Re: BMP file problem help

["wpettit@xxxxxxxxxxxxx" <wpettit@xxxxxxxxxxxxx>]

Andy,

My best guess is the greyscale depth of the image.  Because it's digital as opposed to analogue, the boundaries between the shades are discrete rather than continuous.  Think of it as posterization wherein one makes a number of contrast negatives at different densities that when combined produce an illusion of continuous tone.  I think you are looking at 8 bit depth.  You will see a similar effect in ATSC television continuous tone.  It cant be corrected without significant loss of information.   In "busy" images, the problem is a lot less obvious.  For continuous tone grey scale digital imagry, one needs to have at least 16 bit depth, and preferably 24 bit.

Bill Pettit

-----Original Message-----
From: Andrew Davidhazy
Sent: Jul 6, 2015 8:33 PM
To: PhotoForum educational network
Subject: BMP file problem help

Hi,

I have bmp image files that show these “steps” in gray levels. Hints as to 

why this happens and what might be a corrective action to take?

Andy