008, 06:45 AM   #18
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QuoteQuote:
One more clarification: What exactly do you mean by "limited shooting modes, limited metering modes" for K and M? Does this imply stop-down metering, and the camera automatically sets the shutter speed?
K and M will let you use M mode with stop-down metering, and Av only wide open (at max aperture). No other modes. Also, only spot and center-weighted metering are available, matrix is not available since for matrix metering camera has to know aperture range for proper Tv/Av calculation and K and M lenses do not have electrical contacts to convey that information to the camera body.

QuoteQuote:
Also, what does the "AL" at the end of the lens name signify?
AsphericaL element. Modern design that improves image quality while minimizing number of optical elements. You will also see that some lenses are ED (Extra-low Dispersion Glass, improves contrast in telephoto lenses) and IF (Internal Focus).

QuoteQuote:
I think it is going to be a toss-up between the DA 40, FA 50, and the FA 43. Looking at picture samples to convince myself the FA 43mm is worth the extra money now
All three are very fine lenses, you can not make a mistake with any of them. Take a look at FA 35/2 AL as well, it is fast and optically superb and has normal field of view on DSLR.

See excellent tests here: Pentax Lens Tests
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