Backlit graphic poster production on offset press

Ric

Member
Hello,
I work as a ppm at a print company in Japan and I have some questions about the color matching and management of backlit graphic posters that we produce for our clients. We do color adjustments in our prepress and do print runs in our facility when our clients sign off.

In Japan, backlit graphic posters are very common at department stores and drug stores (e.g. cosmetic brands), and many printers print whatever artwork is on translucent paper such as Yupo translucent paper using UV offset presses. Because density cannot be achieved, the way we do this is to print the artwork front and back of the paper to gain enough density so that the artwork can be seen fairly OK when it is illuminated on viewing boxes. Obviously, the image printed on the back needs to be reversed, and the registration needs to be perfectly aligned, front and back. Printing backlit posters using inkjet printers has been also common for smaller print runs.

My questions are as follows:
1) Is this method common in your countries? (printing front and back for backlit posters on offset press) . I see so much information about printing backlit graphic signs using inkjet printers but not offset press.

2) How do you manage color proofing before having been signed off for the production run? It is always difficult for us to match the colors between the color target proofs provided by designers and the proofs we make on our press during the color proofing procedure. The way we do our color proofing is to gather at our client's color viewing room and compare the colors between the color target proof (reflected light) and the backlit proofs (transmitted light). Everyone (clients and designers) seems to perceive the colors differently, and it gives us a hard time meeting their expectations.

3) Is there any practical way to manage the colors between inkjet printers and the offset press when we handle exactly the same artwork?

I know there are many variables, and the situation is quite complicated, but if you give us some advice I would really appreciate it.
Thanks for your time.

Just for reference, I attached an image of the type of backlit posters that I am talking about although these are not what we produce.
 

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Thanks for your comments.

If designers provide a transmissive proof that would greatly help us review the proof from our press, and surely it would be much easier and it makes more sense.
Is that the way printers do in the US?

Having said that I have never seen any designers providing a transmissive proof in Japan. Designers in general make and provide data (artwork) and the physical target proofs, and our clients expect printers (prepress) to make color adjustments and make the colors look like the colors of physical target proofs. I find this method inefficient and illogical, so I would like to know how printers in other countries deal with similar situations.
 
I don't do offset, so...

if I was doing this on a digital press that has a 5th color option, I'd manually mask out areas with white ink so some is more illuminated than the rest. The white ink area would not need a CMYK double hit on the reverse side.

This is obviously only for short runs, but I have access to printers that can go 1.7meters x 30meters and it usually works pretty well. Another option i've given clients is a mesh substrate.

I've never found the perfect solution with my hardware for backlight, but these seem to work well, so...

can you print white ink on some areas? One of my printers can lay down as many layers of white as necessary, even creating depth, but I think that might be time consuming on offset.
 
Why use a reflective proof?
Use a transmissive proof so it's more similar to final product from press.

I'm guessing they'd have to print both sides of substrate before the client can sign off. Perhaps print the entire quantity of side one, then have client do a press-proof with side two on press so adjustments can be made on side two before running the rest of side two.

I should think that any decent outcome of side one should allow adjustments to side two to be pretty easy?
 

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