Re: Converting to grayscale
Re: Converting to grayscale
- Subject: Re: Converting to grayscale
- From: Ray Maxwell <email@hidden>
- Date: Tue, 19 Jul 2005 10:39:11 -0700
Hi William,
You mention that you are scanning a black and white negative. If it is
truly neutral, all the channels should contain the same information. If
that is the case you can use any of the channels alone and get the same
result as you see in RGB. You can check this by selecting each R, G, or
B channel and see if there is any difference. If you don't see any
difference then all of the methods mentioned here including the L* won't
extract any more useful information. I suggest just taking the Green
channel and then using "Levels" and "Curves" to get the white point,
black point, and tonality the way you like them.
Ray
Will and Pam wrote:
Hi,
This is not exactly a color management question but it does seem to be in
the same universe anyway...
I am doing a black and white negative scanning project in which the raw
scans are 16 bit RGB (scanned as positives). They are then converted to
grayscale in Photoshop, and inverted. I've looked at various ways of doing
this. Most recently I've been converting to Lab, selecting the L* channel,
and then converting to grayscale. My armchair color management knowledge
suggests to me that this is a good idea because it separates any color
information from luminosity, so that the resulting grayscale image is truer
to the luminosity inherent in the original scan. It seems as if this is a
more "accurate" way to do it. However, I do notice that in many cases when I
select the L* channel, the entire image appears much brighter. I've been
including a Stouffer step-wedge in the scans, and the lower densities of the
step-wedge (and the similar densities in the image itself, especially in the
range d.15-.60) really seem to change alot when the a and b channels are
off.
If there is a question in there I suppose it would be:
In principle, is using the L*channel a good way to approach the grayscale
conversion? Are there better ways I should consider? Is there a reason why I
would be seeing such a shift in apparent luminosity when discarding the a
and b channels?
Thanks for any input you might have.
William Real
Carnegie Museum of Art
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Colorsync-users mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Colorsync-users mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden