30D...adjust focus calibration

Started Jan 24, 2007 | Discussions thread
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RicksAstro
RicksAstro Veteran Member • Posts: 3,879
30D...adjust focus calibration

I recently bought a new 85 f1.8 and noticed it was backfocusing severely on my 30D. I had several other lenses, and they seemed to be fine, so I assumed it was a lens issue.

Being a geek, I decided to test my lenses (85 1.8, 17-55IS, 70-300IS, 300 f/4, Sigma 150 f2.8 macro) using a focus test target (like http://www.photo.net/learn/focustest/ ). The 70-300 and 17-55 were in great focus, but I found the 300 and 150 were also just a touch off and the 85 was waaay off.

I've been a big fan of Christian Buil's great camera test pages (being an astrophotographer as well), and noticed he told how to adjust the autofocus for the 350D, and after examining the 30D, it appeared the same method should work:

http://astrosurf.com/buil/autofocus/adjust.htm
(translated to english:

http://translate.google.com/translate?u=http%3A%2F%2Fastrosurf.com%2Fbuil%2Fautofocus%2Fadjust.htm&langpair=fr%7Cen&hl=en&ie=UTF-8&oe=UTF-8&prev=%2Flanguage_tools )

Being a brave/stupid soul, I decided to give it a go.

My main objective was to get the 85 dead on and figured I'd see if it made the others better or worse. I was hoping it wouldn't throw the good focusing ones off.

After some trial and error, I learned that moving the hex wrench up/CCW pushed focus back (increased backfocus) and moving it down/CW pushed focus forward (decreased backfocus)...it works (whew!). I was able to get the 85 just dead-on at f1.8. With trepidation, I tried the other lenses. To my great joy, all were dead on, even the ones that focused well before I started!

I learned that different lenses react quite differently to a miscalibrated camera. Some were far less sensitive to it than others. There was a general correlation to max aperture (wider=worse), but not 100%.

I used sensor cleaning mode to allow the adjustments and ran the camera using the AC adapter I have. I tell you, having a metal object that close to the sensor is nerveracking, but some patience and finesse rewarded me with a now perfectly calibrated 30D, with all my lenses being spot-on. In just doing some random non-geek testing, the sharpness increase is definitely noticeable...OOF images I would normally just blame on "difficult situations" are far fewer and farther between.

This isn't for the faint of heart, and I image there certainly are many ways to mess up the camera, but wanted to confirm that it is possible to calibrate the 30D. There is very little info besides Christian's (french) page out there.

Rick

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