Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Helen Bach" 
<helenbach@...> wrote:
>
> Greg,
> 
> This is a good question. I used to use a TR924 which was calibrated
> with a 1.78 reference for the span, so my D-max readings with K3 
inks
> on glossy paper were well away from the calibration point. With that
> caveat, the readings were around 2.64 for visual D-max. 
> 
> Now I've got a PrintFix Pro, and the readings from that are about 
0.05
> to 0.10 higher for densities in this range after converting L* to
> density. I've decided to get an Eye-One/PM bundle, so I'll remeasure
> when I have that.
> 
> The high D-max readings were obtained with predominantly K3 PK ink,
> with a little K3 LC and R800 blue, coated with Krystal Topkote.
> 
> Best,
> Helen
> 
>

The Printfix Pro (Datacolor 1005) device, and just about all the 
other spectrophotometers from Gretag and Xrite have a specification 
of 2.5D, so when I start seeing numbers below that, I have to 
question where they're coming from. Since I knew you had used 
different densitometers, I thought you might have had something of 
the quality to get accurate readings that low, and thought I would 
ask. To check, I contacted Xrite this morning, and confirmed what I 
thought, here is part of the reply:

"A density value of 0, means the all light is reflected from the 
surface
(again in a specific region of the visible spectrum), a density value 
of
1.0 means that 10% of the light is reflected from the surface, a 
density
value of 2 indicates that 1% of the light is reflected from the 
surface,
a density value of 3 indicates that 0.1% of the light is reflected 
from
the surface. As such values over 2.0 are extremely rare. Because this
metric is log based, when you go beyond 2.5, very small changes in
reflected light will cause very large numerical shifts."

He also said that L*a*b* values can not be directly converted into 
density values, I'll check this later for myself.