CI Photocommunity

Register a free account now!

If you are registered, you get access to the members only section, can participate in the buy & sell second hand forum and last but not least you can reserve your preferred username before someone else takes it.

Help with Sigma 150-500 on my Pentax K10D


New Member
I recently purchased a new Sigma 150-500 with OS. I am having a problem with the focusing. When I depress the shutter release halfway it focuses in and out repeatedly but won't lock in at the proper focus. Occassionaly, it will focus properly. Any suggestions?


Well-Known Member
NBC...I have some questions...

1. Do any of your other lenses hunt...
2. Where are you taking pictures...outside/inside...
3. Are you having the problem at 150mm all the way thru to 500mm ..
4. Are you in Manual mode or Auto/Shutter/Aperture modes....

I am not familiar with the Pentax 10d but on my Sony a900 I can do a fine focus touch-up inside the the lens is a little short or far when it is focused in...I can make little adjustments so that the picture comes in sharper...

Sorry to answer your question with a bunch of questions...but this will help out...

Tony C.


New Member
Hi Tony,
In response to your questions, this is the only lens I've had this problem with. I have a Sigma 70-300-no problem. All my other lenses are Pentax so also no problem. I've tried different settings and haven't had any luck yet. I've used this lens mostly outside. The next time I have it out I'll pay more attention to the settings that I try and post them. Thanks for your help.


Well-Known Member
NBC...The only other thing I can think on my old 50-500 which was made for the Minolta film camera....if I don't use spot focus center weight or choose the focus point on will hunt a lot...the only thing I can think this lens is not a D lens...D=the lens gives the camera metering information when it is other Sigma lenses are fine but they are all "D" lenses...

Where I am getting maybe you have a bad chip that is not communicating well with the camera....I would send it back to get "Spec'd - Out" and also let them know you are having this issue...when you send it off with the receipt you should be covered under there receipt no warrantee....if it is new...less than 30 days...take it back to where you bought it...and exchange it...

Let us know...Tony C. :z04_cowboy: