Still Photography Camera Guide
Image size and pixel size
The first impression of a quality image is the dimension or image size of the source image captured by that camera. In digital camera the image size is measured by the number of pixels. Today's high-end consumer digital compact cameras come with image size of 6~14 megapixels.
A megapixel is about 1 million pixels or 1,048,576 pixels. A pixel is short for picture element or one dot on a video screen. More pixels result in higher image resolution. However, contrary to common belief, high resolution images don't always equal to high quality images. Other factors such as image detail, low noise level, good contrast, dynamic range and colour fedility also have to be considered.
Illustration of a 100 pixels RGB sesnor
A web cam usually has an image size of about 300,000 pixels and will give you a quality picture of about 6cm X 4cm. However the resolution of the web cam is just good enough for what it is designed for -- as a "web" cam and for video phone via the Internet. Compare that to a digital photo with an image size of 6 megapixels you can have quality picture printed to 40cm X 30cm!
If all your photography needs is just some 6R photos (15cm X 20cm or 6in X 8in) prints for the photo album then any 4 megapixels image size digital camera is more than enough. If you need to blow up your pictures to hang on the wall then look for something with an image size above 5 megapixels.
Higher megapixels increase the resolution of the images but equally imporatnt is the quality of the individual pixels. At the moment quality pixel equal bigger pixel size but this may change as new technology and new material for sensor chips are discovered in the future.
A bigger pixel size result in better sensitivity to light and produces stronger image signal. Stronger image signal improve image quality, better colour fidelity and less noise due to improvement in signal to noise ratio.
Increasing megapixels count on a given size sensor chip can have negative impact on image quality. Pushing more pixels on a given sensor chip results in smaller individual pixel size. This means lower quality sensor resulting to increased noise level, lower dynamic range, reduced colour fidelity and finally poor image quality.
The average consumer digital camera has tiny image sensors with size somewhere around 5.6mm X 4.2mm, normally referred as the 1/2.5-in sensor. If you think a 1/2.5-in sensor has a dememsion of 1/2.5-in diagonally or in its length or width, you would be supprised that actually they are much smaller than what their name implies.
Digital SLR uses the bigger Fourthirds image sensor or the APS format image sensor. The professional digital SLR uses the larger full frame 35mm image sensor with sensor size of 35mm X 24mm. Finally the higher end professional medium format digital SLR uses the much larger image sensor with sensor size of 48mm X 36mm.
Due to the larger sensor used in digital SLR that means dSLR has larger individual pixel size. As a result of having bigger pixel digital SLR produces images with much better quality as compared to consumer point-and-shoot digicam.
Moskva-5 Russian Made
6 X 9cm Medium format folding camera
In film camera, the image size is not measured by megapixel but the size of film formats. The largest one used by professional photographers is called the LF or Large Format camera which has films as large as 12 X 10 inches or 30 X 25CM. This is mostly used for blowing up into big posters and billboards.
The next level is the medium format camera that has films around 4.5 X 6cm, 6 X 6cm, 6 X 7cm and 6 X 9 cm. Medium format cameras normally have interchangeable film-back. You can also use digital film-back with them to convert them to a digital camera but this digital film-back is very expensive.
Further down is the once widely used "standard" 35mm camera format. The image size of 35-mm format is 24 x 35 mm. 35mm film format has the best compromise in terms of price, physical size and quality, making it the most widely accepted film format. 35mm film is still available in most professional labs and online retailers such as Amazon.com.
Lower down the range is the APS film format which was designed by Kodak in alliance with some Japanese camera makers to make photography easy for the masses and hopefully to replace the 35mm film format. The image size for APS format is 17 X 27 mm. The APS film is stored in a tiny cartridge even after processing so you can't see or touch the film and an index sheet has to be printed and kept with the film for reference.
APS film camera is history now but the APS format lives on as a very common digital SLR sensor format. At the time of writing APS films are still produced by Fujifilm and available from Amazon.com as well.
Size does matter
Be it the modem digital camera or the traditional film camera, as far as image quality is concerned the dimension of the image size is paramount. We can micro miniaturise electronic chips or reduce the size of the digital camera but we cannot cut corners for image size. While the image size in megapixel is important we must not forget that the quality and size of the individual pixel should not be discounted. We need to have both good image size and pixel size for high resolution and high fidelity digital images.
Size does matter - remember the disappearance of the Kodak Disc camera and the 110 film format? That was all due to the film size being too small and produced poor quality grainy photos. However large image dimension can be a problem too. In film camera it resulted in a large and heavy camera and it also cost you dearly. In digital camera a larger image size results in high memory usage, long processing time and requires a high-speed microprocessor or CPU, heavy battery consumption and generates more heat.Image noise
To assess image noise level of your camera download the image to your computer and use a graphic editing software to view it at 100% zoom or view at 1:1 image size. It is very difficult to assess image noise on the camera's LCD screen. The images on the left are extrame cases to show how dynamic image noise looks like.
Example of a silky smooth noise free photo
Example of an excessively noisy low quality image
Lets meet halfway
After having examined numerous full size digital photo of various brand of digital consumer camera it is quite safe to say this: For point-and-shoot consumer digital camera with a sensor size of 1/2.5-in an image size of 6~8 megapixels is a good choice for preformance, image quality and resolution.
This provides a good balance between size of individual pixel or "photo site" and overall image size in megalpixels. There are only so many pixels that can be squeezed into this tiny image sensor. Squeezing more pixels into this tiny sensor will mean having very small and tiny individual pixel or photo site. That will result in sensor noise, loss of highlight and shadow detail and poor color fidelity that impairs image quality.
For consumer compact digital camera with sensor size of 1/1.8-in 10 megalpixels seems to be a good compromise between Image size and pixel size that will still produce quality images.
The observation above is based on CCD sensor technology for the compact digital cameras available in the market at the time of writing. We do not know how long this observation will hold, as sensor technology is moving very fast with several new patents on sensor being registered lately. A lot of research on imaging sensor is on-going at the moment by all sensor manufacturers. We may see some interesting sensor technology in this area with improved imge quality, lower noise, higher sensitivity and lower power consumsion coming along very soon.
Right Tools for the Job
The smaller image sensor in digital SLR is about 8 times bigger than average point-and-shoot digital camera sensor. Even low-end beginner digital SLR produces higher quality images than the high-end consumer point-and-shoot digital camera. However one negative aspect of digital SLR is they are bulky and ugly as compared to the chic and trendy point-and-shoot digital camera and you can't put dSLR in your pocket.
For comsumer film camera there is only one choice now and that is the 35mm film format. Nevertheless this is the best compromise for size, quality and price even in the old days.
The key point here is use the right tool for the right job. There are times when a bulky SLR is required to get the job done. Sometimes a small sensor compact camera is ideal and less intrusive. It is rather odd to set up an 8 megapixels image size camera for web cam or video conference over the Internet. Stick with your ordinary web cam for those applications.
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