luminance manipulation?

[Tony Zuccolotto]

Mark,

There is no direct luminance manipulation in E-Prime, e.g. all you have
is an RGB specification an as I understand it there is no
reliable/direct/computational way to infer luminance levels just from
that specification, i.e. how a particular RGB specification gets
rendered as a stimulus perceivable to the subject depends on many
factors which directly effect luminance (e.g. ambient/internal lighting,
time of day (e.g. ambient sunlight), contrast and brightness settings on
the monitor, refresh rate, etc.)  

In order to do this you need to have a very controlled presentation
environment and the hardware tools necessary to measure/confirm your
measurements reliably within that environment.

Once you have controlled for the environment and calibrate your
experiment to it you should be able to confidently repeat the
presentation to any number of subjects (...but I'd still re-check the
levels every day or so :) ).

If you find some other way to do this it would be great information to
share with the group.

Thanks,
Tony

*** DISCLAIMER: ALL VIEWS EXPRESSED ARE MY OWN AND DO NOT NECESSARILY
REFLECT THOSE OF PSYCHOLOGY SOFTWARE TOOLS *** 

Anthony P. Zuccolotto
Vice President
Psychology Software Tools, Inc.
2050 Ardmore Boulevard
Suite 200
Pittsburgh, PA 15221-4610
Phone     412-271-5040
FAX       412-271-7077
Email     anthony.zuccolotto at pstnet.com
Internet  http://www.pstnet.com


> -----Original Message-----
> From: Mark G Orr [mailto:morrct at andrew.cmu.edu]
> Sent: Tuesday, May 20, 2003 1:57 PM
> To: eprime at mail.talkbank.org
> Subject: luminance manipulation?
> 
> Hello, I checked the archives for an answer to my problem, but that
did
> not work.  I want to change the luminance of one letter within a 4
letter
> word relative to the other three letters in the word.  Furthermore, i
want
> the degree to which the letter is different from the other words
> modifiable with respect to each individual subjects performance.  Any
help
> will be greatly apprectiated.
> 
> -Mark Orr