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05-06-2012, 03:26 PM   #1
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50mm 1.7 Pentax-M vs Pentax-A

I'm new the world of old lenses, having only my kit lens on my K5 so far. A good start would be to get a fast 50, and most people agree that the F1.7 model is pretty great.

Would you recommend going with the Pentax-M or Pentax-A 50mm F1.7? From what I understand, the M model takes more work. You can only shoot in M, not AV - you have to manually stop down to meter with the green button, and manually set the aperture on the ring, whereas with the A you can just switch the aperture to A on the lens, use the aperture e-dial on the camera, and it meters like a normal lens. Is that right?

But I've also read that the A series has noticibly worse mechanical construction than the M series, with more plastic, crappier focus ring, etc. Is that true?

What about optically? Are they the same lens optically, or does one perform better than the other?

Can both lenses be used with the catch-in-focus mechanism on the K5?

Eventually when I have more money, I may end up getting the F or FA version of this lens too. Are those just as good as the older lenses in optics?


Last edited by SenorBeef; 05-06-2012 at 03:36 PM.
05-06-2012, 03:38 PM   #2
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I can't say much for the A50 F1.7, but I do have the A50 F2.8 macro and the M50 F1.7. Now, no doubt the A50 1.7 and A 50 2.8 macro aren't exactly the same lens, but I think it gives me at least an idea of the A50 general lens construction.

Advantage of A lenses: Tv, Av, etc. Av is my primary shooting mode when I can.

The M50 is most definitely better constructed, but the A50 isn't anything to complain about either. Focus is still long throw and the ring is still smooth and pleasant, with the M being just a little firmer (which I like). That could be the difference between the Macro and the non macro though, so don't take that too much to heart.

I BELIEVE I remember seeing that the M50 and A50 1.7s are the same optical formula.

TL;DR version: I like both, I wish I had A, but i'm very pleased with my M and wouldn't give them up. I like it so much I have 2.
05-06-2012, 03:39 PM   #3
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AFAIK all Pentax 50 f/1.7 have the same optical formula. I have both the M and the F version, both of them are very good.

As you already know, the M version only works correctly in manual mode (and wide-open only in Av); the M also doesn't allow advanced functionality with external flashes (that is, HSS and wireless using the built-in flash as a trigger). So, basically, if you have an external flash, you want the A or one of the autofocus versions. If you don't use a flash, the M version will get a little getting used to but it is not that difficult to use.
05-06-2012, 04:36 PM   #4
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Go for the F version... If not then go A... The build 'is' solid (its just that the 'm' lenses are built like tanks) and its a much quicker process when actually in use... The green button is a great feature when using 'M' lenses but having to use it less is better when trying to get the shot...

Also, I find my 'M' lenses often underexpose by a stop, whereas my A, F & FA's tend to hit exposure bang on much more often... Though again not really a big problem in post...

You'll be happy with whatever Pentax 50-1.7 you get...

05-06-2012, 08:12 PM   #5
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Get what ever 50 1.7 you can get your hands into. I have both. I have an A and I have an M. A is much more convenient because it has the "A" aperture settings meaning you can see your exposure meter in your viewfinder compared to M where you absolutely need to use the green button (K7). And for some reason I like the look of the A lens more vs the M, once mounted in my camera. But still, my favorite lens is the M, I like the feel of it, every time I hold it. that cold piece of awesome glass in my hands just makes me smile.
05-06-2012, 09:00 PM   #6
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I ended up buying a Pentax-M 50mm in good shape for $48, so I'm happy. I'll see if the stop down metering thing is enough of a pain to upgrade to A or FA, but I kind of like the idea of having at least one full manual lens to learn photography the old
fashioned way.

If you're using the lens at 1.7, can you use it in AV mode and have it meter continuously? Since in that case the metering/focusing aperture and the shooting aperture would be the same.

Unnecesary minirant: A couple of months ago a guy on craigslist was selling a Pentax film body (forget which one) with its kit lens, which was the FA-50mm, and he wanted $50 for the whole package. So I responded to him, and asked if I could come out tomorrow to pick it up. He says tomorrow is fine, so I call him the next day... and.... "oh, I already sold it".... damn. We had a deal, and I almost snagged the FA50 (and a camera too!) for $50. Oh well.
05-06-2012, 09:26 PM   #7
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QuoteOriginally posted by SenorBeef Quote
I ended up buying a Pentax-M 50mm in good shape for $48, so I'm happy. I'll see if the stop down metering thing is enough of a pain to upgrade to A or FA, but I kind of like the idea of having at least one full manual lens to learn photography the old
fashioned way.

If you're using the lens at 1.7, can you use it in AV mode and have it meter continuously? Since in that case the metering/focusing aperture and the shooting aperture would be the same.

Unnecesary minirant: A couple of months ago a guy on craigslist was selling a Pentax film body (forget which one) with its kit lens, which was the FA-50mm, and he wanted $50 for the whole package. So I responded to him, and asked if I could come out tomorrow to pick it up. He says tomorrow is fine, so I call him the next day... and.... "oh, I already sold it".... damn. We had a deal, and I almost snagged the FA50 (and a camera too!) for $50. Oh well.
I'd say when you get a chance pick up the A version as well, having the lens be completely auto (aside from focus) definitely has its advantages. To your question about leaving the lens at f1.7 in Av mode you are correct, it will be properly metered - you actually don't even need to set it to f1.7, as it will meter and shoot wide open in Av mode regardless of the aperture ring setting.

To the unnecessary minirant - been there, done that! If you're not willing to drop everything to go get something, there is probably someone else who is, so if you're on the look-out be sharp!
05-06-2012, 11:44 PM   #8
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Are these lenses designed to work without a hood? In all the lenses I've seen up for sale, none have mentioned having a hood included. Are there third party hoods?

05-06-2012, 11:54 PM   #9
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Using a hood is always a good idea, apart from increasing contrast in many situations, especially wide open, they add useful protection to the lens. For my 50's (A and M version, plus a 55-m F1.8) cheap screw in rubber hoods from e-bay are a godsend. The A and M 50s are both threaded at 49mm which is a common size for Pentax. Enjoy your new lens!
05-07-2012, 02:20 AM   #10
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When I saw the difference a hood made to my FA50 (and WHAT a difference!!) I went and got hood for all my lenses... Increasing contrast makes your lenses 'look' sharper in the their produced images..
05-07-2012, 08:37 AM   #11
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INdeed, what Dave and Stephen have said. I got a cheap 49mm metal hood that screws into mine. If you end up getting a lot of manual glass, like many of us do (curse you, LBA), you'll find that 49mm is a very common filter thread. The hood I got is meant for 35 and 50 mm. It's just a round thing that screws into the filters. Next on my agenda is a rectangular hood
05-07-2012, 08:40 AM   #12
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Another vote for hood, especially for older lenses. That will make a huge difference.
05-07-2012, 09:14 AM   #13
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You can use a longer hood when using a 50mm on a crop body. The hood from the Takumar 135mm 3.5 works perfect.
05-07-2012, 10:38 AM   #14
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May have screwed myself a bit on this one. This particular lens has a bend on the outer part of the lens. I figured it was nothing that would affect function and probably took a few bucks off the price. How exactly do the hoods attach?

Would that bend prevent me from attaching a hood, or do you mount them on the outside of the barrel?
05-07-2012, 10:54 AM   #15
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There are some clip ins, but at the very least you'd still need to take some pliers or something and straighten it out. CAUTION - this may wreck the the threads more. If you're careful and use cardboard or something to keep from screwing up the threads, you may be able to get this to the point where you can use a filter to help straighten it even more. I have a takumar 50 f1.4 that has dinged filter threads from what looks to have been a similar ding, but I can put my hood or filters on it after whoever had it before me straightened it.

So, in essence, not all is yet lost, but it oculd take some work, and you may need to be careful. I

One thing to think about, is taking the glass out of a really cheap filter and putting that filter on the lens as a permanent filter thread replacement. Screw it on anyway you can, maybe locktite it in place, and now you've got good filter threads again.
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