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Another weather balloon question from a newbie....

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Offline mrkrinkle

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Another weather balloon question from a newbie....
« on: 02 / March / 2011, 08:47:03 »
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Hi guys- new to CHDK and scripting, so feeling a bit bewildered with it all!

Like a few other first-time posters on these boards, I'm aiming to send a couple of cameras up on a weather balloon.

I was just wondering if anyone had some pointers for settings to use... I want to learn how to write scripts anyway, so I'm not after a pre-made .lua or anything, but could do with some pointers for basic settings such as shutter speed etc. I'm not much of a photographer if I'm honest!

The camera will be in a box attached to a balloon, so will be moving around quite a bit, and will go from daylight on the ground, to a mix of dark and light from the ground below at altitude. Is there a generic setting which would still deliver decent quality images? Not so bothered about the ground level images, but the ones from altitude are quite important!

Is it possible to use parts of the scrip[t like building block? ie: a section of script which makes the camera power on and take a burst of 10 photos, combine that with some lines which control video capture, temperature logs etc.

Sorry if this is all very basic- I'm a complete beginner, but willing to learn!

Will be happy to share what I hope will be successful results once I get them back!
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Offline Microfunguy

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Re: Another weather balloon question from a newbie....
« Reply #1 on: 02 / March / 2011, 09:27:34 »
The first thing you have to do is write, in plain English, the sequence of actions that you would like to be carried out.


David
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Offline mrkrinkle

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Re: Another weather balloon question from a newbie....
« Reply #2 on: 02 / March / 2011, 12:04:26 »
In order to write the scripts, or to get an answer?

I would like to the camera to take a burst of a preset number of pictures, then a video of a preset length. this would repeat until batteries died or memory was full. I think I can cope writing such a script / amending an existing one, but it's things like aperture settings and shutter speed which I'm going to fall over on to be honest.
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Offline Microfunguy

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Re: Another weather balloon question from a newbie....
« Reply #3 on: 02 / March / 2011, 13:11:13 »
A slight misunderstanding  ... to specify the outline of a script  :)

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it's things like aperture settings and shutter speed which I'm going to fall over on to be honest

No mention of that in your 'specification' above.
You must be precise.

Is your 'burst' a series of bracketing exposures ?
« Last Edit: 02 / March / 2011, 13:14:10 by Microfunguy »
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Offline mrkrinkle

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Re: Another weather balloon question from a newbie....
« Reply #4 on: 03 / March / 2011, 06:45:02 »
No worries!

I think I'll need to do some reading around terms... by bracketing, do you mean a series of shots of varying settings, in order to get the best available shot? So for example under-exposing, using "auto" settings, and overexposing each shot- in effect ending up with multiple versions of the same shot, from which you can select the "best"?

I hadn't considered this, but now that you mention it, I think it would be a good choice.

I managed to get a simple script working last night, which takes a shot every 30 seconds (but interval can be edited from the FUNC / SET menu).

If I wanted to add in some lines which set the camera to what I've outlined above (under, auto, over), is it just a case of copying those lines of script in, or would I have to rewrite the whole thing to include those settings? In other words, can this script be used like building blocks, with different elements tacked on?

If so, then the blocks I will need are:

1) Interval timer editable from the camera menu (already got this)
2) Setting to use bracketing as described above, with fast shutter speed, perhaps varying aperture setting? I need to study this more to find out what I actually need. Take a series of 3 bracketed photos (so 9 in total based on under, auto, over)
3) After the photos are taken switch to video mode and take a 30 second video clip
4) Go to sleep mode to save battery until next interval kicks in
5) Rinse and repeat until either a) Battery dies, or b) memory card is full.

I'm finding the learning curve quite steep with CHDK, but after one day of playing around I managed to take a 3 hours time lapse of the sky and I'm hooked! Such a powerful bit of kit- I just wish my brain was powerful enough to understand it!
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Offline Microfunguy

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Re: Another weather balloon question from a newbie....
« Reply #5 on: 03 / March / 2011, 08:43:24 »
Quote from: mrkrinkle on 03 / March / 2011, 06:45:02
by bracketing, do you mean a series of shots of varying settings

Yes.
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perhaps varying aperture setting?

No, by varying shutter speed.
You have not said what camera you are using and it may not even have an aperture.

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I need to study this more to find out what I actually need.

I will test something later with SDM that you can try.

You or others will have to write a CHDK version if that is required.
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Offline NewbieToobie

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Re: Another weather balloon question from a newbie....
« Reply #6 on: 04 / March / 2011, 10:33:49 »
You might want to have a look at http://chdk.wikia.com/wiki/UBASIC/Scripts:_OMNI_Intervalometer (Version 3 at the bottom of that page.) This has the option to do intervals which include both a high-res still-frame and a video of a selected duration for each interval time selected. If you insert a small subroutine to allow you to vary how many still-frames are taken in the :vid subroutine you'll have what you are looking for. You will of course have to tailor the script to commands that your camera understands.

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Offline mrkrinkle

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Re: Another weather balloon question from a newbie....
« Reply #7 on: 04 / March / 2011, 13:21:28 »
Brilliant- thanks guys! I have been playing around with simple interval scripts the past couple of days- have managed to create a couple of timelapse videos (one of the sky and one of a from my bedroom window).

Microfunguy- I'm using a Canon A620 and an A470. I had planned to use the A620 for the video / pictures combo, but it seems that it cannot handle a memory card over 2GB which won't be enough to hold everything :(  The plan now is for the A620 to take a series of bracketed shots, and for the A470 to do the video pic combo.

Thanks for the link NewbieToobie- I've got a weekend free to spend playing around with some scripts.

In terms of bracketing- since the cameras will be moving around quite a lot, woudl this lead to mismatched bracketed shots? Or does the camera take one shot and create 3 versions based on the bracketing settings?

Again, sorry for so many questions- I feel like I've just discovered how to walk again with this software!
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Offline Microfunguy

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Re: Another weather balloon question from a newbie....
« Reply #8 on: 04 / March / 2011, 13:34:45 »
I have the A620 and A470 so that is very similar to yours.
The A470 does not have an aperture, just a ND filter.
You will not be able to use the bracketed shots for HDR, you will never match them, even with commercial software.
The A620 will save a RAW image in one second with a SanDisk Extreme III card.
An external programme converts that to DNG.


David
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Offline mrkrinkle

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Re: Another weather balloon question from a newbie....
« Reply #9 on: 04 / March / 2011, 14:34:13 »
Quote from: Microfunguy on 04 / March / 2011, 13:34:45
I have the A620 and A470 so that is very similar to yours.
The A470 does not have an aperture, just a ND filter.
You will not be able to use the bracketed shots for HDR, you will never match them, even with commercial software.
The A620 will save a RAW image in one second with a SanDisk Extreme III card.
An external programme converts that to DNG.


David

OK- that clears a few things up. Have you managed to get the A620 to accept an SD card larger than 2GB? I just tried a brand new 8GB in mine today and it just displays "Memory Card Error". The card works in a couple of other cameras fine. It's the difference between getting 166 shots (RAW + JPG) on a 2GB card, and over 600 on the 8GB.
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