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Dot-Tune: Autofocus Fine Tuning in under 5 minutes
  
 
snapsy
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p.6 #1 · p.6 #1 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


Thanks for the awesome new OP Fred!


Feb 19, 2013 at 09:01 PM
RAF09
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p.6 #2 · p.6 #2 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


Thanks for your efforts in bringing this process to light. This seems like a great idea, I will be using it ASAP.


Feb 19, 2013 at 11:28 PM
Wahoowa
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p.6 #3 · p.6 #3 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


Just like to thank snapsy for this. It's a simple method that any engineer should be able to think of, but have never thought about. I'm excited to try this out.


Feb 20, 2013 at 02:13 AM
joelconner
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p.6 #4 · p.6 #4 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


tagging...thanks!


Feb 20, 2013 at 04:16 AM
Lars Johnsson
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p.6 #5 · p.6 #5 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


Thanks a lot Snapsy and Fred. I will try it later. And also compare it against my FoCal


Feb 20, 2013 at 04:43 AM
Tapeman
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p.6 #6 · p.6 #6 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


Thanks Snapsy, I played a bit using you method and will set up targets an do all my lenses.


Feb 20, 2013 at 04:50 AM
LizWangPhotog
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p.6 #7 · p.6 #7 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


Very nice, wow, made the FMer family proud! I'm going to try this...


Feb 20, 2013 at 05:00 AM
TTLKurtis
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p.6 #8 · p.6 #8 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


So out of curiosity how does this work with a zoom lens? For example I ran this test with a 24-70mm lens with the following results:

@24mm: -3 to +7 => +2
@50mm: -3 to +4 => -1.5
@70mm: -5 to +8 => +1.5

If you average the three together, you're looking at a +.67 adjustment. So round up to +1 and that's the proper adjustment, or should the adjustment ideally be the same at any focal length of the zoom lens and the lens should be calibrated by the manufacturer?



Feb 20, 2013 at 05:58 AM
Beau.b
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p.6 #9 · p.6 #9 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


This is great.

Just completed Dot-Tune for my 16-35L, 85mm, and 70-200 2.8L IS on my 5d Mark III

Have to say I had to fudge a couple feet on the tight end of the 70-200, hard to find 33 feet to backup.

Excited to play with the results.

Need to do the same on my 7D



Feb 20, 2013 at 07:49 AM
leftcoastlefty
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p.6 #10 · p.6 #10 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


I don't understand why micro focus adjustment is so popular. I have two bodies and nine lenses and have been shooting for years and I have never noticed an issue that could be solved by MA. And I often shoot wide open where focus is rather important. I suspect that many (most?) people are brainwashed into believing they might need it even though they have no evidence that it is really needed. Somebody needs to do a poll to see how many people actually get positive benefits from MA.

TTLKurtis wrote:
So out of curiosity how does this work with a zoom lens? For example I ran this test with a 24-70mm lens with the following results:

@24mm: -3 to +7 => +2
@50mm: -3 to +4 => -1.5
@70mm: -5 to +8 => +1.5

If you average the three together, you're looking at a +.67 adjustment. So round up to +1 and that's the proper adjustment, or should the adjustment ideally be the same at any focal length of the zoom lens and the lens should be calibrated by the manufacturer?


TTLKurtis, I think you need to lay off the KoolAid and go back to shooting. I'm pretty certain that plus or minus 1 on the MA is well within the margin of error. I bet you could set it to +/- 4 and not notice a real-world difference.




Feb 20, 2013 at 07:39 PM
 

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TTLKurtis
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p.6 #11 · p.6 #11 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


leftcoastlefty wrote:
I don't understand why micro focus adjustment is so popular. I have two bodies and nine lenses and have been shooting for years and I have never noticed an issue that could be solved by MA. And I often shoot wide open where focus is rather important. I suspect that many (most?) people are brainwashed into believing they might need it even though they have no evidence that it is really needed. Somebody needs to do a poll to see how many people actually get positive benefits from MA.

TTLKurtis, I think you need to lay off the KoolAid and go
...Show more

Haha, yeah I know that such a minor adjustment isn't going to matter much in the real-world. I'm more-so asking out of curiosity. I've never been a fan of KoolAid myself.



Feb 20, 2013 at 07:49 PM
pbraymond
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p.6 #12 · p.6 #12 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


Tag


Feb 21, 2013 at 01:15 AM
Wilba
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p.6 #13 · p.6 #13 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


snapsy wrote:
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.

Exactly. I think of MA as a BFCV which is specific to the combination of an individual lens with an individual body (stored in the body). Or you can think of BFCV as a microadjustment which is specific to an individual lens with respect to a reference body (stored in the lens).

What I'm not sure about yet is whether BFCV is an array (indexed by focus position), or a table (indexed by...?). I'm working on getting that information.

snapsy wrote:
I imagine the lens could also use the database to offset mechanical nonlinearities in the AF motor/servo.


Yeah, maybe. It might help with speed, to cut down the number of iterations.



Feb 21, 2013 at 04:19 AM
dwweiche
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p.6 #14 · p.6 #14 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


TTLKurtis wrote:
So out of curiosity how does this work with a zoom lens? For example I ran this test with a 24-70mm lens with the following results:

@24mm: -3 to +7 => +2
@50mm: -3 to +4 => -1.5
@70mm: -5 to +8 => +1.5

If you average the three together, you're looking at a +.67 adjustment. So round up to +1 and that's the proper adjustment, or should the adjustment ideally be the same at any focal length of the zoom lens and the lens should be calibrated by the manufacturer?


You have a math error, but ultimately is doesn't change your number. Your adjustment at 50mm is wrong. -3 to +4 yields a +0.5, not a -1.5.

So your average is +1.33



Feb 21, 2013 at 05:53 AM
zacheryjensen
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p.6 #15 · p.6 #15 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


I gave this method a try with my Nikkor 85mm ƒ/1.8G. I already have it tuned so I thought it would be a good test. The resulting range where I got an unwavering digital rangefinder "dot" was nearly 75% of the range of adjustments: 11 to -19.

That hardly gives me a sense of confidence.

That said, the center of that range, -4, is only one off of what I had previously determined to be the correct adjustment of -5.

I had less luck applying this technique to my 70-200/4 zoom. The rangefinder inconsistency seemed greater at some focal lengths than others. In fact, at 200mm, the rangefinder thought every single adjustment, 20 to -20 was in focus… not helpful, especially since test photos showed otherwise.

Anyway, that's just my experience with it.



Feb 21, 2013 at 09:23 AM
Paul Mo
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p.6 #16 · p.6 #16 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


leftcoastlefty wrote:
I don't understand why micro focus adjustment is so popular.



I have a theory. But I am in the same boat as you - I have never bothered with. Neither have the patience or time.



Feb 21, 2013 at 09:49 AM
a.RodriguezPix
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p.6 #17 · p.6 #17 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


bookmarked!


Feb 21, 2013 at 09:58 AM
Davis B.
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p.6 #18 · p.6 #18 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


How do you get the chart, I get a message it unavailable


Feb 21, 2013 at 12:59 PM
Zenon Char
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p.6 #19 · p.6 #19 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


Paul Mo wrote:
I have a theory. But I am in the same boat as you - I have never bothered with. Neither have the patience or time.


What is your theory?



Feb 21, 2013 at 01:01 PM
Ian.Dobinson
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p.6 #20 · p.6 #20 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


OK first let me say im liking the idea of this method and when i have a spare couple of hours in the day i will have to give it a shot.
but I also have an idea (with a question) that may add to this method using Canon's softwre (i have no idea about nikons software)

when your tetherered and using Canon's softwre you can bring up the live view picture on screen. and you can also adjust focus using the '<<< < > >>> ' . my question is how do the smaller step <> buttons have any relation to a step in the MA values.?

if they do then you should be able to :
1:set you MA value to '0'
2: use Phase detect AF to focus on your target
3: using the canon software click > or < until you have the best focus. and count how many presses gave you the best focus.
4: set your MA value to the same number as the number of clicks gave the best focus.
5: put the lens out of focus and have it refocus
6: back to the screen and see if you have the best focus

Just a suggestion. if the <> steps are not in relation to the MA adjustments then it obviously wont work

PS
I would try this myself (and indeed will sometime soon) but at the moment I dont have a USB cable long enough to get my camera in a decent position to my Desctop . and my netbook seems not to like the canon software / tethered camera



Feb 21, 2013 at 01:57 PM
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