Digital BW, The Print

Hi Helen,

Thank you so much for your detailled answer.

I found two formula for converting Y / RGB:

Y=0.299*R + 0.587*G + 0.114*B 
Y=0.222*R + 0.707*G + 0.071*B

Seems that the first one match your's. Did you get your formula from 
few or many (Y,R,G,B) values ?

I have looked à PrintFix pro. Very interesting but still too 
expensive for my need (about $500) :)

Thanks again !

J.


--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Helen Bach" 
<helenbach@...> wrote:
>
> An amber Wratten 106 is used as the 'visual' filter in Macbeth
> densitometers (and maybe others) to make the spectral response of 
the
> sensor simulate that of the eye. The 106 allows almost all the red,
> some green and a little blue through. However, that in itself isn't
> enough information without knowing the spectral characteristics of
> everything else.
> 
> I just did a few quick tests on the Status A RGB and Visual density
> data I have readily available, and I go a reasonable match when
> 
> Dvis = 0.3*R + 0.55*G + 0.15*B 
> 
> That doesn't mean that it is correct, just that it might be close
> enough in the absence of better information.
> 
> Depending on where you are, why not look around for a cheap
> densitometer that has a visual channel, or better still, buy a
> PrintFix Pro on eBay.
> 
> Best,
> Helen
> 
> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, "joejx8"
> <joejx8@> wrote:
> >
> > 
> > Hi,
> > 
> > I am intended to buy an old/used densitometer. I have seen a 
model 
> > which seems to measure only R,G,B *density*. 
> > 
> > Is there a mean to get a BW *density* value (by calculation) from 
R,G,B 
> > density values... I was thinking at a formula like DBW= 0,7*DR + 
0,2*DG 
> > + 0,1*DB  (values are just for illustration) ?
> > 
> > Thanks !
> > 
> > J.
> >
>