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02-24-2013, 12:50 PM   #1
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Anybody tried DotTune AF finetuning?

A photographer has published a video presenting a method for finetuning individual lens AF using the MF focus confirmation. Has anybody tried the method and how well does it work with Pentax MF focus confirmation?

DotTune: Autofocus fine tuning in under 5 minutes - YouTube

02-24-2013, 12:57 PM   #2
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Hm - I'll try this later with my Sigma 50 F1.4. It's a very logical concept.
02-24-2013, 03:13 PM   #3
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Very complicated i think but would like to try it out. I use CIF, first set focus manually then adjust AF microadjustment until the shutter fires, voila. This applies only to MF lenses.
02-24-2013, 03:53 PM   #4
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Looks good to me. I just tried it on my Sigma 70-200 and realized I had dialed-in too much compensation previously. Sure enough, using the new setting works marvelously.

02-24-2013, 04:02 PM   #5
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It's not as complicated as it sounds and seems pretty good.
02-24-2013, 05:25 PM   #6
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Just tried it on tripod with my Sigma 50 1.4. Took a few tries to get it correct. It says my lens needed +85 micrometers, when my previous testing method said I needed +60 micrometers. That's reasonably close to each other, in my opinion. As such, I have it set currently to +80 micrometers.
02-24-2013, 06:00 PM   #7
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this looks like a great method
02-25-2013, 10:18 AM   #8
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K-r with Pentax F 35-70

Using this technique with the lens wide open (f/3.5 - 4.5) I had a usable focus range of +7 to -10 ... that is a lot of wiggle room! The results were about the same at either 35mm or 70mm. I set the AF Fine Adjustment to -1.

I had used this method previously to calibrate the kit 18-55 and came up with -4 at mid-range. I understand I am referring to two different lenses, but to me it does confirm a small front focus deviation with my camera.

The most important thing to me out of this test is that using the focus indicator with manual lenses may not be all that dependable unless I am using a fast lens wide open. The same would likely be true for Catch In Focus shooting.

02-25-2013, 11:15 PM   #9
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Quite a range on my K-30 with the Tamron 28-75 F2.8..
-4 to +8 which gives me a midpoint of about +2

Last edited by crossmr; 02-25-2013 at 11:43 PM.
02-25-2013, 11:28 PM   #10
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Ive used it with my D700 and have had pretty good results with it
02-25-2013, 11:44 PM   #11
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Want to calibrate my 70-300 tamron as well, but I don't really have 3.5 meters in my small apartment to lay it out

managed to get a space with light..
-10 to +5 for this lens..
who knows if it would go below -10 or not.
Not sure what to think when it hits the lower limit.

Last edited by crossmr; 02-26-2013 at 12:11 AM.
02-27-2013, 08:45 AM   #12
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Brilliant ! It works very well, and is by far the easiest AF fine-tuning method I've tried so far.
10-29-2017, 06:14 AM   #13
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QuoteOriginally posted by crossmr Quote
Want to calibrate my 70-300 tamron as well, but I don't really have 3.5 meters in my small apartment to lay it out

managed to get a space with light..
-10 to +5 for this lens..
who knows if it would go below -10 or not.
Not sure what to think when it hits the lower limit.
Hi, can you please share the steps to finetune zoom lenses? The video is about finetuning the AF on prime lenses only. Thank you
03-01-2018, 09:30 PM   #14
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I have used this method, it is quick and works just fine. Now if you want to make things interesting use it on the side focus points. On my 35mm f2.4 & 50mm f1.8 plastic lenses the side point yields substantially different values. When calibrated a side point yields sharp focus on the target but the rest of the image is degraded. I assume this is due to decentered elements. This issued renders the Select Point auto focus setting useless. Note: Unlike what some would say, I found the side point very accurate when calibrated. My 40mm f2.8 limited & 35mm f2.0 suffered much less from this issue.
03-03-2018, 10:19 PM   #15
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QuoteOriginally posted by lushdimple11 Quote
Hi, can you please share the steps to finetune zoom lenses? The video is about finetuning the AF on prime lenses only. Thank you
The video alludes to it briefly, but basically if a lens needs a different adjustment at different focal lengths, you have to decide do you a) pick your most used focal length in the range and tune to that exactly or b) check different parts of the range and find a value somewhere in the middle of the range. The second option is a comprimise because the focal behavior of a zoom changes, but the camera only has a single value to configure.

So for instance, it you have a 16-85, and at 16 your range is -5 to -10 and at 85 your range is +5 to +10, you could say you have two values -7.5 and +7.5 so the midpoint is 0. But that assume the change is linear. So if you try a few more values, you could average them.
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