[timothymarsh]

Using a new K50 with a Pentax-A SMC 50 mm F1.7 lens from Amazon (Third Party).

I have confirmed that the body is working correctly by taking shots with the kit lens and 55-300 AF lenses that I bought with the camera. I decided to pick up a 50mm prime to get something that was faster and (by all accounts from the reviews) better optically than the kit lens.

When mounted, the 50/1.7 does not seem to function correctly. I have set the focal length in the camera to 50mm, MF switch is in the correct position, and Aperture ring enabled setting has been chosen. However when using the viewfinder or live view I cannot get images in focus unless I am about 4-7 inches away from the subject.
From my research of this legacy lens on a K50 I should be able to manually focus to get shots at any distance from the subject, not just close up 'macro' shots.

Any feedback on possible errors is greatly appreciated, I'm new to the DSLR world so I may be overlooking something simple.
Thanks!

[UncleVanya]

It certainly sounds like the lens has a problem. I would have no idea what is wrong with the lens specifically myself. I'm pretty sure the camera isn't the issue given your description.

[Giklab]

Does the focusing ring on the lens turn? You should be able to see the lens barrel extending and retracting as you focus closer/farther respectively.

[jatrax]

This lens has a frequent problem with a small part breaking off inside. A poor design that often fails. I have had to perform a repair on mine as well. Normally this causes the aperture ring to jam though so your problem might be different. Or the small part broken off may have gotten to the focus ring instead of the aperture ring.

More information here: https://www.pentaxforums.com/forums/114-maintenance-repair-articles/88051-pen...ng-repair.html

Personally I would just send it back as defective. These are cheap as chips and almost as easy to come by. It is a nice lens but not worth hassling over, get a nice good one in mint condition.

[timothymarsh]

Focus ring turns smoothly through entire range. I've looked at the aperture blades and they are all intact.
The fact that I cannot point the lens at something 10 ft away and bring it into focus tells me that an element has to be out of place. It seems like the lens needs to be able to turn past the infinity point in order to focus an object at such a distance. Perhaps the lens was poorly serviced before I got it.

[timothymarsh]

[timothymarsh]

Pictures 1-3 are taken within 6 in of subject, F1.7 and then down to F5.6

The last shot shows example of 4ft from subject, best focus that could be achieved.

[paulh]

I just did a quick test with my own copy of the A50/1.7, and an M50/1.7, Both lenses need about 11-12 inches minimum focusing distance. In the lens review section of the forums, it lists the MFD as 45 cm, which is over 17 inches. This is not a close-focusing lens in my experience.
https://www.pentaxforums.com/lensreviews/SMC-Pentax-A-50mm-F1.7-Lens.html

[Not a Number]

The aperture ring problem should not affect the focusing.

As asked above does the focus ring turn smoothly and the barrel of the lens extend or contract as you turn the ring? Does it turn fully from the range of 0.45 meters to infinity?

The problem may simply be that the lens needs to be re-adjusted for infinity to damage of the helical screw for focus. As Jatrax noted it may be simpler (and cheaper) just to acquire another copy of the lens.

[timothymarsh]

Based on the comment of paulh, I believe the lens is damaged in some way. The lens does not begin to focus until inside of 7 in from subject. Basically the complete opposite of how it should behave.

@Not a number, as noted above I believe the focus ring is functioning properly. It turns smoothly through the entire range. And based on the pictures I've seen of other copies of this lens, the focus ring is in the proper orientation on the lens (ie. Not shifted out of alignment).


Plan of action:
Return the lens to the seller on Amazon.
Purchase another A50/1.7, or perhaps just go with a newer lens such as the DA 50/1.8 (Thoughts on this lens are welcome)

Thank you for the quick responses! Looking forward to lots of constructive growth from this online community. Can't wait to start seriously using my new K50.

[Giklab]

Maybe someone modified it for close-focus use? From what you say it seems like the assembly was either un- or re-aligned.
IDK though.

[jatrax]

Purchase another A50/1.7, or perhaps just go with a newer lens such as the DA 50/1.8 (Thoughts on this lens are welcome)

The advantage of the Pentax-A is that it has a focus ring designed for manual focus. Of course if you want auto-focus then this is not an advantage The much newer and updated DA 50mm f/1.8 is also a very good lens though the construction is plastic and will not feel as nice as the 'A'. However, it has much newer coatings, was designed for digital, has auto-focus and is chipped so the camera can read the focal length.

Unless you have a reason to want the manual focus Pentax-A I would just go with the DA model. Price lately has been really amazing.

[mgvh]

Maybe I'm missing something, but enabling aperture ring shouldn't matter. Don't you just set the lens to the "A" setting and use A mode on the camera? I'm sure I read somewhere on this forum that that's the way to avoid the aperture problem.
Now whether this has anything to do with your focus issues is probably another matter.

[paulh]

I misinterpreted your lens problem when I replied to this post earlier. Yes, there seems to be a problem with the lens. As others have said, return it and find another (they are common and plentiful), or maybe go for the DA version, which is a good, inexpensive option.