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.
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)
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.
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!
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.
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...
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?
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.
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.
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 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....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.
