check focus of lens

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ricky1980

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Richard Wong
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sorry i think there has been a number of threads about how to check focus of lens i.e. the amount of front and back focus etc.

can't seems to find the method used. could someone link it for me?

thanks
 
Widest f stop and I shoot washing powder box rear at 45 degrees to lens front noticing what letter on the instructions it focuses on..... Zoom in on image review and check if same letter is sharp!
 
Mark twiglet said:
Widest f stop and I shoot washing powder box rear at 45 degrees to lens front noticing what letter on the instructions it focuses on..... Zoom in on image review and check if same letter is sharp!
Click to expand...
This isn't always reliable, because the autofocus points have a finite size and you can't always be sure exactly what the camera thinks it's focusing on.

It's safer to have the target square on to the camera, and have a separate angled measuring device. Like in this post by @HoppyUK:
https://www.talkphotography.co.uk/index.php?posts/6618361
You focus on the cereal box and, since the box is square on, there can be no doubt as to which part of the tape measure ought to be in focus.
 
Ive had a bit of trouble with this myself, mostly with my Tamron 24-70f2.8 and I've tried most of the techniques and they all seem to vary a lot except the dot-tune program available through the magic lantern mod for canon cameras, basically the magic lantern guys have made an overlay that runs on top of the canon software which is mainly used for extended video and photography settings (focus peaking etc.) if its compatible with your camera I would highly recommend it and its pretty simple and I've used it for both my 7d and 500d anyways; it has this extended set of programs where one of them is called dot tune, basically you manually focus on a subject and then turn af off on the lens and then execute the program and it automatically goes through the range of accepted mf adjustments for that manual focus'd scene and then picks the one in the middle of the range of values. It saves a lot of time and also goes from -100 to 100 mfa rather than canons -20 to 20
 
I used the chat method mentioned above and the dot tune. good to see both method yielded similar tuning values for my sigma 35mm.

however the dot-tune has a problem on my D610. the fine tuning adjustment doesn't seem to have sufficient scope to cover the DoF of my 35 f1.4 between 0.4-0.9m, which seemed strange.

Dot tune is less fiddly when it is working.
 
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