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07-16-2012, 05:48 PM   #1
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SMC-M Pentax 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.

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.

Any input? Thanks!


Last edited by brofkand; 12-29-2013 at 10:29 AM.
07-16-2012, 06:11 PM   #2
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If you are taking them on film I don't think the problem is the lens. I would think everyone would need more information before making a final determination though.

How big were the original shots? Were they portraits that you blew up? Or were they group photos where you cropped down?

I think your problem is the film, not the lens.... just my two cents. I don't own the M version of the 1.7 but I do own the A version of it...I can compare and contrast if you would like to see it digitally.
07-16-2012, 06:12 PM   #3
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Brof, You put up thumbnails ???
https://www.box.com/s/iada51c2ublkjgznvkcs
here is a ~ 3 MB image of a test shot camera jpg , in this case the XR Rikenon 1:1.4 50mm
I expect your lens will be quite similar.
07-16-2012, 06:32 PM   #4
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i happened to take a picture of a robot chess set i made years ago before throwing it away jsut now and saw this post.
i chose my m50 1.7 because of it's sharpness

...also it happened to be on my camera and i didn't feel like switching lenses... that might have had something to do with it to.

either way, here is the pic, and the 100% crop, completely unedited jpegs from the camera, just resized/recropped to 500px in GIMP.

note that there is dust on the figurines from sitting in storage for years, most noticeably on her 2 pom-poms, that is not jpeg artifacts the lens rendered the dust pretty well!

i should note that this is digital not film, but i think it shows how sharp this lens is... also this was taken 1/20 handheld so on a tripod it may have been even sharper...

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Last edited by dominikkolendo; 07-16-2012 at 06:38 PM. Reason: added more info
07-16-2012, 06:34 PM   #5
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I put up thumbnails because there's no need to see the full image---what is needed to get the point across is shown.

At first I chalked it up to poor focusing on my part, but every 50mm shot is uniformly blurry like this, and every 100mm shot is sharper. I grant the shots may not be as sharp or detailed as what one would get from a K-5, but they are comparable since they are from the same medium.

I don't think it's the film or the scanner, since you can clearly see much more detail in the 100mm lens. And you can't blame it on the processing either, since it's the same roll of film processed by The Darkroom in San Clemente.

I am asking if you guys think this is a fault of the lens, or some other phenomenon. If it is just the limit of the lens, what would be a good lens to upgrade to? Is the 50 1.4 any better?
07-16-2012, 06:48 PM   #6
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QuoteOriginally posted by brofkand Quote
I put up thumbnails because there's no need to see the full image---what is needed to get the point across is shown.

At first I chalked it up to poor focusing on my part, but every 50mm shot is uniformly blurry like this, and every 100mm shot is sharper. I grant the shots may not be as sharp or detailed as what one would get from a K-5, but they are comparable since they are from the same medium.

I don't think it's the film or the scanner, since you can clearly see much more detail in the 100mm lens. And you can't blame it on the processing either, since it's the same roll of film processed by The Darkroom in San Clemente.

I am asking if you guys think this is a fault of the lens, or some other phenomenon. If it is just the limit of the lens, what would be a good lens to upgrade to? Is the 50 1.4 any better?
My opinion= not the lens.
07-16-2012, 06:49 PM   #7
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QuoteOriginally posted by alamo5000 Quote
My opinion= not the lens.
What's causing it then?
07-16-2012, 06:56 PM   #8
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my first lens upgrade from the kit back in the day was the FA 50 1.4...
i found a deal on the 1.7 (20 bucks!) and bought it.
after a month or 2 i found that i used the 1.7 and had the 1.4 in my lens bag.
i sold it for 250 and felt like i made the greatest profit of all time.
its just a sharper lens, doesn't purple as much, and even though its manual focus, i never trusted the autofocus much in low light which is why i needed a large aperture in the first place.
i don't know anything about film, but i can tell you that, based on my experience, maybe you need clean or calibrate your lens or something.
if my example didn't show it then that's all i got.

07-16-2012, 06:57 PM   #9
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QuoteOriginally posted by brofkand Quote
What's causing it then?
Since I don't know what your whole set up looks like or the details of the photos its hard to say.

If you are cropping down like mad crazy (ie cropping onto someone's face in a group photo) that's one thing... if you are cropping a portrait of someone's face that's another.

Also need to know your focal distance what kind of light and all sorts of things.

My experience tells me to experiment a little. Try stopping down some. It could be any number of things. Each lens has sweet spots and may not be tack sharp from end to end...

I cannot say with any reasonable confidence what I 'think' it is with the basic information provided...
07-16-2012, 06:59 PM   #10
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I'm going to do some more non-portrait testing of the 50mm.

Going to go out tomorrow with Ektar 100, Delta 400, the 28 2.8, the 50 1.7, and an MX and LX. Hopefully I'll get some good samples.
07-16-2012, 07:21 PM   #11
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The 50mm f1.7 (M) is a very sharp lens, and the f1.4 will not do better. I have super Tak 50mm f/1.4, K 50mm f/4 and M 50mm f/1.7, and for most applications the f1.7 is the sharpest IMO. Likely your lens was dropped/faulty repair/or the like.
07-16-2012, 07:28 PM   #12
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QuoteOriginally posted by brofkand Quote
I'm going to do some more non-portrait testing of the 50mm.

Going to go out tomorrow with Ektar 100, Delta 400, the 28 2.8, the 50 1.7, and an MX and LX. Hopefully I'll get some good samples.
That is the best thing to do---test. Log. Note everything. Take your time and get focus every time.

I just ran some 'test pics' taking sample photos with my various 50's...

I have a ricoh P 50 f1.7, a ricoh P f1.4 and a Pentax A 1.7....

I shot f8, f4 and wide open on each lens. My Ricoh lenses are clearly sharper. But they are not all that far apart IMO in sharpness.

You have a different game all together since you are shooting film. You have to be way more careful from the get go to get your focus perfect.
07-16-2012, 07:37 PM   #13
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Have you looked at the rear element? There's a spot on one of my M lenses that has the notches for tightening of the metal ring that holds the glass in place. Got loose once, caused slightly soft focus till I figured it out.
07-16-2012, 08:04 PM   #14
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Hi Brofkand - I had this happen, not with the 50 mm but with a 28 mm. I am putting it down to taking pictures at high noon or there abouts. The quality of the light at that time of day is horrible.

Those are sure are cute chessmen, Dominik!
07-16-2012, 08:55 PM   #15
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QuoteOriginally posted by brofkand Quote
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.

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.

Any input? Thanks!
Shutter speed? Did you use a tripod? Could the subject have moved after focus/during exposure? It might be wise to retest using an inanimate target that fills the frame corner to corner- a newspaper page taped to a wall would do the trick. Make sure you use a tripod too, MLU and a cable release. Adjust camera position carefully so film plane is parallel to wall.

Your scans look good- I don't think that's the problem.

The M 50/1.7 is plenty sharp. I don't think you would gain a whole lot from a 50/1.4 (I own both.) If you do find a problem after additional testing, you may have a bad sample.

cheers
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