Pentax Brotherhood

I just wanted to say a big Thank You to David Storm for taking time out of his Saturday evening to calibrate my lenses for me tonight, and all for a couple of bottles of beer.

The one thing I have noticed since joining this forum, is how helpful other members have been, and as a bonus how many friendships I have developed.

Long live the Pentax Brotherhood....oh and the Sisterhood too!

Thanks again David

Thanks you too Drew, there really was no need to post a 'thanks' on the Forum, but I appreciate you doing so.

Likewise I have made many friends from this website, some of them now moved over to pastures new but still remain friends.

I hope your camera is now sorted, if not don't worry as there is still more we could do to get it 100%.

Looking forward to the next Peak District day out, let's hope it snows!

Cheers
David

People should always check, or have checked, the AF calibration on their lenses. The parameters are there for that purpose. I'd never buy a DSLR that didn't allow the facility.

Never let anyone put you off from doing it or getting someone to do it for you.

All positive stuff

With manufacturing tolerances there is always the probability of having a camera at one end of the scale and a lens at the other. Although an extreme situation it`s possible. I wonder how many buy a new camera/lens and are seemingly disapointed with their first results.

I wonder if someone would be kind enough to write a simple, straightforward plan for AF checking and post it to the forum.

In the case of Andrew's camera it was front focussing quite a lot on all lenses we tried. In a case like this it is relatively easy to adjust using the 'AF Fine Adjustment' option in the camera menu, assuming of course that this allows enough adjustment to correct the issue. We had to go to -10 on one of the lenses to make it right.

Sometimes this may not be enough, in which case a global adjustment is first required before the AF Fine adjustment is made. This can only be done via the 'debug menu', which on the K-5 can only be accessed when the camera is connected to a PC via 'PK_Tether'.

The simple rule to remember is that a 'minus' adjustment pushes the point of focus backwards, whilst a 'plus' adjustment brings it forwards. We used a method of mounting the camera on a tripod, 2 second self timer, firing at a magazine page with lots of small writing, the page set at an angle of approx. 45 degrees to the camera. The lens was set to its widest aperture and images were viewed in photoshop at a magnification of 200% or 300% to determine the accuracy of focus. It is very simple to see using this method whether the lens / camera are focussing accurately. Just remember if doing this indoors that the subject needs to be well lit to avoid any possibility of focussing errors due to low light.

It's also a very good way of assessing the sharpness and chromatic aberration characteristics of your lenses. What was interesting yesterday was that after Andrew had gone, I re-calibrated my own lenses on my K-5 using the same methods. Andrew has Sigma lenses and I have Pentax equivalents. The Pentax lenses were a tad sharper than the Sigma ones were.

Regards
David

Ricehigh has a quick way of adjusting the AF...

http://ricehigh.blogspot.com/2012/01/focus-adjust-k-5-and-pentax-af-lenses.html


--