Bill Hilton wrote:

From: "Matt"


I heard someone say that 8Mp digital cameras were the equivalent to 35mm
film quality?


A dSLR like the Canon 1D Mark II with 8 Mpixels and a large sensor seems to
produce better large prints for me than ASA 100 speed Provia 100 F or Velvia
scanned with a 4,000 dpi scanner. I'm getting 16x20" prints from the 1D that
are better than any prints that size I've gotten with even Velvia 50.

But 8 Mpix from a smaller sensor camera might give different results, so "it
depends" on where the 8 Mpixels came from and what kind of film you are using
for your comparison.


Does this mean they have the theoretical equivalent resolution?


No, fine grained film still does better at resolving lines on test targets, yet
the digital prints look better ... how? Because of the lack of apparent grain.
Digital simply blows up better than film.


Are they the equivalent to 35mm?


Download some Mark II sample images from the Canon site and resize them
carefully and print them to see for yourself, though these jpegs aren't as
smooth as RAW file conversions.

Here's a good summary by Roger Clark of the film vs digital debate. Others
give digital a wider edge, still others feel film is much better, but what he
describes is close to the majority viewpoint.

http://www.clarkvision.com/imagedeta....summary1.html


While most who have worked with digital camera images agree that
because of the "smoothness" of digital images, they can be enlarged
more than film images. My testing, summarized on the above page,
shows that fine grained film has higher spatial resolution
than 8-mpixel digital camera images, but the digital camera images
have several times higher signal-to-noise. People infer
image quality as a function of both spatial resolution and
signal-to-noise. While this is a subjective concept, I've
started some experiments to test this "apparent image
quality," or AIQ. My initial results are showing to first order
that there is an approximate equal trade for signal-to-
noise versus spatial resolution. Thus, if you had a digital
camera that produced 8 megapixels and twice the signal
to noise as fine grained film, the apparent digital camera
megapixels could be doubled when comparing to film. So that
8-megapixel image would have the "apparent image quality"
of 16 megapixels if compared to the lower signal-to-noise
film. Since my tests show the spatial resolution of fine
grained 35mm film like Fuji Velvia is around 16 mpixels
digital equivalent, then that 8-mpixel digital camera
produces similar apparent image quality to 35mm fine-grained film.

But high end DSLrs, like the Canon 1D Mark II have several times
the signal to noise of film, so this boosts the apparent image
quality by the same factor as the ratio in the signal-to-noise
values, propelling the 1D Mark II images higher than fine grained
35mm film. While my research is preliminary, it does seem to
agree with what people are saying, and because people look at
different things (image smoothness versus spatial detail),
it shows there is a lot of room for interpretation.

Finally, many responses in this group say "film" but not what
kind of film. Fast film has lower spatial resolution and
noise (grain) then fine-grained film. One must specify what
kind of film, as well as film format (35mm versus 4x5) for
these discussions to have any meaning.

It will be a while before I complete my testing on AIQ and get
web pages up. If my research trend holds, then the ~16 megapixel
cameras will have ~64 AIQ mpixel film equivalent, which is well
into the higher medium format size range. Impressive!

Roger
http://www.clarkvision.com