DotTune: Video Tutorial for AF tuning without photographs

Started Feb 18, 2013 | Discussions thread
Horshack
Veteran MemberPosts: 3,810
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Re: DotTune: Video Tutorial for AF tuning without photographs
In reply to clarnibass, Feb 20, 2013

clarnibass wrote:

Hi

Thanks very much, I will try it.

One question though. I didn't read lal the posts so maybe someone already mentioned this, but at one point you mention how each arrow on Nikon cameras already tells you what direction to go. Then, at the actual fine tuning at the end, you are using the negative direction when it was the arrow where you said to go to the positive direction.

Is your first explanation in the middle accidentally a mistake and should be vise versa like you show at the end?

Thank you

It's an excellent question and I too noticed it after I finished editing the video. I'm actually not sure what's going on yet. Here's what I know:

When the rangefinder arrow points to the right, the current focus in front of the subject, meaning the focus ring must be turned to the right (toward infinity), to move focus backwards and bring the subject into focus. When the rangefinder arrow points to the left, the current focus is behind the subject, meaning the focus ring must be turned to the left (away from infinity), to move focus forward and bring the subject into focus. This matches what I said in the video and is easily verifiable, so far so good.

The D800 manual indicates that positive AF tune values move the focus adjust away from the camera (toward infinity), while negative AF tune values move the focus adjust toward the camera (away from infinity). The actual AF tune menu screen on the D800 depicts the same. This means when the rangefinder arrow is pointing to the right (front-focus), AF tune should be adjusted in the positive direction (away from camera), and when the rangefinder arrow is point to the left (back-focus), AF tune should be adjusted in the negative direction (toward camera). This also matches what I said in the video...yet as you astutely noticed, in the D800 DotTune session at the end of my video the exact opposite is happening; in the video, the rangefinder arrow is pointing to the right, yet a negative AF tune was necessary to correct the mistune.

I'm not sure what's going on. I know the rangefinder arrows are pointing in the correct direction, since they match the F-mount focus direction. This implies the orientation of the AF tune scale on the camera is inverted. Or it means my brain is inverted. I see the same behavior on my D3s too. Need to investigate this further.

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