« on: February 28, 2012, 02:09:57 AM »
How do all the high end medium format digital backs get such good DR? do they read at a higher true bit rate though sampling before the AD converter?
The good DR of medium format is a bit of a myth. They do have 16 bit ADC, but that's meaningless since the noise levels are too high, 14 bit would yield the same result. I've also heard the exposure metering is different from DSLRs, underexposing more so you get more highlight headroom so you can push more in Lightroom which some mistakingly think means that there is more dynamic range.
And then there is what you compare with. If you compare with Canon 5D mark II, yes, there is better dynamic range, because the MF sensors are usually very nice random noise, not patterned noise like on the 5D. But compare with a Sony Exmor sensor and the MF sensor has a little bit less DR. All MF vs DSLR tests I've seen has been with Canon cameras, and they always lose. But they would lose against a Nikon or a Sony with a Sony Exmor sensor too.
Then there is the larger sensor area, there is some DR gain from that since you can gather more photons (less shot noise), but that gain is not very large.
Throughout the years many DSLRs have been released with less than perfect DR, while MF sensors has at least since 2003 had good DR. But that's only on base ISO of course, those CCDs are not good at high ISO. DSLRs have always aimed for more all-around performance including high ISO. Anyway for several years if you have got MF you know that base ISO performance will be great, which has helped established the belief that MF is generally superior, although some DSLRs today mave even have greater DR.