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Beach at Lancelin, Approx 31°1'5"S 115°19'49"E

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The Decision


The Decision

In 2000-08 I bought myself a digital camera. I already had a film point-and-shoot, but I never used because I never had any film in it! It never has any film because I would typically take a few photos, then either wait ages for the film to be filled, or else I would take some more photos of the dog Smiley!

The criteria I set myself were:

My research included many online shops and digital camera review web sites. I have links to many of the review sites on my main digital camera page. While I probably looked at dozens of cameras in detail, the following caught my eye for one reason or another:

I briefly considered the Sony DSC-S70: it has a very high quality (Carl Zeiss) lens and the Sony battery technology that shows time remaining to the minute was very tempting, as was the high-res 3.34 megapixel CCD. However, it didn't support CF cards.

I also looked at the Kodak DC290. The 2.1 megapixel camera sounded very nice, and the scripting features were very interesting. This camera lost out because its IR support didn't include my MC218.

I ended up purchasing a Casio QV-3000EX/Ir for the reasons listed below. I did look at the next model down, the Casio QV-2000UX/Ir, but I didn't like the sliding lens cover or the pop-up flash.

The QV-3000EX:


After Nearly A Year

It's now 2001-06, ten months after I bought my camera. I immediately swapped the 8MB CF card that came with the camera with the 128MB CF card I was using in my PDA. The 128MB card never leaves the camera (unless I'm showing off how small the card is!)

The NiMH batteries work very well. The most intensive use I've put the camera to so far was a day trip to visit three US Navy warships that had berthed at the local port. I took 80 photos and 2 30-sec movies. A few photos (probably no more than five) used the flash. At the end of the day the set I had started off with were still showing full! I was very impressed.

Also impressive is the ease with which photos are transferred from the camera. When it is connected via USB it appears as a removeable drive and if you want to you can drag-and-drop files in the Explorer just like any other drive.

As a programmer, I found an pleasant surprise in the remote control protocol. Remotely controlling the camera via the serial port is as easy as sending the letter corresponding to the button you want to press! No fancy control codes, checksums, or whatever. Very simple. I've already developed a few projects to control the camera:


After Nearly Two Years

2002-06-15: I don't have much to add to the above. On a recent holiday I took just over 200 photos before having to change batteries! That was a set of 1500mAh NiMH batteries and using a 1GB Microdrive!

As you might figure out from reading my JPEG vs TIFF pages, I've found that when photos are taken using the 'Fine' quality they end up being virtually identical to TIFF images, while being a lot smaller and taking far less time (and battery power) to save.

I'm still very happy with it - I'll keep on using it until it dies! The only disappointment so far is that I can't connect it easily/cheaply to my telescope to take photos of the moon, stars and planets.


General Factors When Deciding on a Camera

There are several things to consider when buying a digital camera. In no particular order they are:

Some would have you believe the only thing to look for is what quality photos the camera takes and nothing else is relevant. That's not true. The photo quality should be the most important factor, but the other items must also be considered.

Theory of Operation

Before covering the features outlined above, it might be best to cover how digital camera operate.

The Lens

"In the beginning..." light enters the camera through the lens which focusses it onto the CCD. Bigger lenses are "faster" - they let in more light.

The CCD

The CCD is simply a "light bucket". Each pixel on the CCD responds to light by building up a voltage. The more light (brighter and/or longer), the higher the voltage. Eventually CCD pixels will be able to hold no more light and any extra light will make no difference. A properly exposed photo will stop the exposure before too many (or any) CCD pixels reach this point.

CCD pixels react solely to light - light of any colour, including some infra-red light! Without help, a CCD pixel cannot distinguish different colours of light. In most digital cameras, a special pattern of coloured filters is placed over the CCD. Usually it is Red-Green-Blue-Green, but other colours are possible. Some really expensive cameras have three CCDs - one each for Red, Green, and Blue light!

This colour pattern is called a Bayer filter. In a typical camera, half the pixels are green, a quarter red, and a quarter blue. For example, a 3MP camera takes 2048×1536 photos. The total pixel count is 3145728. Of those 1572864 are green, 786432 are red and 786432 are blue.

You'll note I mentioned CCDs are sensitive to infra-red light. Manufacturers place a filter in front of the CCD to filter out the infra-red light. It doesn't filter it all out, otherwise it would affect how well the camera registers red light. The colour filters are not placed by the manufacturer of the camera, but are built into the CCD by the manufacturer of the CCD.

Amplifiers

In low-light conditions, there is so little light that the CCD voltages might be too low for the next step, the analog-to-digital conversion. To handle that, digital cameras have amplifiers that can be set to provide different levels of amplification. The sensitivity or ISO settings on the camera adjust the level of amplification. This is one of the benefits of digital cameras over film cameras.

Increasing the amplification also increases what noise is present in the CCD voltages, and often adds new noise of its own!

The ADC

You might note that a CCD converts light into volts. The next step is to convert those volts into numbers. That's the job of the ADC. The main difference between ADCs is how many bits they use to represent the input voltages. Typically they start out at 8 bits and work up to 16. More than 16 is almost unheard of.

At this point your photo is now made up of a sequence of numbers, one number for each pixel on the CCD. Due to the Bayer filter, half of these numbers will be for green, a quarter red and a quarter blue.

From this point on, the exact digital processing performed on the number depends on the camera. Different manufactures, models, even firmware versions within the same model may (will) do things differently. Whatever the exact process is, the general operations described next are fairly close to reality.

If your digital camera allows you to save RAW files, this is where it will save it. You may read in places where people recommend that saving pictures in their RAW format allows you to do colour balance correction later. This is true, but only because you can always colour correct your photos, no matter what the format. Colour correction is not limited to RAW files.

To work out the likely size of a RAW file, multiply the number of pixels by the number of bits and divide by 8 to get the number of bytes. For example, a 2048×1536 pixel CCD recording at 12 bits/pixel will end up with a 4718592 byte file (4.5MB).

De-Bayerization

This is the process of turning the CCD pixels, each of which is one of red, green, or blue, into full-colour RGB pixels. It does this by averaging the red, green, and blue colours around each pixel position. The exact process isn't important, but something to consider is that the averaging will tend to smooth out the photo. Often cameras can be set to sharpen photos automatically to counter this.

At the same time as the de-Bayerization, the camera will also perform any colour balance correction that it deems necessary.

Saving

Once the photo is processed, it is saved. Usually the JPEG compression method is used, but some cameras also support a TIFF format.

Pixel Count / Printing

See also my page on resolution.

NOTE: MP = "megapixel" = 1000000pixels

How many pixels you need depends on what you want to do with your photos. For web and email use a tiny 640×480 (0.3MP) or possibly smaller would be enough.

For printing, the generally accepted guideline is a minimum of 250-300 PPI. Note, this is not DPI. DPI is a measure of the capabilities of your printer. The bigger the number the better.

Let's say you want to print mostly 6"×4" photos. Digital camera aspect ratios aren't usually 3:2 like 35mm film, typically they're 4:3 like your TV or computer screen. This means you'll probably end up with something more like 5.25;"×4" to fit four-up on a sheet of paper. At 250PPI you'll need 5.25×250×4×250 = 1.3MP (or 1.9MP at 300PPI). Two-up printing will probably be 7"×5.25" which is 2.3MP (or 3.3MP at 300PPI) and one-up printing will probably be 10.5"×8" and you'll need 5.25MP (or 7.56MP at 300PPI).

I won't go into any further detail on printers - that would be a whole 'nother web page!

Lens

A bigger lens lets in more light. The camera will operate better in low light conditions, and because it doesn't need to drive the CCD amplifiers as much, there will most likely be less noise in your photos.

Removable lenses allow you extra flexibility, perhaps an extra-long telephoto or a really wide field of view.

Optical Zoom

A nice value here is 3×. Some cameras offer up to 10× and that's very nice, but you'll need to use a tripod unless the camera provides some sort of automatic image stablization.

Digital Zoom

Digital zooms can be evil. If the camera is re-sampling the photo it's faking it. Other cameras (such as my Casio QV-3000) just crop the photo to give the effect of a zoom. This is much better as the camera isn't inventing details, it's just dropping those details you don't want.

Most camera manufacturers don't give any indication of what sort of digital zoom they use. You'll have to actually try the camera out. If the resolution of the photos is the same with the digital zoom as without, the camera is faking it. The best form of digital zoom is where the camera drops resolution.

Storage Media

This is only important if you already use Compact Flash or Smartmedia (or whatever) already. Having the flexibility of swapping memory between the devices you own can be vital in emergencies! If you don't already own something that uses memory cards (and you don't plan to), then what media the camera uses doesn't matter at all.

Having said that, I much prefer Compact Flash. It's physically the largest, which means it will always have the highest capacity, should you need it. Many cameras support the IBM Microdrive, which gives the cheapest money/MB storage around, although it requires a bigger CF2-sized slot as opposed to a standard CF/CF1-sized slot.

Some people oppose big capacity cards on the "all eggs in one basket" idea. The truth is, a high capacity card is likely to stay in your camera all the time and never come out. While in the camera it is protected from dust and dirt, fingers, static electricity, water and drops/falls (unless you drop your camera, and even then it's better protected inside than out!). I don't have any hard-and-fast figures on the comparitive reliability of cameras vs the different memory cards, but I would bet on the memory cards (whatever their type) outlasting your camera.

My recommendation: buy the biggest memory card you can afford and connect the camera directly to your PC via a cable. No mucking about with card readers, either.

Batteries

I'll always prefer a camera that uses standard batteries, either AA or AAA. My reason for this is when I'm out camping, my PDA, GPS, small torch, computerised telescope and walkie-talkie all use AAs. On one occasion I'd wandered into the desert several kms from the car when the GPS batteries went out. While not a disaster (I have a good sense of direction), it was very handy to be able to swap the batteries from my camera into the GPS.

The other benefit to using the same batteries is that I only need to carry the one charger. Not to mention that most chargers that come with things only operate off the mains and not in a vehicle.

Something else to consider is that often proprietary batteries can only be charged in the camera.

Size/Weight

Obviously, the smaller the camera, the more likely it is you'll take it with you when you go out. You should remember, though, it also means a smaller lens (less sensitive/more noise, little or no optical zoom) and smaller battery.


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