What is a "Megapixel" and how does this compare to film?


Quadophile

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A digital image (from either a film scanner or a digital camera) is basically a grid of lots of tiny dots called "pixels." Pixel is an abbreviation for "Picture Element."

A digital image is usually stated in terms of the number of pixels in the image which can be expressed several ways. One way is the actual dimensions, such as 2272x1704 pixels. This means that for this particular image there are 2272 vertical columns of pixels and 1704 horizontal rows.

A second way to express the number of pixels is the "megapixel" rating. A megapixel is simply the number of pixels in millions of a particular image. For the example above if we multiply 2272 by 1704 we get 3,7951,488 total pixels in hte photo. With a little rounding we could call this image a 4 megapixel (4 million pixel) image.

Comparing digital images to film is difficult. Film images are made up of many tiny pieces of silver grain or dye pieces. Since these pieces are not all regular shaped they appear as many little dots, or grain, in the print. Different film types have larger or smaller pieces of grain which makes it hard to compare with digital images which have nice, uniform size and shape picture elements.

In general the industry uses about 20 megabytes of information for a high-quality 35mm transparency. If you scan a 35mm slide at more than about 20MB you only get larger pieces of film grain and not necessarily more data from the scan. Around 20MB (if you do the math described above in reverse) comes out to about a 6 megapixel image. Scanning at higher resolutions (or using a higher megapixel camera) gives you the ability to both print a larger image and crop in on a part of an image but you do not get more image detail in a given area from the larger file.

Since color negative film has much less detail than slide film we can assume that something less than 6MP would be equal to 35mm color film.



(Source: Nikon Tech Support)
 
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Becky

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That's very interesting, I'd never thought about that before! :)
 
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will have to disagree :)

the 20MB is bytes,., not bits.. so..

the example above if we multiply 2272 by 1704 we get 3,7951,488 total pixels - ok, so that's 3.7 MB of data (or to round it up 4 MB / 4 mpixels)

a 20MB scan is equiv to 20 mpixels? :)

Sil

PS, generally the dpi / dots per inch is the number you look at on a film scanner and relates to the number of pixels (umm 35 millimeter = 1.3779528 inch - assuming a dpi on the scanner of 5400 - then the horizonal number of pixels is 7440)
 

Quadophile

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The megapixal war is actually over and most of the manufacturers are now concentrating to improve the the picture taking capabilities of the camera rather than going high in Megapixels. The new cameras which are coming out have better features and better LCD panels. For an amatuer photographer 6-8 MP camera should be more than sufficient and for casual snapshooter who really does not bother to print anything bigger than say 5x7 3-5 MP will serve the purpose pretty well.
 
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Quadophile said:
The megapixal war is actually over and most of the manufacturers are now concentrating to improve the the picture taking capabilities of the camera rather than going high in Megapixels. The new cameras which are coming out have better features and better LCD panels. For an amatuer photographer 6-8 MP camera should be more than sufficient and for casual snapshooter who really does not bother to print anything bigger than say 5x7 3-5 MP will serve the purpose pretty well.
I agree Quad - the 'casual' or amateur' photographer probably doesn't have the cash to buy and run a colour printer bigger than A4 size, so even 2-3mp will give good results if the lens quality is good. Most people still only print snaps on 6x4 paper. Having said that, I have a 2mp camera (original Canon Ixus V) and do notice a strong improvement on my brother's 5mp Ixus, on pc display at least, so i would definitely like to get at least a 4mp camera soon. But - and here I think you're right again - I will be taking more notice of the lens quality and LCD display size/quality etc, than the number of pixels.

Bottom line is that megapixels are giving way to lens quality and other camera features. It's only peeps who don't know any better who will spend more just for the biggest mp number they can buy. In many ways, i'm glad that people will start paying attention to the real quality of what they can see rather than simply going by the numbers.;)
 
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Camera resolution versus print resolution

Quadophile said:
Since color negative film has much less detail than slide film we can assume that something less than 6MP would be equal to 35mm color film.

(Source: Nikon Tech Support)
The comparison above refers to the resolution on film. This comparison fails to take into account that prints from most 35mm films are processed in a photo lab (using a chemical process with a virtually endless number of colours), where digital camera images are either seen on screens (which have their own resolution) or printed on inkjet printers, which produce a perceived colour through different coloured dots from a limited number of basic colours. A test printing a 30”x20” poster from a 2 MB jpeg at the online photo lab http://fotoinsight.co.uk produced a very well perceived, hi-res result, which shows that even smaller jpegs can provide large format prints if the right technology is used.
 
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1nteger said:
I agree Quad - the 'casual' or amateur' photographer probably doesn't have the cash to buy and run a colour printer bigger than A4 size, so even 2-3mp will give good results if the lens quality is good.

Most dont your very right! I do tho :p

Upto A0 size to be exact. At any time ;)

Sorry had to get that in LOL

Yeah yeah I can hear the name calling from here lol :D
 
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