Calculating Dynamic Range
I have devised a simple test to calculate the dynamic range
of any imaging system. A test subject is photographed at a wide range
of exposures, digitised and then inspected to see whether a change in image
brightness can be detected.
The test subject consists of a grey rectangle in the middle
of a page with background split into black and white.
The grey rectangle represents a single exposure value of
the current exposure.
The difference between the grey rectangle and the white
portion of background represents a subsequent increase in exposure.
The difference between the grey rectangle and the black
portion of background represents a subsequent decrease in exposure.
- Set your ISO to its lowest possible value (unless you want to test
a higher ISO of course)
- Turn off all pre-processing (sharpening etc...)
- Save your images in the highest quality format, preferably RAW
- Acquire your images at the greatest bit depth
- Shoot exposures ranging from -7 stops to +13 stops
This may require bright conditions to keep exposure times reasonable
- Reset the scanner to factory defaults
- Turn off autoexposure and all pre-processing (sharpening, dust
- Set desired colour model and scan at the highest possible bit
Once you've collected your images you're ready to