Hi all, This is the first time I have posted in this forum and I've got a few questions. I run a school project that sends probes up into the Stratosphere. We use cameras and video cameras as well as an array of electronic sensors to record conditions. For our camera we have been using a Canon A560 running off Lithium Energizers (alkaline doesn't work at temperatures below 0C and Lithium ion/polymer rechargeables seem to either stop working or explode). We've been using the CHDK firmware and a basic Intervalometer script to automate the camera and take photos every 3.75s. The focus is set to infinity and everything else is left to default. Here are the results: The photos at ground level seem okay to me but above the clouds at >1km we get a hazy effect that washes the photos out. Conditions up there are interesting (bright white in/around the clouds, predominantly black background above 15km) with temps often falling to below -40C and searingly bright sunlight with much less interference from the atmosphere (as there is much less atmosphere up there!). Can we do any image processing to improve the photos and the level of detail (the originals are in the Canon Raw Format CRW file format)? What package would you recommend for such editing (we are beginners at this but are willing to research and learn)? The full project can be found here if you are interested: http://forums.bit-tech.net/showthread.php?t=228177
COOOL. Those made me smile With regards to haze there isn't that much you can do about it, I think its caused by water vapour in the atmosphere. When shooting b&w I use a yellow filter to cut through it but obviously that won't work in colour. The contrast at high altitude is probably wider than the sensor can cope with and since you can't control the exposure settings or bracket you need to work with what you've got. GIMP with some practice will let you get the fiddle with curves etc which will help as will lightroom for (quite) a few quid. Have a google for basic image editing tips to help get the most from your raw files. If you're not having much luck I'm sure some of the membership would be happy to help.
Extreme aerial photography of the kind you are doing can certainly present it's share of challenges, but correcting the images isn't especially difficult. As far as the exposures go, be careful of leaving the exposure set to auto. It might work well enough when the camera is at low altitude, but once you hit a certain elevation and your frame has lots of black space, your camera's light meter may get fooled. It happens occasionally on the Space Station when crew members use an auto setting for Earth observations. They might suddenly decide to take a nice wide angle shot showing and Earth limb with lots of space and they forget to change the exposure setting. The meter sees all that black space and defaults to a long exposure because it thinks the scene is too dark. The result is black space with an overexposed Earth. If in doubt as to what manual settings to use, you can always rely on the 'sunny 16' rule. You're basically exposing for a large area of the Earth that is lit by the sun, and you're shooting above the cloud line. In some of the old Space Shuttle photo/tv procedures, Earth observation photography often had the 'sunny 16' rule as a safe fall-back setting for crew members to use. Even if you nail the exposure, some photos may still look a bit hazy. This is natural, and we see it on a lot of Earth observation photos taken from the Space Station. Some images have more or less haze, depending on the lens and/or window that they use. Even correctly exposed, it's still common to boost the contrast a bit and reduce the amount of blue in the picture to compensate for the atmospheric haze. Around 12 years ago someone wrote a very basic guide that is featured on the Gateway to Astronaut Photography of Earth. The guide is here. It's a bit outdated and there may not be as much information as you want, but it's still somewhat interesting. Keep posting your results. I love this kind of stuff. EDIT: Here's an example: This recent photo from ISS was shot at ISO 200, 1/500 sec, f/11. That's roughly the same exposure value as what you would get using the sunny 16 rule (ISO 200, 1/250 sec, f/16).
All useful stuff but the Sunny 16 rule isn't possible as we can't control aperture or shutter speed on the A560. I might look into a new camera with a more current sensor and see if I can get something in the 'A' line that will take AAs but also has these features and a more up=to-date ccd.
since you're using a Canon camera, to me it makes sense to use Canons algorithms, rather than someone else's reverse engineering... Canon have their own proprietary piece of software Digital Photo Professional, which I always put my raw images through first, it doesn't give you as many options as photoshop/gimp/etcetera but it covers white balance, brightness, sharpness, and allows you to control the RGB curves together or independently which is probably most of what you need.
Even if you can't make it take AAs you could easily make up a batter pack using what ever cells you currently use. As for exposure you could accept that you can't work for both and set the cameras exposure settings in advance for high altitude and sacrifice the ground level shots.
The battery pack idea is a fine one and would give us a lot more flexibility. We probably should sacrifice the gound shots as we can build quadcopters that will take those with greater reliability and stability. Also, Ook = Listen, it may be several million dollars worth of wood pulp and hard timber to you mate, and it may represent your kids college fees and that new extension to your castle. It could also conceivably be considered a a means of keeping thousands of under developed people in work, (all be it at slave labour wages), but sorry to say to me its a rainforest and its where I happen to live, so be a good chap, and stop cutting it down and pass me another banana while your at it. Orangutan to English Dictionary - Is this what your sig refers to?
