Pixels Aren't Just Pixels
by Paul Butzi
Regarding Mike's post "How Many Pixels Do You Need," I agree, but...I disagree.
It is not true that resampling simply "throws away" data, such that a 12mp image resampled to a 6mp image is essentially what you’d get if you had used a 6mp camera to start with.
This is because:
1. When you resample, you can make judgments about what data to preserve. One such judgment is feature preservation—the difference between resampling with "bicubic" and with "bicubic sharper" in Photoshop. That is, it’s possible to preserve detail in the lower rez image which would have fallen below the resolution of the 6mp camera, but was detected with the 12mp camera, and then preserved when the image was resampled.
2. When you resample, you are effectively oversampling the signal. Oversampling allows you to merge multiple samples into a single value—and this has the effect of reducing noise. As a rule of thumb, doubling the sampling rate reduces noise by a factor of the square root of two.
In other words, not all pixels are created equal. An image resampled from a Phase One P45 to the same pixel count as an image that was captured with a 6mp camera will contain more information and less noise, because although the number of pixels are the same, the image from the P45 has higher quality pixels.
In any case, on the larger issue, I agree—enough is enough. I have a friend who’s been doing very strong work with his 6mp Nikon, printing it on his Epson 2200. I swapped him two prints for two prints—getting the better end of the deal as usual. I put those two prints up in the room where I exercise, and I looked at them darn near every day, and they’re half of what convinced me to go ahead and buy an EOS 5D. The prints are roughly 10x15 inches, and they are luscious.
I make large prints, and for a great deal of the work I am now doing, the increased flexibility and speed of use of the EOS 5D I bought last November outweighs the advantage that my Linhof Technikardan 45s has in resolution. The 5D has defects (all of the work I am doing now is essentially landscape work on a tripod, and the camera has some unfortunate design features that make using it on a tripod at or above eye level a hassle), but so far in my life there have been three cameras that lit my brain on fire—the Linhof TK45s, the Leica M6, and the 5D. The rendering of the 5D is so noise-free, with such incredible smoothness and lush tonality…the first work I did with it when I got it was B&W (shot raw, converted to B&W in PS) and I thought I’d died and gone to heaven.
Posted by PAUL BUTZI