Re: Colorsync-users Digest, Vol 2, Issue 183
Re: Colorsync-users Digest, Vol 2, Issue 183
- Subject: Re: Colorsync-users Digest, Vol 2, Issue 183
- From: Andrew Rodney <email@hidden>
- Date: Fri, 06 May 2005 11:22:40 -0600
On 5/6/05 11:12 AM, "Mark Rice" wrote:
> If we gathered 1000 people, and 99% reported it was bluer, and instruments
> reported it had a lower color temperture, I would say there was something
> wrong with the instrumentation protocol.
No, the values are right and your visual system is being fooled. But I agree
that what counts is what you see. There are many such examples of when your
eyes and visual system are far more useful than an instrument in one such
example. None the less, you could view the same images under a different
light box using a different illuminant and see something totally different.
The instrument can at least provide some non ambiguous values to give you an
idea what's going on between the two illuminants. It's not that one is
"right" and one is "wrong" but one is based on empirical measurements and
one is based on your visual system. My main point was that you used two
instruments and one is much better suited for providing you a numeric value
and one (the light meter) is not. Both could provide values that don't sync
up with what your eyes and brain tell you but one is providing a set number
that could be describing all kinds of colors while the other (the
Spectrophotometer) is providing a very exact and specific value. So let's
separate what you see and perceive from the measurement data you're getting
from two instruments. The light meter isn't the device to use even if in
this one situation it appears to be telling you what you see and what it's
providing are correct. Flip a coin and the opposite could happen in another
situation.
> By the way, I have an OTT lite here, and the eye-one reports that it has a
> CRI of 99, and a temp of 5003K. Compared to the GTI, it looks green. I am
> not sure what green is on the color temperature scale, but I have not been
> able to get my monitor to match it. So I don't know what that means.
As for CRI, it's a bit of a kludge to make a light source appear to be
closer to daylight for marketing and light manufacturers. CRI was developed
in large part to aid in the sales of Fluorescent tubes. There are tiles used
to compare these illuminants under a reference light source but only such
eight. That's too small a set of tiles. The manufacturers pick the tiles.
That make it easy to create a spectrum that will render the 8 tiles and
doesn't tell us that the light source is full spectrum. It doesn't tell us
how the other colors will render. My understanding is there are two
reference sources; Tungsten for warm bulbs and D50 for cool ones. That means
that a normal tungsten bulb and perfect daylight both have a CRI of 100! As
such, a high CRI is a decent gauge of how well a light will perform in your
home but not such a great indicator of how well it will work for photography
and proofing. Both a Solux 48 and a "full spectrum" tube from home depot may
have a CRI of 97. I can assure you the Home Depot bulb has a giant mercury
spike and some spectral dead spots.
> Also interesting is this: I can get the monitor to match the GTI
> visually,the eye-one (using GM PM) reports the light box as 4700K and the
> monitor at 5900K! What does that mean?
It illustrates why we need to define this as Correlated Color Temperature
and now somewhat ambiguous this is compared to the D Illuminants and why
they are necessary.
Andrew Rodney
www.digitaldog.net
_______________________________________________
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