MonthJuly 2017

Managing Image Color and Quality – Part two of two

The second part of this post on managing image color and quality focuses on the variables that are out of your control… and lucky you – under your printer’s control. I’ve tried to not get overly detailed about this technical stuff. There’s a line that we designers do not need to cross in our understanding of printing technology and I’ve tried to stay on the designer side. Having that said, I have never met a designer who was not interested in how graphic things work. And because of this experience and understanding of how designer’s minds work, I’ve included here the stuff that directly impacts you.

Things Your Printer Controls

Screening
This section assumes that your print provider is capable of AM and FM screening. (These two screening methods are defined in the following paragraph.) If your printer is not capable of both screening techniques or hybrid screening (which combines both on the same plate), and you are doing critical catalog, book, or annual report work, you need to find a printer that can handle those projects. This section also assumes that your printer’s prepress expertise allows her to adjust her plate curves for the substrate. (These are adjustments made in prepress to manipulate the halftone dot to create the optimum dot size for the job conditions.) These are not parameters you can send to your printer. Each pressroom adjusts its own settings, based on the equipment it has, to produce its best work. Between screening and other adjustments made in their prepress department, your printer makes sure that images print at the best possible representation of the file.

Conventional (AM) vs. Stochastic (FM) Screening Methods
In order to print an image via a printing press, of nearly any type, the image must be converted to a halftone; that is, the image must be made up of dots. There are two ways to convert the image to dots, and they are both referred to as “screening.” The older and more common method is conventional or AM screening. Conventional screening puts the dots in fixed rows, varies the size (Amplitude Modulation) of each dot, and places each ink color at a different angle. The second method is FM screening, and it scatters the dots at variable distances (Frequency Modulation). In FM screening (also called stochastic), the dots are a fixed size, but they are microdots (microdots are called spots). The two forms of FM screening include first order and second order. Stochastic is an example of first order FM screening, wherein the dot size is fixed and the frequency is variable. Second order FM screening allows for altering the dot size in areas where there is high density. Staccato (a Kodak product) is an example of second order FM screening.

AM screening varies the size of the dot while
keeping the distance fixed.

FM screening varies the distance between
spots and the size is fixed. 

Second-order FM screening varies the size and
distance between spots.

Your print provider can also vary the type of dot used; in addition to round dots, there are elliptical, diamond, linear, and square dots. A dot that is not round may be used to fine tune an image such as a photograph due to the effect the dot has on very small gradations. Your printer will choose the type of rosette and dot shape that is best for your job. It will depend on the paper, line frequency, type of press, and the characteristics of the images in the printed piece.

Whether your project is being screened with AM or FM, your printer will manage dot gain by adjusting the image in prepress for the type of paper you are printing on. Printers store characteristics for paper types and specific brands and finishes so that they do not have to re-key the information for each print job. When printing images with geometric patterns, such as fabrics with linear textures or repeating geometric backgrounds, all fm screening is superior. It’s random dot placement eliminates the interference that conventional screening produces when the angle of a line of dots intersects with the angle of a design element. This phenomenon is called a moiré, and it produces an undesirable ripple-like effect in the image.

Screen angles placed to produce a moiré

Conventional screen angles for CMYK and the resulting “rosette”.

Although nearly every digital prepress system is capable of producing stochastic screening, its adoption has lagged behind conventional screening because of the spot/microdot it generates. The spot is more difficult to proof and image on a printing plate. Only newer, higher-end platesetters can image a microdot. Some high-end prepress systems are able to generate hybrid screening, which is the use of FM and AM screening on the same plate. Therefore, FM screening can be used for a difficult fabric pattern and AM for the text so that each image type is reproduced with the more advantageous type of screening. The AM and FM screening methods each have their own advantages and disadvantages.

Advantages of AM Screening
• Easier to make adjustments on press
• Clean, perfect screen tints

Disadvantages of AM Screening
• Patterns can cause moiré in screening.
• The background/paper color shows through more, which affects the overall color more than with FM screening.

Advantages of FM Screening
• FM is better for touch plates printing together with AM CMYK (as in Hi-Fidelity printing)
• FM is more forgiving of mis-registration, which is an advantage when printing across the grain and dealing with paper stretch.
• Larger CMYK gamut may be possible depending on paper choice
• Better reproduction of geometric patterns
• Less dot gain with the microdot of stochastic/FM screening.

Disadvantages of FM Screening
• First order FM screening does not store the ripped file for repeatability.
• Tints are not as smooth as in AM.
• Making moves on press may require new plates (due to less range of movement on press,) which is expensive and time-consuming.
• Small plate imperfections cannot be manually touched up and require a new plate be made.
• Unexpected color shifts can occur in tints of spot colors.

Ink substitution and touch plates
There are ways to work around CMYK being a smaller gamut than RGB. One method is with ink substitution. This keeps a job on a 4-color press, and it works if one color or range of colors is not in the desired gamut. For example, if purple is a dominant color and there are no skin tones or other critical color areas to worry about, rhodamine red or another spot red can be substituted for magenta. Or a fluorescent yellow substituting for process yellow is another example of how you might obtain the results you want. This is not a very scientific process. You need to rely on experienced print professionals whose color sensitivity borders on the paranormal. Many of these people have been in pressrooms and prepress departments for decades and have honed their color sensing skills into a supernatural ability.

Another method of increasing CMYK’s gamut for better color reproduction is Hexachrome printing. Hex is a different prepress workflow that separates and screens the file for the six Hex print colors: Hexachrome Yellow, Hexachrome Orange, Hexachrome Magenta, Hexachrome Cyan, Hexachrome Green, and Hexachrome Black. These are not the regular process colors plus orange and green. These colors are more intense
and designed specifically for high-fidelity color reproduction. Creating a touch plate in your Photoshop file for Hexachrome
Green will not work. The true Hexachrome colors are produced in a Raster Image Processor (RIP) with specialized software for
ripping the six plates necessary at the proper screen angles.

Touch plates are additional plates that are added on additional ink units, requiring a 5 or more color press. Color experts analyze images that are out of gamut and figure out how and where to add a touch plate and also the ink color(s) that will be used. Common touch plate colors are true red, bright green, orange and flourescent colors, colors that are impossible to achieve with CMYK.

Under Color Removal (UCR)
UCR is a method of reducing ink density in areas that have dense, dark colors. Too much ink on the printing sheet can result in a mottling of shadow areas and a loss of detail. UCR is normally done in prepress software. UCR is used to remove density in areas where too much ink would be applied. For example, a “non-standard” rich black of 100% black and 50% each of magenta, yellow, and cyan will result in a screen build of 250%. Adding the percentage of each ink together gives you the total amount of ink you are laying down. A DMAXof 250% is a bit much; 240% is the maximum DMAX (maximum density) recommended for most uncoated paper. (Each printing company sets its own DMAX level depending on its equipment.) In this case, your printer’s prepress department may adjust those percentages by deploying UCR whether those percentages are in an image or in a specified CMYK ink recipe in a program like InDesign.

Gray Component Replacement (GCR)
When there are several inks mixing in the shadow area of an image, sometimes they just muddy up to gray. Substituting a little bit of black ink will create a crisper, deeper, shadow with more detail. In this case, the prepress gurus will identify areas where GCR will help. I do not believe that is standard operating procedure in every print shop, though. For example, don’t expect this service on your brochure for the local Certified Public Accountant with the group picture taken at last year’s holiday party. However, expect it on a coffee table book or a high-end catalog.

Repeatability
Now that run lengths are getting shorter and far more digital repurposing of imagery and branding elements exists, matching printed material from run to run and project to project is critical. You want to be able to print 50,000 brochures for your client and repeat that print run six months later with hardly any visible shift in the color. Second-order FM screening can store job information down to the dot, as can AM screening.

I would love to know how you felt about this topic. Was this too technical? Not technical enough? Do you have any questions about this or would you like me to further explain something?  Do you have a request for a topic for me to cover or elaborate on? I’d love to know, comment or email me at marina @ designingforprint.com

(all illustrations © 2017 “Designing for Print”)SaveSave

SaveSave

SaveSave

SaveSave

SaveSave

SaveSave

SaveSave

SaveSave

Share

Managing Image Color and Quality – Part one of two

One of the things designers worry about the most is being disappointed with how a print project turns out. Seeing their project print in the “wrong” colors or not as sharp as it looked on the screen are common issues but there are also others. Many of these issues are surprisingly easy to manage. The good news is that only part of this management is on the designer’s end, some of it is on the printer’s end and out of the designer’s hands. Because printing problems can be expensive, or very expensive to fix (as in redo the entire job ?), there is usually some finger pointing going on when a job goes south. If a designer messes up on their part – they are responsible for paying to reprint the job and I know firsthand, it’s a bitter pill to swallow.

I’ve put together a list of the things you, the designer, controls and those which the printer controls. In this post, I will address the designer’s responsibility. In part two I will address the printer’s responsibility!

Things the designer Controls

Specify the Right Paper
The most important decision you can make is choosing the right paper for your project. No matter what you do on the prepress side to enhance image quality if you are printing a finely detailed image on the wrong paper, the details are going to be lost. Paper choice significantly affects reproduction quality.

Color Manage Your Devices/Workspace
Most designers who are disappointed by color are using a proofing workflow that is not calibrated, ie: their monitor and desktop printer. There’s a reason why the proofing printers that printer’s buy cost five figures (and the color management RIP can cost six figures!), they are way better than your desktop printer. It could be that your printer happened to predict how a job printed in January when you used photo paper and an OEM ink set, trust me, you got lucky. But in June when you are using copy paper with non-OEM ink the whole picture could change (picture, pun, LOL).  Either manage your color at your studio/office or rely on supplied proofs at every step of the process. It’s that simple.

Don’t put off color management thinking you can wait until you see the first set of final proofs from your printer. This can lead to a major color rework during the final hour, delaying the job delivery, and that is not good for you or your client.

  1. There are some really quick and easy ways to calibrate your monitor so you can check color: Google “how to calibrate my monitor,” follow the instructions, and take your monitor’s age into account; as monitors age, they become less accurate.
  2. Get your print provider’s ICC profile, (a standardized data set that describes the color space of an input or output device,)
    and apply it to your monitor and desktop printer. If your desktop printer cannot load an ICC profile, ask your print shop for work-around help or hire an outside firm. Sometimes spending $100 is the best thing you can possibly do.
  3. Take a rhem lighting indicator (RHEM indicator) with you when you show proofs to a client. There’s one in the back
    of the Pantone Color Bridge set. If your proofs look odd or different in your client’s office, it might be the light.
  4. Where are you looking at your proofs? In the parking lot? In the kitchen? In a room with purple walls? Try to check
    proofs in a color-neutral environment; a color booth is best. Specify color while you are in the booth too.
  5. Install 5000k fluorescent lights and daylight incandescents in your workspace.
  6. Do not convert your files to CMYK unless your printer specifically asks you to. Chances are the printer is going to
    want to handle that conversion, especially if your files are printing on a digital press.
  7. If you are printing on colored paper, proof on colored paper. If you can’t proof on colored paper, change the “paper” color in InDesign to approximate your paper color. It will not reflect how transparent inks appear on colored paper, but it’s a step in the right direction.

Rhem indicators show you if your lighting is correct. You can purchase them on a card or a pack of stickers to place on proofs and there is currently one in the back of the Pantone Bridge set. In correct lighting, both halves of the rectangle are identical. Here it is shown in incorrect lighting.

Specify Color Precisely
Using your monitor to select color is a sketchy proposition. You can specify color precisely if you use printed color guides to select your colors. I highly recommend the Pantone Bridge Selector, which gives you Spot, RGB, and CMYK equivalents for each color. When working on identity systems, it is an invaluable tool. You can immediately see how out-of-gamut some Pantone greens and reds are when rendered in CMYK. And for the RGB equivalent enter the values shown in Adobe Photoshop and see how that compares (knowing the browser, monitor and hardware will serve it up differently in each case).

 

Use the Correct Resolution
Resolution is worth mentioning because it causes so many problems in the prepress department. Any image you want to print must be a minimum of 300 dpi at 100% of its actual size. If you pull an image from a website, and it is 4 in. x 4 in. and 72 dpi (the typical web resolution), when you place it in your page layout, it must be sized to 24% of its original size or 0.96 in. x .96 in. in order to be at the correct resolution for printing. (Web designers take note!)

There is absolutely no way to take a low-resolution image and make it look like a high-resolution image. Interpolating a file to a higher resolution makes the image look like an image that was interpolated up to a higher resolution to improve its appearance. One low-resolution image can make collateral look unprofessional. Make sure all the images you provide are the correct resolution for their output size.

The same photo shown in three different light sources, from left: store light, daylight, and home light. Consider the challenges inherent in designing packaging where the product will be viewed in several lighting environments. (Photo courtesy gti Graphictechnology Inc.)

Use Correct File Formats
Each software program creates a native file format that it “gets along with” best. For Adobe Photoshop, that would be bit-mapped files like tiff, jpg, and png. For Adobe Illustrator, it is eps files. Adobe InDesign is a composition program that can accept nearly any file type for inclusion into a document that will be printed or published to the web.

Some file formats work well for print, and some work best for the web. Here are some common file types and their best uses:

Print
• Tiff for high-resolution photographs and scanned graphics
• eps for infinite scalability
• Pdf for high-resolution printing when properly saved with embedded fonts and bleeds, etc.

Web
• Jpg for many compression options and fast loading
• Png for more image depth. The trade-off is its large file size, no CMYK, RGB only.
• Gif limited color (256 only) but very fast loading

Don’t use image compression unless you absolutely have to. Every time an image is compressed (when it is saved) and uncompressed (when it is opened), it rewrites the data in the file and leaves little artifacts/noise in the image. Compression is left over from the days when a 44mb (yes, that’s MB, not GB or TB) Syquest drive cost $200. Nowadays, storage is cheap. Compression works well for the web, but it isn’t necessary for anything else. For example, Tiff files and images are not compressed. Jpeg files and images are.

I hope this helps you to feel super confident the next time you send a job to your printer! Stay tuned for part two – What Your Printer Controls!

Do you have a question about this topic or would you like me to further explain something?  Do you have a request for a topic for me to cover or elaborate on? I’d love to know, comment or email me at marina @ designingforprint.com

Get notified when the Kickstarter campaign launches July 25, 2017!

Ready to get the book and rock the early-bird specials? Sign up and we'll let you know the instant the book is kickstarted on July 25th, 2017

We respect your privacy.

SaveSave

SaveSave

SaveSave

SaveSave

SaveSave

SaveSave

SaveSave

Share