Why is low opacity pattern printed much darker?

[keyvan]

Hello everyone
I recently printed a fabric backdrop that had a pattern on the background with the opacity set to about 4%, but it came out much darker.
- I use Caldera Grand 11.2
- The printer is MS-Italy
- The color profile I use is created according to the material manufacturer's specifications

So my questions are:
1- What can I do to prevent this in the future?
2- In Caldera, where can I see the preview closest to what would actually be printed?

I'd appreciate all comments or suggestions

 

[tulsagraphics]

Not specific to Caldera -- and not that relevant to your technical issue -- but in general, I avoid using <100% opacity whenever possible because it's too unpredictable. Instead, I'll choose the exact colors I want (often from Pantone) that give the desired effect without opacity.

For example, white letters with a drop shadow on a medium purple background? I'll use a darker purple for the shadow -- not a low opacity black. I always get the results I'm after when using this method. YMMV, of course.

 

[prizmimaging]

I'm assuming it's a vector file and you are working from Illustrator. Make sure that the color you use on the pattern is not a spot(PMS) color. If it's spot color, convert it into process. If this still doesn't fix the problem, flatten the layers. If flatten the layers doesn't fix it, Expand the Appearance. If that still doesn't work, rasterize it. Not familiar with Caldera. There's no way to 100% prevent transparency problem unless you ask the client to give you a rasterized file.

 

[keyvan]

Not specific to Caldera -- and not that relevant to your technical issue -- but in general, I avoid using <100% opacity whenever possible because it's too unpredictable. Instead, I'll choose the exact colors I want (often from Pantone) that give the desired effect without opacity.

For example, white letters with a drop shadow on a medium purple background? I'll use a darker purple for the shadow -- not a low opacity black. I always get the results I'm after when using this method. YMMV, of course.

You are completely right. but unfortunately, this was a file from a customer and I try to avoid altering the Customer's design if possible. And even if I wanted to change it as you suggested, is there a way to know they have used <100% opacity?

 

[keyvan]

I'm assuming it's a vector file and you are working from Illustrator. Make sure that the color you use on the pattern is not a spot(PMS) color. If it's spot color, convert it into process. If this still doesn't fix the problem, flatten the layers. If flatten the layers doesn't fix it, Expand the Appearance. If that still doesn't work, rasterize it. Not familiar with Caldera. There's no way to 100% prevent transparency problem unless you ask the client to give you a rasterized file.

The file is created in Illustrator, but the pattern I'm having problems with is a png and not a vector.
Thanks for the suggestions, I'll have to try them out. I'm guessing rasterizing the artwork might work in this case. But do you think it would impact anything else during printing? I'm wondering if it is a good idea to rasterize all files I'm printing to avoid this issue.

 

[prizmimaging]

It is a rule of thumb not to touch customer's file. When something like this happened and when we have time, we will go into the file to troubleshoot the problem and then have the customer fixes it and send us the file again. The prepress person needs to be very experienced and detail oriented when rasterizing partial layers of a file. What I do is make a duplicate copy of the file to work on and keep to original artwork as reference, open both at same time and compare the result of the change to the original artwork. Pay special attention to artworks with drop shadows when rasterize them. The files that being used by printer are raster data after they are being converted/processed by the RIP anyway so as long as you included all of the affected layers and rasterize them at enough resolution and color space, then it shouldn't impact anything. Not sure what your printer's file/image resolution requirements, for us between 100~150 DPI at final output size works well for rasterizing background images. If you rasterize the entire file that contains texts, line arts, and/or other vector elements, you can go higher resolution than 150 dpi at final output size. You should run a test print of the rasterized effect/quality to determine your own acceptable resolution. For us, 150 dpi is go good balance between quality and file size and the time it takes to do so. Some back ground will look good even at 100 dpi. All the resolutions I'm referring to in here are for large-format digital printing, not for commercial offset/web printing.

 

[keyvan]

It is a rule of thumb not to touch customer's file. When something like this happened and when we have time, we will go into the file to troubleshoot the problem and then have the customer fixes it and send us the file again. The prepress person needs to be very experienced and detail oriented when rasterizing partial layers of a file. What I do is make a duplicate copy of the file to work on and keep to original artwork as reference, open both at same time and compare the result of the change to the original artwork. Pay special attention to artworks with drop shadows when rasterize them. The files that being used by printer are raster data after they are being converted/processed by the RIP anyway so as long as you included all of the affected layers and rasterize them at enough resolution and color space, then it shouldn't impact anything. Not sure what your printer's file/image resolution requirements, for us between 100~150 DPI at final output size works well for rasterizing background images. If you rasterize the entire file that contains texts, line arts, and/or other vector elements, you can go higher resolution than 150 dpi at final output size. You should run a test print of the rasterized effect/quality to determine your own acceptable resolution. For us, 150 dpi is go good balance between quality and file size and the time it takes to do so. Some back ground will look good even at 100 dpi. All the resolutions I'm referring to in here are for large-format digital printing, not for commercial offset/web printing.

Thank you for the detailed explanation. I really appreciate it.

I tried rasterizing the artwork and although it didn't fix the problem, it would have saved us a lot of time if I have done it before printing as it actually resulted in the pattern becoming as dark as it printed. So I guess it could be a way to recognize problem areas before printing, but there must be a better way

 

[prizmimaging]

Anytime! I'm glad to be helpful in the community. I don't mind if you want to share that problem file either upload here or pm me the file. I'm interest in why it turns out that way. If I can figure out the problem, I'll send you back the file and share what I did to resolve the issue.

 

[prizmimaging]

Did you render in rbg or cmyk? When I'm searching for a customers preferred color, not matching anything, I'll take the supplied RGB (almost always rgb) color and print both it and a version of it rendered in CMYK. They often produce radically different results by the time the RIP and printer is done with them.

I'm not the one having problem with the file but yes printing RGB files can have unpredictable result. We've learned thru out the years that spot-color gradients and transparency don't go well together. We recently received a job file where the client applied color to a gray scale picture using transparency overlaying the picture. Look fine on the screen but just won't print like how it shows in Illustrator. We solved the problem by flatten and rasterized all of the background layers.

 

[keyvan]

Anytime! I'm glad to be helpful in the community. I don't mind if you want to share that problem file either upload here or pm me the file. I'm interest in why it turns out that way. If I can figure out the problem, I'll send you back the file and share what I did to resolve the issue.

I've attached the file, it is just the problematic background, for convenience.
I'd like to have your opinion as well, but JBurton's idea seems to be on point. I haven't been able to do a test print, but rasterizing the design in RGB seems to be more accurate.

 

[keyvan]

Did you render in rbg or cmyk? When I'm searching for a customers preferred color, not matching anything, I'll take the supplied RGB (almost always rgb) color and print both it and a version of it rendered in CMYK. They often produce radically different results by the time the RIP and printer is done with them.

We usually Send files to RIP in CMYK, and you are right, this seems to be the issue. I haven't been able to do a test print, but the RGB file seems to preview much more accurately in Caldera

 

[prizmimaging]

I've attached the file, it is just the problematic background, for convenience.
I'd like to have your opinion as well, but JBurton's idea seems to be on point. I haven't been able to do a test print, but rasterizing the design in RGB seems to be more accurate.

The file you attached is just the image layer which doesn't work for troubleshooting the problem you were facing. Will need the actual problem print file to be able to troubleshoot the problem/suggest the actual solution. However, I tested it with a layer of magenta fill below your image layer. I tested it 3 different way. 1. As Is with just a magenta layer below it; 2. Rasterized the everything; 3. Remove Overprint of the image layer and then print as is(no rasterizing). Test RIP all 3 versions on Fiery FX RIP, Viewed the RIP file from our Vutek printer's control side and all 3 versions turned out exactly the same, no difference in the darkness of the pattern.

 

[keyvan]

The file you attached is just the image layer which doesn't work for troubleshooting the problem you were facing. Will need the actual problem print file to be able to troubleshoot the problem/suggest the actual solution. However, I tested it with a layer of magenta fill below your image layer. I tested it 3 different way. 1. As Is with just a magenta layer below it; 2. Rasterized the everything; 3. Remove Overprint of the image layer and then print as is(no rasterizing). Test RIP all 3 versions on Fiery FX RIP, Viewed the RIP file from our Vutek printer's control side and all 3 versions turned out exactly the same, no difference in the darkness of the pattern.

Thank you for the time. It is much appreciated