pentax smc m 1.7 50mm on K50


Link Posted 13/05/2016 - 10:54
I have been experimenting with this legacy lens on my K50, gone through all the steps, setting focal length at 50mm, Av exposure at f1.7, very high shutter speed etc. However the photos are extremely soft though they do have a beautiful quality. I used the same lens a year ago with an adapter on a Fuji Xe1 and the photos were quite sharp. Is it possible that the extra distance from the sensor resulting from the use of the adapter brought the lens into a better relationship with the focussing screen or what ever it was the Xe1 used to calculate the correct focus?


Link Posted 13/05/2016 - 11:01
I have used this lens on a KX and my current K3ii with no issue, got any pictures we can look at?


Link Posted 13/05/2016 - 12:45
If it is an M lens it won't close the shutter down in Av mode so you'll be stuck at f/1.7. Don't forget to "enable use of aperture ring" (or whatever the menu setting is actually called) or it won't close the lens down in any mode. Are you relying on the green hexagon or using your eyes? I found the hexagon was a bit approximate with older manual glass and did better concentrating on the image.

Kris Lockyear
It is an illusion that photos are made with the camera… they are made with the eye, heart and head. Henri Cartier-Bresson
Lots of film bodies, a couple of digital ones, too many lenses (mainly older glass) and a Horseman LE 5x4.

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Link Posted 13/05/2016 - 13:17
Thank you Paul and Womble.

I didn't want the lens to close down. Aperture ring was enabled. I was relying on my eyes. I believe I now understand why the Xe1 worked well with the lens. It has an electronic viewfinder. I have since read on the internet that focusing with live view is the way forward if it is a static subject. Unfortunately that is not always desirable. Thank you for your comments. Sample photo below. Eain


Link Posted 13/05/2016 - 15:27
Just looks like either you or the lens are back focusing a bit, does the top of that flower look sharp in the view finder when you take the shot?


Link Posted 13/05/2016 - 16:54
It all looks sharp in the viewfinder. I am going to have to retry with tripod and live view. Eain


Link Posted 13/05/2016 - 20:48
Eain wrote:
It all looks sharp in the viewfinder. I am going to have to retry with tripod and live view. Eain

Diopter adjusted properly? Is it just this lens with the problem?


Link Posted 14/05/2016 - 14:33
Diopter fine.

I found an article in that seems to explain the situation. I am sure it would be OK to quote it:

"Dialing in accurate focus can be tricky as the range of movement of the manual focus lens’ focus mechanism and front/back focus issues can throw the focus sensor off. The focus indicator will often stay illuminated over several degrees of focus ring rotation (in-focus range). This can be especially frustrating when using fast lenses with extremely short depths of field while trying to achieve critical focus on a specific point of the subject. Trial and error with lots of high magnification LCD review is the best way to get it right. Each lens will likely have its own characteristics that will need to be learned"

Also elsewhere I learned the DSLR viewfinders are different to film viewfinders and much harder to focus visually, hence provision of automatic focus with indicator which causes problems (see above)



Link Posted 15/05/2016 - 13:41
Used this lens on the K110 D and KR without any problems. The cameras bleeps also to confirm focus.

Regards Ian


Link Posted 15/05/2016 - 16:10
You can use smc k and m lenses in AV mode if you press in the lens release button and rotate them about 10 degrees anticlockwise on the mount they are still quite tight or do as i do and drill a 3mm hole in the lens mount so the locking pin on the camera locates in it locking the lens on.Does away with the green button stop down metering
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