DotTune – Autofocus Fine-Tuning in under 5 Minutes

It’s been 2 1/2 years since I posted my DotTune video on YouTube and I’m only now getting around to posting a blog entry for it 🙂 Once I’m done with the V1.1 release of Airnef I plan to create a home page for DotTune, where I’ll post some updates and a FAQ.

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22 Responses to DotTune – Autofocus Fine-Tuning in under 5 Minutes

  1. Jerry says:

    Hi,

    I have written a simple Android calculator for this method of AF fine tuning. I’m planning to make it a free app in the play store.

    If you have no objections I would like to include a credit to you for the method and possibly a link to the video / website in the app / app description.

    Best regards

    Jerry

  2. Adam says:

    Hi Jerry,

    Sorry for getting back to you late. Sure, that sounds great, thanks!

    Adam

  3. cymon taylor says:

    sorry if i missed something where can we find the download please. Many Thanks

  4. James says:

    Hi Adam,
    I noticed something while calibrating my D810 that wasn’t mentioned in the set up procedures. I got consistently 1 point off when compared to setting in camera Picture Control to [SD]Standard, rather than [FL]Flat. So my Midpoint in [SD] was 4, while the midpoint in [FL] was 5. I would suggest that [SD] mode with its increased contrast is likely more accurate even though I shoot mainly Raw mode with the Picture Control set to [FL]. This is likely due to the visual effect of the Picture Control setting influencing the LCD when focusing in Live View mode.
    James

  5. Noel West says:

    On canon systems is there a difference between setting the focus using live view af vs quick mode where the mirror flips up and the cameras af chip sets focus? I used the latter and was finding quite a lot of variability in my results using the same lens with two different bodies.

    Thanks!

    • Adam says:

      Hi Noel,

      Sorry for the late reply. Yes, there is a difference. Normal LV AF uses contrast-detect AF, which is the more accurate and precise method (at least on Canon bodies). Canon’s “quick mode” uses the normal phase-detect AF, which is the same as the VF AF mode. For the AF step of DotTune you definitely want to use CDAF or manual AF.

  6. Paul Blount says:

    I have created an Excel spreadsheet that does the calculations for you so that you don’t have to be connected to the internet to use yours. I would like to credit your work on the spreadsheet and then share the spreadsheet with others. Do you have any issues with this? Thanks.

  7. I’m trying to use Dot Tune to fine tune my Nikon 105mm Macro lens. I’m getting a solid dot at -17 thru -20! I’ve tried it at approximately 17 feet and also at the minimum focus distance, not sure what distance to use on a macro lens. Does anyone have any suggestions on testing this lens?

    Thanks – Rick

    • Adam says:

      Hi Rick,

      I’ve documented a method for performing a DotTune on lenses that have +/- 20 in their confirmed AF range. You can see it here: http://www.fredmiranda.com/forum/topic/1187247/23#12503510

      • Dragos says:

        Hi Adam
        plese tel me in what direction to defocus the lens? i also have two lenses that reach confirmed -20 range.

        and second question, it’s normal to have from +3 to -20 confirmed range, or it’s to big?
        regards

        • Adam says:

          The direction depends on whether your at -20 or +20. For simplicity you can just use trial and error to figure out which focus-ring direction will get you away from the -20/+20 boundary.

          The width/size of the confirmed range is not an issue – that’s a function of the lens, focal length, focus distance, DOF, etc.. As long as the full range fits within +/- 20 then the midpoint will give you the optimal tuning value.

  8. mel says:

    Are there any other considerations for doing long lenses? 600mm or with an additional 1.4 converter? If I calculate the distance for a 600mm it would be around 100 feet if you still use the 50x lens length?

    Thanks

    • Adam says:

      I’ve switched to using infinity for most of my tuning rather than 50x, so try using a distant object like a mountain or house.

  9. Phil Olenick says:

    Adam,

    I used your method and I’m happy with the result. I’m thinking about getting a circular polarizer that would fit onto two of my lenses (my walk-around 18-135 and my 10-18 wideangle – I use a crop-sensor Canon) but I’m deterred by concern that it might throw off the tuning.

    Is this something to worry about or not?

    • Adam says:

      Hi Phil,

      It’s a good question. It’s been a while since I’ve used my polarizer so I can’t say for certain. However anything along the optical path has the chance to affect the AF tuning, particularly any element that may introduce decentering issues.

      • Phil Olenick says:

        What I would do is record the values without the polarizer and then run the test again with the polarizer, and write those values down as well. It would be a pain to have to re-enter the tweaks every time I put the polarizer on or take it off, if I’ve written the two sets of values down, it wouldn’t be insurmountable.

        Since I’m going on vacation in a little over a week, if I’m going to do this, I’d have to order the polarizer and quickly dot-tune for those two lenses (which take the same size filter) with it, before going away.

        If I spring for the polarizer – which isn’t cheap – and do this, I’ll let you know if it makes any difference!

      • Phil Olenick says:

        The other question I have is whether different orientations of the polarizer would require different tweaks – if so, viewfinder focusing would be out of the question. Instead, I’d have to rely entirely on LiveView focusing, which at least is pretty fast with the current dual-pixel Canon sensors.

  10. Dave says:

    Hi Adam,

    I have a couple questions:

    1) At about 11:18 of the video, you say that if the range finder arrow points to the right, then move in the positive direction or the negative direction if the arrow points to the left. But then at about 15:10 of the video, the arrow points to the right but you are going in the negative direction! Am I missing something here?

    2) In the case of a fractional midpoint, is it better to round in the direction closest to zero or is this lens dependent?

    I saw in the YouTube comments that you verified that a midpoint of -13 to +5 is -4 and not +4.

    Thanks.

    • Adam says:

      Hi Dave,

      Sorry about the late response. You are correct about the arrows – I had it backwards in the video. For fractional midpoints I would try to round in direction that favors the strongest confirmation at either end, which is hard to establish most of the time so you should be fine rounding in either direction.

  11. Amy says:

    Hi. What a fabulous video. Thank you. I have a Canon 6d and a 70-200 2.8 that is older. If I did everything correctly, I got a +8 for the 200 and got a start range of -16 down to -20 for the 70, and it did not end. I could tell it was way off when I looked at images. Any advice? I am going to try and clean the contact points tonight to see if that helps. And last summer, when I got the camera, I also used a 24-70 2.8 and it worked for 8 frames and then flashed error and the lenses sounded like there was sand when you tried to focus. I may try to pull that one out again and see if it works. But thanks. I have been shooting with the camera out of focus for a year and had no idea that you had to calibrate lenses. Old lady here had a film camera which never had to be calibrated. Lol

    • Adam says:

      Thanks for the kind words. If you’re range is starting at -16 and continues through -20 then all you can really do is set it to -20 if you plan to be shooting at that focal length. If that doesn’t produce good results (which is likely since the range is starting so far near the edge of the range) then you’re only alternative would be to send the body and/or lens in to adjust the AF. Another alternative would be to use Magic Lantern on your 6D, which supports AFMA values beyond +/- 20, although I have never tested values outside of +/-20 before. Good luck!

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