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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18 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.

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