U of S | Mailing List Archive | alt-photo-process-l | RE: Measuring DMAX

RE: Measuring DMAX


Vuescan users need not do any math. The log values are displayed on screen.

Don Bryant

-----Original Message-----
From: Yves Gauvreau [mailto:gauvreau-yves@cgocable.ca] 
Sent: Tuesday, January 15, 2008 11:11 AM
To: alt-photo-process-l@usask.ca
Subject: Re: Measuring DMAX


In the limit you dont even need the equation, simply compare the raw pixel
level from a scan of the various process, relative values are plenty good
enough for this. If you need an absolute value then only a densitometer can
give it to you.


----- Original Message -----
From: "Kees Brandenburg" <ctb@zeelandnet.nl>
To: <alt-photo-process-l@usask.ca>
Sent: Tuesday, January 15, 2008 10:25 AM
Subject: Re: Measuring DMAX

> On 15 jan 2008, at 15:22, Yves Gauvreau wrote:
> > In the case of scanned image, while in VueScan or some other scanning
> > software you may want check it out with a gamma of 1.
> Not with the vuescan density measurement tool. Any setting will give
> the same density reading (but not the same scanned file). Vuescan uses
> the raw output of the CCD for this. Optical density readings are
> measured as log (max_colour from CCD/raw_colour from CCD). These
> density readings can be accessed in Vuescan when moving the pointer
> over the scanned image while holding ctrl.
> -k