Mega Pixel

Mega Pixel
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What is the the functioning of mega pixel, optical zoom and digital zoom in a digital camera.?

What is the the functioning of mega pixel, optical zoom and digital zoom. Which of these should be given more important. Which facility should be seen for good quality at night photography.

Firstly, i feel the optical zoom is the most important zoom feature. I allows you to zoom in onto the subject by adjusting the lens, at minimum compromise on quality.
Digital zoom, however, is not very useful. I never ever use it. Digital zoom is basically digitally cropping the image, by cutting off a portion and then stretching it. As there are only so many pixels in that area, if you pull them apart, the end result will probably be a very rough picture and hell a lot of picture noise. Not very ideal.

A common misconception is that the higher the megapixel, the better. This is not entirely true. The megapixel need not be to the extreme, but only high enough. Megapixel is related to the clarity of the image, only to a certain extent. If the megapixel is very very low, such as 1, the image resolution will be low and details will not be captured. However, if the megapixel is too high, all the extra pixels may just turn out as noise. Large Megapixel gives you large image resolution, allowing you to blow up the image. That is all. For beginners, 7 megapixel is more than enough, allowing you to print good A4 sized images.

Dots Per Inch is a useful measure of relative resolution. But if you don't know the image size in inches or some other measure of size, then the amount of dots per inch doesn't mean much. That's why DPI is used in conjunction with scanner Specifications, because you know that the size is going to be 3.8 by 1.7 inches!

Different resolutions are used for different purposes. 72 or 75 DPI for screen viewing; 250 for digital photography and 300 dpi for printing. See how this is a nice comparison, yes, you can get away with 50 less pixels per inch in your photographs than would be required for A4 printing, this is because of the physical size of the photo!rnrnDots Per Inch specifies how much information is resolved in a picture, whereas the number of megapixels is usually used to describe the total output size (in pixels) of an image.

Example: I want to reproduce the standard photograph size. This would be 6 by 4 inches. Digital photography requires a minimum of only about 250dpi, So: 6 * 250 = 1500 and 4 * 250 = 1000, so you need an image sized about 1500 * 1000 pixels (about 1.5 megapixels). Thus you can get a perfectly good standard print from a 1.5 megapixel camera! rnrnIf you take a photo twice, one at 5 and the other at 1.5 megapixels, than ask your self which one looks "better"? They will both look reasonable because your computer generates colours such that the image looks better than it really is; if you were to print both as a 6 by 4 image, they will look identical, because your printer can't generate more than 300 dpi so the "better" image is effectively reduced in quality anyway. This example demonstrates how it is possible to literally waste memory, ie for everyday use the additional memory required for the other 4 megapixcels gives you no real benefit!

This is quite good because a 36 Megabyte media card can store 50 to 65 images at 1.3 megapixcels but only 8 to 10 at 5 megapixcels, so unless you are planning on getting your images printed larger than 6 by 4 there's no real advantage to the full 5 megapixcels.

Now we have established that a 1.5 megapixel camera will produce a 6 by 4 inch standard photograph, that is, it will generate a resolution such that each pixel is simply reproduced "as is", we come to the more interesting issue of enlargement.

If you wanted to print your 6 by 4 inch image as a 10 by 8 photo (which would normally need the full 5 megapixels), there would not be a sufficient number of pixels for the additional surface area, so we now need to scale up the existing pixels by "resampling" the existing pixels, a process which estimates how the "missing" pixels should appear, and fills them with the appropriate "colour".

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