Megapixels vs Quality?

[chris]

Hey guys,

Newbie here with some questions that hopefully you experts can answer

I own a Sony P-72 Cybershot digital camera. In the manual, it speaks about image size and image quality. For instance, I can select from the following image sizes: 3.1M, 2.8M, 2M, 1.2M, and VGA. Furthermore, I can select the following quality: Fine, or Standard.

Kind of a dumb question, but what exactly is the difference between the size and the quality? I was under the impression that the quality of the image is determined by the number of Megapixels (3.1, 2.8 etc); however, the manual seems to give me the impression that MP determines size, NOT quality. Can someone please shed some light on this issue? Moreover, does anyone with a Sony camera know the difference between "Fine" and "Standard" ? I know this has something to do with the compression ratio, but I am uncertain as to what the relationship is.

Furthermore, I always like to develop my pictures with the postcard size. In the manual, it says that 1.2M should be used for printing postcard size images, while VGA is for creating your homepage. This may also seem like a dumb question- but, is it possible to select the size as 3.1M (in the manual it says this applies to A4 size images), and print it out as a post-card size? ie) I am thinking that if I can have more megapixels, and somehow shrink the size to a post-card, the quality will improve. Something tells me this is not right, as the quality is determined by Fine/Standard, and the MP has nothing to do with this (it only affects size, not quality).

Thanks in advance for all comments,

Chris.

[ratcheer]

Well, in a sense, megapixels does relate to size. But, it is all relative. If you take a one MP picture, and a 4 Mp picture, then print them at the same physical size (say 4 x 6), the the 4 MP shot will have more info than the 1 MP shot in the same area. More info per same area loosely means better quality.

But, there are other factors to consider, as well. Lens quality, dynamic range, sharpness, etc.

Megapixels are important, but they are by no means everything.

Tim

[LeeSowden]

At the same time though, if you compare 4MP and 5MP pictures both printed out to 6x4, you'd be hard pressed to tell the difference.

And yes; you can take a photo at 3.2MP and print it out as small as you like. Basically any extra information would be discarded (someone else could probably word this a lot better) to make the picture fit into as small a space as you want.

[chris]

Thanks guys.

Do you think there'd be much of a difference between a 3.2MP pic and a VGA pic, both printed at 6 X 4? It's hard to tell the difference by looking at them on the computer- I bet that there would be a noticeable difference when printed out though? Is this assumption correct?

Chris.

[ratcheer]

Yes, that would be quite a difference. VGA is 640 x 480 pixels, which is only 307,200 pixels. So, a 3.2 MP picture would have about ten times as much detail.

Even very hi-res computer screens, say 1280 x 1024, would only be about 1.3 MP.

Tim