# DotTune: Video Tutorial for AF tuning without photographs



## horshack (Feb 19, 2013)

I've just posted a video tutorial of the DotTune technique. Here is the link:
DotTune: Autofocus fine tuning in under 5 minutes


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## digital paradise (Feb 19, 2013)

Thanks for the video.


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## eninja (Feb 19, 2013)

Thanks. Will try it.


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## AlanF (Feb 19, 2013)

Thanks for all the efforts - the video is a great tutorial and involved a lot of work. Much appreciated. Unfortunately, it's not working for my Series II 300mm f/2.8 and and Series III extenders on the 5D III. It's way, way out. This is bad news for me because the dot light is out of step with live view, and I know live view is correct. It;s not your method that is wrong, it is the Canon protocol. It is also very disturbing that there is such a wide span of dot focussing in manual mode. It means that you can't rely on it for manual focussing but you have to use live view.


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## East Wind Photography (Feb 19, 2013)

Too bad the video still does not make this method work reliably. Failed on all attempts with both a 5DIII and a 1DX.

18 minute video to demonstrate a 5 minute process?


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## horshack (Feb 19, 2013)

AlanF said:


> Thanks for all the efforts - the video is a great tutorial and involved a lot of work. Much appreciated. Unfortunately, it's not working for my Series II 300mm f/2.8 and and Series III extenders on the 5D III. It's way, way out. This is bad news for me because the dot light is out of step with live view, and I know live view is correct. It;s not your method that is wrong, it is the Canon protocol. It is also very disturbing that there is such a wide span of dot focussing in manual mode. It means that you can't rely on it for manual focussing but you have to use live view.



Thanks Alan. I actually own a 300mm V1 and extender but not with me unfortunately.


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## horshack (Feb 19, 2013)

East Wind Photography said:


> Too bad the video still does not make this method work reliably. Failed on all attempts with both a 5DIII and a 1DX.
> 
> 18 minute video to demonstrate a 5 minute process?



It's worked well for most, though I don't reasonably expect it to work for everyone or in all situations, the same as how other methods don't work in all scenarios. LOL about the 18 minute video description for a 5 minute procedure, I thought the same thing after I was done editing it. I tried to present the material as concisely as possible but it's always a juggling act between brevity and thoroughness. The sample DotTune session at the end of the video is only 3 minutes though.


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## Rienzphotoz (Feb 19, 2013)

EXCELLENT Video ... will look forward to your follow up video. Thanks for all the hard word you put into this video and for sharing.


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## Rienzphotoz (Feb 19, 2013)

Do you have any plans on making a Dot Tune video for zoom lenses? ... I suppose it'd be very tedious but it would be awesome if did make a video for zoom lenses.


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## AlanF (Feb 20, 2013)

Maybe DotTune is a test for the calibration of the phase detection calibration of the camera. If the requirement for AFMA is that the camera has correct calibration and the lens needs correction, then DotTune should surely work because live view and PD will be correctly aligned. But, if the lens is correctly calibrated and it is the camera that requires calibration, then DotTune will fail. For example, if the camera's PD leaves the factory at effectively -10, then if you test a lens that is perfect using FoCal or the sloping ruler method, an AFMA of +10 is required. But, if you use DotTune, then a reading of -10 for AFMA will be found because the miscalibrated PD will be 10 units less than it should be. Similarly, if the camera is -5 and the lens is +5, FoCal or the ruler will give +10 but DotTune will give +5.


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## East Wind Photography (Feb 20, 2013)

Your AFMA value will only be as good as the accuracy of the AF detect. If the AF detect in your model is ineffective at determining where the AF DOF falls off then it can't accurately calculate the AFMA value. Has nothing to do with the PD calibration of the camera. In fact some have shown that the AF detect fall off is not symmetric around the ideal AFMA value. Without symmetry your setting will always be off. The lack of symmetry cant always be blamed on the camera either. PD system works more or less efficiently depending on how parallel the light rays are coming into it's sensor. Some lenses also tend to be OOF in front of the subject but have more DOF behind the subject. In those cases the symmetry will be off and an incorrect AFMA value may be calculated when using the Dot method. There are lots of factors that throw off the AF detect systems which is why this is not reliable.



AlanF said:


> Maybe DotTune is a test for the calibration of the phase detection calibration of the camera. If the requirement for AFMA is that the camera has correct calibration and the lens needs correction, then DotTune should surely work because live view and PD will be correctly aligned. But, if the lens is correctly calibrated and it is the camera that requires calibration, then DotTune will fail. For example, if the camera's PD leaves the factory at effectively -10, then if you test a lens that is perfect using FoCal or the sloping ruler method, an AFMA of +10 is required. But, if you use DotTune, then a reading of -10 for AFMA will be found because the miscalibrated PD will be 10 units less than it should be. Similarly, if the camera is -5 and the lens is +5, FoCal or the ruler will give +10 but DotTune will give +5.


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## horshack (Feb 20, 2013)

AlanF said:


> Maybe DotTune is a test for the calibration of the phase detection calibration of the camera. If the requirement for AFMA is that the camera has correct calibration and the lens needs correction, then DotTune should surely work because live view and PD will be correctly aligned. But, if the lens is correctly calibrated and it is the camera that requires calibration, then DotTune will fail. For example, if the camera's PD leaves the factory at effectively -10, then if you test a lens that is perfect using FoCal or the sloping ruler method, an AFMA of +10 is required. But, if you use DotTune, then a reading of -10 for AFMA will be found because the miscalibrated PD will be 10 units less than it should be. Similarly, if the camera is -5 and the lens is +5, FoCal or the ruler will give +10 but DotTune will give +5.



This gets into the inner workings of PDAF and how it relates to AF tune. My working theory is that AF tune addresses mis-alignments/mis-calibrations of anything to do with the full optical path of the PD sensing mechanism. This particularly includes the lens, which can have optical aberrations that lead to incorrect PD phase readings (since the split light beam on the mirror is sampled from opposite sides of the lens, any decentering, even slight, can cause the PD phase readings to be off). It also includes lens mount alignment of the body+lens, mirror and prism alignment, and the AF sensors themselves. Basically everything but the lens AF motor/servo. Since PDAF has been found to demonstrate closed-loop attributes, any AF-motor/servo specific issues should in theory be automatically corrected during the multiple iterations of the sensing+movement cycles involved in a single PDAF acquisition.


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## horshack (Feb 20, 2013)

Rienzphotoz said:


> Do you have any plans on making a Dot Tune video for zoom lenses? ... I suppose it'd be very tedious but it would be awesome if did make a video for zoom lenses.


DotTune works the same for zoom lenses. The only difference is that some zooms exhibit focal length-specific tune differences, which isn't unique to the tuning method used but is instead a property of the lens or lens+AF system. The typical recommendation is to tune at the focal length you use most often, or to tune at some in-between focal length as a compromise, provided that compromise produces acceptable results for you.


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## AlanF (Feb 20, 2013)

Thanks East. It's clear whatever the reason that DotTune doesn't work for me. The sloping ruler method does because it is a direct readout of where the lens is focussing. My focus is spot on using it.


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## Rienzphotoz (Feb 20, 2013)

horshack said:


> Rienzphotoz said:
> 
> 
> > Do you have any plans on making a Dot Tune video for zoom lenses? ... I suppose it'd be very tedious but it would be awesome if did make a video for zoom lenses.
> ...


OK ... thanks


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## Northstar (Feb 20, 2013)

Nice video, I look forward to trying out dot tune.


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## PhotoCat (Feb 20, 2013)

Very informative video and it took a lot of work to make it. 
Thanks horshack for sharing this idea freely.
Highly appreciated. I will definitely give that a try.


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## Northstar (Feb 21, 2013)

PhotoCat said:


> Very informative video and it took a lot of work to make it.
> Thanks horshack for sharing this idea freely.
> Highly appreciated. I will definitely give that a try.




I agree about sharing the idea freely BUT...as Horshack, once he knew the answer to the afma question he had to scream to the dslr world....OH OH OH....OH OH OH OHH OHH OHH!!

Welcome back Kotter.


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## PhotoCat (Feb 21, 2013)

It worked on my 5D2 and 85/1.8 combo! This is the first time I have any consistent results from AFMA!
A value of -10 makes my full length portrait much sharper at f1.8 at a shooting distance of 12 to 17.5 feet.

A -10 AFMA would however make any shots less then 10 feet away slightly OOF and I am not surprised as this appears to be one limitation of Canon's AFMA implementation to date IMHO. Canon's AFMA appears subject distance dependent.
For that kind of shorter distance (< 10 feet), I needed to turn off AFMA to get a sharp image.

It seems that Canon's factory lens calibration is much better than can be achieved by on-camera AFMA, as far
as distance dependence is concerned.

Now sigma has the USB lens dock for focus calibration, I hope Canon would catch up quickly by offering a Canon USB lens dock so we can perform factory quality lens calibration at home...


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## PhotoCat (Feb 21, 2013)

Mmm... forget about the lens dock... Canon can do better by incorporating the lens calibration software right inside EOS Utility and calibrate the lens while it is attached to the specific camera body... It is 100x better than a lens dock!


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## horshack (Feb 24, 2013)

*Magic Lantern DotTune*

FYI, the guys over at Magic Lantern have implemented an automated version of DotTune. You establish critical focus in LV the same as the usual DotTune method but then ML takes over and automatically scans the AF tune range to find the optimal value, and saves the value into the camera when done. 

Here's a video demonstrating the alpha version of the feature running on my 5DM3:
DotTune coming to Magic Lantern!


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## East Wind Photography (Feb 24, 2013)

*Re: Magic Lantern DotTune*

Will the AFMA value be retained if you remove ML and boot in native mode? ML is great but most versions still are not stable enough to use in critical shoots.




horshack said:


> FYI, the guys over at Magic Lantern have implemented an automated version of DotTune. You establish critical focus in LV the same as the usual DotTune method but then ML takes over and automatically scans the AF tune range to find the optimal value, and saves the value into the camera when done.
> 
> Here's a video demonstrating the alpha version of the feature running on my 5DM3:
> DotTune coming to Magic Lantern!


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## horshack (Feb 24, 2013)

*Re: Magic Lantern DotTune*



East Wind Photography said:


> Will the AFMA value be retained if you remove ML and boot in native mode? ML is great but most versions still are not stable enough to use in critical shoots.



Yep, it stores the calculated AFMA value in the same non-volatile memory position that the Canon firmware uses, so it will be persistent across power cycles and available even if you're not using ML.


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## East Wind Photography (Feb 24, 2013)

*Re: Magic Lantern DotTune*

Congratulations! This is an excellent first step which will only improve going forward.



horshack said:


> East Wind Photography said:
> 
> 
> > Will the AFMA value be retained if you remove ML and boot in native mode? ML is great but most versions still are not stable enough to use in critical shoots.
> ...


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## digital paradise (Feb 24, 2013)

Well DotTune did confirm my suspicions. First off the using the new method where you stop at the instant AF acquisition worked good. It only made a difference for +3 to +2 for my final MFA but still much easier to work with.

It did confirm my new 70 to 200 2.8 II is way out at 200. It still beeps at +20 and stops beeping at +7 which put me around +14. That was confirmed by real world shots. Major difference at 0 and +14. Not even thinking about a work around - it is off to Canon.


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## East Wind Photography (Feb 24, 2013)

OMG, before you spend $$$ shipping your stuff back to Canon + insurance, You better validate your results with a sloped ruler test. Dont rely too heavily on the DT results as the AF detect systems are not very accurate. It may get you in the ball park but unless you have a way to categorically verify your setting, it could be way off. I cant get DT to give me an accurate AFMA. When I compare with my lensalign target it's off by 8 AFMA and for that lens it's a full DOF.

More work needs to be done to make the AF detect system accurate and reliable.



digital paradise said:


> Well DotTune did confirm my suspicions. First off the using the new method where you stop at the instant AF acquisition worked good. It only made a difference for +3 to +2 for my final MFA but still much easier to work with.
> 
> It did confirm my new 70 to 200 2.8 II is way out at 200. It still beeps at +20 and stops beeping at +7 which put me around +14. That was confirmed by real world shots. Major difference at 0 and +14. Not even thinking about a work around - it is off to Canon.


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## digital paradise (Feb 25, 2013)

There is no doubt that lens is out. My shooting partner has one, he tried it and found it was soft. I noticed it right away after I got it. After comparing shots @0 and +14 you could see +14 was much sharper. +14 is unacceptable for what I paid. I appreciate your support but I'm sending it in just for the piece of mind alone. 




East Wind Photography said:


> OMG, before you spend $$$ shipping your stuff back to Canon + insurance, You better validate your results with a sloped ruler test. Dont rely too heavily on the DT results as the AF detect systems are not very accurate. It may get you in the ball park but unless you have a way to categorically verify your setting, it could be way off. I cant get DT to give me an accurate AFMA. When I compare with my lensalign target it's off by 8 AFMA and for that lens it's a full DOF.
> 
> More work needs to be done to make the AF detect system accurate and reliable.
> 
> ...


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## digital paradise (Feb 25, 2013)

Oh yes. I tried DotTune with my 24-70 II using the new focus acquisition method. -1 @ 24 and +1 @ 70 which basically matched my real world results I'm getting.


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## digital paradise (Feb 27, 2013)

I would love to see an app for this. I don't really want to download ML at this point. Something that worked like this. It could do several LV readings, establish the best one and then run through the - + routine several times. You could do this anywhere in minutes. 

http://www.shutterbugremote.com


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## tomscott (Feb 28, 2013)

What I dont get is that if you are using a zoom is where to AFMA. I use a 24-105mm and according to LR I use it all across the zoom range. Ive read that with zooms your better off AFMA'ing at the tele end so say a 24-105 at 105 or 70-200mm at 200.

Also if you AFMA from the distance calculated does that mean at other distances the lens wont operate as well. Im a bit confused.

Seems like a complete pain.


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## digital paradise (Feb 28, 2013)

You are supposed to MFA at the longest focal length. Probably to the second question. If you have a camera like the 5D3 you are covered at both ends.


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## tomscott (Feb 28, 2013)

So you can have 2 AFMA values for one lens on the 5DMKIII? For wide and tele?


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## East Wind Photography (Feb 28, 2013)

Only for zooms and only for the full wide and full tele positions. No guarantee that an extrapolated AFMA will work for in between values. However because your DOF is deeper at wide angles it's "less" important as at full tele.

So depending on how far off the AFMA is through the range, you might be able to get away with using an AFMA value for the wide setting that is more in tune with one of your most used MID ranges and let DOF mask the error wide open.

Depends a lot on the lens and how far off the AFMA is through the zoom range. If the AFMA swings wildly through the zoom range it might not be possible to fudge the AFMA.



tomscott said:


> So you can have 2 AFMA values for one lens on the 5DMKIII? For wide and tele?


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## tomscott (Feb 28, 2013)

Ok great thanks for the information!


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## digital paradise (Feb 28, 2013)

My new 70-200 is plus 2 @ 70 and plus 18 @ 200. It is go ing to Canon


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