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Dot-Tune: Autofocus Fine Tuning in under 5 minutes
  
 
snapsy
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p.12 #1 · p.12 #1 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


sritri wrote:
Snapsy - Being pretty anal about my equipment's shape rather than using it to enjoy photography, I sent in my 7D to Jamesburg for a paid AF check. It came back with a note that everything was in perfect order. However when I ran the FocalPro on it all my lenses showed a +/- 7. I resent it under repair warranty back to Jamesburg and now I can't seem to get a definite reading from FocalPro. I tried your excellently documented Dot-Tune method and the entire range of -20 to +20, the light is instantaneously green. Any tips to lead
...Show more

What lens and focus distance did you try your DotTune at? (I checked the EXIF on your image but didn't find any lens info).



Apr 02, 2013 at 09:43 PM
sritri
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p.12 #2 · p.12 #2 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


Both the photos with 300/4 L IS on a tripod. I also did try the 500/4 L IS. Similar result. From the 500:






*









Apr 03, 2013 at 01:25 AM
wardy
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p.12 #3 · p.12 #3 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


Tag


Apr 03, 2013 at 01:38 AM
Stilltime
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p.12 #4 · p.12 #4 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


snapsy wrote:
Did you make sure to leave your D600 body and lens in AF mode and use back-button focusing? Otherwise you'll get a tune range that includes +20 and/or -20. The reasons are discussed here (Nikon-specific).


D'oh! I was following the video and didn't see that update.. Thank's for pointing that out!! I will re-do it tomorrow, once I got the hang of it the process went very quick. Should be interesting to see how close they will result regardless.

Thanks again,

Chris C.



Apr 03, 2013 at 02:55 AM
KF
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p.12 #5 · p.12 #5 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


I really want to give it a try too. Sound all very interesting

Just a few practical questions about the recommended minimum test distances (50x the focal length) if I may.

-This means for my 800mm this will be 40 meters.....
and if I use the 1.4x extender on this lens as well, the test distance should be 56 meters?
Seems a bit much and not very practical maybe
I think I read somewhere that for super tele lenses you could use 20x or 25x focal length

-What about a 100mm macro lens, does the 50x rule apply for this lens as well?

-Zoom lenses: should I change the distances for the wide and tele end of the zoom lenses (if used on a Canon 5DMkIII or DX) for best results or just leave the distance at max focal length x 50 ?

Thanks,

Koen.



Apr 03, 2013 at 04:41 PM
sritri
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p.12 #6 · p.12 #6 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


I redid everything from scratch again with the 7D and 300/500 f/4 L. As always I placed the target on a well lit wall and 50 x f/l distance. The median for the 300 seems to be +/-11 and +/- 7 for the 500. Not sure if I need to get mama Canon involved to lower the MA

* 7D + 300/4 L IS - IS turned off - Weighted tripid + remote release







* 7D + 500/4 L IS - IS turned off - Weighted tripid + remote release









Apr 04, 2013 at 01:18 AM
ChrisPiX
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p.12 #7 · p.12 #7 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


I was not very happy with my 24LII's focus performance, so I tried the dot tune on my 1DX with three of my lenses.

These are my findings:

50L f1.2: -11 -> +6 MA: +3
24LII f1.4: +1 -> +19 MA: +10
135L f2: -2 -> +14 MA: +6


I was rather surprised that my 135L was so far off, but I'm looking forward to try them all out in real world after calibration.

Chris



Apr 04, 2013 at 08:12 AM
robinlee
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p.12 #8 · p.12 #8 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


Hi KF,

Canon recommended between 25x to 50x of the lens FL. However I did my EF500mm near MFD and it is now tack sharp. Before it needed +10 MFA, I rechecked twice or 3 times before adjusting it and tested outside and it seems to confirm that +10 MFA is needed for the lens. My house is small and could not achieve the minimum 25x the FL unless I do it outdoor which is not that convenient. This is my first lens that needed MFA otherwise my 24-105mm, 50mm 1.4 and 70-200mm F4 IS does not require MFA.

Hope that helps.

KF wrote:
I really want to give it a try too. Sound all very interesting

Just a few practical questions about the recommended minimum test distances (50x the focal length) if I may.

-This means for my 800mm this will be 40 meters.....
and if I use the 1.4x extender on this lens as well, the test distance should be 56 meters?
Seems a bit much and not very practical maybe
I think I read somewhere that for super tele lenses you could use 20x or 25x focal length

-What about a 100mm macro lens, does the 50x rule apply for this lens as well?

-Zoom lenses: should I
...Show more



Apr 04, 2013 at 11:08 AM
schlotz
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p.12 #9 · p.12 #9 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


ChrisPiX wrote:
I was not very happy with my 24LII's focus performance, so I tried the dot tune on my 1DX with three of my lenses.

These are my findings:

50L f1.2: -11 -> +6 MA: +3
24LII f1.4: +1 -> +19 MA: +10
135L f2: -2 -> +14 MA: +6

I was rather surprised that my 135L was so far off, but I'm looking forward to try them all out in real world after calibration.

Chris


hmm... -11 to +6 is 17 so the midpoint is 8.5 -11+8.5 = -2.5 or -3 vs. +3



Apr 04, 2013 at 05:13 PM
KF
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p.12 #10 · p.12 #10 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


Thanks for your reaction Robin.
My house is not that big either
So I will just go ahead within my possibilities...

Koen.


robinlee wrote:
Hi KF,

Canon recommended between 25x to 50x of the lens FL. However I did my EF500mm near MFD and it is now tack sharp. Before it needed +10 MFA, I rechecked twice or 3 times before adjusting it and tested outside and it seems to confirm that +10 MFA is needed for the lens. My house is small and could not achieve the minimum 25x the FL unless I do it outdoor which is not that convenient. This is my first lens that needed MFA otherwise my 24-105mm, 50mm 1.4 and 70-200mm F4 IS does not require MFA.

Hope that helps.





Apr 04, 2013 at 05:43 PM
 

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Bones74
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p.12 #11 · p.12 #11 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


I just completed the test with my 5D3 and 35L and 70-200 ii (wide end only). I used a white sheet of A4 paper with black print on it stuck to a window at + - 50 x F/L for both. I used manual focus and live view focus to get initial optimum. Both lenses came up with a +1 result. Well the 70-200 was 1.5 so I chose 1. Thanks Snapsy


Apr 04, 2013 at 06:26 PM
james.d53
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p.12 #12 · p.12 #12 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


Snapsy,

I read somewhere that for lenses with a focal length of 200 or over use 25X. Can you or anyone else confirm this?

James



Apr 04, 2013 at 08:44 PM
Rajan Parrikar
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p.12 #13 · p.12 #13 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


Excellent method. Thank you, Snapsy. Extra care required while calibrating lenses f/2 and faster for consistency in measurement.


Apr 04, 2013 at 08:47 PM
Bones74
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p.12 #14 · p.12 #14 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


Rajan Parrikar wrote:
Excellent method. Thank you, Snapsy. Extra care required while calibrating lenses f/2 and faster for consistency in measurement.


True, I tested each end of the range 3 times with the 35L. It changed the second time but was consistent the third and last time.



Apr 04, 2013 at 09:16 PM
ChrisPiX
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p.12 #15 · p.12 #15 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


schlotz wrote:
hmm... -11 to +6 is 17 so the midpoint is 8.5 -11+8.5 = -2.5 or -3 vs. +3



Ooops... Thanks for the correction, and sorry for the confusion.
You are right it should read:
50L f1.2: -11 -> +6 MA: -3



Apr 05, 2013 at 09:18 AM
jmvdigital
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p.12 #16 · p.12 #16 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


I don't know about everyone else, but I repeated the Dot Tune procedure a couple of times, choosing a slightly different part of the focus chart I was using each time. I got multiple results for each lens. Some calculated tunes varied from +1.5 to +8 for the same lens. The biggest swing was with the 70-200mm 2.8L II + 1.4x extender. I tested that combo about a dozen times and got ten different results, I just kind of averaged them. Maybe I was doing something wrong?

I also determined that you get different results if you choose an only horizontal target, versus a vertical one, versus a target that has mixed horiz/vert under the focus point.



Apr 05, 2013 at 08:49 PM
ChrisPiX
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p.12 #17 · p.12 #17 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


I MA'ed a few more lenses today, plus check of some of my first results.
To my relief they were quite consistent with my previous results.
It seems that there is a tolerance of about 16 MA steps on the lenses, if your results are out of scale (fx.: +12 -> out of scale), I guess it would be fairly accurate to adjust it to +12+(16/2)=+20. Or if you are lazy just add +8 to your lowest value.

Also I noticed that when I was unsure of AF confirmation, you can try pressing quickly multiple times, to check if the AF confirmation flashes accordingly.


50L mm: -11 -> +6 MA: -3
24L mm: +1 -> +19 MA: +10
135L mm: -2 -> +14 MA: +6
85L mm: -8 -> +9 MA: 0
100L mm: 0 -> +16 MA: +8
200LII mm: -2 -> +14 MA: +6

Chris



Apr 06, 2013 at 03:45 PM
robinlee
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p.12 #18 · p.12 #18 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


Since I have MFA my EF500mm, I managed to borrow 1.4x tc at my locals, following picture is a coal tit which landed on top of the overhead cable whilst doing my test. It is nearly 70% crop and it was stacked 1.4x which gives 980mm effective FL. Shot raw converted in ACR, some exposure correction, default sharpening, opened in CS6 and resize for web (bicubic auto), I am impressed




Apr 06, 2013 at 07:18 PM
gschlact
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p.12 #19 · p.12 #19 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


Sritri- did you remember to put the lens into to manual Focus mode? I think it might impact it.
snapsy wrote:
What lens and focus distance did you try your DotTune at? (I checked the EXIF on your image but didn't find any lens info).




Apr 06, 2013 at 10:22 PM
gschlact
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p.12 #20 · p.12 #20 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes


I dwelled on this post below that I found relevant after getting quite frustrated with a manual focus f1.8 old Nikor lens on my Canon 7D and attempting MFA with an AF confirm adapter...
(Proper MFA should be set into the adapter itself as instructed.)

Please let me know what you think of the following new modified method - Guy's Method for MF AF Confirm Adapters (GMFMACA) I thought up...

Consider the following.....
-Since Each body has the range of working MFA values that gives AF Confirm, when using the manual focus lens to take a shot the AF Confirm Light will beep/ turn on if your turn on confirming focus to anywhere in the MFA range.
- you cut your error in half by DOTuning to proper value.
- I have this new idea to add to try and remove MFA/2 error.
---- if you offset the proper mid-point mfa setting by 1/2 of the Camera's MFA range, and use this offset Sum you now can utilize the "edge" of AF detection knowing it really is the true center point.
---- let's use an example to demonstrate on the MF lens..
------- sample lens has range of 14 with midpoint at +7 true correct setting.
------- taking a shot with non modified method on this lens would actually turn on the confirm light within range by as much as front or back focus value focus shift equal to 7mfa units (what ever that translates into in distance for that situation)
------- now we utilize my New method and enter 0 as the modified MFA value pulling the rear edge of focus forward to the actual correct point of focus. (I hope this is clear)
----------- Using this method, we must always start from an infinity focused lens. As the user manually focuses to nearer distances to take a shot they will eventually hit the rear edge of AF confirm and know that is best choice of focus.

Let me know if you think is helps optimize results??

-Guy
gschlact


Papathanassiou wrote:
I Apologise Ian because I couldn't get my head around what you meant!

What I should have stated with these Third Party Manual Focus lenses is that most are wide angle, say up to 50mm,
and doing the Dot Tune adjustment if required, and then going by the VF confirmation in the view finder you will be after the adjustment, getting a more accurate focus. Hope you get what I 'm trying to explain, sorry that is the best I can do!

Papa.




Apr 06, 2013 at 11:30 PM
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