Re: Density readings with a Spectroloino
Re: Density readings with a Spectroloino
- Subject: Re: Density readings with a Spectroloino
- From: Phil Green <email@hidden>
- Date: Thu, 28 Mar 2002 23:55:11 +0000
- Organization: LCP
David Remington wrote:
>
This is a non digital question but involves eguipment and techniques
>
(I hope) the group is familiar with. I would like to take some
>
tradition RGB and neutral density readings from film with our
>
Specrolino/SpecroscanT. I have 4x5 transparencies of a Macbeth target
>
taken with various lighting set ups (all our work is copy work). I
>
want to calculate RGB and neutral density for a middle gray patch in
>
order to calculate the proper correction filtration. Anyone have a
>
handle on how to accomplish this?
In essence you multiply the spectral transmittance factor from the
Spectrolino by the effective spectral product of the 'filter' you want to
use, and then take the log of the summed products. For an example based on
ISO visual density, have a look at the section 'Calculating density from
spectral data' at
http://www.digitalcolour.org/understanding, which has a
spreadsheet you can download. You can probably get the spectral product data
from Kodak; alternatively if you have a physical filter you want to emulate
to hand you could make a measurement of it and insert the spectral data into
the spreadsheet.
--
Phil Green
Colour Imaging Group
LCP
Elephant and Castle, London SE1 6SB
Tel: +44 020 7514 6759 Fax: +44 020 7514 6772
http://www.digitalcolour.org
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