[hadi]

perhaps i'm doing something wrong. i'm not entirely sure. i recently got a rokinon 85mm lens (perhaps that was my issue) and whenever i'm using it, however i'm using it, i cant seem to get the image sharp enough. they look sharp due to the crazy bokeh. however, the subject on the other hand doesn't seem to ever get sharp.
so i thought it was a calibrating issue as i've heard others talk about their samyang/rokinon/bower/etc lens not calibrated properly.

i got a sypderlenscal and calibrated my 50mm. it didn't need adjustment at all.
then i tried the 85mm and it seems to not like any of the settings i dial in on the camera for it.

heres what i'm using:
a spyderlenscal on a flat table
a k5 body on a tripod
lens attached to body at about 5 feet apart
the lens is set to wide open
i have it set for 2 second timer
i manually focus till i hear the beep. i confirm with my eyes if that is the sharpest it will go and i take the pic

when i close examine it i get variable results that i cant seem to replicate. i first see the entire image a blur. then without having to change anything, i take a second pic (mind you, i didn't change the focus or anything) and now, somehow the pic is sharper (but still not sharp). i try to take a third pic, and its somewhat similar result and it seems to be front focusing. so i adjust the calibration on the body, and refocus again and try taking the pic. it seems to either focus back, or forward, at random intervals. i zero it out, and it back focuses. i adjust it and it front focuses. i zero it out and its still front focusing. i adjust, and its back focusing. then randomly focuses just right, but not spot on.

i try the pentax 50mm 1.4 again and it seems to focus just fine (granted, not as sharp as i would like, but sharp enough to get me by)

perhaps i'm in the wrong to trying to adjust a manual focus lens? perhaps a manually focusing lens can not be calibrated? perhaps its my aging k5 body. i recently went on a trip and took several pics and came across the same issue. some pics are just fine. others are not. i was using multiple lenses on the trip, not just one. so perhaps the body itself is the issue?

for what its worth, i am able to get pics like this wide open using the rokinon 85 hand held.


its almost focused, but not quiet. and perhaps its due to the extremely shallow depth of field, where only his ear is in focus?

anyone care to help with this?

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Last edited by hadi; 04-05-2016 at 10:44 PM.

[Unregistered User 8]

Hi hadi. I'm pretty sure that lenses that need the focal length put in the camera at start up cannot be calibrated ( AF adjustment ). The camera has no memory of these lenses so the calibration cannot be stored. I could be wrong, and will be told soon if I am !! Good luck.

[stevebrot]

You cannot do per-lens AF fine adjustment on a non-AF lens. Non-AF lenses lack the data contact on the mount that provides a unique lens identifier. My experience with my KMZ Jupiter 9 85/2 is that focus is very difficult to attain using the optical focus and somewhat worse with focus confirmation. DOF is very thin. I finally solved the problem by going to a split-image focus screen.


Steve

[zapp]

Pentax AF system will not really work with a f/1.4 lens - it will detect the sharpest area, but the leverage of the system is for f/2.8. If you are using the AF indicator for focusing your lens can happily front/back focus after alignment. More forum reading here: https://www.pentaxforums.com/forums/172-pentax-k-3/289352-what-means-f-2-8-af-points.html
Try the same thing with live view, setting the focus really correct. Nothing should change anymore unless some parts are lose in your lens.

[Adam]

As others have said, AF calibration only applies to AF lenses.

What you'll want to do is use live view, magnify the image using the OK button, and adjust the focus until your subject is perfectly sharp. If you're shooting wide-open, you will have to be extra careful. Good luck!

[UncleVanya]

To clarify a global all lens correction should work but it will impact every other lens unless you add it only when using this lens.

[Na Horuk]

To clarify a global all lens correction should work but it will impact every other lens unless you add it only when using this lens.

Yes, you can try adding a global adjustment for the 85mm, but you will then need to put "anti-adjustment" for all your other lenses (camera does not recognize manual lenses, so it cannot remember). OR just turn it on/off.

Pentax AF system will not really work with a f/1.4 lens - it will detect the sharpest area, but the leverage of the system is for f/2.8. I

This. And the viewfinder is small, optimized for AF composition, not for actual MF. You can help with this if you install a viewfinder loupe (magnifier) or a focusing screen (there are many types, some are rather cheap, you can install them yourself, but it is a little tricky. Many threads about this. It works well for fast primes, but it can interfere with small aperture lenses (like f4-5.6 zoom).

its almost focused, but not quiet. and perhaps its due to the extremely shallow depth of field, where only his ear is in focus?

This is part of problem, too! Some lenses have so shallow DoF, you cannot even get both eyes in focus at the same time! And sometimes it can be so shallow, you get the eyelashes, but not the full eyes! 85mm at f1.4, especially if you focus near, will be very shallow DoF. So imagine, you get focus correct - but you breathe in as you push shutter button, and you move the camera by 3mm, and your subject is standing there, he moves 3mm in other direction.. and now your focus is wrong!
Another thing is that lens wide open, at maximum aperture, will usually be less sharp than if you stop it down one or two stops. Most lenses are not amazing wide open, but if you stop down just a little, they improve a lot.

Finally, there is technique! Over time, with practice, your photos will get sharper. Because you will subconsciously learn how to focus, you will learn how to push trigger button gently, how to stop your breath when you take photo, how to stand and hold the camera, how to use post-processing settings to add sharpness or clarity, and so on. Don't give up, keep practicing! The photo you posted is on the right track.

But maybe you want to buy a viewfinder loupe, if you have many MF lenses. They are not very expensive on ebay (I think Seagull makes some?) and can make things easier.

[fb_penpho]

I have this lens, and there are many online DoF calculators available. I use them because under extreme conditions the DoF can be VERY small. The calculator will hammer home the point that possibly if the ears are in focus, the lips may be just going out.

[hadi]

awesome tips guys!

i do have a question regarding the samyang/rokinon/bower 14mm lens. moreso than any other lens in their line, it seems the 14mm is 'miscalibrated' and there are several posts around to calibrate it properly. if i understand correctly from previous posts, manual lenses cant be calibrated. so how is it that the 14mm is calibrated?

i ask as that is the lens i'm looking forward to getting once the k1 is out

[stevebrot]

awesome tips guys!

i do have a question regarding the samyang/rokinon/bower 14mm lens. moreso than any other lens in their line, it seems the 14mm is 'miscalibrated' and there are several posts around to calibrate it properly. if i understand correctly from previous posts, manual lenses cant be calibrated. so how is it that the 14mm is calibrated?

i ask as that is the lens i'm looking forward to getting once the k1 is out

Many of the Samyang wide angle lenses do not have their focus rings set properly for infinity focus or to agree with the printed scale on the lens barrel. I have only done it on the 8mm Fisheye, but that lens can be adjusted by loosening screws under the rubber focus grip and moving the ring to correct.


Steve