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Question about taking aerial imagery.

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Offline waterwingz

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Re: Question about taking aerial imagery.
« Reply #20 on: 04 / July / 2013, 17:03:43 »
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Quote from: msl on 04 / July / 2013, 15:44:27
'if get_nd_present() ~= 0' => all cameras with iris diaphragm.
According to this - if get_nd_present() == 1 then there is no diaphragm.
http://chdk.wikia.com/wiki/Script_commands#get_nd_present

Quote
Are you sure that the command is ignored when the camera has no iris diaphragm? I have only cameras with iris diaphragm.
I'll take a look at the code and do some testing.  I have two cams with no diaphragms.
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Offline msl

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Re: Question about taking aerial imagery.
« Reply #21 on: 04 / July / 2013, 17:24:51 »
Probably my German documentation is wrong.  :(

Thanks for the correction.

msl
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Offline reyalp

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Re: Question about taking aerial imagery.
« Reply #22 on: 04 / July / 2013, 17:36:15 »
Code: [Select]
  int to;
  if (camera_info.cam_has_nd_filter == 0)
  {
    to = 0;
  }
  else
  {
    if (camera_info.cam_has_iris_diaphragm == 0)
      to = 1;
    else
      to = 2;
  }
  lua_pushnumber( L, to );
  return 1;
so
0 = no ND.
1 = ND only
2 = ND + iris

In practice, 0 means "has iris" since Canon has (AFAIK) never sold a camera with neither, and we don't have a way to represent that situation if they did.

"ND" here includes a swing in aperture that performs the same function in some early cameras.

not the clearest thing in the world  :blink:

edit:
so "has iris" is get_nd_present() ~= 1

ubasic uses identical logic
« Last Edit: 04 / July / 2013, 17:38:17 by reyalp »
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Offline peabody

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Re: Question about taking aerial imagery.
« Reply #23 on: 04 / July / 2013, 20:13:35 »
Quote from: waterwingz on 04 / July / 2013, 15:07:16

Thanks !  I think you are the first person to try AutoISO and report back here on how it seems to work. There is not a lot of documentation about the function beyond what you just wrote and this : http://chdk.setepontos.com/index.php?topic=7284

Well, unfortunately, what I was doing was based on a CHDK version back in 2009.  The current version's Custom Auto ISO, as described in the link you provided, is completely different, and apparently there is no explanation available for what the menu entries do.  Things like "Second alternative min shut".  Maybe tsvstar's post has it in there somewhere, but I simply couldn't understand him.  I hate it when things like this happen.  They just shouldn't put stuff in that nobody understands.

So I don't know where this leaves me.  I may restore the old version and just use that.  But that's not an acceptable solution for most others.
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Offline peabody

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Re: Question about taking aerial imagery.
« Reply #24 on: 04 / July / 2013, 21:59:39 »
It turns out that in Custom Auto ISO you can turn off the second alternative and overexposure stuff, and then it's supposed to work just like the old version.  I'll test that tomorrow when the sun is out.

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Offline peabody

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Re: Question about taking aerial imagery.
« Reply #25 on: 07 / July / 2013, 18:01:30 »
I wanted to report that the CHDK Custom Auto ISO function performed well in a KAP test I did today with my A590.  I set the Mode dial to [P]rofessional, and ISO to AUTO.  I had manual focus locked at infinity, IS off, zoomed all the way out, Daylight white balance.  Then in Custom Auto ISO I set the minimal shutter speed to 1/1000 second, and the ISO range from 80 to 800, with no alternate or overexposure settings.

On a sunny day, the camera took all the pictures at 1/1000 second, and the great majority were at ISO 100, F4.  The exceptions varied only in the ISO chosen - either 80 or 160 - so clearly the algorithm likes F4 for some reason  All the pictures were tack sharp, which you would expect at 1/1000 second even though the camera was swinging all over the place on the picavet rig.

A better test will be when there's less light, so we can see what it does when it has to compromise.  But I suspect this will end up being really useful in overcoming the camera movement that's inherent in KAP.

By the way, the script was just to SHOOT at the chosen interval.
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