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INDI Library v2.0.6 is Released (02 Feb 2024)

Bi-monthly release with minor bug fixes and improvements

Canon DSLR auto focus issues

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I think it is the latest version - but I‘ll check tonight to make sure.

I have thought about an explanation, why the focussing worked better with the former timer based version for the tamron and why I can use the far3...far1 selector in the indi panel but cannot use the buttons in the focus module - which are supposed to do literally the same thing.
I think the problem with the Tamron is that the focuser is slow. In the actual version, view finder mode is turned on, the far3...-command in being sent to the cam and viewfinder mode is switched off immediately. The slow focuser does not have enough time to act - maybe the cam needs the view finder mode during the full lens movement and the loss of view finder mode makes it terminate the movement.
In the timer based mode, far/near-commands were sent to the cam every 50ms during e.g.1000ms. So there was time to complete at least some of the far/near movements.
When I do it manually with the indi-panel, I don‘t switch off viewfinder mode at all between the movements and the capturing. There seems to be no problem taking images with the view finder mode turned on.

Maybe it would help (me?) if the viewfinder mode would not be switched on and off before and after everey focussing step but only once when entering the module? Then one has to make sure to re-enable view finder mode after a live preview window has been closed.
5 years 2 weeks ago #36208

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Ok, I just ordered an artificial star so I can test these things. At any rate, I add the fake "steps" now, so give that a go and see if it improves the behavior over the older method. Currently in gphoto_ccd.h you will see two constants here:

FOCUS_HIGH_MED_RATIO = 7.33
FOCUS_MED_LOW_RATIO = 6.36

Maybe these can be configurable later, but test with these value and change if necessary. Report back.
5 years 2 weeks ago #36213

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One idea:
Maybe it is worth trying to use the settle-value that can be adjusted in the focus module to introduce an adjustable time lapse between sending the focus command to the cam and disabeling view finder mode. If it is true, that lenses with slow focusers cannot complete the lense movement if viewfinder ist switched off too soon after the focussing command, this could help. Or one could put a sleep-time into the gphoto_ccd.h?
5 years 2 weeks ago #36220

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I just tried the new method.

My overall impression is that it works better than before. A strange thing is that I have to enable viewfinder mode manualle AND to force one focus move using the indi drop-down menu (far..-near..) to get the autofocus work.

I had several runs terminating successful. Some of them really lead to an excellent focus. Most of them either terminated not too far away from the actual focus (but it was still clearly visible that the actual focus had not yet been reached) or they the algorithm was stuck hunting an apparent minimum far away from the actual focus position.

I can see the algorithm is trying to find the minimum of a complete v-curve. The principal problem is that the absolute focuser position is only a fake value, and since the lense does not return to the same position with the exact counter-command, there happen to be more than one HFR at one focus position, which makes it hard (actually impossible) to calculate a slope. Sometimes the algorithm was iterating several steps very near an excellent focus position but did not stop to finally terminate in a far worse position.

The good news is that if I start near the actual focus, it is quite probable to terminate near the actual focus, in several cases nearer to it than initially.
5 years 2 weeks ago #36244

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Let me report some encouraging results:

I built the v-curve manually. I started in the acual focus position. At iso 800 I got an HFR of 3.9 for the optimal focus. I moved away from the optimal focus position in far3 steps, until I could see a really substancial increase of HFR. One far3 step did not change anything. The second gave a small change. The third step shifted HFR to 11.28. Since I new I had moved in far-direction I started moving inwards in near2 steps. Over the first 8 steps HFR did hardly vary. Then HFR started to decrease almost linearly until it reached a value of 3.91. Then the HFR started to increase almost linearly. I got a beautiful v-curve with a clearly visible minimum.

At HFR 12.36 I turned the direction of movement again and moved outwards again in far2 steps. Again over 8 steps nothing happened and then HFR decreased to the minimum and increased again.

At the next turnaround I tried 1 near3 before moving inward in near2 steps. Now I only had 4 backlash steps before HFR began to decrease.

Continuing this type of systematic variation I found that the change of direction should be done by two big steps in the oposite direction. This has the same effect as a instantaneous turnaround (no backlash) and about 3 steps of medium size in the oposite direction.

One safe way to reach the optimal focus position might therefore be to build the v-curve moving in equidistant steps in one direction. After the minimal HFR has been passed, one should continue at least 3 more medium steps into the same direction. Then make a turnaround with two big steps in the oposite direction and return to the minimal HFR in medium (or small?) steps.

I attach some screenshots and an excel sheet with the data I took. ...no, it won‘t let me attach the excel sheet.

One issue is, that the backlash is probably specific for different lense types.
The following user(s) said Thank You: Jasem Mutlaq
5 years 2 weeks ago #36296
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Here comes the zipped excel.

File Attachment:

File Name: focuser_test.zip
File Size:28 KB
5 years 2 weeks ago #36298
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Maybe the existing algorithm could be made working correctly if we introduce a backlash on every turnaraound, which might be adjustable. For my tamron the backlash would be 8 medium steps.
5 years 2 weeks ago #36301

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Replied by Alfred on topic Canon DSLR auto focus issues

Today my lense does not move at all no matter what I do. It won't focus neither with or without LiveView activated. I'm unsure whether or not this is a user error.
5 years 2 weeks ago #36305

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Try to enable view finder mode in the action panel of the indi dirver and select an item from the far3...near3 drop down menu (no matter which item you choose). This worked for me.
5 years 2 weeks ago #36306

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Replied by Alfred on topic Canon DSLR auto focus issues

Nope, sorry. Have there been any changes to the driver lately? It did work recently, albeit moving the mirror 80x up and down. No click-clack today at all.
Last edit: 5 years 2 weeks ago by Alfred.
5 years 2 weeks ago #36310

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I didn‘t upgrade today ...
5 years 2 weeks ago #36311

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Replied by Alfred on topic Canon DSLR auto focus issues

Then don't do it. ;-)
5 years 2 weeks ago #36312

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