Mamiya DM33, LEICA M9, Canon 5D Mark II, Nikon D3 and Canon S90 Tonal Differentiation
Let's compare the tonal differentiation among state-of-the art 35mm DSLR, rangefinder and medium-format digital cameras.
Tonal differentiation means the ability to see subtle variations between light and dark.
To do this, let's shoot a flat scene with little variation between light and dark, and then greatly amplify those small tonal differences. Then we easily can see whatever differences there may be among these cameras.
Our eyes can't see 16- or 12-bit data. They barely can see 5 bits, which is why many LCD monitors have driver circuits that only work in 6 bits!
The reason some people care about bits of tonal (z-axis or brightness) resolution is if they need to screw around with curves. When tweaking levels and curves, some parts of the image will have their contrast increased. With enough tonal resolution there won't be any artifacts if we have to fiddle with the image later.
Ideally, good photographers light a set so that nothing needs to be tweaked at all.
I then ridiculously increased the contrast of a very flat section to let us see what, if any, otherwise invisible differences in tonal differentiation there are among these cameras.
Here is a dull sky, or at least as dull as it ever gets in sunny La Jolla. The dark line at the bottom is the sea's horizon, as seen from Kellogg Park at La Jolla Shores on 02 March 2010:
And here is the grayness inside the cropped area, enlarged to 100%:
If the entire image was printed at this magnification, we'd have 48" x 64" (4 by 5 feet or 125 x 160cm) prints.
Now let's increase the contrast by ten times, which is extreme. This is the devious part of this world's first test. I had to find a subject with little variation in tone, then I magnified that small variation in tone to make it easy to compare how each of these cameras handle subtle variations. In other words, I insanely magnified the variations in tone so that we can see what is normally so subtle as to be invisible.
At this magnification and this much of a contrast increase, we're going to see noise and artifacts which would never be visible otherwise.
Each was shot in raw, opened in Photoshop CS4 ACR and then resized so that each is the same size. I then expanded the small brightness range (about 27 Q-steps at 8-bits) to the entire 256 levels displayed here. In other words, I took a cropped part of an image as shown above, which filled only about one-tenth of the middle of a histogram, and pulled that small range of gray out to the full range from light to dark as shown below.
Here's what we have:
Wow, the DM33 is easily in a class by itself. All the 35mm rangefinders and DSLRs look pretty much the same, and the point-and-shoot is the worst.
I've also shown the fallacy of falling for claims of 12-bit, 16-bit or 24-bit image processing in-camera.
As those of us who have done this for a living since the 1980s know, the noise level of any of these sensors is much larger than even 12-bit processing. Throwing more real bits at the ADC only serves to quantize the noise more accurately; there isn't any meaningful image data needing that precision.
The reason the Mamiya DM33 is so obviously superior is that it has far less noise than any of the other cameras. When I wildly increase the contrast, we're seeing more noise than any potential for tiling or artifacts that could come from too few bits.
The biggest real reason to use more bits is that the analog signals coming from sensors are in the linear domain before they are quantized. All the gamma and log conversion happens in DSP, so more precision allows potentially better looks into the shadows or for creating higher ISOs, but as we can see, the noise levels coming off the sensor are still so great that they will self-dither any converter used today.
If tonality matters to you, the medium format camera is clearly superior.
Compared to 35mm, medium format always has been, and always will be, superior.
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