RE: Measuring DMAX
Yves, 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 Kees, 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. Yves ----- 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 >
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