Raw format
Posted by photonovice on April 18th, 2007
Before the dead pixel issue I used raw (NEF in Nikon terminology) format only occasionally when I wanted to do some HDR after-work with a picture. Since then I’ve been making photos excusively in raw format. Most of the digital cameras of these days are capable of recording pictures in JPEG and raw format as well. There are good and bad things with raw format.
The bad things are that the image files are bigger (sometimes close to 10 megs on Nikon D80), so saving them to memory card is slower, and you need some decent software package to work with them. (Picasa is showing colors of Nikon NEF files inaccurately.)
However I - and many professional photographers - find the advantages of raw format to weight much more than its disadvantages. The list of good things must be started with the color depth. Color depth of a Nikon NEF file is 12 bit per color channel instead of the 8 bit of JPEG.
Some maths here:
| color depth |
number of values per channel |
R x G x B | number of colors per pixel |
| 8 bit | 28 = 256 | 2563 | 16,777,216 |
| 12 bit | 212 = 4096 | 40963 | 68,719,476,736 |
It means much much more information for each pixel. It means that shadow areas - those that in case of JPEG would just be dark patches - can be effectively lighten and burnt out areas can be recovered as well, just like in HDR pictures made from multiple, differently exposed source images. (It is actually HDR due to the much higher color depth.) The list can be continued with the flexibility in white-balance settings, exposure compensation on the PC and not loosing any detail with the compression.
You can’t leverage these advantages if you simply convert your raw images to JPEG as a first step of your image processing workflow. This conversion should actually be the very last step. But in order that you can professionally process you raw files you need a software that can keep the colordepth throughout the procedure. Currently I’m testing Nikon Capture NX and Photoshop Lightroom as two similar - at least from marketing point of view - commercially available tools and a slightly different open source - and free - alternative: UFRaw.
You can find a much more scientific description of tonal quality and dynamic range of digital cameras here written by Norman Koren.
April 20th, 2007 at 2:23 pm
[...] Raw format [...]
May 2nd, 2007 at 9:11 am
[...] the result. The Color control points recovered the details that were actually there - due to the 12 bit color depth of the raw format - just could not be seen before the [...]
May 24th, 2007 at 2:46 pm
[...] of photography I’m keen to find the best software package for my image processing tasks. As I wrote earlier, I shoot only in raw format for its unarguable advantages. I’ve been testing Adobe Photoshop [...]
May 24th, 2007 at 8:17 pm
[...] the result. The Color control points recovered the details that were actually there - due to the 12 bit color depth of the raw format - just could not be seen before the [...]