[Conor Rowlands]

Hello, I recently sent my Sigma APO 150-500mm lens {second hand on ebay} to Sigma UK to give it a software update so it could be used for my Pentax K-70. Since its return I have noticed that while I can now use it on the K-70, there appears to be an issue with the focusing. I've tried using both auto and manual focusing.; though the red dot focus appears through the viewfinder and the subject seems to be in focus, the picture itself comes out blurred.

I also own a Pentax K-50, which seemed to work fine with the lens before I sent it for the update that would allow for its use on the K-70. Now, it is also not working properly on the K-50.

Any ideas as to why this might be happening? I'm very tempted to send it back as I think it might have something to do with the update that they may have done to it.
Am I supposed to alter any camera settings for use with the lens?

Many thanks,

Conor.

[stevebrot]

Any ideas as to why this might be happening? I'm very tempted to send it back as I think it might have something to do with the update that they may have done to it.
Am I supposed to alter any camera settings for use with the lens?

No, you should not have to do anything special to your camera to have AF work with that lens. That is what the firmware update from Sigma was for. It might have something to do with other work that Sigma did on the lens. Have you contacted them?


Steve

[DWS1]

No, you should not have to do anything special to your camera to have AF work with that lens. That is what the firmware update from Sigma was for. It might have something to do with other work that Sigma did on the lens. Have you contacted them?


Steve

This is what I was thinking also. Perhaps something could have been knocked out whack during shipping.

[peggers]

Interesting. I have a similar issue with a Samyang 85mm f1.4. I swear I have focussed correctly but usually find that somehow the lens has actually focussed just in front of my intended focal point. My solution is just to avoid f1.4 like the plague. Not really satisactory though

[K(s)evin]

..."though the red dot focus appears through the viewfinder and the subject seems to be in focus, the picture itself comes out blurred."

The red dot in the viewfinder only indicates which focus point is active. A green hexagon will show steadily in the middle of the info line at the bottom of the viewfinder when your subject is in focus.

Hope this helps. Good luck!

[climbmountainway]

Do you have the OS HSM APO version? My manual says it takes 1 second for the lens to achieve both OS and focus, perhaps you are shooting too soon? Try the two OS settings, one for horizontally moving subjects, the other usually for vertical or stationary subjects. Also, one cannot use both the in camera stabilization and the in lens stabilization at the same time (if you have that feature), so, when the shutter is pushed half way, then all the way, it can affect the final in lens choice of stabilization and related focus accordingly..

[Conor Rowlands]

Do you have the OS HSM APO version? My manual says it takes 1 second for the lens to achieve both OS and focus, perhaps you are shooting too soon? Try the two OS settings, one for horizontally moving subjects, the other usually for vertical or stationary subjects. Also, one cannot use both the in camera stabilization and the in lens stabilization at the same time (if you have that feature), so, when the shutter is pushed half way, then all the way, it can affect the final in lens choice of stabilization and related focus accordingly..

Hi all, thanks for taking the time to respond!

The lens doesn't have any OS settings. The only two buttons present on the lens are the AF/M switch and Lock/Unlock switch. I'm starting to think the issue stems from the update that Sigma carried out on the lens!

Thanks again,

Conor.

[DeadJohn]

The fact that the lens will no longer work with your K-50 suggests that something went wrong during the upgrade. Firmware bug, shipping damage, etc.? Contact Sigma.

Before sending the lens back, I suggest using liveview to confirm that the lens is mechanically/optically capable of getting a sharp photo. Put the camera and lens on a sturdy tripod or table. Set the shutter to the 2-second timer to avoid shake from pressing the shutter button. Turn on liveview, aim at some object with fine details, focus, take a photo. Test auto as well as manual focus; remember that you can zoom liveview for manual focus.

If liveview works well, there might still be a lens issue, but maybe not. Try adjusting your viewfinder diopter to get better manual focus. Try the focus finetuning menu (there are other threads describing the process) to get better viewfinder autofocus.