35mm vs Digital

[artwell]

I heard that digital cameras need to be at 11 megapixels to be comparable to 35mm film quality. Is this true?

[steven]

This is true in terms of being able to enlarge the picture.

But unless you are looking at enlarging to poster size you don't need 11 mega pix.

(This for one who owns a 1Ds :oops: )

[Belmondo]

It depends.

As a general rule, though, it's not true. It depends on how large you're planning to print. Up to 8 X 10, 4 megapixels will give you a picture nearly equal to average 35mm print.

I've made 11 X 17 prints from 6 MP pictures that are probably fully equal to anything you can get from 35mm. Same thing with 13 X 19 with my 8 MP Mk II.

Whoever told you that wasn't trying to sell you a 1Ds, were they?

[Jon]

It's always the short questions that need the long answers.

It depends. An 11 MP 24x36 mm sensor has about the same resolving power as a good 35 mm film. BUT a 6 MP camera is capable of making images that can be printed up to 16x20 (with suitable post-processing) and be indistinguishable from a comparably-sized 35 mm print.

There's a thread running around here that suggests that the EOS D60, 10D and DR have sensors that are diffraction-limited at f/11 (the resolution's so fine that the sensors will start picking up diffraction effects at f/11).

And a 4 MP camera's certainly got better resolution than Kodak 2475 Recording, for instance. So "What film?" (and "how was it processed?")becomes a factor.

Since very few 24x36 mm sensors are in use, how do you compare a picture taken from a smaller sensor to one taken full-frame 35? Crop the 35 to fit the coverage of the smaller one, while using the same lens? Enlarge the digital, using whatever lens necessary to get the same coverage (introduces 2 variables - the lens' resolving power and differing degrees of enlargement)?

Using the first approach (crop), you might find that the 6 MP camera can resolve the same as the 35. Using the second, you could skew the results however you wanted by careful choice of film, sensor size, sensor density, and lens characteristics (force a comparison where one or the other had to use a less-capable lens).

What it boils down to is that for most purposes, you could be equally happy with a 6 MP camera or with film. If you're just doing snapshots, up to 5x7, you may find 2-4 MP are plenty. If you're doing commercial work for major enlargement (billboards, for instance), you might want an 11 MP camera, or you might need to go to a 22 MP back on a 6x4.5 or 6x6, since you'd be competing in that arena. But if you're hyper-concerned about getting the ultimate resolution, you need an 8x10 or larger view camera. Just remember, our spy satellites use digital technology, and commercial imaging satellites resolve down to 1 m on the ground from several hundred km up. Imagine what the secret ones can do.