essential skills: digital photography in available light
Advantages and disadvantages of 16-bit editing
When the highest quality images are required there are major advantages to be gained by using
Photoshop or Elements 3 to edit an image fi le in ‘16 bits per channel’ mode. In 16 bits per channel
there are trillions, instead of millions, of possible values for each pixel. Spikes or comb lines, which
are quick to occur whilst editing in 8 bits per channel, rarely occur when editing in 16 bits per
channel mode. Photoshop CS/CS2 has the ability to edit an image in 16 bits per channel mode
using layers and all of the editing tools whilst Elements 3 supports only a single layer when editing
in 16 bits per channel. The disadvantages of editing in 16 bits per channel are:
~ Not all digital cameras are capable of capturing in the RAW format.
~ File sizes are doubled compared to 8-bit images with the same pixel dimensions.
~ Many fi lters do not work in 16 bits per channel mode.
~ Only a small selection of fi le formats support the use of 16 bits per channel.Editing in 16 bits per channel
It is still preferable to make major changes in tonality or color in the RAW dialog box or in 16-bit
mode before converting the fi le to 8-bit mode. Most of the better scanners that are now available
(fl atbed and fi lm) now support 16 bits per channel image capture. Remember, you need twice as
many megabytes as the equivalent 8-bit image, e.g. if you are used to working with 13 megabytes
for a full-page image (8in x 10in @ 240ppi) you will require 26 megabytes to work with the same
pixel dimensions in 16 bits per channel.If you are editing in 16 bits per channel the comb lines that appear in the histogram palette will disappear when
the uncached view is selected