View Full Version : Correcting barrel distortion on K7 with a Sigma 17-70 f2.8-4.5 DC Macro Lens

27-03-2011, 3:22pm
My Sigma 17-70 F2.8-4.5 DC Macro is producing Barrel Distortion when attached to my K7 (not that I have another camera to chech it aganist)
how do I correct it when the function is disabled for non pentax lenses on the K7?

The Photo attach is take at the 17mm FL of a 10mm grid with the front of the lens sitting at the minimum focual lenght about 2000mm from the page, spirit leveled on a tripod....

The second at 50mm FL

27-03-2011, 3:39pm
What program are you using? LR and PS have barrel distortion correction tho I tend to use LR.....

27-03-2011, 4:41pm
Jan ... I have neither, I use Coral PaintShop Photo Pro X3 or the Pentax Software, I notice that both of these do have distortion correction.
but i was hoping on doing it at the camera instead of having to correct almost every photo I take.
Although PSPx3 does batch process, which isn't practical because the amount of distortion is relative to the focal length (so I have noticed in taking incremental shots).

27-03-2011, 7:40pm
Have you tried it anyway on the K7 as sometimes the Pentax manual can be misleading.

27-03-2011, 8:04pm
Hmmm I have a feeling that the distortion can only be reduced by reducing the zoom length. I have ditched pspx3 and moved to PS I am afraid. Never tried the pentax program.......I use LR to remove distortion from my 10mm lens as it has the correct profiles. It can be done manually but yes it is time consuming!. DXO is another program/plugin that will do it .....but not sure if it works with PSPx3..........sorry I cant be more help! Maybe someone else will chime in??

27-03-2011, 8:05pm
OK, and then how important is it to you? If critical, you may have to invest in something like Adobe PS. Check the wwweb out to see if Adobe Elements (which is cheaper than Photoshop) has the distortion correcting feature. I don't know if the free Picasa and Gimp have it. But note that I have Adobe CS2 and I have NOT used the barrel distortion feature since the early days, MUCH preferring the Edit-Transform-Warp feature instead.
Edit: typed b4 I read ricstew's reply.

28-03-2011, 8:39pm
Hmmm I have a feeling that the distortion can only be reduced by reducing the zoom length.

actually it is worse at the short end (17mm) and is barley visible for 50mm up