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Thread started 19 Feb 2013 (Tuesday) 17:01
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DotTune: AF fine tuning without photographs

 
john_galt
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Feb 21, 2013 22:34 |  #16

just watched the vid. ive always relied on the af confirm beep sound or the viewfinder lighting up red. never really noticed the green dot. is it possible the af confirm beep can sound but the green dot still be flickering?


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Feb 21, 2013 23:14 |  #17

I don't think so. I think the audible beep sounds and viewfinder lights every time the AF green dot is fully activated. The green dot may flicker but only when it lights up fully, if only for a brief second is when the beep and viewfinder react.

I have never heard the beep sound raspy/squeaky or the the red light in the viewfinder look like it is flickering on any camera I have opened.


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dphorshack
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Feb 21, 2013 23:30 |  #18

john_galt wrote in post #15638416 (external link)
just watched the vid. ive always relied on the af confirm beep sound or the viewfinder lighting up red. never really noticed the green dot. is it possible the af confirm beep can sound but the green dot still be flickering?

That's a really good question, because it opens the door to using the audible beep for confirming tune values rather than just the viewfinder dot. I just tried it on my 5DM3 and the beep sounds for every flicker of the green light, so one could use multiple beeps to detect a non-confirmed tune value. However I'm not certain if the beep will always cycle for really fast green-dot flickers, although it appears to in the test I just tried. You also get the same delay of the beep whenever you get a delay of the green light, which means you can also used the delay of the beep as a non-confirmation signal. I just tried it on my D800 as well but there is no beep in manual focus mode like on the Canon. So for Canon at least we can call this BeepTune in addition to DotTune :)




  
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digital ­ paradise
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Feb 21, 2013 23:47 |  #19

Is that during the DotTune procedure or normal AF acquisition? I just tried my 5D3 during normal operation and every time I half depress the shutter and AF is acquired the green dot, red screen illuminate and audible beep sounds. A second later the beep is silent and red focus screen goes black but the green dot stays fully illuminated until I take my finger off the shutter. No flickering during normal focus acquisition. I have only seen the green dot flicker when using DotTune.


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francis_a
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Feb 22, 2013 10:04 |  #20

This is brilliant. So basically use the contrast-detect's AF as the base and adjust the phase-detect's AF to match.

Thank you for sharing.


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Ember42
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Feb 22, 2013 15:20 |  #21

This is basically like something I suggested should be implemented directly into the camera software years ago. It would use live view to focus on on something flat but with high contrast (and confirm it was an appropriate subject). Drop the mirror. Take a phase detect read. Set the calibration so the value read is considered to be zero. Change focal length. Repeat. Easy.
Maybe this would be something ML would be able to do?




  
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jhayesvw
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Feb 22, 2013 15:54 as a reply to  @ Ember42's post |  #22

If I shot with a prime I would do this but I'm not sure how helpful it will be for the massive range of 100-400mm that I use on my wildlife lens.
Im mostly (90% of the time) at 400mm but I dont want OOF pics when I do pull back a bit.

it looks like a good method though.



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Feb 22, 2013 16:30 |  #23

Ember42 wrote in post #15641030 (external link)
This is basically like something I suggested should be implemented directly into the camera software years ago. It would use live view to focus on on something flat but with high contrast (and confirm it was an appropriate subject). Drop the mirror. Take a phase detect read. Set the calibration so the value read is considered to be zero. Change focal length. Repeat. Easy.
Maybe this would be something ML would be able to do?

From the ML website on the "Do not request - we can't do this" forum.


AF microadjustment
Not possible to control AF outside LiveView.


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dphorshack
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Feb 22, 2013 16:43 |  #24

digital paradise wrote in post #15638617 (external link)
Is that during the DotTune procedure or normal AF acquisition? I just tried my 5D3 during normal operation and every time I half depress the shutter and AF is acquired the green dot, red screen illuminate and audible beep sounds. A second later the beep is silent and red focus screen goes black but the green dot stays fully illuminated until I take my finger off the shutter. No flickering during normal focus acquisition. I have only seen the green dot flicker when using DotTune.

Mine does the same. But if the green dot does ever flicker then you'll get an additional beep and focus screen flash.




  
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dphorshack
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Feb 22, 2013 16:45 |  #25

WaltA wrote in post #15641290 (external link)
From the ML website on the "Do not request - we can't do this" forum.


AF microadjustment
Not possible to control AF outside LiveView.

They must have put that there after getting lots of requests for the feature in the past. There's an active effort to get DoTune implement into ML. ML Thread Link (external link).




  
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Rai33
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Feb 22, 2013 20:38 |  #26

dphorshack wrote in post #15638062 (external link)
If you're not comfortable relying on your own judgement for critical focus you might consider using contrast-defect AF in LV for the focusing step instead. CDAF is not infallible but Roger Cicala's tests at LensRentals indicate it is highly accurate and precise.

IMO something like Focal saves all that hassle especially when you have multiple lenses and multiple bodies. Interesting comment re. LV contrast-detect AF - though maybe more accurate who's to say there's not a degree of error there also.


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Invertalon
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Feb 25, 2013 17:30 |  #27

I must say, I was skeptical with Dot-Tune... But once I did it, I was VERY surprised how good it is. Without a single shutter actuation to boot...

I have tried every single MA process out there... FoCal, Lens Align, etc... They work, but are a lot of work to get accurate results.

After I setup my target outdoors (FoCal target) and got everything aligned on the tripod, I followed the Dot-Tune method. I would live-view focus, carefully switch to MF, and cycle through the MA values. This is very quick once you get a feel for the "range" of your camera. For the 5D3, it appears to be +14 or +15 from either end to the other, so once you find one, you can very quickly get the other value in seconds.

I had my lenses calibrated via FoCal, so I had a baseline to compare with and improve on. First up, was my 24-70 II.

Ran the process at 24mm 5 times, which took about 3-4 minutes roughly. Live-view also has a slight focusing tolerance, so you do get a little variance. I just removed the line or two that was abnormal from the other 2-3. I chose the most consistent pairs of numbers. My final value came out to -2W... My Focal value was -2W...

At 70mm, same process as above. My final value came out to +1... FoCal was +1 as well. Easy enough.

With my 70-200 II, FoCal alwayssssss has a hard time with this lens for whatever reason. Not my specific lens either, as I have tested a few different ones... Either way, my values were +5W and +4T via FoCal. After running this method, I got +4W and +3T. Results look excellent!

With my 1.4x III attached, FoCal had me at around 0 (each result was different) at 98mm and +8 to +12 at 280mm... I ran this method and got -1W and +8T...

I am quite happy to have this method versus using FoCal which was a pain with the software crashing, inconsistent results all the time, etc...

Excellent way to MA your lenses, for sure.


The only "trick" is choosing your end values... For example, at -5 it may give a green dot instantly and beep but if you click it a few times you may get a few delayed beeps signalling you are beyond correct focus lock... So go to -4 and see if it beeps each time instantly. I check each point 5-10 times (quick enough), to make sure. Also, if your MA value is +/- 10 units in either direction you may get beeping all the way up through +20 or -20... That is why it is good to know your camera AF "spread" which is quite consistant. On my camera, it was always around 14 units from min to max, almost always. So if you got a beep at +10 and not +9, you can assume your other end is +24, and your MA value would be +17 for example.


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Feb 25, 2013 19:33 |  #28

I did a bunch of tests yesterday and so far seems to be sound. It confirmed that my 70-200 II is way out. I could establish + 2 @ 70 for my final average but at 200 it was still beeping @ +20 so I could not go further. It would not beep at any negative value, did not beep from + 1 to +7. Finally beeped at +8 so at this puts me @ +14 but I'm not sure how much higher it would have gone past +20. This confirms my real world shots I'm getting. My shooting partner as the same lens, tried it and he said it was quite soft. It is going to Canon.

My 24-70 II is spot on. -1 @ 24 and +1 @ 70 which basically matches my real world results.


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Feb 26, 2013 01:37 |  #29

It seems you guys use a focus chart target to focus on. Is there any good focus target aside from focus charts? I dont have a printer available at the moment thats why I cant print a focus chart. Do you recommend using real life objects like bottles or something?


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Feb 26, 2013 02:14 |  #30

I have tried this out in the field with my 500 and 1DIV and 5DIII. Taking the middle point of the values never worked for me, I was always 10cm infront of the focus point. So I looked and found things to note, and I was 30M or more from subject... so variations will apply depending on distance and focal length.

"The DOF beyond the subject is always greater than the DOF in front of the subject. When the subject is at the hyperfocal distance or beyond, the far DOF is infinite, so the ratio is 1:∞; as the subject distance decreases, near:far DOF ratio increases, approaching unity at high magnification. For large apertures at typical portrait distances, the ratio is still close to 1:1. The oft-cited rule that 1/3 of the DOF is in front of the subject and 2/3 is beyond (a 1:2 ratio) is true only when the subject distance is 1/3 the hyperfocal distance."

From here:


http://en.wikipedia.or​g/wiki/Depth_of_field (external link)


http://natureimmortal.​blogspot.com (external link)

http://www.natureimmor​tal.com (external link)

  
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DotTune: AF fine tuning without photographs
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