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  Previous versions of Mike K's message #11321975 « Dot-Tune: Autofocus Fine Tuning in under 5 minutes »

  

Mike K
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Re: New AF tune technique - looking for testers


An alternate PD AF calibration technique comparing to Live View 10X

I have a different variation based upon my confidence in Live View Manual Focus. This method requires a high resolution LCD; all recent models of Canon DSLRs since the 5DII have about 1M dots or more. The fundamental premise is the with Live View 10X, the focus will be exactly as you see it on the LCD. Focus wise; What you see is what you get.

1. Canon strongly suggests performing phase AF calibrations at 20-40X the focal distance of the lens. Thus for a 50mm lens this is 1.0-2.0 meters from the target to the camera. Don't do PDAF calibrations at really close distances, like MFD, as there is much greater chance of that calibration being way off. For telephoto lenses, choose a detailed subject some distance away.

2. I like to use a resolution chart with very fine interference lines such as






For a much larger higher resolution version of this image visit
http://forums.dpreview.com/forums/post/50791608

However your choice of charts or subjects is not critical. The target does not have to be a monitor or a large print and can be nearly anything with a uniform distance from the camera, but should be well lit and with good contrast and detail.

3. Use a solid tripod so you can see the camera LCD well.

4. PD AF on the chart above. Switch the Live View on and magnify the LCD image to 10X. Carefully adjust the lens to maximize the Live View focus. Turn LV off. Look at the lens as you press AF again. Did the focus band move? Turn LV on and again manually turn the focus ring on the lens to maximize the LV 10X focus. Again turn LV off and watch the lens as you press PD AF. Based upon the amount and direction of miscalibration between the PD AF position and the LV 10X position, go into the micro adjust menu and change the MA calibration for that lens.

5. Do step 4 again, multiple times. Its very fast, so one can repeat the comparison of PD AF Vs Live View 10X several times in a few minutes. There is some imprecision in both the PDAF position and the LV10X focus position, so repeat the exercise until you are happy that the AF and LV results are very close to one another. If you have a 1dX, 5DIII or 6D body, you need to perform this calibration at both ends of the Zoom position. Repeat this exercise for all of your Canon AF lenses.

6. Variation with greater resolution: using the HDMI output, hook up your camera to an external monitor such as laptop or monitor such as

http://www.fredmiranda.com/smallhd/

Press the info button several times to maximize the screen resolution and adjust the monitor to yield 1:1 resolution (1 pixel on the external monitor = 1 pixel from the camera output). This will make it easier to visualize fine adjustments of in/out of focus. Perform steps 1-5 above.



Feb 03, 2013 at 10:23 PM



  Previous versions of Mike K's message #11321975 « Dot-Tune: Autofocus Fine Tuning in under 5 minutes »