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!

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.

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?

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.

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?

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

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

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!

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.

Ian Grant said:

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

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+1

I have plenty of Takumars: Super-Multi-cated are the best; in 50mm f1.4: 55mm f-2

Unless you have a bad example, the M 50mm f1.7 has plenty of sharpness as in my test below only limited by the sensor's resolution.

Link to full size -> Pentax 50mm lenses


I always thought my example M 50mm f4 macro was sharp so I tested the lot using ultra high res Kodak Techpan shot at ISO 25 and developed in Technidol and happy to see that the lenses were not the bottleneck in holding back the resolution.

Link to full size -> Pentax SMC Macro 50mm f4 series

I've been meaning to add my Takumars and others too. I think I have three different versions of Takumars that are 50mm f1.4.

I think it is another case of badly performed comparison. When you compare lenses, the very first thing you do is to use a tripod and a static subject matter. In this case the model might have moved a bit out of focus, and the camera might not have been on a tripod.

Besides, I would clean somehow the noise in the pictures posted, because noise, as strange as it may seem, contributes to the impression of sharpness. Finally, what is posted should be 100% crop (pixel by pixel) taken with a decent film scanner (not a flatbed scanner).

I agree that all the 40mm or 50mm of the last decades (at least before autofocus era) are more or less built according to the same "recipe" and tend to be exceptional performers. The "slower" lenses tend to perform better than the "faster" ones.

Maybe some producer tended to optimise optical performance of 90mm or 100mm at short range, 2 - 3 metres, as those lenses were typically bought as "portrait lenses" and used with people, pets etc. at relatively short distance. So even if not "macro" type of lenses, it might be that at short distance they were better corrected than the normal focal length.

50mm lenses are typically optimized to give best performance at infinite distance as far as I know.

To the OP: If you want to have a definitive answer regarding your lens I suggest you repeat the test with tripod, static subject with full of details. For "static" I mean no trees and no grass they are not static. Something like a newspaper on the wall would be. If the 50mm performs actually badly, then I would keep if for dangerous missions (such as seaside photography or hiking) and buy another 50mm somewhere, they are too inexpensive to bother aligning them.

I sent the lens in and it turns out the main barrel was out of alignment. Eric Hendrickson is fixing it up and CLAing an MX.

brofkand said:

I sent the lens in and it turns out the main barrel was out of alignment. Eric Hendrickson is fixing it up and CLAing an MX.

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Glad to hear that you were able to find the problem. He just returned my M 200mm f4 that needed a bit of adjustment to clear a tight spot in the focus. Even lenses need a little love sometimes.

It was bought used and I just trusted it was good before a shoot---I'll never do that again. Good thing the shots weren't a total loss, and even if the shots were good the close-ups with the 100mm 2.8 were better I think.

This is an important point to keep in mind when acquiring any used gear. I use old lenses on my 8x10 camera, and by old I mean pre WW I old. To get the lenses I now use, there was a selection process - for instance 3 9 1/2" Goerz Dagors were needed to find one good one in a good shutter. Then another good one in a barrel mount came along.... so now I have to get a 5x7 Graflex or Speed Graphic to use it with.

Any used lens, or other used equipment, should be suspect until it has been proven to be a good example.

E. von Hoegh said:

This is an important point to keep in mind when acquiring any used gear. I use old lenses on my 8x10 camera, and by old I mean pre WW I old. To get the lenses I now use, there was a selection process - for instance 3 9 1/2" Goerz Dagors were needed to find one good one in a good shutter. Then another good one in a barrel mount came along.... so now I have to get a 5x7 Graflex or Speed Graphic to use it with.

Any used lens, or other used equipment, should be suspect until it has been proven to be a good example.

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I always just assumed, as I think most people would, that gear purchased used from someone reputable (a longtime member of the PentaxForums site is who sold me the 50 1.7) wouldn't sell a broken lens. I'm assuming the best and believing it got jostled unduly in shipping or he didn't use the lens much and didn't notice the blurriness.

The good news is I will have a newly refurbished example in a few days or so. I'll still run a roll of film through the camera to test it and the lens obviously, but I have confidence in Eric Hendrickson's work. He worked on my LX a few months ago and did a fantastic job.

brofkand said:

I always just assumed, as I think most people would, that gear purchased used from someone reputable (a longtime member of the PentaxForums site is who sold me the 50 1.7) wouldn't sell a broken lens. I'm assuming the best and believing it got jostled unduly in shipping or he didn't use the lens much and didn't notice the blurriness.

The good news is I will have a newly refurbished example in a few days or so. I'll still run a roll of film through the camera to test it and the lens obviously, but I have confidence in Eric Hendrickson's work. He worked on my LX a few months ago and did a fantastic job.

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Well, you just learned that assumptions are unsafe. Even when buying new, you don't know something works until you yourself verify that it works. When buying used, this goes double - if not quadruple. Even though the merchant is honest and reputable, you cannot expect that every item for sale used has been thoroughly tested as it would be at the factory. Usually, it's been eyeballed for obvious flaws or damage and then put up for sale. My experience with the three lenses I mentioned was in dealing with reputable and honest sellers; one lens was returned as unacceptable, one was traded to a friend who didn't care about the unrepairable shutter (which is precisely how it was represented to me), and one was kept and is still used. Oddly enough, I bought this last one as a junk lens at the end of a camera show.
So the best practice is "trust but verify". And never ever use a piece of equipment, be it new or used, on a job until you yourself know it does what it's intended to do.

brofkand said:

I always just assumed, as I think most people would, that gear purchased used from someone reputable (a longtime member of the PentaxForums site is who sold me the 50 1.7) wouldn't sell a broken lens.

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Without testing the image output, its near impossible to identify a problem like that. Most sellers will inspect the item and make sure there is nothing visibly wrong.

E. von Hoegh said:

Well, you just learned that assumptions are unsafe. Even when buying new, you don't know something works until you yourself verify that it works. When buying used, this goes double - if not quadruple. Even though the merchant is honest and reputable, you cannot expect that every item for sale used has been thoroughly tested as it would be at the factory. Usually, it's been eyeballed for obvious flaws or damage and then put up for sale. My experience with the three lenses I mentioned was in dealing with reputable and honest sellers; one lens was returned as unacceptable, one was traded to a friend who didn't care about the unrepairable shutter (which is precisely how it was represented to me), and one was kept and is still used. Oddly enough, I bought this last one as a junk lens at the end of a camera show.
So the best practice is "trust but verify". And never ever use a piece of equipment, be it new or used, on a job until you yourself know it does what it's intended to do.

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Lesson learned the hard way. I can't wait to get the camera and lens back from Eric.

I've used Pentaxes in the past. In my opinion the "star" Pentax lenses were those old Super Takumar lenses for the screw thread Spotmatics. I believe at some stage Pentax stopped making their own lenses and the production of their bayonet mount lenses was taken over by Tokina. At what stage this was I don't know. This is not to imply there was a drop in quality with the change, but those old screw thread Takumars had a certain quality that is not simply defined by lines per millimetre.

rolleiman said:

.....the "star" Pentax lenses were those old Super Takumar lenses for the screw thread Spotmatics......

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I agree. I've been using Pentax lenses for decades, and the older screw-thread Super Takumars are outstanding.