# AFMA for my 70D and Len'es



## ronaldbyram (Apr 23, 2015)

Hi does anyone have a good example on how to perform a AFMA on there 70D and lens?

Any special equipement needed?


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## takesome1 (Apr 23, 2015)

Buy Reikan Focal, that is my suggestion.

http://www.reikan.co.uk/focalweb/


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## Mt Spokane Photography (Apr 23, 2015)

I use Reikan Focal, but there are many devices and home grown methods available. Results may vary depending on your understanding of the AF system, its weaknesses and limitations.

AFMA is most useful for wide aperture lenses f/2.8 or wider.

FoCal is rather expensive, so you might want to check to see if you need adjustment.

The trick is to be absolutely sure that the camera is trying to focus at the right point, and some of the home brew methods tend to cause problems. Make sure that the camera is stable, vibrations can blur the image. Lots of light is essential.

A flat wall with texture and lines like a brick wall works well as a target. Don't use a slanted ruler, that will cause errors. Be careful to setup your camera perpendicular to the wall or target. Position the camera on a tripod about 50 focal lengths away (35mm X 50=1750mm or 1.75 meters or 5.7 ft). Make absolutely sure the camera is stable, and has bright lighting.

Then:

1. Place the camera in AV mode and set the lens to full aperture.

2. Set the lens to infinity focus before each shot. 

3. Take 10 shots with the normal phase detect Autofocus. Make sure you identify them.....

4. Turn on live view, using the same steps in 1 & 2 above and take another 10 shots using live AF (NOT Quick).

Now, analyze the shots taken with each method. Don't be surprised if they are not all the same sharpness, the AF system is not that good.

Compare the focus between the two groups. If they are about the same, your AF does not need AFMA. If the Live AF is noticeably better, AFMA will improve the autofocus accuracy. If the live AF is worse, something went wrong in your test. It should always be a tad better.


Here is a snapshot of my setup using FoCal.


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## wsmith96 (Apr 23, 2015)

@ Mt. Spokane - nice set up. I especially like the Ethernet switch you have on the shelf there! It looks like an HP Procurve. If so, thanks for helping to feed my family!  

-w


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