Digital BW, The Print

I've "known" and used levels and curves...ok...but using them this 
morning I wondered, are they the same tool looked at in different 
ways?

I'll read the book but was wondering if others saw it this way.

Cleavis

on 11/5/01 7:13 AM, Cleavis wrote:

> I've "known" and used levels and curves...ok...but using them this
> morning I wondered, are they the same tool looked at in different
> ways?
> 
> I'll read the book but was wondering if others saw it this way.

Levels gives you three points from which to alter the tonality of a
channel/image (the two end + middle). Curves gives you 256 points at which
to you may alter the tonality, though I don't know exactly how many of them
can be points can be attached at any one time, but let it suffice that it's
many. The net result is that curves gives you far greater and finer control.
I only use levels to set my endpoints (because of the histogram, and if you
hold down the option key while you slide your end points it gives you a
representation on your image of which pixels are being affected (Mac PS 6)),
for anything else I use curves for the finer control.

Todd

Cleavis,

They are indeed quite similar. Anything you can do in the levels tool 
can also be done in the curves tool. However, the curves tool gives 
the user greater control and flexibility, and allows the creation of 
response curves that the levels tool cannot match (an extreme example 
would be creating a curve with all kinds of zigzags).

An example use of the curves tool might be to preserve the straight-
line response in the shadows portion of the image, and to lower gamma 
in the remaining portion of the image to lighten up the image without 
screwing up the shadows.

Note that in Photoshop 6, the levels tool has a wonderful feature for 
setting black and white points, which as far as I know does not exist 
in the curves tool. In the levels tool, on the input control, if you 
hold down the ALT key (in windows - some other function key in Mac 
OS) while adjusting either of the end sliders, you get a visual 
feedback for which portions of the image will become clipped by the 
adjustment.

...Ben

 --- In DigitalBlackandWhiteThePrint@y..., "Cleavis" <lyonscox@m...> 
wrote:

> I've "known" and used levels and curves...ok...but using them this 
> morning I wondered, are they the same tool looked at in different 
> ways?
> 
> I'll read the book but was wondering if others saw it this way.
> 
> Cleavis