Tuesday, April 21, 2009

35mm Film vs. Digital - Which Medium Has Better Resolution?

A large format camera

So, which is better- film or digital??  Film has some tonal quality that is unique to that medium, something that can't be easily replicated with digital.  Large format film can capture images well over 700 megapixels, more than seven times the resolution of the human eye.  This medium, however, is quite specific in it's callings because each negative is extremely expensive, requires lots of large equipment (larger than a DSLR), and take a lot of time to set up.  It is safe to say that large format has a specific purpose.

I'm talking more specifically about 35mm film vs. today's digital cameras.  I'm taking on an anonymous comment I received: "35mm film can beat any Canon/Nikon" (specifically, they were talking about Fuji Velvia 50).
Let me take a closer look.  The person who commented did the following math:

Fuji Velvia 50 is 160 lines per millimeter. This is the finest level of detail it can resolve, at which point its MTF just about hits zero.

Each line will require one light and one dark pixel, or two pixels. Thus it will take about 320 pixels per millimeter to represent what's on Velvia 50.

320 pixels x 320 pixels is 0.1MP per square millimeter.

35mm film is 24 x 36mm, or 864 square millimeters.

To scan most of the detail on a 35mm photo, you'll need about 864 x 0.1, or 87 Megapixels.

But wait: each film pixel represents true R, G and B data, not the softer Bayer interpolated data from digital camera sensors. A single-chip 87 MP digital camera still couldn't see details as fine as a piece of 35mm film.

Since the lie factor factor from digital cameras is about two, you'd need a digital camera of about 87 x 2 = 175 MP to see every last detail that makes onto film.

That's just 35mm film. Pros don't shoot 35mm, they usually shoot 2-1/4" or 4x5."

At the same rates, 2-1/4" (56mm square) would be 313 MP, and 4x5" (95x120mm) would be 95 x 120 = 11,400 square millimeters = 1,140 MP, with no Bayer Interpolation. A digital camera with Bayer Interpolation would need to be rated at better than 2 gigapixels to see things that can be seen on a sheet of 4x5" film.

My response:

That's a lot to do just to get wrong. Actually, assuming high-quality optics, a Velvia slide can hold detail up to 160 lines per mm, this is true. However, this is only a resolution equivalent to around 22 megapixels in the full frame 35mm format. So if you want to switch film in your camera after a few shots to have less than one more megapixel than me, go ahead. Also take into account Velvia's well-documented reciprocity failure in any long exposure. I’d rather be able to hold 400 reliable 21 megapixel RAW photos on my camera at any given time.

Digital full frame cameras such as the Canon 5D Mark II or 1Ds Mark III take as sharp or sharper than any 35mm film. My sources?? 



And Here

Where are your sources??

Now, when talking slide, med format, large format, etc. yes, Film is much better. But for how much longer?? And who wants to carry around an 8x10 at a wedding? Not me.