Photoshop curve custom eyedropper settings: time to burn the witch?

[lowep]

A few years ago I was given the following custom cmyk photoshop eyedropper settings by the commercial printer I was working with to use for preparation of CMYK files for their offset printing press. The results were very satisfactory so being both ignorant and superstitious I have used these settings ever since. Now I am working on a different project on the other side of the world that has started me thinking maybe it is a dumb idea to keep using these settings, so would like to know if anybody else uses custom eyedropper settings when you prepare files for offset printing or do you just stick with Photoshop's default values and keep your fingers crossed?

Here are the custom eyedropper settings that were recommended to me for offset printing:

Shadows:
C=75
M=68
Y=67
K=93

Midtones:
C=55
M=44
y= 43
K=0

Highlights:
C=5
M=2
Y=2
K=0

[stefohl]

This is like asking, will it rain tomorrow? Somewhere it probably will. Somewhere your CMYK values will be a perfect choice, but to ask if it will fit your new printer is impossible to answer. The last book I made was printed with a profile which says that highlights should be 4, 3, 3, 0 and midtones should be 49, 40, 39, 27 and a dark shadow area should be 80, 71, 64, 83.

[lowep]

"This is like asking, will it rain tomorrow?"

+1. This may be the closest I ever get to farming  

The question is if you do not know where the rain will fall tomorrow [or which printing press the files will be ultimately printed on] how do you configure the eyedropper before you start working on your files? In my case this task takes many hours and there is not enough time to readjust everything if the decision about which printer will be doing the job is not taken until the last moment for reasons beyond my control.

Interesting to note there is considerable difference in the figures you share with the ones I was given, which is a little scarey -particularly if it is not an old wives tale that too much adjustment of any particular file can degrade the IQ.  

[pfigen]

Unfortunately, you can't rely on just highlight, shadow and midtone readings for good offset reproduction. You have to know the paper, the press, the proper black generation, what the maximum allowable ink on that press happens to be, whether the inks are UV cured or not. You also have to know the best way to get to CMYK - which is usually with the proper profile to convert to CMYK in the first place.

The advice you got from your printer years ago sounds like the type of advice you used to see from printers that really don't understand the process very well - printers who used the old default CMYK setup in Photoshop to convert to CMYK and then applying those values regardless of whether or not they are right for the job.

Newer presses printing on good paper can actually show less than a one percent dot.

The topic of proper CMYK file preparation is and endless one and really requires years of experience of seeing the ink hit the paper to get really good at it.

[lowep]

some mornings I hesitate to get out of bed just in case something happens during the day that I cannot fully control but usually I manage to bumble through the day somehow due to a mixture of listening to my elders, attempting to apply the little knowledge I have, learning from my mistakes, eating my vegetables and dumb luck.  

the process I follow is to do the major work on the files as well as I can in rgb using whatever I already know from experience, convert to cmyk, tweak the file according to whatever specific input or general advice the printer I end up working with is ready or able to provide, then tweak again after looking at whatever proofs I can get.

is there a better way to do this?

given that this process often requires decisions to be made ahead of time without full control over the outcome it may be best to start off using the default settings instead of custom ones and go to church more often.

 

[pfigen]

Generally, starting out in RGB and converting to CMYK at the end of the process is a good thing. How are you converting to CMYK? Is it just a mode change, or are you converting to a specific profile based on the printer's recommendations or perhaps, some other criteria?

How far off are the first round of proofs? If you're using a CMYK profile that is perfect for the proofing system and subsequent press, then your first round of proofs should be very very close to being perfect. If you're making any significant change on the second proof, then it's very probable that your conversion is not right for that proofing system. This, of course, does not take into account subjective decisions that you make once you see the proof. That is, the proof could be a very close match to your monitor buy after seeing the proof you want to change something even though that's how it appeared on screen.

All too often, printers will give you the wrong information about their process or claim they comply to SWOP or GraCol standards when they really don't.

In the event of having little or no solid information regarding printing conditions, about all you can do is to separate using Photoshop defaults. Because that's what so many people use who don't know what they're doing, there are a huge number of images that printers get that have been converted that way, which forces them to be able to print them at least somewhat in the ballpark.

My goal is always to take that a step further whenever possible, including pre-emptive strikes to keep skies from going to purples or grass too yellow that are likely to look better in print than if I didn't do them. I also typically choose black generation schemes that help the image to print better on press, but will not show an improvement at the proofing stage, as the proof can never mimic certain aspects of the dynamics of the press.

[digitaldog]

I have used these settings ever since. Now I am working on a different project on the other side of the world that has started me thinking maybe it is a dumb idea to keep using these settings, so would like to know if anybody else uses custom eyedropper settings when you prepare files for offset printing or do you just stick with Photoshop's default values and keep your fingers crossed?

The correct values for that output, which is totally unknown, are the right values <g>. Or to put it another way, it probably will rain somewhere tomorrow. We have no idea today where with absolute certainly.

Anyone providing you values without having a profile for the output, or having sent known values to the output and measured or at least viewed the results is wasting everyone’s time. CMYK is highly device dependent! A mix of CMYK values optimal for one condition are totally inappropriate for a different condition. 

You want to know the correct values, get an ICC profile for the process (and ensure it fingerprints that process).

[lowep]

 Thanks very much Pfigin for this clear and detailed advice.

I am happy you say “generally, starting out in RGB and converting to RGB at the end of the process is  a good thing” as this means the [too] many hours of work I spend on each file at this stage of the process need not be duplicated for other outputs like large format prints. Instead I only have to BBQ once then concern myself with the right sauce to finish off each dish.

I have tried two routes for CMYK conversion. One is to do it myself via a mode change in Photoshop before I get to the printer then try to meet and discuss the job with printer and sheperd the colors towards my idea of how the files should "look" depending on the outcome of that discussion that may or may not include ICC profile information for their specific printer. Alternatively I handover the files to the printer to do the CMYK conversion (probably also by a straight mode change ☺) then tweak the files either together with the printing staff or working alone on her/his computer overnight to get them back in my ballpark before proofs and final adjustments are made. Neither is very satisfactory but both approaches work.

A big problem as you have pointed out is that printers often do not have as much expertise as they claim and/or they have too much work to do to spend much time dicking around on a specific job – particularly outside mainstream markets. Hence the need for educated guessing and to have everything as ready as possible when it is handed over to the printer.
 
“In the event of having little or no solid information regarding printing conditions, about all you can do is to separate using Photoshop defaults. Because that's what so many people use who don't know what they're doing, there are a huge number of images that printers get that have been converted that way, which forces them to be able to print them at least somewhat in the ballpark.”

Now I know and do not need to lose sleep about that and can concentrate on other concerns. I can see that I also need to google “black generation schemes.” Does this have anything to do with money laundering?

How far off are the first round of proofs?

If all goes well a couple of months by which time I need to have about 100 images ready for a quick dash through the printing process. But so far the printer who will do the job has not been selected by the client who is not a professional publisher and has a lot of other more important distractions etc etc ie a normal situation. In this case all I can do is to be as well prepared as possible and hope the printer who wins the contract is a good one.

My guess is that I am probably not the only ignoramus who is fighting with Photoshop to squeeze out the best results possible on a tight budget with a distracted client and overstretched printing staff, so hopefully this advice you have given will be useful to others who find themselves in the same situation as I do.

[lowep]

"CMYK is highly device dependent! A mix of CMYK values optimal for one condition are totally inappropriate for a different condition."

Got it! 

[pfigen]

The biggest problem with using eyedroppers to set endpoints is that while CMYK "is" device dependent, the endpoints, in particular, the highlight with detail numbers, are remarkably similar across presses and papers, the shadow points less so but much harder to see when they are off a bit.

It's the overall color rendition and contrast that is most important, and that's what the right profile does for you. Even if you've got the right profile, you still need to check the numbers and set them accordingly. You're probably better off setting those using Curves rather than the eyedroppers.

When you get your printer picked out, talk to their prepress department if that's possible, and ask them for their profile if they have one, or what standard they aim for in their proof and press. Unfortunately, as has been previously mentioned, prepress departments are notoriously ill and or mis-informed and all too often secretive beyond reason.

While prepping files to print well is not hard, it's not something you can learn simply from reading. You need to see the ink hit the paper time and again to see where the theory works and where it falls flat. Profiles get you close, but they're only a start, and sometimes you just have to go with your gut.

[Luca Ragogna]

I do all my colour correction in RGB. CMYK conversions are mainly done in-RIP or during .PDF generation (we send .PDF to the RIP sometimes). Our RIP mimics the .PDF export settings and both are set up with an .ICC profile for our press. It's a system that works really well for us and saves us a ton of time (imagine opening every image in a textbook to do a CMYK conversion versus doing it all in-RIP)

My advice is to find a shop that has a good handle on colour management and let them handle the conversion. If you don't know the press or the preferences of the pressmen how can you make an accurate conversion?

[pfigen]

Yes, you can use a RIP to do all of your conversions, but you lose all of your ability to fine tune and fully optimize, not to mention sharpen in CMYK. The automated route is great for images or catalogues that don't need that level of care, but if you look at Peter's images, you'll see that his deserve much more than that.

Even though I use great custom profiles that I create myself, I can almost always improve the image after it's been converted to CMYK.

There are many approaches that work and it really depends on what your needs and expectations are for each project.

[digitaldog]

The biggest problem with using eyedroppers to set endpoints is that while CMYK "is" device dependent, the endpoints, in particular, the highlight with detail numbers, are remarkably similar across presses and papers, the shadow points less so but much harder to see when they are off a bit.

Close only counts in hand grenades <g>

Original RGB values (255 and 0) and the value from 4 different press conditions (notice the scum dot in one?). 3x3 average on solid target patches from ColorMatch RGB (a good fit for conversions to CMYK due to its gamma encoding).



Here’s the white and black Macbeth color checker squares:

[Luca Ragogna]

Ok, I'll agree with that.

In that case, I'll amend my advice. Find a shop that has a good knowledge of colour management and either get a profile for their press to do your own CMYK conversions, soft proofing and tweeking/sharpening or see if they'll let you sit over their shoulders while they do that stuff.

I was giving the reality of our prepress environment and would argue that in-RIP conversions with a good .ICC profile specific to the printing conditions would provide better results than a generic PS conversion and generic eye-dropper values not knowing anything about the press the job will be running on.

[lowep]

re: "value from 4 different press conditions"

proof of the pudding is in the eating - even I can see the unpredictability of the variations in these 4 sets of figures. 

looks like working together with knowledgeable & friendly people as Luca suggests is still the best solution