DotTune: Video Tutorial for AF tuning without photographs

Started Feb 18, 2013 | Discussions thread
OP Horshack Veteran Member • Posts: 5,803
Re: DotTune: Video Tutorial for AF tuning without photographs

clarnibass wrote:

I don't have a D800, though I checked it for a while. I eventually bought a D600 and the manual is the same. I only have a few minutes now so I checked it a bit hand held etc. but I think I figured it out. It's just a matter of "visualizing it".

The manual is right about the direction of the fine tuning and you are right about what each arrow shows. However there is one confusing part and I think at the end, where you actually do it, it makes sense and your explanation in the middle is a mistake.

To clarify, when I say the left arrow I am talking about the one on the left of the confirmation light dot, which is pointing to the right, and vise versa for the right arrow, which is the one on the right side of the light dot, pointing to the left. Also it is not my first language so I hope I can explain it clearly.

Let's say focus is accurate and requires no fine tuning. You focus and then turn the focus ring slightly to the left, it will "front focus" and the left arrow will light up. Opposite when turning to the right. So far it is correct about the arrows.

Then if you fine tune to e.g. +10 you will get back focus and the opposite if you fine tune to e.g. -10, you'll get front focus.

However, when the lens is not focusing correctly, the situation is different. Let's say it is back focusing. The camera thinks it is focusing correctly, but when you turn the focus ring to the left to have correct focus, the camera will light up the left arrow. Since it's back focusing, what you need is negative fine tuning, when the left arrow lights up. Vise versa for front focus.

First, if English is not your first language, you must be pretty incredible in your native language because your English is near perfect. Second, you're explanation is exactly right. My brain was indeed inverted. I'll restate what you said in my own terms, just so that when I refer back to this my inverted brain with understand

If a body+lens tunes perfectly at +0 and I establish critical focus, then we get a green dot. If I then change AF tune to +10, I'm telling the camera "you are front focusing and I need to correct it by moving the focus +10 units toward infinity, so reinterpret what you think is perfect focus as actually being -10 tune units of front focus, so that you give me a right-pointing arrow indicating front-focus and I'll know to move the focus ring +10 units toward the left (infinity) before you give me a green dot".

Your explanation is better but my brain thinks in the garbage above :). Thanks again!

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