On Mar 11, 2004, at 12:51 PM, David Kay wrote:
In the 8-bit device, once we hit the noise floor of the CCD, all
lower subject tones are mapped to black or 0. The overall
contrast is the same in both devices, however, there are more f
stop equivalents resolved in the higher bit depth device.
While a higher 16-bit image does not *technically* have a higher
dynamic range, through image processing it does. Whether that
processing is on the computer with Levels adjustments, or on the
camera hardware.
An under-exposed image can be easily adjusted (levels/curves) to
bring it back into proper tonal range. The problem with 8-bit
data is that you are permanently deleting color data, and to an
extreme would cause image posterization. With a 12 or 16-bit
image you are able move the colors values and still have smooth
transitions between colors.
I have no doubt that ISO-equivalent ratings for the CCD sensors
are just applying a standardized level adjustment (like a Photoshop
Action) to the raw base ISO rating of the CCD. This combined with
the JPG compression (even in Camera RAW mode) produces the noise
for higher ISO ratings.
------------------
www.fortana.com
===============================================================
GO TO http://www.prodig.org for ~ GUIDELINES ~ un/SUBSCRIBING ~ ITEMS for SALE
