How to change K in a raster object

slush11

Well-known member
I feel like there is likely a really simple solution here and my brain is just fried...so don't judge.
I have a client who consistently sends in art that is VERY heavy in black. The best black on my (wide format) printer is 40,30,30,100 so I have asked them to ensure that they are sending me art with those values in their blacks. The problem is that they are often using black raster images in their backgrounds. (Like for example, a starless night sky). So while they change all of their vector text to 40,30,30,100, the raster images remain whatever they are and come out as a greeny-black every time.
My question is, is there any way to change the black values of a raster image? If so, is it something I can do using PitStop or something or does it have to go back to the client?
 

MacTwidget

Well-known member
No Title

In Acrobat, I would use the "Edit text & images" tool. Select the image you want to change and right-click on it. Then select the "Edit Using > Adobe Photoshop.
Once the image is open in Photoshop, go to "File > Edit > Convert to Profile..." and replicate the settings in this screen capture.
 

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Stephen Marsh

Well-known member
I would use PitStop Pro and a DeviceLink profile (or Workflow software, a colour server etc).

In PitStop Pro with an Action List:

Select All
Select by Ink Coverage (basic object check), more than 200%, include images etc.
Apply DeviceLink (Both, CMYK)

The key is of course getting hold of a DeviceLink ICC profile, not to mention having the ability to specify the desired ink build for the black point of the profile (I personally would use Kodak ColorFlow Pro for this task, which has this feature).

The same could be done in PitStop Pro or Server with an Action List:

Select All
Select by Ink Coverage (basic object check), more than 200%, include images etc.
Override Colour Management Settings (setting source/destination CMYK profiles
Convert Colour to CMYK

Again, the key is to have a standard device ICC profile that delivers the correct shadow value build.

As mentioned, the edit/touch-up image tool in Acrobat Pro is of course another method where you can use the full power of Photoshop to edit the image and then update the saved image back into the original PDF. If taking the time to go into Photoshop, one could elect to alter the colour build of the darkest areas of the image to a specific value, without affecting any other areas of the image.


Stephen Marsh



I feel like there is likely a really simple solution here and my brain is just fried...so don't judge.
I have a client who consistently sends in art that is VERY heavy in black. The best black on my (wide format) printer is 40,30,30,100 so I have asked them to ensure that they are sending me art with those values in their blacks. The problem is that they are often using black raster images in their backgrounds. (Like for example, a starless night sky). So while they change all of their vector text to 40,30,30,100, the raster images remain whatever they are and come out as a greeny-black every time.
My question is, is there any way to change the black values of a raster image? If so, is it something I can do using PitStop or something or does it have to go back to the client?
 

Stephen Marsh

Well-known member
I feel like there is likely a really simple solution here and my brain is just fried...so don't judge.
I have a client who consistently sends in art that is VERY heavy in black. The best black on my (wide format) printer is 40,30,30,100 so I have asked them to ensure that they are sending me art with those values in their blacks. The problem is that they are often using black raster images in their backgrounds. (Like for example, a starless night sky). So while they change all of their vector text to 40,30,30,100, the raster images remain whatever they are and come out as a greeny-black every time.
My question is, is there any way to change the black values of a raster image? If so, is it something I can do using PitStop or something or does it have to go back to the client?

With correctly implemented colour management for WF printing, neutral shadow colour values in the input file should be mapped to neutral colour values in the final wide format output colour space.

Stephen Marsh
 

slush11

Well-known member
OMG Stephen. You're so far advanced I'm not sure you're even on the same playing field lol. Let's say I were to stick with the photoshop route, I actually don't think I know how to convert a raster image's colors in Photoshop. So lets say the image is of a night sky with grass at the bottom. I suppose I would just your the selection tool to grab all the black, then can I change it in the color palette? (Sorry-I'm not near Photoshop right now).
 

Stephen Marsh

Well-known member
OK slush11, let’s try to keep this “simple” to start with (keeping in mind that simple may not lead to the best results)…

In Acrobat Pro, use the image editing tool to open up the image in Photoshop for editing.

Once the image is open in Photoshop, plant a fixed colour sampler tool into the dark area you wish to change (keyboard shorcut: i). Reference this colour sampler readout in the info palette window (F8 key).

Next, use an adjustment layer edit with the selective colour command and change the drop down colours menu to blacks.

Then adjust the CMYK sliders using absolute mode to hit your preferred colour values in the info palette.

Save the file so that it will in theory update into Acrobat Pro when it is closed in Photoshop – however my advice is to first duplicate the image into a second file just in case it does not update into Acrobat when closed (that way all of your hard work is not lost).

You will likely note that the image probably looks very poor onscreen due to the above simple edit. Print it out and see how it compares to the original. You may find that even though the screen preview is not great compared to the original image, it prints acceptably. You also may find that such a brute force edit is probably not the best way to perform this task – which is why many use a colour conversion to a different ICC profile or even better, use a DeviceLink profile.

To be continued…


Stephen Marsh
 

Stephen Marsh

Well-known member
A “better” approach may be to convert the original image in Photoshop to an ICC profile that delivers values close to what you are looking for. You could then leave it as is, or perhaps use the previously mentioned selective colour edit to tweak the shadow colour values to where you need them to be. This should be a less drastic edit of colour values than the example in my previous post.

The problem with colour conversions is that you need to first describe the source colour profile, before describing the destination colour profile.

In Photoshop, use the edit/convert to profile command to convert to the CMYK destination profile of your choice (the source will either be “tagged/embedded” in the image or will be presumed from your Photoshop colour settings if the image is “untagged” with no source description).

The reason that I hesitate to get into this whole discussion about conversions and profiles is that it is not an easy topic to go into.


Stephen Marsh
 

slush11

Well-known member
Thanks for breaking it down. I'm pretty new to pre-press so the functionality of Acrobat isn't something I'm very proficient at. I appreciate the help.
 

Correct Color

Well-known member
Slush11,

What you need is a proper color managed workflow for your large format printers.

It isn't over your head. You can learn it. It's simply the correct way to do it.

Every. Single. Issue. you're having is simply caused by not having proper printer profiles, and by not using a proper color managed workflow. And while you may eventually get a result that you can sell, the time you waste getting it is time you can't sell.

What you're doing here is all second-rate work-arounds. There is simply no substitute for doing it right.



Mike Adams
Correct Color
 

slush11

Well-known member
Slush11,

What you need is a proper color managed workflow for your large format printers.

It isn't over your head. You can learn it. It's simply the correct way to do it.

Every. Single. Issue. you're having is simply caused by not having proper printer profiles, and by not using a proper color managed workflow. And while you may eventually get a result that you can sell, the time you waste getting it is time you can't sell.

What you're doing here is all second-rate work-arounds. There is simply no substitute for doing it right.



Mike Adams
Correct Color



Well we have had this thing for 5 years now (I've only been here for 6 months) and there are countless ICCs set up on the printer, none of which will produce a decent looking RGB file - or change the blacks automatically. My assumption is that the tech set up the profiles (which work very well for the different substrates so long as the file is CMYK). We were taught that each printer will have different specs that the designer should be following so that is what we've been trying to do but some of them just. Don't. Get it.
In any case, if you say I need proper printer profiles, where do I learn how to set them up beyond what is already on here? I am well aware of how to access setting up a profile, but I just don't know what all the different terms mean or what the heck to be striving towards.

PS. I haven't wasted much time at all doing these "second-rate workarounds". The question I was asking in this thread was actually info to pass on to a client designer who couldn't seem to understand what I was talking about.
 

Stephen Marsh

Well-known member
Slush, I think that the problem that Mike is referring to is highlighted in your OP:

"I have a client who consistently sends in art that is VERY heavy in black. The best black on my (wide format) printer is 40,30,30,100 so I have asked them to ensure that they are sending me art with those values in their blacks.”

This is exactly what I was referring to back in post #5.

Unless you have CMYK colour management turned off (not a good idea), it should not matter what CMYK values the source file has, as they will be transformed to the profiled CMYK state of the media.

Input values of 100c100m100y100k should map to the darkest point that the inkjet profile offers. Input values of 0r0g0b or L*0a*0b*0 should also map to the darkest point that the inkjet profile offers. A “lesser” rich black CMYK source such as say 71c61m51y100k would map to a neutral dark colour that is “very very black” (presuming Fogra39 as the assumed source CMYK space). For a particular inkjet and media, the final converted value may be say 62c56m50y84k, which has the same L*a*b* appearance as the original Fogra39 CMYK values of 71c61m51y100k

For a traditional press type workflow, same CMYK values in = same CMYK out (not 100% true/accurate, however I don’t wish to complicate this general point).

For inkjet/WF/GF output workflow, CMYK values in = different CMYK values out (which are then transformed into the actual device inks which are often CMYK+).

Put another way, when working with a traditional press, we often work in final device CMYK, however when working with an inkjet, we don’t work in final device values.

In the RIP colour settings, there will be a “simulation” or “source CMYK” profile setting, where you tell the RIP what profile the CMYK input actually is, usually SWOP or GRACoL or ISO Coated v2 etc. Of course, the RIP may also read embedded colour profiles too, or ignore them and assume the setting previously mentioned. The same is often true for RGB input. Many RIPs offer separate colour controls for vector and raster, so there could be 4 places where default assumed profiles need to be setup as defaults (2 for RGB and 2 for CMYK).


Stephen Marsh
 
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slush11

Well-known member
Stephen Marsh I understand what you're saying. I know our CMYK is turned on...the tech warned me about turning it off...however we did some testing of blacks on different substrates and all of them show 40,30,30,100 as being the best looking black. You would think it would be 100,100,100,100, but it really isn't. Maybe I should be learning more about SWOP or GRACoL or ISO Coated v2 etc...
 

Correct Color

Well-known member
Slush11,

We were taught that each printer will have different specs that the designer should be following so that is what we've been trying to do but some of them just. Don't. Get it.

It's not for them to get.

Sorry, but you were just taught wrong. And don't feel bad, that's far from uncommon in this industry.

Think about it. What you're saying there is printing madness. You've got however many printers you've got there, and you're going to task designers to prepare individual files for each one?

I'll go you one further: Not only does each of your printers have different characteristics, each of your printers also has different characteristics depending upon the media on which it's printing. That's the nature of large format, and it's also the reason why doing it the way you do it is a colossal waste of time.

And, again, I can tell you I've been doing large format color management around the world for the past ten years. In fact I'd be very, very surprised if I haven't set up workflows for and profiled every single RIP/printer/ink/media/resolution combination you've got in your shop, and all of them many more times than once.

And I can tell you that every single one of them is using a late-binding workflow, and sending primarily RGB files to the RIP. Once again, if your workflow is correct, it makes no difference to the RIP whether an incoming file is RGB or CMYK. None. The RIP is going to do a transform to the final printing space in any event, and when it does, it does it pixel by pixel, L*a*b* value to L*a*b* value. And it does it exactly the same, regardless of the color space of the incoming file.

Just what printer/RIP combinations do you have?

In any case, if you say I need proper printer profiles, where do I learn how to set them up beyond what is already on here? I am well aware of how to access setting up a profile, but I just don't know what all the different terms mean or what the heck to be striving towards.

You could hire me. It's what I do for a living.

I can also tell you I've been doing it for ten years, that I've heard the exact same song you're singing many more times than I can count, and since day one, this link has been on my website...

Correct Color Guarantee

...and I've never not been paid yet.

And yes, it is more than a little unseemly to out-and-out pitch here.

But in your case, I can tell you that even a disinterested observer who knew all the facts would tell you that this is exactly what you need.

(Edited to add:

PS. I haven't wasted much time at all doing these "second-rate workarounds".

Well, yeah, you have. You're not aware of it, but you do it every day and with every file you send.

What if, just what if...

You could prepare every single file for every single printer for every single media exactly the same?

What if you could send each of those files with absolute confidence that each print would be the best color and gamut and ink laydown that printer could print on that media, first time, every time?

And what if you never ever again had to print test swatches to chase color?

See, if that's not what you're doing now, then every single step you take to get a sellable job, is a workaround.)



Mike Adams
Correct Color
 
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Stephen Marsh

Well-known member
Stephen Marsh I understand what you're saying. I know our CMYK is turned on...the tech warned me about turning it off...however we did some testing of blacks on different substrates and all of them show 40,30,30,100 as being the best looking black. You would think it would be 100,100,100,100, but it really isn't. Maybe I should be learning more about SWOP or GRACoL or ISO Coated v2 etc...

I believe that in a WF/GF inkjet setting you would be best served by learning more about your RIPs colour controls for input profiles, embedded profiles, PDF output intent, simulation profiles, spot colour handling, proofer device profiles, proofer gray balance for each media, proofer total ink limits for each media etc.

Knowing about different offset press CMYK reference conditions may come into that, however it would only be weighted with say 5% relevance compared to the inkjet production specific issues.


Stephen Marsh
 

slush11

Well-known member
Slush11,



It's not for them to get.

Sorry, but you were just taught wrong. And don't feel bad, that's far from uncommon in this industry.

Think about it. What you're saying there is printing madness. You've got however many printers you've got there, and you're going to task designers to prepare individual files for each one?

I'll go you one further: Not only does each of your printers have different characteristics, each of your printers also has different characteristics depending upon the media on which it's printing. That's the nature of large format, and it's also the reason why doing it the way you do it is a colossal waste of time.

And, again, I can tell you I've been doing large format color management around the world for the past ten years. In fact I'd be very, very surprised if I haven't set up workflows for and profiled every single RIP/printer/ink/media/resolution combination you've got in your shop, and all of them many more times than once.

And I can tell you that every single one of them is using a late-binding workflow, and sending primarily RGB files to the RIP. Once again, if your workflow is correct, it makes no difference to the RIP whether an incoming file is RGB or CMYK. None. The RIP is going to do a transform to the final printing space in any event, and when it does, it does it pixel by pixel, L*a*b* value to L*a*b* value. And it does it exactly the same, regardless of the color space of the incoming file.

Just what printer/RIP combinations do you have?



You could hire me. It's what I do for a living.

I can also tell you I've been doing it for ten years, that I've heard the exact same song you're singing many more times than I can count, and since day one, this link has been on my website...

Correct Color Guarantee

...and I've never not been paid yet.

And yes, it is more than a little unseemly to out-and-out pitch here.

But in your case, I can tell you that even a disinterested observer who knew all the facts would tell you that this is exactly what you need.

(Edited to add:



Well, yeah, you have. You're not aware of it, but you do it every day and with every file you send.

What if, just what if...

You could prepare every single file for every single printer for every single media exactly the same?

What if you could send each of those files with absolute confidence that each print would be the best color and gamut and ink laydown that printer could print on that media, first time, every time?

And what if you never ever again had to print test swatches to chase color?

See, if that's not what you're doing now, then every single step you take to get a sellable job, is a workaround.)



Mike Adams
Correct Color


OK. So I TOTALLY understand what you're saying here. We need color management workflow and you've heard it all before. We have one large format printer. I don't care what the rest of our shop has because this is my department so I am only concerned with this printer. I have seen countless websites that list printer specs right on their websites. I get that there may be more specific specs that pertain to each media and whatnot, but I am referring to the standard "1/4" bleed, trim marks, 300dpi, etc....". To that I would add, make your blacks 40,30,30,100.

I would love to hire someone like yourself, but it is not my call, and it would likely cost us an arm and a leg to fly you out here for something that we're not REALLY concerned about at this point. The only color that I don't like is the black and that's a fairly simple fix. The only mode that I don't like is RGB, and now I know that I just don't have the right profiles set up to print it so I will just continue converting to CMYK before I print like I always have. Other than that, we have never had a complaint about colors, nor have we had to print any swatches other than the black testing I just did recently.
 

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