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09-09-2009, 03:12 PM   #1
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Focus ring M & A

I have been told that the SMC-M 50mm F1.7's focus ring is better than the SMC-A version. Is this true? Does the M version seem more firm/solid ?

Kind regards
.lars

09-09-2009, 09:26 PM   #2
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I've heard people say that, but I don't notice any difference myself. I've also heard there might be different generations of the "A", though. The *aperture* ring is clearly a lot more solid on the M. Of course, with the A, you don't normally use the aperture ring - you just leave it in "A". But just mounting and unmounting the lens without knocking the ring off the "A" position is a bit of a challenge.
09-10-2009, 12:00 AM   #3
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Thanks!

Kind regards
.lars
09-10-2009, 10:26 AM   #4
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I own both the "A" and "M" versions of this lens (50/1.7) and have both of them in front of me as I type this comment. My general impression is that the build quality of the "A" version is somewhat below that of the "M". Here is my summary comparison:
  • "M" version build is on a par with the Pentax-K and SMC Takumar equivalents
  • "M" version is more compact, but slightly heavier than the "A" version
  • "M" version focus and aperture controls are smooth and solid due to quality metal construction
  • "A" version looks and feels cheaper, in general, than earlier versions due to use of plastic parts
  • "A" version focus ring is smooth, though not quite as nice as the Pentax-M
  • "A" version aperture ring feels cheap and "notchy" even in the best examples due to inferior plastic parts. In worst cases, the aperture ring may be completely inoperable off the "A" setting. The Pentax-A 50/1.4 is much better, but is also much more expensive.
As noted above, the main advantage of the "A" version lens is that you have full body-driven aperture automation with bodies that support that feature. The Pentax-A lenses also have the benefit of accurate metering with current Pentax dSLR bodies. The "M" and "K" series suffer in this regards. As a result, you can expect to pay more for the "A" version than for a "M" version in similar condition.

I hope this helps.

Steve


Last edited by stevebrot; 09-10-2009 at 10:34 AM.
09-10-2009, 11:30 AM   #5
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Thanks for the detailed comparison.
09-10-2009, 11:48 AM   #6
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QuoteOriginally posted by stevebrot Quote
I own both the "A" and "M" versions of this lens (50/1.7) and have both of them in front of me as I type this comment. My general impression is that the build quality of the "A" version is somewhat below that of the "M". Here is my summary comparison:
  • "M" version build is on a par with the Pentax-K and SMC Takumar equivalents
  • "M" version is more compact, but slightly heavier than the "A" version
  • "M" version focus and aperture controls are smooth and solid due to quality metal construction
  • "A" version looks and feels cheaper, in general, than earlier versions due to use of plastic parts
  • "A" version focus ring is smooth, though not quite as nice as the Pentax-M
  • "A" version aperture ring feels cheap and "notchy" even in the best examples due to inferior plastic parts. In worst cases, the aperture ring may be completely inoperable off the "A" setting. The Pentax-A 50/1.4 is much better, but is also much more expensive.
As noted above, the main advantage of the "A" version lens is that you have full body-driven aperture automation with bodies that support that feature. The Pentax-A lenses also have the benefit of accurate metering with current Pentax dSLR bodies. The "M" and "K" series suffer in this regards. As a result, you can expect to pay more for the "A" version than for a "M" version in similar condition.

I hope this helps.

Steve
Interesting Steve, thanks for the comparison. I only have K series lenses and always thought the M lenses were inferior build wise to the A series. Do you have the K55/1.8 to
compare it with the 50/1.7 A & M?

Phil
09-10-2009, 12:15 PM   #7
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QuoteOriginally posted by gofour3 Quote
Interesting Steve, thanks for the comparison. I only have K series lenses and always thought the M lenses were inferior build wise to the A series. Do you have the K55/1.8 to
compare it with the 50/1.7 A & M?

Phil
I do have the Pentax-K 55/1.8. I bought it from a guy in Alberta to complement my KX. Its build quality is about the same as the Pentax-M 50/1.7...that is to say, excellent. It is a pleasure to use.

Build quality on the Pentax-A lenses is a little hit or miss. Some are quite good with all metal construction, while others are not so good. A friend of mine owns the Pentax-A 70-210/4. It is very well made and good optically as well. My dad's Pentax-A 50/2 (bought new with a K1000), on the other hand, was junky-feeling from the factory.

Steve
09-10-2009, 12:33 PM   #8
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My A50/1.7's aperture ring is totally unoperable. I can't use it on k-mount film bodies. It's only good for the digital body. I did have another A50/1.7 lens with much better aperture ring, but it had a lot of dust inside so I let it go.

09-10-2009, 12:56 PM   #9
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I'd concur with the overall comparisons in build quality: K and M are generally the same - all metal, solid feeling in all ways, but the M's are generally lighter simply because they are smaller (and hence less metal, and often a simpler optical design too, at least in the shorter forcal lengths). I haven't handled many "A" lenses, but would agree they are more variable, with the A50/1.7 being clearly not as nice as the M overall - but the focus ring is *not* what is noticeably worse in particular.
09-12-2009, 04:29 AM   #10
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As you can see from my signature I have several K, M and one A series lens. My A 100/2.8 macro is all metal and built like a tank. I can't speak for all A series lenses but this one is built. I have seen several A series lenses in which a lot of plastic is evident. This was never the case in the K or M series and in general I think it is fair to say, with some exceptions (A* 135/1.8, A* 85/1.4 etc.) that the K and M series are better built.

While the M series lenses are well constructed they are not, in general, as well built as the K series. I don't think this is just a question of relative size. Both series are all metal of course but Pentax seems to have lavished more attention on the detail in the K series. There is a knurled ridge to assist in attaching and removing the lens on all K series glass. This is not the case in the M series. It is missing on my M 28/2.8, M 35/2, and M 50/1.4 for instance. The lens hoods on the telephotos such as the K 200/2.5 and K 300/4 are also much more substantial than my M 200/4 or M 150/3.5. The rubber on the focusing rings on all K series glass I have held is thicker and wider and the lenses seem to focus more smoothly than my M series. Finally, and again this is totally subjective, the K series just “feel” a lot better to me than the M or A series. If you get the chance hold a K series lens in one hand and an M or A series in the other I think you will come to the same conclusion.

For sheer build quality, of course, nothing compares the old Takumar lenses. These babies seem to have been machined out of solid blocks of aluminium and represent the height of craftsmanship in the Pentax line IMO. Everything else seems like a cheap toy in terms of build quality.

Tom G

Last edited by 8540tomg; 09-12-2009 at 04:39 AM. Reason: typo
09-12-2009, 05:15 AM   #11
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QuoteOriginally posted by pasipasi Quote
My A50/1.7's aperture ring is totally unoperable. I can't use it on k-mount film bodies. It's only good for the digital body.
There is a fix for this.

Pentax 50mm lens fix
09-12-2009, 07:47 AM   #12
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QuoteOriginally posted by tomwil Quote
There is a fix for this.

Pentax 50mm lens fix
Thats indeed a common problem with those plastic A lenses.

General, K series (just the latest takumars with bayonet) have a higher quality build than the M series.
The focussing heliocoid uses brass in a lot of lenses.

The M series uses aluminum on aluminum, also the finish of the first generation M lenses is more like the K series.
Later generations M lenses are clearly cheaper produced.

The A series can be divided in two catagories,
- the high volume lenses (50/1.7, 28/2.8 etc.) have a lot of plastic, heliocoids partly plastic, aperture rings plastic etc.
- the 'expensive' low volume A lenses have similar build materials as the M series.

Also noteworthy is that the takumar-a 28/2.8 is all metal and glass, and the smc-pentax-a 28/2.8 (same optical construction but with SMC) is partly plastic.

George
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