Manual Focus @ Infinity not working

waterwingz

12140

Re: Bump : Manual Focus @ Infinity not working

« Reply #120 on: 26 / November / 2015, 20:58:01 »

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Quote from: srsa_4c on 26 / November / 2015, 20:38:12

While this sounds like a good plan, it may present some difficulties, especially on cameras with longer zoom.

I've actually thought about longer zoom cameras quite a bit. As I have access to a "megazoom" (SX50) I considered experimenting with interpolating across larger zoom steps. Don't know if that will work but it's not a difficult experiment to run.

And the issue about what the camera actually focuses on might be manageable if the script, at each zoom step, requires the user to press "Func/Set" to focus & refocus until the observed result is good, and "Menu" to accept the result of that focus. A somewhat painful process, and you would only have the LCD to judge focus quality by, but you would only have to do the whole process once per camera and only if you want to be able to set focus at infinity reliably when using CHDK.

I'm open to better ideas. Right now we have nothing for cameras that don't set MF as expected.

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Also, there will be users who only need accurate focus at wide angle.

I suppose you could start the calibration script at wide angle, record calibration data one zoom step at a time, and allow the user to abort when they have the focus range they need covered?

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Ported : A1200 SD940 G10 Powershot N G16

c_joerg

1250

Re: Manual Focus @ Infinity not working

« Reply #121 on: 27 / November / 2015, 04:22:42 »

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As I have access to a "megazoom" (SX50)

Me as well

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Right now we have nothing for cameras that don't set MF as expected.

I played a lot of time the last days, to get sharp pictures with SX50 with full zoom from the moon.

But what should I say; I get only really sharp pictures from the moon with autofocus (I have not tried Hyperfocal Distance yet). All pictures with manual settings are not really sharp, independent if I use a CHDK script with -1 setting or in the Canon Menu. On the Canon MF Settings, I have to go a little bit lower as infinity, to get sharp pictures, but this also changes from time to time (I think it is temperature dependent).

I have also some not sharp pictures with autofocus. Interesting is, that I found on these pictures an infinity value in the EXIF data. All sharp pictures have a value smaller than infinity.

I think, they do the same as on my DSLR lenses. These lenses can focus above infinity. One reason to do this is to compensate temperature changes.

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waterwingz

12140

Re: Manual Focus @ Infinity not working

« Reply #122 on: 27 / November / 2015, 08:45:01 »

Quote from: c_joerg on 27 / November / 2015, 04:22:42

But what should I say; I get only really sharp pictures from the moon with autofocus (I have not tried Hyperfocal Distance yet). All pictures with manual settings are not really sharp, independent if I use a CHDK script with -1 setting or in the Canon Menu. On the Canon MF Settings, I have to go a little bit lower as infinity, to get sharp pictures, but this also changes from time to time (I think it is temperature dependent). I have also some not sharp pictures with autofocus. Interesting is, that I found on these pictures an infinity value in the EXIF data. All sharp pictures have a value smaller than infinity.

Again lending credence to my theory that the calibration of native Canon MF settings is not particularly good. And that we might be able to calibrate the lens mechanical position needed for an accurate infinity focus at specific zoom settings.

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One reason to do this is to compensate temperature changes.

Agree - it might be a temperature issue too - which will tend to throw off calibration a bit. But I think that some of the issues we saw were much bigger that something caused by temperature changes.

Also, in addition to simple calibration errors, there might be so much slop/backlash/hysteresis/chatter in the inexpensive plastic gear drive of the focus controller mechanism that the actual physical position changes with every focus attempt for the same MF setting.

I guess the only way to find out is to write the script and see how well it works.

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Ported : A1200 SD940 G10 Powershot N G16

msl

1280
A720 IS, SX220 HS 1.01a

Re: Manual Focus @ Infinity not working

« Reply #123 on: 27 / November / 2015, 15:20:05 »

In my opinion it is the wrong approach, when you think you always get a sharp photo, if you set the focus to infinity. This is more a matter of chance.

The manual focus of our cameras only works at close range very good.
Try the native MF mode of cameras with this mode. You get the same bad results in the infinity.

Work more with the DOF Calculator. The subject distance should be between near and far limit and not infinity. The hyperfocal distance is also a very good helper because this is a fixed physical value.

Depending on the lens and the focal length are only very few large focus values adjustable. Try to jump from a higher to lower value you will get different values than vice versa. This means setting the focus distance also depends from the starting point.

msl

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CHDK-DE: CHDK-DE links

waterwingz

12140

Re: Manual Focus @ Infinity not working

« Reply #124 on: 27 / November / 2015, 15:51:03 »

Quote from: msl on 27 / November / 2015, 15:20:05

In my opinion it is the wrong approach, when you think you always get a sharp photo, if you set the focus to infinity. This is more a matter of chance.

@msl : Thanks for the well thought out response. Like srsa_4c and c_jourg you raise many good questions.

The problem is that there are situations where you really want to automatically lock focus at infinity (or far away). This comes up a lot in KAP photography when the camera AF mechanism focuses on the kite string and not the landscape. And when shooting quicky (UAV and other intervalometer applications) you may not want an AF step between each shot - both for time and power consumption reasons.

So how do we tell users to set their cameras if we can't automatically focus out at infinity?

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The manual focus of our cameras only works at close range very good. Try the native MF mode of cameras with this mode. You get the same bad results in the infinity.

Yes - I agree. This is something important that I think we have learned. Although some (many? most?) cameras seem to do quite well with the CHDK set_mf (655232) approach to infinity. And almost all camera will find a sharp setting for distant object using AF mode.

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Work more with the DOF Calculator. The subject distance should be between near and far limit and not infinity. The hyperfocal distance is also a very good helper because this is a fixed physical value.

Using near and far limit values might be useful if you are attempting to manually focus and have an AF setting to use as a starting point. Or am I missing something that would allow an unattended camera on a moving platform to use this method without needed to engage autofocus?

I did play with hyperfocal distance as a replacement for "infinity" but as I recall, the results were not much better on cameras that could not crisply focus at infinity in the first place.

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Depending on the lens and the focal length are only very few large focus values adjustable. Try to jump from a higher to lower value you will get different values than vice versa. This means setting the focus distance also depends from the starting point.

I've noticed that too. But having only a few valid "focus steps" (I think that's what you mean) should simplify the problem. We only need to get close to make this work much better than what we have today.

The question remains - can we provide a script that generates a table of values relating zoom step to mechanical position, that may not be perfect but that will give an acceptable 'infinity focus' for those circumstances where it is needed / wanted ?

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Ported : A1200 SD940 G10 Powershot N G16

Michel2e

79

Re: Manual Focus @ Infinity not working

« Reply #125 on: 27 / November / 2015, 16:47:29 »

Having received good support some months ago here, i would be pleased to help if you want me to test some scripts for you. I've been using multiple s100 for kap, and after multiple tests i came back to AF to ensure appropriate/reliable results. only one of my cameras can properly work with MF. and i recently found a second hand s100 which is the worse i've used. when setting AF, when focus is good at infinity, the get_focus command returns some values around 2m.
I could maybe look also if i have list of associated distance/lens_mecha/zoom steps. i usually record these datas, but do not necessarily keep them very long.

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waterwingz

12140

Re: Manual Focus @ Infinity not working

« Reply #126 on: 27 / November / 2015, 18:35:33 »

Quote from: Michel2e on 27 / November / 2015, 16:47:29

Having received good support some months ago here, i would be pleased to help if you want me to test some scripts for you.

That's great - thanks for that!

Maybe it's because it's a popular KAP camera, but the S100 seems to have the most reported problems. Your comment about 2m being the focus point for infinity (assuming a full wide angle setting) is inline with what srsa_4c saw on his camera.

I'll work on a two test scripts tonight - one to generate a zoom position vs mechanical position file and the other to use the resulting SD card file to try and set focus at infinity and shoot. As long as you have a distant subject scene that won't distract the camera at wide angle with nearby objects, it should be a quick test on each of your S100's

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Ported : A1200 SD940 G10 Powershot N G16

reyalp

14110

Re: Manual Focus @ Infinity not working

« Reply #127 on: 27 / November / 2015, 18:58:18 »

FWIW, one thing I noticed while writing the script for http://chdk.setepontos.com/index.php?topic=12103.10 is that there are (at least) 3 different sd values: chdk get_focus, and two propcases. The get_focus value comes from some DOF calculator code I didn't dig into, and in some cases disagreed substantially with the propcases. I don't recall the two propcases having different values.

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Don't forget what the H stands for.

waterwingz

12140

Re: Manual Focus @ Infinity not working

« Reply #128 on: 27 / November / 2015, 19:33:13 »

Quote from: reyalp on 27 / November / 2015, 18:58:18

FWIW, one thing I noticed while writing the script for http://chdk.setepontos.com/index.php?topic=12103.10 is that there are (at least) 3 different sd values: chdk get_focus, and two propcases. The get_focus value comes from some DOF calculator code I didn't dig into, and in some cases disagreed substantially with the propcases. I don't recall the two propcases having different values.

Thanks - so noted. I remember that DOF code and I'm hoping to avoid using either CHDK's or Canon's SD values. If, on a per-camera basis, we can find a stable mechanical position at each zoom step that gives a sharp infinity image in AF mode, and then use that to set the mechanical position for our current zoom step when we want an infinity focus, I think we are done.

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Ported : A1200 SD940 G10 Powershot N G16

Michel2e

79

Re: Manual Focus @ Infinity not working

« Reply #129 on: 28 / November / 2015, 06:06:23 »

if of interest here are typical results
here are 2 pics from this testing session. JPG direct from camera.
https://www.dropbox.com/s/8q6lqn1l3x6nevh/IMG_1435.JPG?dl=0
https://www.dropbox.com/s/cucllxv7kswrs4j/IMG_1436.JPG?dl=0

the first one seems sharp (AF), the second blurred(MF). (basic idea is to have automatic reshoot in MF if AF results is not infinity. of course this is couter productive there)
in the xml files datas recorded show opposite results
https://www.dropbox.com/s/8nxed0j1f41wce4/1435.XML?dl=0
https://www.dropbox.com/s/prm6e2j4tkj4k3o/1436.XML?dl=0

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