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09-13-2013, 06:00 PM   #1
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Shooting with two similar lenses? what are the differences?

I am having fun playing with some new lenses I found thrift shopping. I am not a seasoned photographer - just someone who likes it and does a lot of trial and error.

So -
What is the difference between SMC pentax-M 1:2 50mm and Pentax-A 1:2 50MM
I am shooting around in the backyard but some insight might be helpful as I trial and error it. I am really liking both!

09-13-2013, 06:24 PM   #2
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With the 'A', you can use all the modes on your camera (P, A, Sv, Tv, TAv, M, etc..) and you don't have to use the green button to meter for the light. You have more creative control.

With the 'M', you can only use Av or M modes, and you need to use the green button to meter for the light.

Obviously with both you do not have autofocus.

I've never had either lens, so optically I do not know the differences.
09-13-2013, 06:28 PM   #3
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Optically I believe they are identical, I have 2 Ms and an A, I can't tell the difference between them. The M certainly has a nicer feel to it, but the convenience of the A can't be beat.
09-13-2013, 11:00 PM   #4
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The M, and A are almost identical, with only perhaps cosmetic differences, and the fact that the A lens, as others have mentioned, allows you to use all exposure modes, including in addition to what is mentioned above, P-TTL flash metering , high speed flash sync, and matrix metering.

With the M lens the flash will fire at full power (for on board flash ) and in manual mode , or auto mode, if supported by a shoe mounted flash. For metering even if you set it to matrix metering, you will get center weighted metering

09-14-2013, 06:45 AM   #5
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QuoteOriginally posted by elliott Quote
Optically I believe they are identical, I have 2 Ms and an A, I can't tell the difference between them. The M certainly has a nicer feel to it, but the convenience of the A can't be beat.
Interesting - I agree the M does "feel" better.
09-14-2013, 09:23 AM - 1 Like   #6
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I have several M 50mm lenses and one A 50mm. Very little difference, but each had its own character. The A 50mm f1.4 is my favorite, M50 f 1.7 next. After that...well I rarely use any of the others...

I notice very little difference in build or "feel" between the two, but the M does seem a tiny bit more solid. I have the A 50 on right now, I use it a lot with my binocular lens rig. I guess the nicest thing is I can use the rear thumbwheel (K30) to adjust aperture whereas I have to use the aperture ring with the M lens.

I rarely use the in camera metering, but when I do it works for both, but it seems to want to change the aperture with the A series lens, so I try no to use it, I'd rather change shutter speed. 95% of the time I set it myself by looking around at the ambient light and I can pretty much tell what shutter speed I need, since I almost always start at ISO200 and f8. From there I can adjust and get it right with no trouble. Usually only one test shot is needed...

Those are both f2 lenses, should do ok, but if you have a chance, pick up a f1.7 or f1.4. I have a couple of f2's, almost never use them the others do such a nice job...I can see a difference, the f1.7 and f1.4 versions are almost always a little sharper. So IF you get a chance at a deal on one, don't pass is by just because you already have a 50mm...I didn't know any of that when I got them, I was shooting film and grabbed used cameras at yard sales, 5 bucks, why not? Only later did I find out I had a couple of good, usable 50mm lenses and a couple of killer I know why...
09-14-2013, 12:59 PM   #7
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The older M50/2s are built similar to the M50/1.7. The oldest are made in Japan, written on the front of the lens. When production moved, they just stopped putting JAPAN on the name ring. Later versions are built like the A50/2s, mostly in Taiwan. That might be the reason they feel different.

The coating looks less complicated on the f2 lenses than all others, making me suspect it's not as good. I suppose I should test this some day.

09-14-2013, 02:57 PM   #8
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The 2.0 has 5/5 elements/groups, the 1.7 has 6/5.
The 2.0 has a smaller diameter of most or all of the elements.
With the 2.0, the front lens sits much deeper inside the tubus, which acts a bit as a shade.

These combined facts mean that the 1.7 needs a better coating to reach the same flare resistance as the 2.0. Maybe that's why Pentax has saved a bit on the coatings of the 2.0, without risking to worsen flare resistance too much.

When I bought my first (new) Pentax lens in 1981, it was the M2 (DM 99), because the M1.7 was 50% more expensive.

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