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07-18-2010, 12:25 AM   #1
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M-Series primes vs A-Series

I've just pulled the trigger on a k-x (with a Sigma 17-70) and I'm thinking of grabbing a couple of cheap(ish) manual focus primes. I've read about M-Series primes needing to use a stopdown metering workaround.

I'm wondering how difficult/annoying/limiting using stopdown metering is? For example, can I use a focus screen (e.g. Katzeye) and still stopdown reliably? In short, is it really worth springing the extra cash for an A-Series with the extra aperture capability it provides?

07-18-2010, 12:42 AM   #2
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QuoteOriginally posted by nlilith Quote
I've just pulled the trigger on a k-x (with a Sigma 17-70) and I'm thinking of grabbing a couple of cheap(ish) manual focus primes. I've read about M-Series primes needing to use a stopdown metering workaround.

I'm wondering how difficult/annoying/limiting using stopdown metering is? For example, can I use a focus screen (e.g. Katzeye) and still stopdown reliably? In short, is it really worth springing the extra cash for an A-Series with the extra aperture capability it provides?

In my oppinion, no. They usually fetch MUCH more than their M equivalents, and I personally don't mind pressing the green button every once in a while so its a no brainer for me.

Focus screens IIRC only affect spot metering, whether its an A or M lens.
07-18-2010, 01:54 AM   #3
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Well, problem is that K-x CAN'T change focusing screens. So you can't use other than original focusing screen that you have now.
As for stop down metering, it depends on camera (from my experience) My K10D is kind of all over the place, my wife's K-x is better but not quite there, according to users, K-7 is the best in this respect. Personally I managed to get used to my camera-lens combo and surrounding conditions. That means, I do green button, take 1-2 test shots check histogram and adjust if necessary. After that, I don't use green button anymore, only adjust Tv depending if I'm in shadow or brighter light etc... it takes a while to figure this out and get your skills up to level where your exposures will be correct when conditions change but it's doable, and it makes you think more about the shot you want to take.

Aside from that, Ms a regarded as the smallest Pentax glass, optically I believe it's a wash. 50s, 28s 24s are the same. Some advantage of As is that you can use automatic (PTTL) flash. With Ms you can't.
Looking at the money As command, I'm with yeatzee on this one, unless you really don't need the f stop info (whether for your thing or flash) the A series is not so much worth than M.

BR
Peter
07-18-2010, 03:24 AM   #4
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QuoteOriginally posted by axl Quote
Well, problem is that K-x CAN'T change focusing screens. So you can't use other than original focusing screen that you have now.
Dear Axl, fortunately it is not so: K-x and K-m/K-1000 can very well change focusing screens. See katzeye et al web sites.

Regards, daniel

07-18-2010, 04:05 AM   #5
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I use all A series now (except for 28mm shift) purely for ease and speed in use.

There's some rather nice fast glass in the A series too.
07-18-2010, 04:10 AM   #6
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both will work well. A are more convenient but more expensive. You can more easily fine-tune aperture steps with A lenses, that's another perk. Yoir budget should decide.
07-18-2010, 04:43 AM   #7
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The OP might also consider the predecessor of M: the K series. K series inherit a lot from their takumar "parents", some are even completely identical apart from the mount. M series were mostly complete redesigns trying to reduce size, weight and... price.

M series feature a number of gems (M 2/85, might be compared to FA 77) and excellent lenses (M 4/20, M 3.5/28, M 3.5/135 come to mind). So does the K series with gems (K 2.5/135) and excellent lenses (K 3.5/28, K 3.5/35). (subjective examples)

So to choose from K- M- or A series might well be a matter of the particular focal length envisioned, leading to consider far more criteria than just the "A" setting or the market price.

Last edited by danielausparis; 07-18-2010 at 04:52 AM.
07-18-2010, 05:23 AM   #8
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I’ve got a bag full of K and M series glass and only one from the A series – the A 100/2.8 macro. The A series is certainly far easier to use but that shouldn’t preclude your exploring the K or M series. You might find working with them a bit difficult at first but once you get used to them it won’t be a problem. There are a lot of good lenses in both series. As for metering issues I use a KatzEye screen with optibright and the only issue is with spotmetering on the K10. No problems with center weighted metering.

In terms of build quality I think you will find the K series is the larger and features the most robust build quality. The Ms, designed for use with the diminutive M Series cameras, are quite a bit lighter/smaller and almost as well built with many accepting a less expensive 49mm filter. While also very good I don’t think the A series, with some exceptions, as a group are quite up to the build quality of the K or M series. This seems to be true of the 28 and 50mm lenses I have seen. This may not hold true for the entire group as my A 100/2.8 is built like a tank.

Optically, as Axl said, it is pretty much a wash as there are no real dogs to be found in any series. That being said I prefer the “look” of the images I get from the K series. This is subjective of course and opinions will vary. The A series also has some the “consensus” best lenses Pentax ever made such as the A* 85/1.4, A* 135/1.8 and A* 200/4 macro.


In any case have fun exploring the various groups.

Tom G

07-18-2010, 05:31 AM   #9
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I also have quite a bit of older glass in my bag. I do believe that the inconvenience and inconsistency of metering the M and K series lenses justifies the price difference in most cases. When changing from an A lense to an M lens, it is just too easy for me to forget to press the green button first, and the buttons on the various bodies are not in exactly the same place. That is not to say I don't use them, but the convenience factor would definitely be worth a premium to me.
07-18-2010, 07:50 AM   #10
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As long as you realize that you will run out of metering range from time to time with stop down metering, then most of the pre A lenses will do fine.
07-18-2010, 09:06 AM   #11
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QuoteOriginally posted by GeneV Quote
I also have quite a bit of older glass in my bag. I do believe that the inconvenience and inconsistency of metering the M and K series lenses justifies the price difference in most cases. When changing from an A lense to an M lens, it is just too easy for me to forget to press the green button first, and the buttons on the various bodies are not in exactly the same place. That is not to say I don't use them, but the convenience factor would definitely be worth a premium to me.
With shorter focal lengths using M glass is fine as one is more likely to be more landscape and background oriented to set up the shot.

For longer lenses, auto-aperture and metering becomes more of an issue, especially if you have a moving subject. The more telephoto seeking a subject, the more likely you will move to another metering range.

The inflection point is, natch, 50mm IMO.
07-18-2010, 09:22 AM   #12
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QuoteOriginally posted by Wheatfield Quote
As long as you realize that you will run out of metering range from time to time with stop down metering, then most of the pre A lenses will do fine.

Thank you Wheatfield for pointing out the low light limitations of stop-down metering. It is one of my pet peeves and I thought I was the only one on this forum who knew that meter response goes flat in dim light when stopped down. The meter may be linear to EI 1@100 at the sensor, but that comes quickly when you stop the lens down.

With the K-x and K-7 green button, stop-down metering work quite well. The main issue with A vs. non-A lenses in my opinion is the matter of build quality. All of the K and M series lenses feature high quality all-metal build. Plastic was introduced in the A series and some lens models suffered as a result.


Steve
07-18-2010, 09:59 AM   #13
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BTW, if you're curious about the specific procedure for using fully manual lenses like the M series, see the sticky thread at th top of the Beginner's forum.

In my view, the big difference isn't so much in the need for stop down metering per se, but in the fact that fully manual lenses require M mode. If you are not accustoemd to using that mode, that takes some getitng used to. On the other hand, if you typically use M mode anyhow even with your more automatic lenses, you're already used to hitting a button or turning a periodically (when the light changes) to adjust expousre. Whether pressing the button actually performs the stop down operation before setitng a shutter speed for you or not is immaterial. Not having a full time metering display is unfortunate, but DOF preview gives you one any time you want, and that becomes second nature quickly enough.

So I'd say if you don't already use M mode much, give that a shot for a while, and that will give you some idea of what using an M lens is like. You might find - as I did - that you end up liking M mode so much you stay there all the time, even with your most modern lenses.
07-18-2010, 10:47 AM   #14
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QuoteOriginally posted by danielausparis Quote
Dear Axl, fortunately it is not so: K-x and K-m/K-1000 can very well change focusing screens. See katzeye et al web sites.

Regards, daniel
How so?
according to every specs I found (our very own camera review section on pentaxforums included) K-x does NOT have exchangable focusing screen....
07-18-2010, 10:48 AM   #15
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QuoteOriginally posted by Marc Sabatella Quote
In my view, the big difference isn't so much in the need for stop down metering per se, but in the fact that fully manual lenses require M mode.
I sometimes forget to go to M mode after a lens change or bump the dial. Then all my pics are taken with the aperture wide open. That's OK with some lenses but better with others.
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