How many mega-pixels would cameras have to be to be roughly equal to the resolution of normal 35 mm film?

Pey's argument about the resolution of the eye is not correct.

The density of receptors (rods and cones) in the retina is not uniform. The density is highest at the fovea where the eye has the highest acquity. You never take an entire picture in with the fovea at one time. Your view moves across the picture so every area of the picture is "sampled" using the high density part of the retina.

Even if the recpetor density were uniform, Pey's claim would only be valid is the projected iamge of the photo filled the entire senisitve surface of the retina. This is virtuvally impossible.

Pay refers to the number of nerve fibers in the optic nerve, not the number of receptors (rods and cones) in the retina. The retina is extremely complex with multiple layers of cells between the receptors and the nerves that feed the optic nerve. Some of these cells do basic image processing even before the signal goes to the brain. For example, some cells combine the stimulus signals from nearest neighbor receptors to produce a signal that enhaces edges in the image. Others are senistive to motion in the scene. These processed signals are then sent directly to the brain.

Regarding your original question:

Take my word for it, a 1 MPixel photo wil not look good unless viewed at a pretty good distance.

I have 2 digital SLR cameras.

Canon 10D (6 megapixels) - when shot in the highest quality (compressed not raw) mode I have been able to get very high quality 11 x 14 prints. If you start to crop the image and try to print to 11 x 14 you will start to see "pixelation".

Canon 40D (10 MPixels) - very little pixelation unless shooting in lower quality modes (high "iso" speeds) and / or doing heavy cropping.

Another point - the quality of any image is only as good as the quality of the lens.

A pixel is a single point that is attributed with a color. Generally, computer screen pixels have three light bulbs (red, green and blue) that with certain combinations make whatever color you want.

Resolution is determined by the density of the pixels. The more condensed they are, the sharper the image is. If you could fit 1 mega pixel (1 mil. pixels) in a single, standard-sized image, you would have a medium resolution picture. If you could fit 10 mega pixels (10 mil. pixels) in a single, standard-sized image, you'd have a very high resolution picture.

Let me tell you a little secret: the optic nerve only has 1.2 million fibers. i.e. you can only see 1.2 million different points (digitally meaning, we have an eye resolution of 1.2 mega pixels).

No matter how much higher the resolution of a picture is above 1.2 mega pixels, you won't see the difference, unless you look really close, or zoom in.

DPI (dots per inch) is a measurement of printing resolution. According to Wikipedia, "An inkjet printer... is typically capable of 360 measurement". Assuming the size of a printed picture is roughly 5 x 3.5 inches, we get about 2,268,000 dots. That's about 2.2 mega pixels.

If you're talking about pictorial sheets (the kind of paper that film is printed on), that would amount to zillions of pixels, because (as far as I understood) the image produced is made of light-effected chemicals. I guess you'd have to count the molecules on a film strip in order to figure that out.

But like I said, this is entirely irrelevant, because we wouldn't see the difference...

Camera reports batteries low, but is it low charge or bad electrical contacts? Overcharging can ruin good batteries! The secret to making digital cameras work better is having good electrical contacts between batteries and camera.

Digital cameras require lots of power. If electrical contacts are not really good, this can cause lots of problems so battery and camera contacts must be cleaned properly. Batteries may be fully charged, but will be viewed as low if contacts are not really good. The LCD is a low steady load, but when lens extension, optical zoom, focus, and flash charging are added in the capture mode; the load is very heavy. With bad contacts, cameras do strange things like making bad pictures or shutting off with the lens out.

Check the second source link for other camera tips and help with cleaning battery and camera electrical contacts.

I am no expert on this, but my Uncle Randy (who is a graphic designer) uses an 8-megapixal camera that takes unbelievable pictures. Of course, he has all kinds of fancy lenses, too, but I imagine 8-megapixals would be fine.