[basikal_kusayang]

Hi,i have this lens for about a year now with my k20d and i notice that,what i think is a backfocus problem.sometimes the lens will backfocus at 50mm 2.8 but most of the time at 17mm and above (<35mm or 40mm i guess).if i want to do the focus adjusment

1.what is the focal length should i use?
2.do i need to do the focus adjustment for all my lenses?(i dont think my other lenses have similar problem).
3.does it going to effect the focus of my other lenses?

Thanks.

[ironlionzion]

1) check it for all focal lengths. depending on severity, you might just need to do the average focus correction. For example, on my K-x, I need more compensation at 50mm than I do at 17mm. So I just do an average of what I need. The focus throughout the range is "good enough" but not spot on at f/2.8. For almost all my purposes, like landscape, portraits, etc, this works out. Only if I try to work close to the minimum focusing distance at 50mm do I encounter focusing problems.

2) you can check, but it could be that there are no problems.

3) I don't think the K20d recognizes individual lenses and stores settings like the K5 does, so yeah you're going to need to change the focus adjustment every time you switch lenses.

[L33tGreg]

3) I don't think the K20d recognizes individual lenses and stores settings like the K5 does, so yeah you're going to need to change the focus adjustment every time you switch lenses.

It does. It's either 10 or 20 slots, can't remember.

[ironlionzion]

Didn't know that! Strange that they removed that when they built the K-x

[basikal_kusayang]

It does. It's either 10 or 20 slots, can't remember.

Thanks for the replies guys..

So,it does not effect my other lenses?and I dont have to do the focus adjustment for the other lenses?

[ve2vfd]

Back/front focus with the 17-50 is a well known problem. Do a google search for Tamrom 17-50 backfocus and frontfocus. You'll get thousands of results on almost all camera mounts.

If it's within your K20d's lense adjustment range, just adjust that lens and enjoy... if not then send it for service, I believe the 17-50 has a 5 year warranty.

Pat