[I robert]

Is it worth investing in M SERIES lens for digital cameras as A SERIES on seem to work better thoughts.

[pres589]

Compare the reviews and see. I don't think there are any lenses that are exactly common to both the M and A lines that don't perform better on the A version. There are, however, some lenses that use different optical designs or don't exist in both M and A version. 50mm Macro, for instance; M version is classic Tessar and max f4, A 50 Macro goes to 2.8 and is of a different optical design. Or the M 85 f2 which doesn't exist in the A line; there, the closest match is probably the A* 85 f1.4. Both seem excellent (I've owned neither) but are very different lenses.

On k-mount lenses like an M, on a DSLR like my K-5 II, I use M mode and use the DoF Preview to activate the light meter "needle" output to tell me how I'm doing with the exposure and aperture I've picked. I think it works quite well and prefer it to the Green Button. Having a decent sized top-plate LCD helps. Not knowing which body you're wanting to use with an M lens makes it hard to know if you'd have a similar experience.

The M's all seem well made from what I remember, they were intended to be small for the focal length of the lens vs. the K's before them or competitor's lenses, and most of them seem like good performers. My M 50 f1.4 is a decent lens in my opinion; I find that I like using it more on a film body than my K-5 II. I don't think that having in-body aperture control would make me like it any more than I do now. Autofocusing would; I wouldn't care if I still controlled the aperture with the ring if it had AF.

[ChristianRock]

For investment? Probably not...

As for taking pictures, they are quite capable. The look of the pictures, IMHO, is a bit more natural in the M models than the A series, and I love the A series. That of course is a generalization - within each individual lens model there will be differences, so you're probably better off judging the lenses by themselves rather than as a part of a series.

What you do probably know already is that the A series provides aperture automation via camera controls, allowing for all program modes to be available. In the M and previous series, the aperture needs to be set on the lens itself and when using Pentax DSLRs the lens needs to be shot in M mode, or wide open in Av mode. M mode allows for stop down metering.

This might help:

https://www.pentaxforums.com/forums/122-lens-clubs/32801-club.html (A Club)
https://www.pentaxforums.com/forums/122-lens-clubs/27739-m-club.html (M Club)

[baro-nite]

A-series lenses are certainly more convenient to use, because the contacts on the lens mount allow the use of all exposure modes. That's the main reason they cost more than the equivalent M-series lenses. Unless you are a collector, it is probably more helpful to compare specific lenses for specific needs, rather than entire lens series.

[TaoMaas]

Regardless of series, most Pentax prime lenses are good performers so I wouldn't worry much about whether a lens is a K, M, or A mount.

[Adam]

If you're fine dealing with stop-down metering, manual lenses do have pretty decent optics (and are a great value). A lenses and newer are more convenient to work with, though.

[stevebrot]

Is it worth investing in M SERIES lens for digital cameras as A SERIES on seem to work better thoughts.

Thoughts:

• The main advantage to A-series is that the aperture may be controlled by Pentax dSLR bodies allowing for full exposure and flash automation on those cameras
• P-TTL flash with A-series lenses is not as reliable as with auto-focus lenses
• With few exceptions, A-series primes are equivalent optically to M-series primes of the same focal length/maximum aperture
• Build quality of K and M-series lenses is better than any of the plastic-construction A-series. Metal-bodied A-series have the same build quality as the earlier lenses.
• One should expect to pay a modest premium on price between equivalent M and A series lens with emphasis on modest
• I own two A-series lenses
  • Pentax-A 50/1.7 -- lives on my Super Program film camera and seldom used on the K-3. Funky aperture ring (almost all are non-functional or headed that way) makes for limited utility with bellows or extension rings.
  • Pentax-A 70-210/4 -- Very decent tele-zoom that performs well above its usual sale price...high recommended (nice build too)

Unless one is thoroughly intimidated by the prospect of full-manual operation on Pentax dSLRs, my vote typically goes with M-series unless price is very close to the A-series equivalent.


Steve

[pschlute]

You have had some good advice.

I would add that there are some stand-out lenses in the M lineup:

M 20 f4 a great wide-angle
M 40 f2.8 probably not for it's image qualities but for it's design
M 50 f1.7 for being simply the workhorse of thousands of pentax photographers and a lovely sharp lens
M 85 f2 a very compact fast portrait lens
M* 300 f4 a very classy telephoto
M 2000 f13.5 reflex (I wish I owned one)

[tvdtvdtvd]

Pentax-A 70-210/4 -- Very decent tele-zoom that performs well above its usual sale price...high recommended (nice build too)

Except for zoom creep. My copy was so bad to be almost useless. If the lens wasn't level the zoom would slide like a well lubed trombone. I absolutely
had to hold the focus/zoom barrel at all times to avoid creep. I'll admit I prefer primes as a general rule and thus my experience with K/A/M series zooms is
very limited, starting and ending with the A 70-210/4. However, that zoom creep was bad enough to make me wary of ANY zoom with a push/pull zoom
barrel.

Otherwise, very nice comparison of the M & A series.

[DW58]

I just got my first M series lens yesterday. A 50mm Macro f/4. I'm going to like this lens. So far I've just had the aperture on the lens set to f/4 and camera in Av. No need to use green button to meter. Changing ISO to get the shutter speed I want. Works pretty good.
Only other manual lens I have is an A series 50mm f/1.7. Set the lens aperture to A and I'm good to go. I wish I had got interested in manual lenses earlier as it seems prices have been going up recently. I plan on buying a few more.

[Cerebum]

I have the M 50mm f2 because it was ludicrously cheap (£20), the m 135mm f3.5 which is brilliant and was also pocket change (£25) and an m 200mm (£39 in its original box and case). All are built to survive a nuclear war, the longer ones have built in lens hoods and are a delight to use. So you are in Manual mode, and are in control of pretty much everything! I see that as part of the appeal! Sometimes it is nice to step back and slow down. I would like to get a full set of M primes but sadly prices are beginning to climb, what the hell, I am not going anywhere you never know, if I hit enough charity shops I may stumble across a 20 or 30mm, maybe, ..... one day? buy a nice, very cheap M 135mm f3.5 and feel the love, you know it makes sense

[I robert]

thanks some good info

[Cerebum]

I just noticed a 200mm for £17 on fleabay. They are still out there

[lytrytyr]

Is it worth investing in M SERIES lens for digital cameras as A SERIES on seem to work better thoughts.

The M series 50/1.4,
with its flatter cemented join,
seems to be optimized more towards infinity
than the other Pentax 50/1.4 lenses.

And the M 20/4 is about as compact
as a full frame super-wide can get.
Beautiful color rendering,
but weird mustache distortion
and softer at landscape distances.

[pschlute]

So you are in Manual mode, and are in control of pretty much everything! I see that as part of the appeal!

Exactly. Spend a day with any lens in manual mode and you will learn more about exposure than in a year using an auto setting.

---------- Post added 04-03-18 at 11:29 PM ----------

I would like to get a full set of M primes......... if I hit enough charity shops I may stumble across a 20 or 30mm, maybe, ..... one day?

You will be lucky if you find a M 20mm, but you wont find an M 30mm