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Dot-Tune: Autofocus Fine Tuning in under 5 minutes
  
 
RonMJ
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p.5 #1 · p.5 #1 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


schlotz wrote:
Process as described has the lens set to MF using the half shutter to activate the green AF dot.

Right. Not sure what I was thinking. I've been using MF the entire time.



Feb 17, 2013 at 04:10 PM
RonMJ
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p.5 #2 · p.5 #2 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


snapsy wrote:
Any delay between the shutter half-press and confirmation dot is an immediate disqualification of confirmation for that tune value. It's when there's no delay that I then suggest you keep holding the shutter for 5 seconds to see if the confirmation dot remains solidly lit. I also suggest additional 5-second half-presses at the same value when you're near either end of the tune range, to better confirm the feedback.

Thanks. That explanation cleared everything up. I ran four tests on the 85/1.8 again: -5 to -11; -6 to -12; +2 to -8; and -3 to -12. I'm tossing the +2 to -8 as an outlier and will average the MA scores for the other three, which were remarkably consistant (-8, -9, -7.5)



Feb 17, 2013 at 05:04 PM
Lasse Eriksson
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p.5 #3 · p.5 #3 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


Very interesting. I will try it the next weekend


Feb 17, 2013 at 05:09 PM
snapsy
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p.5 #4 · p.5 #4 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


I've created a simple AF tune midpoint calculator on my website. Here's the link:

http://testcams.com/DotTune/CalcMidPoint.html



Feb 17, 2013 at 07:11 PM
mrfozibear
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p.5 #5 · p.5 #5 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


Snapsy,

The newest version of the Reikan Focal Pro calibration software has a new method only available for Canon called Turbo Calibration Test (Plus/Pro). The DotTune results and the Turbo Calibration were very close. The only difference was that the Reikan system is fully automatic.

Chris



Feb 18, 2013 at 03:38 AM
snapsy
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p.5 #6 · p.5 #6 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


mrfozibear wrote:
Snapsy,

The newest version of the Reikan Focal Pro calibration software has a new method only available for Canon called Turbo Calibration Test (Plus/Pro). The DotTune results and the Turbo Calibration were very close. The only difference was that the Reikan system is fully automatic.

Chris


Thanks Chris. Someone on the canonrumors threaded posted the link as well. It appears they released it just a few days ago. Have you tried the TurboCal? Can you describe the process they have you go through to use it, and what it appears to do? Thanks!



Feb 18, 2013 at 03:57 AM
mrfozibear
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p.5 #7 · p.5 #7 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


It's a very simple process. 1) Setup Target, 2) Switch lens to MF, 3) Hit Start. The software does the rest. A series of beeps are heard as the software takes the lens through the process of acquiring focus. The software records several data points, then it predicts the AFMA.

Chris



Feb 18, 2013 at 05:08 AM
snapsy
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p.5 #8 · p.5 #8 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


mrfozibear wrote:
It's a very simple process. 1) Setup Target, 2) Switch lens to MF, 3) Hit Start. The software does the rest. A series of beeps are heard as the software takes the lens through the process of acquiring focus. The software records several data points, then it predicts the AFMA.

Chris


Are you required to establish the correct focus prior to starting the procedure? Do you see the lens actually acquiring focus as the test progresses, ie. distance scale moving indicating movement of the focus element? Is Live View ever entered during the process? Thanks again...



Feb 18, 2013 at 05:21 AM
dwweiche
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p.5 #9 · p.5 #9 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


snapsy wrote:
Are you required to establish the correct focus prior to starting the procedure? Do you see the lens actually acquiring focus as the test progresses, ie. distance scale moving indicating movement of the focus element? Is Live View ever entered during the process? Thanks again...


I'm curious how it could be completely automatic if you switch the lens to MF. There's no way for the focus motor to activate, correct?



Feb 18, 2013 at 05:56 AM
snapsy
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p.5 #10 · p.5 #10 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


I've published a DotTune tutorial on YouTube. Video Link


Edited on Feb 18, 2013 at 11:32 PM · View previous versions



Feb 18, 2013 at 07:59 PM
 

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Psychic1
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p.5 #11 · p.5 #11 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


snapsy wrote:
I've published a DotTune tutorial on YouTube. Video Link


Needs more volume



Feb 18, 2013 at 08:20 PM
ciprian.trofin
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p.5 #12 · p.5 #12 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


Love it. Autofocus fine tuning in under 5 minutes.

The video is 18+



Feb 18, 2013 at 10:04 PM
snapsy
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p.5 #13 · p.5 #13 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


Psychic1 wrote:
Needs more volume


Done, thanks! New link is here



Feb 18, 2013 at 11:32 PM
RonMJ
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p.5 #14 · p.5 #14 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


snapsy wrote:
I've published a DotTune tutorial on YouTube. Video Link

In the video, the correct midpoint is -4, not 4.



Feb 18, 2013 at 11:54 PM
snapsy
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p.5 #15 · p.5 #15 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


RonMJ wrote:
In the video, the correct midpoint is -4, not 4.


Thanks Ron! The video shows -4 but it seems I said "4" instead of "minus 4". Hopefully it'll be clear from the video. I can't believe you caught that - I would have watched it a 100 times and probably failed to notice every time. Thanks again.



Feb 19, 2013 at 12:10 AM
Wilba
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p.5 #16 · p.5 #16 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


snapsy wrote:
That a lens can be consistently out-of-spec in regards to its mechanical positioning relative to where its directed, and that this condition can only be fixed through manufacturer shimming/adjustment as the 50mm manual you referenced indicates, is actually further support for the notion that AF tune cannot correct for such conditions, and that it wasn't designed to.


Okay, I see where you're coming from. BFCV doesn't have anything to do with mechanical positioning. (It doesn't matter for AF accuracy if there is a mechanical positioning error, since the body will command the lens to move until the AF sensor sees an in-focus subject - accuracy depends on detection, not motion. You can induce a mechanical positioning error by using a short extension tube, and the system will still achieve accurate focus.)

AFAIK shimming only affects where "infinity" focus via the focus ring ends up.

BFCV is a number sent by the lens to the body on request, which tells the body how to align a phase match with optimum focus, just like MA does with a value stored in the body. Check out Doug Kerr's Canon EOS Autofocus - BFCV and micro-adjust (MA) for more info.



Feb 19, 2013 at 03:38 AM
Psychic1
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p.5 #17 · p.5 #17 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


snapsy wrote:
Done, thanks! New link is here


Excellent, Thank you Can you lower the volume of my wife



Feb 19, 2013 at 10:19 AM
Stoffer
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p.5 #18 · p.5 #18 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


snapsy wrote:
Done, thanks! New link is here


Most excellent!




Feb 19, 2013 at 12:53 PM
nalax
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p.5 #19 · p.5 #19 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


Thanks, I "snapsy'd" five lenses this morning!


Feb 19, 2013 at 08:18 PM
snapsy
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p.5 #20 · p.5 #20 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


Wilba wrote:
Okay, I see where you're coming from. BFCV doesn't have anything to do with mechanical positioning. (It doesn't matter for AF accuracy if there is a mechanical positioning error, since the body will command the lens to move until the AF sensor sees an in-focus subject - accuracy depends on detection, not motion. You can induce a mechanical positioning error by using a short extension tube, and the system will still achieve accurate focus.)

AFAIK shimming only affects where "infinity" focus via the focus ring ends up.

BFCV is a number sent by the lens to the body on request, which tells
...Show more

That's a really interesting post, thanks Wilba. So it sounds like the lens has an internal database of offsets which the camera can use to bias the PD sensing mechanism to account for positional-specific lens aberrations that would otherwise produce incorrect PD sensing. I imagine the lens could also use the database to offset mechanical nonlinearities in the AF motor/servo.



Feb 19, 2013 at 08:57 PM
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