A900 Bit Depth

Started Sep 9, 2008 | Discussions thread
Dan Wells Contributing Member • Posts: 551
Re: Bit Depth is not marketing ploy...

While I haven't seen the data on whether any current sensor (apart from medium format backs, which can) actually captures more than 12 bits of real data - that would be a 12 stop dynamic range, which is at or above the extreme edge of what any DSLR can capture , there is a case where the data NEVER get reduced to 8 bits. That is the case of printers with 16 bit drivers! Canon was the first to do this, and both Epson and HP have followed suit on certain models. Since both Windows and the MacOS reduce data sent to the printer through the operating system to 8 bits (although I wouldn't be surprised if MacOS 10.6 will allow 16 bit printer drivers), these drivers bypass the normal printer driver mechanism and function as Photoshop (or other image editor) export plugins. Here's a workflow that never drops below 12 bits...

12 or 14 bit RAW ---> 16 bit edit in Photoshop using Adobe RGB or ProPhoto RGB colorspace ---> 16 bit export to printer ----> printer drops back to 12 bits to print (as far as I know, all "16 bit" printers so far are really 12 bit).

As long as you never go through JPEG, which is inherently 8 bit, and you avoid the sRGB colorspace, which is so clipped that you lose all data above about 9 or 10 bits, you can keep an image in 12 bit form (encapsulated in a 16 bit file) from RAW to print. A DSLR that really used even 12 bits fully, for 12 stops of usable dynamic range, would record a wider dynamic range than all but a VERY few films through history - the only one I can think of offhand that recorded more than 12 stops was Kodak Technical Pan (there may be others).

Most current 17 inch and larger printers support some form of high-bit printing through Photoshop, and some 13 inch models might as well. A high-bit image off a modern inkjet printer offers as much or more dynamic range as any photographic process has EVER put on paper (with the possible exception of a platinum or palladium print made by a master - I have heard that master printers could get as much as 14 stops onto platinum paper in the right conditions).

The reason the Zone System has 10 zones is that Ansel Adams could get 10 stops onto silver-based paper (and nobody ever got more). The right combination of DSLR, printer, ink and paper can get 10 stops down on the paper, and may even reach 11. Of course Ansel chose WHICH 10 stops he wanted very carefully - that was a part of his genius - if he had a bright highlight and a shadow 11 stops lower, he was going to lose one of them, but he could choose which one at will, and he generally made the best choice for the image at hand. We now have tools that give us the same range of light he had, but we need to use them as wisely.


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