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Interesting method of adjusting micro-focus...

26-09-2011 2:46pm

#1

kelly1

Registered Users, Registered Users 2 Posts: 5,026 ✭✭✭

Join Date: January 2007

Posts: 4865

Found on Amazon:

3. Oh my god I love this feature: lens micro focus adjustment. Previously only available to lucky owners of the 1D series, this allows you to check the autofocus feature of any lens, and adjust the focus if you find it to be slightly soft (e.g. the focus is slightly behind or in front of the target). I spent 3 hours last night in full-on nerd mode, and finally figured out a way to do it simply. Skip the next bit if you're not a total optic nerd. The more in-focus an image is, the larger the file size. By varying the micro-adjustment from -20 to +20 in stages, you can later review the file sizes of the images and the one with the largest file size (if you keep all parameters the same) will be the setting with the most accurate focus. To do this, set up the camera and lens on a tripod and get it exactly perpendicular to a target. The target should fill the frame. I taped an old "start here" poster from a printer to the wall, and used a level to level the tripod. Tether the camera to a laptop and use live view shooting. Defocus the lens manually. Go into the custom functions and select the adjust by lens, and set it to -20. Then click the autofocus on the laptop to focus it. I repeat this focus click 3 times to make sure it is perfect. Then shoot 4 shots (to get an average reading). Move the micro-adjustment to -10 and repeat at intervals of 10 until you reach +20. Make sure to defocus the lens manually each time to make sure you force the autofocus to work through the problem again each time. Lets say +10 gave the largest average file size. Then go back and shoot at +5, +10, and +15. Lets say you decide +10 is still best, then go for +7, +8, +9, +10, +11 until you find the perfect focus. Nerds rejoice!! Actually it's not just nerdyness for the sake of being nerdy - I spent 3 hours on my 85mm f/1.2 last night and it is now WAY better than it was previously. It's razor thin depth of field at f/1.2 is now slightly behind where it was at it'd default (0) setting. So instead of a lovely in-focus image of an eyebrow and the tips of eyelashes, I now get the eyeball itself in clear focus. This is obviously a lens issue, but the fact that I can fix it in-camera without sending my lens off for re-calibration is a joy!!

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