Procedures for DIY SD14 MF/AF calibration

Started Apr 5, 2008 | Discussions thread
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Joseph_Lam Regular Member • Posts: 317
Procedures for DIY SD14 MF/AF calibration
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I found and tried the instructions on:
http://leongoodman.tripod.com/d70focuspart3.html

The article is for D70 but most of it applies to SD14 as well. For SD14, you'll need a 1.5mm hex wrench (rather than 2mm mentioned in the article). The procedure is not difficult but it takes a lot of time and patience.

The basic mirror box structure of SD14 is the same as D70:

What you'll need to do is to first calibrate manual focus by turning knob 2. If you have back focus problem, then rotate the knob CLOCKWISE bit by bit, checking the focus each time and taking note if it. If over-adjusted (i.e. start having front focus), then turn it back a little. You may have to repeat many times, putting on and taking off the lens and IR filter, and loading the pictures into your PC to check the focus. I suggest you take at least 5 shots each time to reduce chance of error.

Once you're happy with the MF accuracy, then do the same with knob 1 to calibrate AF. Again you turn it CLOCKWISE if AF is back focusing. Also, when verifying AF, take a few shots with the lens starting from the nearest focusing distance and another few starting from infinity. This is because I found that the AF motor may occasionally 'overshoot' or 'undershoot' a little, causing very slight ff/bw depending on where it start focusing from, and confusing the results.

I used the focus test chart from this site: http://focustestchart.com/chart.html

I've gone through this twice on my SD14. The first time was done in a hurry (for about an hour) so it not wasn't very precise but acceptable. I did it again last night for a few hours to get better precision. I only calibrated my 30/1.4 (which is my walk-around) and after that both my 70/2.8 and 10-20 became accurate. My guess is that if the mirrors were not properly aligned, different lenses may exhibit different degrees of bf/ff problems making it confusing. Lenses are engineered with very precise registration distance and the manufacturing tolerance shouldn't be as big compared to the mirror box structure (which contains manually adjustable parts such as those knobs).

Note that the sensor/filter may get a lot dust during the lengthy process so expect some cleaning work to do afterwards.

Regards,
Joseph Lam

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