"L* Falses"


#1

The first column of numbers in the CURVE tab of the smoother (129STEP_PIEZODN_CGATS_SMOOTHER.xlsb) is labeled “L* Falses.” What is the significance of these numbers? I assume zeros are good. I’m seeing lots of non-zeros. I have been ignoring them, but perhaps they’re trying to tell me something important.


#2

You can safely ignore them based on the examples you have shown me. It is a combination of hand-coating, illumination variation, device error, and maybe printer ink pressure as seen in the periodic nature of the peaks and valleys.


#3

just take care not to have L false within first three boxes and last three. Otherwise linearization won’t work.

I suffered from that

Pablo

 


#4

So I guess SMOOTHER looks for patterns in the raw data and shows you the results as L* Falses. What is needed is a way of looking at their values and telling if there’s a problem or everything is good; otherwise, the numbers are useless. For example, I often see an INCREASE in the L* value between cell 11N and cell 11N+1, where N is the row number (N = 1, 2, 3, …). I can plainly see the pattern in the graph and in the L* values themselves. But do the L* Falses have anything to say about this? I know now to avoid them in the first three and last three rows.

Regarding the increase in L* at the beginning of each row: I don’t think it’s the coating because I still see the increase if I rotate the paper 180 degrees. I don’t think it’s my exposure unit, because I still see the increase if I rotate the contact printing frame 180 by degrees. That leaves the target tif file or my P400 printer. Could it be that unidirectional printing causes an ever-so-slightly lighter application of ink at the beginning of each pass?


#5

The graph showing the raw data and smoothed data (to the right of the numbers) is what is useful for figuring out if there is a problem.

The word “false” in this context is simply showing errors in raw measurement due to changes in light fall-off, brush coating, etc, that inevitably occur during alt-process printing. There will ALWAYS be a lot of falses with alt-process but you can safely ignore most of them. As Pablo said (and the instructions say) handle the top and the bottom ones.

 

best,

Walker