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Forum: Pentax SLR Lens Discussion
05-11-2018, 05:20 PM
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$25 for the total is good indeed. Enjoy your "new" lens.
Steve
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Forum: Pentax SLR Lens Discussion
05-11-2018, 08:11 AM
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As noted in the comment...f/5.6, the same as your test photo. Mine is in EX condition, but excellent performance from the ST 55/1.8 and the successor Pentax-K 55/18 is the norm and was well-known when the lens was new.* Your original lens has problems and probably should be returned had problems and probably could have been returned.
Steve
* I have two and both are excellent performers. The other is an early version probably dating 6-8 years before the one used for the photo.
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Forum: Pentax SLR Lens Discussion
05-10-2018, 08:05 AM
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Well, I guess you have it pinned down, though your mirrorless camera does have a shutter and rock solid is always relative in the world of tripods, particularly when using the center column as a horizontal arm. Leveling the camera for copy work generally requires a small carpenter's level at the lens front bezel and is a pain without a geared head. Sorry if that sounds snarky, but I have done a fair amount of lens testing and copy work and that sort of thing is a common source of poor results. Assuming the setup is rock solid and true to the subject, three more questions:- How sharp and/or contrasty is the sheet music? Is it an original or a photocopy? I was struck by the low contrast.
- Are you certain your adapter positions the lens at right angles to the sensor. I don't use your tools, but have read multiple reports of adapter issues that include poor alignment.
- What is the physical condition of the lens? Specifically:
- Is there evidence of internal fungus, crazed rear or internal elements due to botched cleaning
- Is there evidence the lens has been subjected to amateur service? (This would include scratches on or around screw heads or bunged screw heads.)
It is quite likely that your lens has a problem traceable to physical damage and/or foreign substance on the optical path. The image of the staple at center (point of focus?) on the f/5.6 example was my first clue. It simply looks yucky. The ST 55/1.8 is a very fine lens and while it a bit of an antique, it is not a macro lens, and has some field curvature, it is still suitable for general copy work. Below is a test image I did with my ST 55/1.8 and a setup similar to yours.*
Pentax K-3, 1/10s, f/5.6, Super-Takumar 55/1.8, in-camera JPEG (highest quality)
The full-resolution JPEG may be downloaded (12.5MB) from: https://farm1.staticflickr.com/953/40211014180_d5c9a7de2f_o_d.jpg
Here is a full-resolution snippet from near the bottom edge of the APS-C frame
I deem the results adequate and much better than what you got from your lens, though if I were working from RAW, I would have applied a little sharpening and correction for the very slight chromatic aberration present towards the edges. If I were to do it over, I might also give it at least an additional 1.0 stops exposure and a tweak to white balance, but I was in a hurry. If it were a copy for my own personal purposes, I would also be at f/8 to defeat whatever field curvature might be lurking. ;)
Since your lens is new to you, I might suggest contacting the seller.
Steve
* Subject (back of computer power supply box) on floor, natural window light, Giottos 9360 tripod with center column configured as horizontal arm, focus using magnified live view.
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Forum: Pentax SLR Lens Discussion
05-08-2018, 08:21 PM
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Forum: Pentax SLR Lens Discussion
05-08-2018, 04:57 PM
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What was the intended point of focus? Was it the center of frame? Also, how was the tripod set up? Was a remote release or self-timer used?
I know these all sound silly, but document copying is harder than it sounds with the most common problems being document flatness, inadequate depth of field, camera motion, camera not parallel to subject, and lens field curvature.
Steve
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