BetterPhoto Q&A
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Greg		Emulsion and Megapixels How many megapixels should a digital camera have to be equivalent in sharpness and every other way to quality ISO 400 film (and ISO 125, 50, 800 if you know) to create pictures of the same size? How many DPI should a scanner have to scan an image to the same resolution it has out of the darkroom? How many DPI should a 35 mm film scanner have to replicate the film perfectly? key words are "perfection" and "exactly the same." thanks To love this question, log in above June 30, 2002

doug Nelson		You're into some technical stuff that's beyond my competence, but if you are concerned to this degree, I'd look at a top-of-the-line digital SLR and a 4000 pixels-per-inch scanner. You're not going to be satisfied with less. To love this comment, log in above July 04, 2002

Greg		i have done some research about my own question and you can read about it yourself at www.howstuffworks.com and I can at least talk briefly about digital cameras. there are two types of sensors which are analog in themselves but their signals are converted to digital data: CCD and CMOS... CCD is more expensive but as of now gives sharper images. CMOS has more circuitry than CCD, but they both have it. Circuitry is black on the sensor and thus absorbs no light, however it contributes to lowering the quality of the photo. A statement such as "this is a 4.1 megapiexel camera" includes these black spaces I gather. To find out how many black pixels you are bargaining for, subtract the product of the resolution numbers (1200x1600 e.g.) and you have your number of working pixels. consider that. also consider how the sensor chooses the color for the pixel. there are two practical methods. in the first the light entering the pixel is split into three beams which read to sensors for the three primary colors. the readings of these sensors mix producing a final color which is definite. this is the most precise way. the other way is to assign each pixel a red, blue or green filter in something called a Bayer Pattern. These pixels average with surrounding pixels and use algorithms to determine the color for each pixel. thus you always fade from one color into another and images cannot be as sharp as possible. also... the number of megapixels is not determined by the denisty of the pixels but rather by the size of the sensor. a camera of about 6 megapixels has a sensor about the same size as a frame of 35mm film. this means the focal length is also the same and it can use equivalent lenses! a 50mm focal length on a slr is the same as a 7.7mm focal length on a 1.6 megapixel camera... the focal lenth ratio depends on the megapixels. one more point of interest is that a 3.1 megapixel camera has higher resolution than most computer monitors. that's all... I thought it was pretty interesting when I read it. To love this comment, log in above July 04, 2002

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