Washed out colors with illuminated lightboxes

[Magman]

Okay, if this has been asked and addressed before I apologize.

I build a lightbox with a white polycarb UV coated panel. My digitial print is printed on a translucent printable vinyl. When not illuminated it is spot on beautiful. When I light it up. the colors are all washed out.

So I'm wondering how we keep the print vibrant when illuminated? I've attempted high pass Icc profiles-- help a little but not much... Does this occur due to the diffusing properties of polycarb and or acrylic? If so would adding Avery 30 or 60% diffusing vinyl on the inside?

I've printed on both Eco solvent translucent and my UV and both look ugly washed out once illuminated. What is the best way to get excellent results here with illuminated translucent vinyl , or should I print clear?

When looking at backlit films that looks awesome illuminated....???

 

[Solventinkjet]

It's a fairly common issue but worth bringing up once in while to see how everyone is doing it these days. The double strike or overprint option in your RIP is used for this in a lot of cases where it prints the same pass multiple times to get more ink density. The problem is ink pools up and can cause quality issues so you tend to have to crank the heat up and add a delay between passes. I have also seen people print a second print on clear in reverse and layer them with the translucent and poly carb in a way that makes it look good when lit as well but hopefully someone will chime in who has done it and can give more pointers on how it works.

 

[Bobby H]

About a decade ago we switched from using a thermal inkjet printer to using latex-based printers for back-lit sign face graphics. That offered some improvement over the washing out effect. Results were still not optimal. We have a flatbed printer than can print layers of white in between passes of color. That delivers far better results. Our current latex printers are getting "long in the tooth," so when we replace them we'll next one or more new machines that can print layers of white and color for even better backlighting quality.

 

[danno]

When I was printing UV we would print the image twice, one on top of the other. With our roll printers, we would print 2 images. One would be to an optically clear. We would then overlay on our light table to achieve correct registration.

 

[Magman]

So maybe the solution is to reverse print on clear, then overlay the reverse print with Avery or 3m White 30% or 60% diffuser vinyl? So say you're building a 4'x8' lightbox. If you have a UV flatbed , reverse print on a clear 4x8' polycarb panel, then apply white 30% or 60% diffuser vinyl... Anyone every try that to see if that keeps the graphic from washing out with illumination? Backlit film works great, even in bright lights. But if you print and overlay a tranlucent graphic it will look washed out everytime....

 

[Gino]

Ya hafta remember, these inks are basically translucent and need some kinda base. If ya don't have white capabilities, ya need to double or even triple hit, regardless of solvent or flatbed printing. We have profiles on our printers for various substrates and they do a great job. We created them ourselves. What looks good for us is a double hit in reverse on a back side of clear with a white face backing it up.

 

[DieselPoweredNun]

On our Epson 80600 we use one of the inbuilt translucent or clear vinyl profiles and it can hit a PMS color when lit up. I think the clear uses 48 passes, translucent 36.

Problem is, it's too dark when not lit. We end up picking a PMS a couple up or down from the target and that splits that difference. Which way depends on if the sign is mostly seen lit or unlit.

One set of signs we do works out really well doing that. The base uses two blue PMS colors, one light blue and one dark blue. The lit part matches the dark blue when not lit, and the light blue when it is.

We had to put diffuser on the back of clear acrylic and printed clear/laminated vinyl on the front of that.

Well there was a router cut logo stuck to that acrylic and the clear vinyl was cut to fit, but you get the idea.

 

[2B]

We try to use Modified Acrylic "white" 7328 to help with the washout.

we also add white vinyl on the 2nd surface if needed, especially if the cabinet is too bright or an LED retrofit

 

[SignMeUpGraphics]

Do you have a white channel in your UV printer?

We do 3 layered CMYK/W/CMYK and backlits look great when the lights are either on or off.

 

[P Wagner]

We do 3 layered CMYK/W/CMYK and backlits look great when the lights are either on or off.

+ 1

This is the optimal way to produce high quality frontlit (day) and backlit (night) signage and graphics. Color/white/Color is the only way to avoid over-inking/ under-inking based on the illuminant - which changes from reflective (frontlit) to transmisive (backlit) over the course of the day & night.

 

[Boudica]

We double strike on our Epson, but lately We've been doing backlits on our flatbed, but we don't use white.

 

[Gino]

Ya know, even when you use die-cut translucent vinyls they appear one way during the day and when lit up they look different. Adding lights to anything is gonna change the final outcome. Try educating your customers so they understand this modern phenomenon. When we used to spray baclkits they had a daytime look and a backlit look.

I just find it hard to believe that some of you can achieve the correct color with lights on or off.

 

[Bobby H]

Cut translucent vinyls don't wash-out when they're back-lit. Some translucent vinyl colors are more translucent than others, so the biggest problem is some colors look too dark when back-lit. Certain blues and purples are really prone to that issue. Then there is a limited selection of only so many colors. Lately some colors have been a PITA to order from suppliers.

Every kind of digital print will wash out to some degree when back-lit. Some print methods just yield better results than others. IMHO, thermal inkjet just sucks for any kind of back-lighting purposes. Standard latex is better, but still not great.

Any printer that can lay down a layer of color then a layer of white and then another layer of color will always be better for back-lighting purposes than printers without white printing capability. The colors don't wash out anywhere near as bad as prints from printers without white inks. It doesn't matter how many passes a non-white printer makes, the back-lighting results are just going to suck.

I still specify cut translucent vinyl for certain lighted signs. Sometimes that results in arguments with co-workers. Because some people just only want to digitally print everything because it's faster and easier than applying one or more layers of cut vinyl. They knee-jerk gravitate toward wanting to do that even if the end product looks like infected $#1T when back-lighted. It's one thing for a temporary sign to look like crap. It's another thing entirely when it's a sign that will be installed on a pylon or building for many years.

 

[Bobby H]

The translucent vinyl I really notice that with is 3M-3630-87 Royal Blue. It's really dark looking, but when light is shined through it really pops as a deep but very brilliant blue. Some of the more medium and lighter translucent blues seem more opaque. So it's tricky combining different blue vinyls together on the same sign face.

 

[Magman]

Ya know, even when you use die-cut translucent vinyls they appear one way during the day and when lit up they look different. Adding lights to anything is gonna change the final outcome. Try educating your customers so they understand this modern phenomenon. When we used to spray baclkits they had a daytime look and a backlit look.

I just find it hard to believe that some of you can achieve the correct color with lights on or off.

But Navy Blue should not wash out to white light. Which is what I got from a bunch of letters from my channel letter vendor. Just awful... I also want to make sure my lightboxes we make don't wash out to an unreasonabale level.

 

[Magman]

+ 1

This is the optimal way to produce high quality frontlit (day) and backlit (night) signage and graphics. Color/white/Color is the only way to avoid over-inking/ under-inking based on the illuminant - which changes from reflective (frontlit) to transmisive (backlit) over the course of the day & night.

So would reverse print translucent, white diffuser 30-60% , and printed translucent do the trick? Would you do that on white acrylic letters, or clear acrylic for best result?

 

[petepaz]

we usually print right on the panels with our flatbed printer but on occasion have to print on clear or trans vinyl with our roland eco solvent printers.
in both cases we just do an over print which is an option in the rip program. usually that is enough to get good colors when illuminated

 

[Gino]

Any translucent vinyls will wash out or change their colors to some extent.... unless they are opaque. Ink, paint and anything else that is meant to have light travel through will change.

I'm not sure if this was said or referred to, but ANY white you put down is gonna impede light going through, therefore changing the color somewhere. Either before being lit or afterwards. You can get white translucent vinyl, but again it is still cutting down the amount of light coming through. Darkening the surface at any point is making it 10% darker, 20 % darker and up to I think 40% darker. So, during the day, it looks great, but at night, your white is actually grey and anything on top of it has now been altered.

 

[unclebun]

You need to understand the physics of what happens when you look at a sign. If the sign is viewed by reflected light, i.e. sunlight, the light passes through the ink twice, since the ink is transparent. It goes through the ink on the way to the white substrate, and then again after it bounces off the substrate and comes back to your eye. You take that same printed vinyl and light it from behind and the light only travels through the ink once, leading to the print looking washed out because the color density is halved.

If you try to compensate for this by printing double strike and having greater density of ink, you may achieve an improvement when backlit because you have more ink density, but the print will be too dark and oversaturated with altered contrast when frontlit because the light, again, is passing through the ink twice.

That's why the ONLY way to achieve a sign that looks good both front and back lit is to have color/white/color on the vinyl. There are a couple of ways to achieve this. If you have a printer with white ink capability, you can do it in the printer/RIP so it prints that way. This works well with UV printers and I've bought some great direct-printed faces done this way. I haven't been able to achieve as good a result with roll fed solvent printers, most likely because the white ink isn't dense enough and the solvent inks tend to mix with the layers below.

The method that has become my standard is to layer the vinyl. We print the same regular print on clear vinyl and on translucent white vinyl, which we laminate for UV protection. If you have calibrated your printer for each material so they print dimensionally correctly, it's a simple matter to mount the clear print on your substrate, then mount the white print on top of it. This achieves as close to perfect color in both front and back light as I have seen anywhere.

 

[RabidOne]

We just did a series of tests to find the best compromise and the winning result is a sandwich print with the white at 75%.
We print on an HP 800W.