Digital BW, The Print

A few years back, before I retrieved a spectro from storage, I tinkered around with an ED100 EFI densitometer given to me by a friend. I found it's readings seemed to vary with the time of day for some reason. In tying to determine why, I learned it wasn't temperature related but was related to the general daylight level in the room even though the room had heavy window shades. So,I covered the samples and probe with a piece of old changing bag to stabilize the readings. I also found that it required a short wait time in the dark before measurements in order to stabilize readings, as well as waiting between multiple near same spot readings because taking them too soon caused steady changes. I also tried putting the instrument and sample in a box with part of the sample sheet outside of the box. With a small pen light on the sample outside of the box(about 3 inches from the probe measure point) I could influence the measurement as well and it took time for the measurement to stabilize when the light was removed.

What's all this mean?--Well, I took it to mean(aside from the ED100 being a pain) that there is a lot going on in the interactions between paper/coatings/OBA or not/environment/instruments and light. It's small wonder that it's difficult to exactly compare readings between one instrument or place and another or even from different times in the same place with the same instrument. I think some differences may well be the best we can do and not particularly due to the instruments alone.

Regards,
Duane




--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Ernst Dinkla <edinkla@...> wrote:
>
> It isn't limited to papers with OBAs.
> 
> I first thought of a spectral response of an inkjet coating component at 
> that range, whether caused by a specific component or a fluorsecence 
> effect. But sometimes another measurement of the same paper gives a 
> smoother curve. I really think it is the short interval of 5Nm, a small 
> peak  in the Xenon light near 530Nm and the curve fitting not coping 
> with that to produce a smooth curve. It is one of the things I want to 
> correct, redo some measurements and on the other hand dampen the hickups 
> in the curves. I find it more important to get  more data that can be 
> compared than getting that range in order.
> 
> 
> -- 
> Met vriendelijke groeten,   Ernst
> 
> 
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