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  1. #1

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    Pentax SMC-M 50mm f/1.7 Not Sharp?

    I know a lot of people say this lens is very sharp, but that isn't my experience. This lens is not able to resolve fine detail at all. I am wondering if this is a normal occurrence or if I may have a lens with abnormally poor performance?

    If this is normal, would the 50 1.4 improve sharpness and fine detail?

    Here are two sample images. The one of the full mouth was taken using the 50mm f/1.7 at f/8. The one of the side of the mouth was taken with the 100mm f/2.8 (not the Macro, the M-series prime) at f/8. Both shot at 1/75; the sync speed of the LX using soft box camera right.

    These were both taken at the same time using the same lighting on the same Pentax LX camera using the same roll of Portra 160 film. The film was scanned using a Plustek 7400 scanner at 7200 dpi, down sampled to 3300 dpi and cropped to the sample shown. The only prints I have are at 4x6, and they both are acceptably sharp at that level of enlargement. It's only blown up, as I would do if printing 11x14, that the 50mm becomes unacceptably soft to me.

    At first I chalked it up to a focusing error on my part, but every 50mm shot on this roll is soft, and every 100mm shot is sharper with more fine detail.

    Any input? Thanks!
    Attached Thumbnails Attached Thumbnails 5017.jpg   10028.jpg  

  2. #2
    Klainmeister's Avatar
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    Seems odd. Have you printed optically above 4x6? I'd be really curious. I have the 1.4 and it's exceptional in every way. I have heard the 1.7 gives it a run for it's money, so i'd be plenty surprised.
    K.S. Klain

  3. #3

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    Of course the macro is going to look like it has more detail, it's closer in. I own the Pentax 50mm f/1.4 M and it's easily the worst 50 i've ever used, by any brand from any time.

    I don't know if I have a bad copy, but it's just got abysmal performance compared to my Nikon 50mm f/1.4G or the Zeiss 50mm f/1.4 I use on my F3. Didn't Pentax make a decent 50mm f/2?

  4. #4

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    I have two 50mm-1.4's, a M and an A version. I am not impressed with either until stopped down to 2.8 or more. Even then they cannot match my 50mm, 2.8 macro, also an A version.

  5. #5

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    Hello,
    your attached pictures are not the best for testing lens performance. Asahi made one of the best 50 mm lens of all times (perhaps besides the Apo Summicron Asph.) the 1:1,4/50 mm SMC-Takumar. The 1:1,8/55 mm and the 1:2/55 mm SMC-Takumar (same construction but rated down to f/2) were also world-class. So I cannot imagine that the 1,7/50 mm SMC-M should be so much worse. Maybe your example is misaligned or a lens is loose. Did somebody tinker with it and reassembled it wrong?

  6. #6
    Pioneer's Avatar
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    At the risk of being a thread killer I am going to repeat what has been said many times, here and on many other forums. We are discussing very old lenses. The M series dates back to the late 70s, which means that many of them are around 40 years old. How many times has that lens been dropped? Has it spent a large part of its life rolling around in a box with other hard objects? Has it been torn apart by some ham fisted repairman, or another do it yourselfer who knew next to nothing, and then re-assembled improperly? For crying out loud, how well will you work at 40 years old? The SMC Pentax M 50mm f1.7 lens is very sharp, in many cases more so than the M 50mm f1.4, and neither lens is a slouch. I own them both and they are both exceptional lenses. In fact, if I were to get rid of either of them, which is not likely to happen anytime soon, it would be the 1.4. The optical formula for a 50mm lens really is not that different between lens manufacturers and each one of their individual 50s have very, very similar designs, whether they are Nikon, Canon, Pentax or anyone else. If someone tries to make you believe different they are wrong. If you don't believe me do some reading, you might be surprised at how similar they all are beneath their brand names. You appear to have gotten your hands on one that has a problem. Do some more testing, toss it in your own box, post it up on E-Bay (as many do), or do the right thing and send it to a competent camera repair person and have it checked out and fixed if possible. But please don't give the impression that your lens is representative of the entire series. It's not!

    Man I am getting grumpy...time to go to bed.

    Happy shooting

  7. #7
    Ian Grant's Avatar
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    I'd be extremely surprised if it's a lens issue. I've used various 50/55mm Pentax standard lenses over the years from f1.4 through to f2 and all have been superb performers. Loss of definition could be movement in this case either the subject or camera shake either way the subject is not ideal for checking a lens.

    Ian

  8. #8
    tony lockerbie's Avatar
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    I don't know, 40 years doesn't sound too old to me! The late seventies were, like, yesterday. Must agree with the sleep deprived pioneer though, as the Pentax 50's are nothing if not sharp. I don't own any K or M series lenses, but do have a truck load of screw mount Takumars including the 50mm 1.4 and 1.8. The 1.4 in particular is my favorite low light lens, even in the single coated Super Takumar, and the 1.8 is no slouch either. Agree with pioneer in that you may have a bad sample so don't give up on these lenses. Like FSU lenses you just keep buying them until you get a good one!

  9. #9

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    As per some of the previous commenters, I've had excellent experiences with Pentax 50mm lenses. My favourite was probably a screwmount Super Takumar 50mm f1.4, but I still have a Pentax-A and Pentax-M 50mm f1.7s, and a Pentax-M 50mm f1.4 and they are all good. I think the f1.7s are slightly sharper than the f1.4, but they are all good.

  10. #10
    Pumalite's Avatar
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    Quote Originally Posted by Ian Grant View Post
    I'd be extremely surprised if it's a lens issue. I've used various 50/55mm Pentax standard lenses over the years from f1.4 through to f2 and all have been superb performers. Loss of definition could be movement in this case either the subject or camera shake either way the subject is not ideal for checking a lens.

    Ian
    +1
    " A loving and caring heart is the beginning of all knowledge " ~ Thomas Carlyle ~

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