loss of liearization troubleshoot


#1

I’m looking for the cause and solution for a system that was all set up and nicely linear, with new problems. Visual symptoms were dumping of values resulting in loss of shadow detail. A chart print out reveals the curve shown in the attachment. My suspicion based on that is that the medium Gray might have been refilled with dark gray ink.

Any thoughts on what you see here would be helpful. This is the cold side of a Pro setup, the warm side seems good to me, as well as it’s measurements.[attachment file=28648]

Thanks for any input,

Tyler


#2

Yep. It looks exactly like that to me. Oof.

 

-Walker


#3

This is a 9900 setup, K5 cold and K4 warm, one ink channel is out. The problems seem confined to the cold side as seen in the chart above.

Here are the L values of each ink measured from inkseparation10.tif printout in calibration mode.

Ilford Gold Fiber Silk (no gloss overprint)

Cold Very Light Gray= 71.7

Cold Light Gray= 44.9 Warm Light Gray= 46.7

Medium Gray= 7.5 Warm Medium Gray= 7.0

Dark Gray= 6.2 Warm Dark Gray= 4.1

P Black= 3.5

Photo Rag

Cold Very Light Gray= 67.4

Cold Light Gray= 42.2 Warm Light Gray= 44.7

Medium Gray= 22.7 Warm Medium Gray= 23.5

Dark Gray= 19.6 Warm Dark Gray= 21.3

M Black= 17.2

I have no individual ink measurements from the system when it was working well, and don’t know what the densities are “supposed” to be. Any advice about which inks may have gotten topped with the incorrect ink would be helpful. We’re trying to avoid a total flush and starting all over.

Thanks very much, Tyler


#4

Can you ZIP and upload the curves you are working with? This helps me debug. At first glance, your channels look fine. edit> Although the medium gray may have gotten dark grey in it . . .

 

best,

Walker


#5

I appreciate this Walker but I’m not sure it will help. These curves were very linear before some change occurred, and I don’t have relinearized curves of the new situation, we’re trying to find the problem before starting over. The curves are attached and I really appreciate the attention to this. These are PhotoRag and Ilford Gold Fiber Silk curves. As mentioned, the warm side seems ok, it’s the cool side that is printing dark with blocked up shadows. The neutrals were made with the curve blender from these W and C curves, of course printing dark too, being largely the cold side. I’m not sure what else on a windows system could change and result in this. We were going to purge what was hopefully an obvious channel ink mistake, now not sure.

9900_CRVS.zip (17.6 KB)


#6

Ok. So you have remapped your LC channel to you Orange channel correct? So you have Cool Medium Grey in your Orange channel?

You may want to test that . . .

Debug by remapping the Orange channel on the cool curves to the LM channel. This will use the Warm Medium Grey ink and if it is linear then you know that the Orange channel ink got contaminated.

best,

Walker


#7

Well oddly that didn’t help, so somehow the linearization changed. Troubleshooting why got nowhere so a new linearization got things on track. Any thought s on particle settling with these newer inks? I think this printer may sit for w few weeks at a time occasionally. Thanks for the help.

Tyler


#8

No way it would settle out like that (and lift the HLs at the same time). So far I have seen much less settling on this ink than other Piezo ink.

It’s a conundrum.

-W