In May I gave a talk for LUV about the basics of creating video on Linux. As part of the research for that I investigated which cameras were good for such use. I determined that 720p was a good enough resolution, as nothing that does 1080p was affordable and 1080i is lower quality. One thing to note is that 854*480 and 850*480 are both common resolutions for mobile phones and either of those resolutions can be scaled up to full screen on a 1920*1080 monitor without looking too blocky. So it seems that anything that’s at least 850*480 will be adequate by today’s standards. Of course as Dell is selling a 27 inch monitor that can do 2560*1440 resolution for a mere $899 in the near future 720p will be the minimum that’s usable.
Cheap Digital Video Cameras
The cameras I suggested at the time of my talk (based on what was on offer in Melbourne stores) were the Panasonic Lumix DMC-S3 which has 4*optical zoom for $148 from Dick Smith  and the Olympus MJU 5010 which has 5*optical zoom camera for $168 (which is now $128) from Dick Smith . Both of them are compact cameras that do 720p video. They are fairly cheap cameras but at the time I couldn’t find anything on offer that had significantly better specs for video without being unreasonably expensive (more than $600).
Update: In the comments Chris Samuel pointed out that Kogan has a FullHD digital video camera for $289 . That’s a very tempting offer.
More Expensive Digital Video Cameras
Teds Cameras has a good range of Digital Video Cameras (including wearable cameras, and cameras that are designed to be attached to a helmet, surfboard, or car) . These are specifically designed as video cameras rather than having the video function be an afterthought.
For my use I can’t justify the extra expense of the digital video cameras (as opposed to digital cameras that can take video), I don’t think that they offer enough. So a cheap $128 Olympus MJU 5010 is what I will probably get if I buy a device for making video. I can afford to replace a $128 camera in a year or two but a device that costs $500 or more needs to last a bit longer. I expect that in a year or two I will be able to buy something that does 1080p for $200.
Features to look for in Great Digital Cameras
The other option when buying a camera is to buy something that is designed to be a great camera. It seems that RAW file capture  is a requirement for good photography. RAW files don’t just contain uncompressed data (which is what I previously thought) but they have raw sensor data which may not even be in a cartesian grid. There is some processing of the data that can be best done with raw sensor data (which may be in a hexagonal array) and which can’t be done properly once it’s been converted to a cartesian array of pixels. Image Magick can convert RAW files to JPEG or TIFF. I haven’t yet investigated the options on Linux for processing a RAW file in any way other than just generating a JPEG. A client has several TB of RAW files and has found Image Magick to be suitable for converting them so it should do.
The next issue is the F number . A brief summary of the F number is that it determines the inverse-square of the amount of light that gets to the CCD which determines the possible shutter speed. For example a camera set to F1 would have a 4* faster shutter speed than a camera set to F2. The F rating of a camera (or lens for interchangeable lens cameras) is a range on many good cameras (or lenses for detachable lens cameras), if you want to take long exposure shots then you increase the F number proportionally. A casual scan of some web sites indicates that anything less than F3 is good, approaching F1 is excellent, and less than F1 is rare. But you don’t want to only use low F numbers, having a higher F number gives a larger Depth of Field, that means that the distance between the nearest and furthest objects that appear to be in focus is greater. So increasing the F number and using a flash can result in more things being in focus than using a low F number without a flash.
Another important issue is the focal length, cheap cameras are advertised as having a certain “optical zoom” which apparently isn’t quite how things work. The magnification apparently varies depending on the distance to the object. Expensive cameras/lenses are specified with the range of focal lengths which can be used to calculate the possible magnification. According to DPReview.com Optical zoom = maximum focal length / minimum focal length, so a 28mm-280mm lens would be “10* optical zoom” . Finally it seems to be that the specified focal length of cameras is usually in “35mm” equivalent. So a lens described as “280mm” won’t be 28cm long, it will be some fraction of that based on the size of the CCD as a proportion of the 35mm film standard (which is 36*24mm for the image/CCD size).
Update: In the comments Aigars Mahinovs said: Don’t bother too much with the zoom. The view of a normal person is equivalent to 50mm lens (in 35mm film equivalent). Anything under 24mm is for landscapes and buildings – it is for sights where you would actually have to move your head to take in the view. Zooms are rarely useful. Something in 85-100mm range is perfectly fine to capture a bird or a person some distance away or some interesting piece of landscape, but anything more and you are in the range of silly stuff for capturing portraits of football players from the stands or for paparazzi photos. And the more zoom is in the lens the crappier the lens optics will be (or more expensive, or both) that is why the best optics are prime lenses with no zoom at all and just one specific optical length each. For example almost all my Debconf photos of the last two years are taken with one lens – Canon 35mm f/2.0 (a 50mm equivalent on my camera) and only the group shots are taken with a lens that is equivalent to 85mm.
So I guess if I was going to get an interchangeable lens camera then I could get fixed focus lenses for things that are close and far away and one with a small zoom range for random other stuff. Of course that would get me way outside my budget unless I got some good deals on the second hand market. Also having a camera that can fit into a pocket is a real benefit, and the ability to rapidly get a camera out and take a picture is important!
A final item is the so-called ISO Number which specifies how fast the film is. A higher number means that a photograph can be taken with less light but that the quality will generally be lower. It seems that you have a trade-off between a low F number (and therefore low Depth of Field), good lighting (maybe a flash), a long exposure time (blurry if the subject or camera isn’t still) and a grainy picture from a high ISO number.
Comparing Almost-Affordable Great Digital Cameras
I visited Michaels camera store in Melbourne  and asked for advice about affordable cameras that support RAW capture (every DSLR does but I don’t want to pay for a DSLR). The first option they suggested was the Samsung EX1 that does 10MP, F1.8-F2.4 with a 24-72mm equivalent focal range (3* optical zoom), and 640*480 video  for $399.
The next was a Nikon P7000 that does 10MP, F2.8-5.6 with 7* optical zoom (28-200mm equivalent), and 720p video  for $599.
The final option they had was the Canon G12 that does 10MP, F2.8-4.5 with 5* optical zoom (28-140mm equivalent), and 720p video  for $599.
3* optical zoom isn’t really enough, and $599 is a bit too much for me, so it seems that RAW format might not be an option at this time.
I can’t get what I want for great photography at this time, there seems to be nothing that meets my minimum desired feature set and costs less than $550. A client who’s a professional photographer is going to lend me an old DSLR that he has hanging around for some photography I want to do on the weekend.
I am also considering buying a Olympus MJU 5010 for making videos and general photography, it’s better than anything else I own at this time and $128 is no big deal.
Please let me know if I made any errors (as opposed to gross simplifications) in the above summary of the technical issues, also let me know if there are other things to consider. I will eventually buy a camera that can capture RAW images.
-  http://dicksmith.com.au/product/XG3755/panasonic-s3-digital-camera-black
-  http://dicksmith.com.au/product/XG6111/olympus-mju-5010-digital-camera-black
-  http://www.teds.com.au/digital-video-cameras
-  http://www.cnet.com.au/sony-handycam-hdr-cx110-339300807.htm
-  http://www.techradar.com/reviews/cameras-and-camcorders/camcorders/panasonic-hx-wa10-961477/review
-  http://en.wikipedia.org/wiki/RAW_file
-  http://en.wikipedia.org/wiki/F_number
-  http://www.dpreview.com/learn/?/key=focal+length
-  http://www.michaels.com.au/
-  http://www.photographyblog.com/reviews/samsung_ex1_review/
-  http://www.dpreview.com/reviews/q42010highendcompactgroup/
-  http://www.dpreview.com/news/1009/10091412canong12.asp
-  http://www.kogan.com.au/shop/kogan-full-hd-1080p-23x-video-camcorder-camera/