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12-22-2015, 05:47 AM   #1
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SMC Pentax A f1.4 50mm VS SMC Pentax M f1.4 50mm

Hello,

This is my first post on here. I moved from Nikon recently and bought the K3ii. Which I am very happy with. To date my best lens is the SMC Pentax A f1.7 that I picked up for 30.00 and one of the reasons I moved to Pentax (I'm not a rich man!). I have managed to get some nice shots from it.

I'm interested in the f1.4 version of the lens and was wondering what the difference between the A and M versions was (aside from the obvious!)

Is everything the same save for the M being fully manual? If that was the case I will opt for the M. It is obviously more hands on, but also a bit more fun and satisfying when you get a shot you really have to work for (IMHO) and it's cheaper (I'm a Yorkshire Man, what can I say!).

Thanks for any help.

12-22-2015, 07:04 AM   #2
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Optically the M and A 50mm F1.4 are the same, so go for the M since you are ready to settle for stop down metering.
12-22-2015, 07:57 AM   #3
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QuoteOriginally posted by Ole Quote
Optically the M and A 50mm F1.4 are the same, so go for the M since you are ready to settle for stop down metering.
I don't think that is quite correct, even though this forum's lens review section uses the same optical design picture for both. This is the M 50 1.4 according to Bojidar Dimitrov:



And this is the A/F/FA 50 1.4:



The number of elements/groups is the same (as it is with most 50 1.4 designs) but the elements themselves are quite different.

Usually, people say the A is the better design, but I haven't had either. My 50 1.4 is a Rikenon. But honestly I don't think they'll be that different in real world pictures.
12-22-2015, 07:59 AM   #4
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There's a reason that the A lens is more expensive. I'd much rather have the A, since the camera knows the aperture and metering is automatic and changeable within the camera by the control wheel. You won't have to do stop down metering which is inconvenient and much less accurate, nor have to play with the aperture ring when you want to change aperture. Plus, with the A, you'll have the aperture data in the EXIF file.

12-22-2015, 08:06 AM   #5
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On the contrary I would tend to advise the A, because it "works the same" as your other lens and you will not constantly be adjusting your methods as you change lenses (with the risk of fluffing one or more shots if you are in a hurry). On the other hand, if you intend to get rid of the f/1.7 either in exchange or to support the purchase, this does not apply so much.
12-22-2015, 08:12 AM   #6
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The 1.4 is a it softer wide open (nice for portraits), but very sharp by F5.6, and it has a nicer bokeh (8-blades vs 6).

I have all 3 manual focus k-mount 1.4s, but I really only use the A on a DSLR.
12-22-2015, 08:18 AM   #7
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Build quality is better on the M series. The aperture rings of A lenses have a more plasticky feel and don't click nearly as smoothly. I guess though if you're gonna leave it parked in the 'A' position, that might not matter that much.

FYI, I just picked up the lens cousin A50/1.7 off eBay and the difference in build is clear. Weirdest thing is that someone had switched the mount flange on it with one from an A50/1.4 - I could tell this by the aperture contact pattern on the back and a "gap" around the rear element. Lens works fine but of course the cam thinks it's a 1.4 and starts at 1.4. Caveat Emptor!
12-22-2015, 09:29 AM   #8
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There is also the K50/1.4 to consider, as well as the various Takumar 50/1.4's.

Phil.

12-22-2015, 09:35 AM   #9
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QuoteOriginally posted by ChristianRock Quote
I don't think that is quite correct, even though this forum's lens review section uses the same optical design picture for both.
Dimitrov is authoritative, but not always accurate. IIRC*, lens reviews from that time were explicit that the optics for both the 50/1.4 and 50/1.7 were carried over unchanged from the M to the A series. Perhaps Jussi (Nesster) will weigh in. He has scans of most of the published lens reviews from that era.


Steve

Last edited by stevebrot; 05-13-2016 at 10:51 PM.
12-22-2015, 09:42 AM   #10
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So...If the optics for the 1.4 were carried over from the M to the A, the only real drawback of the M is the lack of aperture data in the EXIF file and light metering, which is just a press of the green button or a DOF preview which is right next to the shutter button, so not much effort required, unless I am mistaken. On the plus side build quality is better and the M seems to be half the price.
12-22-2015, 09:43 AM   #11
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QuoteOriginally posted by digital029art Quote
Build quality is better on the M series. The aperture rings of A lenses have a more plasticky feel and don't click nearly as smoothly. I guess though if you're gonna leave it parked in the 'A' position, that might not matter that much.

FYI, I just picked up the lens cousin A50/1.7 off eBay and the difference in build is clear. Weirdest thing is that someone had switched the mount flange on it with one from an A50/1.4 - I could tell this by the aperture contact pattern on the back and a "gap" around the rear element. Lens works fine but of course the cam thinks it's a 1.4 and starts at 1.4. Caveat Emptor!
Well, that is not good. How is the camera-set aperture as compared to the aperture-ring set aperture? (Check in B mode at f/1.7 and f/22.)

As for the build quality...yes, many of the A-series lenses are very plasticky, though I believe the A 50/1.4, along with several other models, is full metal build.


Steve
12-22-2015, 09:52 AM   #12
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QuoteOriginally posted by stevebrot Quote
many of the A-series lenses are very plasticky, though I believe the A 50/1.4, along with several other models, is full metal build.
You can get A series lenses that essentially look like F series lenses without autofocus, and I've even heard tell of rare, late M series lenses that were built with the contacts (thus in effect making them pre-production A models).
12-22-2015, 09:57 AM   #13
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In some ways the Pentax 50/1.7 formula is better than the 50/1.4. It is generally sharper. Unless you particularly want that extra 1/3 stop of speed and or the slightly thinner depth of field at max aperture, consider a different focal length for your next lens.
12-22-2015, 10:25 AM   #15
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QuoteOriginally posted by plunkstar Quote
So...If the optics for the 1.4 were carried over from the M to the A, the only real drawback of the M is the lack of aperture data in the EXIF file and light metering, which is just a press of the green button or a DOF preview which is right next to the shutter button, so not much effort required, unless I am mistaken. On the plus side build quality is better and the M seems to be half the price.
You are a small bit mistaken. Yes, you can do stop-down metering with the M-series lenses, but the meter is limited to center-weighted averaging only and may not be fully reliable as compared to open-aperture reading with the A-series lens equivalent.

The advantages of A-series over M-series on a Pentax dSLR go like this:
  • All exposure modes fully supported*
  • Better meter accuracy**
  • All three meter modes supported (matrix, center-weighted, and spot)
  • P-TTL flash support***
  • Exif includes set aperture
I shoot with both A-series and M-series lenses and would choose A-series over M-series for general shooting. That being said, I also would not pay a high premium just to get the "A" contacts. Some consider stop-down metering an inconvenience and I generally concur, though I learned on and currently own several stop-down meter film cameras. In practice, I swing both ways fairly easily.


Steve

* When "A" contacts are not present, all modes except M, B, and X default to Av mode at maximum aperture only.
** The reasons for this are complex, but stop-down metering with even current model Pentax dSLRs is not fully linear with most lenses nor will there be consistent agreement with a wide-open reading for the same subject. This is a general problem across dSLR brands.
*** P-TTL support for A-series lenses is not as good as for AF lenses, but at least works for most subjects.

Last edited by stevebrot; 12-22-2015 at 10:37 AM.
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