All good info, in the spirit of "giving back" here is a summary of something that confused the hell out of me some years ago.
1.) When you shoot a picture the image sensor captures the energy level on each photo site and records them into a file. This is basically what a RAW file records. The resulting data is a black and white logarithmic matrix of exposure information stored in a TIFF like format.
2.) To turn this information into a color image your camera processes this data using the algorithms provided by the manufacturer while applying the in camera setting you have chosen like color space, contrast and white balance.
3.) Finally the result is saved to your memory card, either as a JPG where the initial raw capture is discarded and a compressed rendering of the final image is stored. Alternatively if you choose RAW the pure energy data is stored with a copy of the JPG and sometimes some meta data.
Most of the time your cameras processing engine does a good job and the resulting JPG image is fine. But sometimes, it doesn't, for example the white balance is off or the 8 bits of exposure data it chose out of the available 14 to 16 bits resulted in an under / overexposed image. In which case having the original raw capture gives you the flexibility to re-process the image with updated settings.
Since a raw image records the light energy glimpsed by your sensor over a fraction of time only a few camera settings affect the recorded light levels (and therefore cannot be changed after the shutter is released). These include.
- Shutter speed
- Aperture
- ISO
- Focus
- Nature (Subject, light levels, composition etc.)
- Your camera / lenses physical characteristics
Everything else is up for grabs. You noise reduction setting is a tradeoff between sharpness and noise, shooting raw will allow you to adjust this iteratively on a big screen.
Some not so obvious implications:
1. RAW engines get better over time, for example noise correction was terrible on most cameras a few years ago with noise ninja or Lightroom 3 noise is almost a non issue. Re-processes you pics over time.
2. As a rule (therefore there are exceptions) RAW engines throw away your in-camera settings. You need to re-implement them in software if you want your images to match the onscreen preview.
2. Not all RAW engine are the same. For example Adobe Camera RAW does a great job of processing Canon images but lacks Nikons secret sauce when it comes to complicated color and gamma. You might want to play with variety of raw engines over time.
2. Your image preview, histograms and readouts are based on the processed JPG not your raw image data. Adjusting contrast for example will change what your histogram looks like but has no affect on your raw capture. I don't mess with these setting in camera so avoid over compensating one way or the other.
Advice:
Change to RAW now, hard drives get cheaper every year I regret years of images I shot JPG which could have been saved. At worst you get what your camera chose for you.
If nothing else you will have more control over exposure (dynamic range) , white balance and noise shooting raw.
The only negative I see to shooting raw is a complicated workflow, programs like Adobe Lightroom or Apple Aperture solve this problem. Aperture is $79, and Lightroom as just been re-priced to $150. A fraction of the cost of a 7D.
Brett
