Datacolor User to User Support Group.

This should be a real simple question and my appologies if it has been answered in the past (I did a search, but didn't find it)...

What would be considered an acceptable range of readings for measuring the white calibration tile.

I measured mine and got L=90.40, a= -0.98 b= -1.09 (Density 0.11).

Then I cleaned the tile using a paper towel and Sparkle Glass Cleaner (like windex but is pink rather than blue).  

I measured the tile again and the "b" value seemed to have changed quite a bit.  The new values are L= 90.67, a= -1.04  b= -1.59 (Density = 0.11)

Are these values within acceptable range and did it get better or worse after cleaning?

Thanks,
Rick

On Sep 2, 2010, at 1:53 PM, ryanrm2007 wrote:

> This should be a real simple question and my appologies if it has been answered in the past (I did a search, but didn't find it)...
> 
> What would be considered an acceptable range of readings for measuring the white calibration tile.
> 
> I measured mine and got L=90.40, a= -0.98 b= -1.09 (Density 0.11).
> 
> Then I cleaned the tile using a paper towel and Sparkle Glass Cleaner (like windex but is pink rather than blue).  
> 
> I measured the tile again and the "b" value seemed to have changed quite a bit.  The new values are L= 90.67, a= -1.04  b= -1.59 (Density = 0.11)
> 
> Are these values within acceptable range and did it get better or worse after cleaning?

Your sense of "quite a bit" might be out of calibration. Half a point is not really very significant. You might have actually cleaned some dirt or dust off your tile... or you might have used a paper towel with artificial whiteners in it, which were deposited on the tile causing it to read "bluer"... if recleaning it with a lens cloth instead of a cloth or paper product which may contain whiteners does not return it to the original value, than we'll assume it was dirty.

Either reading is within the acceptable range for a white tile.

C. David Tobie
Global Product Technology Manager
Digital Imaging & Home Theater
CDTobie@...

Thanks David,

I tried cleaning it with a two part, single use (the little foil pack
things, like what you ship with your products) optical cleaning pads from
Calumet Photo.

I got just a small change in the "a" value (went from -1.06 to -1.32 with
the L and b staying about the same).  So I guess I can assume the tile was a
little dirty and it sounds like it is OK now.

Values now are 90.69 ; -1.32 ; -1.56

 

I am not real familiar with the L-a-b values so I thought it best to ask and
make sure I am starting from an appropriate place.

Rick