color proof to press

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color proof to press

Postby inkslinger » Thu Feb 11, 2010 8:11 pm

Im not sure how to post this but I'll try to explain it as best I can, we are having SO much trouble matching our color proofs from the art room to what we get off the press for our process work. Im the press operator and I get a proof called a kooltone, a pandot proof, and a proof from an epson 4000 printer. Problem is I can't match any of them. Is this a press problem or is this a problem that needs to be worked out in prepress? The press has been fingerprinted twice. This is an ongoing job to job problem not just 1 job. I've got faith in you guys. thanks
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Re: color proof to press

Postby BMS » Sun Feb 14, 2010 8:58 pm

We have had the same problem with our latest plate vendor. They are using an Epson for the color proofs and not once have we been able to get close with the shading on backgrounds and such. We never had this problem until they went from analog plates to digital, now nothing matches... not the proofs or the new printing when we have to remake the analog plates. It's quite frustrating to not be able to match your previous run from less than a month ago.

Our trials and tribulations have led us to fingerprint again with another vendor that can give us multiple plate materials and a flat dot on the new digital plates. I'll keep you aprised of our progress but let us know if you find a solution in the mean time.

Good luck!

BMS
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Re: color proof to press

Postby magician » Mon Feb 15, 2010 1:52 pm

Thank you for your responce.However our position has not changed.We use in house plates with a fully equiped art room using a negitive to make plates.The customer sends in the file,a color proof is made on the epson 4000,plates are made and the results are the same. labels do not match color proof.Our press has been fingerprinted,The ink densitys have been checked,prints have been pulled perfectly and the stock is quality.I do not beleive this is a press problem and assume their is a step we are missing in the artroom. We need to solve this, can anyone help. Thanks.
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Re: color proof to press

Postby Shawn » Mon Feb 15, 2010 8:42 pm

Are press samples light to the proof?
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Re: color proof to press

Postby inkslinger » Tue Feb 16, 2010 1:50 pm

Press samples are always darker to the proof. We have been cutting inks and going out of spec just to come close to proof.
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Re: color proof to press

Postby Shawn » Tue Feb 16, 2010 9:39 pm

What linescreen are the plates, what stickyback are you using and what is the volume of the anilox rolls? Also, what Ink densities are you shooting for?
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Re: color proof to press

Postby inkslinger » Tue Feb 16, 2010 10:53 pm

we use 150 line screens, our stickyback is 3m 1115, we use harper 1200lpi 2.0bcm. The ink densities were supplied by our ink supplier, they are y-1.00 m-1.35 c-1.40 and k 1.50. we use many different substrates but the problem happens no matter which one we happen to be using.
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Re: color proof to press

Postby BMS » Wed Feb 17, 2010 10:10 pm

Just a shot in the dark here but, have you thought about the inks on the Epson? Like I said above, we have had the same problem with our outside vendor but it started to happen when the went from analog to digital plates. Check with the vendor on your Epson inks and see if the switched something on you.

BMS
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Re: color proof to press

Postby Shawn » Wed Feb 17, 2010 10:49 pm

Good density targets, I would recommend a 1.3 to 1.5 bcm for the C,M,Y aniloxs but as long as you are hitting the densities, I cant argue.

Are you sure your art department is calibrating to the fingerprints correctly? If you are able to measure dots (like on a betaflex) Check your 50%. You should be printing around 56-58% on a 50% dot. I found that hitting 50% exactly tends to print a little light...
I'm not being sarcastic but are you setting your impressions correctly? If you are then I recommend getting the art dept to cut their curves by around 10% starting in the midtones and test the plates.

I have an epson 3800 and have had a 4000 in the past using Kooltone proofs and have had pretty good success matching colors to the Epson inks. The Epson 3000 had problems...the C was around PMS 3005 and the Magenta was PMS 214...
Hope this wasn't too schitzo...
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Re: color proof to press

Postby Luc St-Pierre » Thu Feb 18, 2010 5:29 pm

In my book, a press does not have to match a proof . . . a proof needs to match a press !!! The whole idea of fingerprinting a press is to set the tracks for prepress to simulate the most exactly possible the press results. If and only if the variables on your press are pretty much under control and similar to those on fingerprinting day, prepress is definitely guilty. Now, this does'nt mean a war must be started. Only a good understanding of color management and cooperative work will settle this very complicated but not uncommon problem. Good luck.
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Re: color proof to press

Postby inkslinger » Fri Feb 19, 2010 12:58 pm

Thank you for your help Luc St-Pierre. I have another question. When the color proof comes to press their are color bars [squares] from the epson on the proof,should the color bar densitys match the press printed densitys? If so, can the colors be adjusted on the epson to duplicate the press?.
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Re: color proof to press

Postby Shawn » Fri Feb 19, 2010 11:06 pm

Yes. You want the epson maximum densities to match your press densities. Your proofer can lay down a lot more ink than you want... The key is to get the epson to print down to the quality of flexo.. kooltone is a great way to show a true printed label. You want to set your proofs up so you can be successful on press. It's easier to explain to your customers that the proof is matched to your press than come up with excuses as to why your press samples dont match the beautiful 2880 x 2800 proof on glossy paper (which by the way, I recommend using either Epson Luster paper or InkPress luster for proofing).
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Re: color proof to press

Postby Luc St-Pierre » Wed Feb 24, 2010 6:01 pm

Many proofing systems produce color bars along with a proof. More than often, these color bars are there for proofing quality control. It does not necessarily relate to press density targets. If a press profile was used to proof your targets, you should be documented on the solid density and dot gain targets that fit that profile. If not, ask for it. In our company, we always tag along a solid and 50% patch somewhere on plate with targeted density and gain values. If proofing was done with an off-the-rack profile, then welcome to the wonderful world of guess-work !!! You may or may be not capable of getting to target, the only thing you can do is keep track of all necessary information in order to be at least capable of repeating the print someday in a less painfull manner. As a general advice, keep working with one or two prepress houses, and keep communicating. Rome was not built in one day. If you always run after the lowest cost plate per square inch, you will often have bad surprises. I don't know about plate buyer's feelings, but me, when I ride in an elevator, it scares the *** out of me to think that the lowest bidder is doing the maintenance for it.
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Re: color proof to press

Postby inkslinger » Tue Sep 07, 2010 3:51 pm

well said,you have givin us alot to thing about.any and all info you give is being passed along to the prepress dept.Thanks
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Re: color proof to press

Postby exflexo » Fri Sep 10, 2010 1:10 am

Characterizing a press has always been a three step process in my experience...

1) Output a gradiant patch plate with 1/2" x 1/2" squares of every dot percentage from 1% to 100%. Hit correct density for each color and use this to determine your minimum highlight dot (something you MUST know to proof accurately) and where your quarter tone, mid tone and three quarter tone are hitting. As said earlier, you would like your 50% to print around 58%. Once you have this information you can develop a cut back curve for this particular press.

2) Now that you now the minimum highlight and what your midtone cutback is, you can output a full color fingerprint target. My favorite is from the FTA First manual, but DuPont has an equally good one. Output this target with your min highlight and your adjusted 50% dot. Run this job like you would any other 4 color process job... hit densities... make sure the highlight and midtone etc are consistent with your gradiant patch target and print samples on ALL SUBSTRATES THAT YOU REGULARLY USE.

3) Use the press samples from step #2 to characterize your proofing device (also mentioned earlier). The proofing device is what gets the final characterization curve.. NOT THE PRESS. Here is where a color spectrophotometer and calibration software (X-Rite, Gretag etc) come in handy. You can create a calibration curve for use in Photoshop... but it takes lots of experience. Otherwise, it IS a science and should be treated as such.

Honestly, I have never been a fan of Epson or any other inkjet proof. The problem with them is three-fold. First, they are not halftone dot proofing devices... so there will always be that inherant difference. Secondly, they all use a light magenta and a light cyan to increase their color gamut. While this is great for producing really nice photographic images, it also tends to produce colors that are difficult to reproduce on a printing press (BTW: Make sure you use CYAN and NOT PROCESS BLUE on press.. or you will never match an Epson with stock colors). You can however do wonders with the right color management software though. The last issue I have with inkjet devices is that you cannot proof on the same substrate that the final printed piece will be printed on. This fact MUST be taken into consideration as many clay coated & other stocks have a blue-gray cast that dirty's up yellows & highlights. I would actually go the extra step of "tinting" inkjet stock by creating a file to simulate the color of the stock and printing it in a separate step before I would print the actual proof image. My favorite proofing device is a Kodak Approval because it can proof on many substrates, uses C,M,Y,K inks and it outputs Halftone dot screens (and angles) that were the same as our direct to plate device.

Anyhow, there is my two cents worth... ; )
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