CMYK vs RGB

RGB versus CMYK is something that we get a lot of emails about so here’s a quick walkthrough to help you understand what’s best for your project and when.

RGB stands for Red, Green and Blue and is the way that your computer monitor or tablet displays colours on screen
CMYK stands for Cyan, Magenta, Yellow and blacK and is the way that colours are displayed when printed on paper
RGB is an additive colour model – colours come from a source that emits light (your screen) and light colours can be mixed together until white light is created
CMYK is a subtractive colour model – colours come from inks (or paints, or dyes) that are overlaid until they shut out different wavelengths of light and produce different colours
RGB is best when you’re working on a piece of digital art on your screen
CMYK is best when you want to print a piece of digital art on paper
The problem with working in RGB and then converting to CMYK is the difference in colour and tone that this can create – especially with green tones. Take a look at the image above and you’ll see that the RGB seahorse looks bright and shiny, while his CMYK friend is a bit dull and muddy. So how can we make an RGB image look good as CMYK? Two words: Adjustment layers! Once you’ve converted your image from RGB to CMYK, create a new Adjustment layer for Hue/Saturation and bump those tones back up, typically by pushing the Hue towards the greener part of the spectrum and increasing the Saturation. Experiment with your own images to find the result that works for you – Adjustment layers are non-destructive so if you don’t like the effect you can just delete it without affecting your image. Remember to save your original RGB before you experiment with CMYK too!

When you working on a printing job always remember to use CMYK colors ONLY.
There is NO WAY to print RGB colors without them looking different on print!

Good luck!

Going to print basics

Before we begin, printing has an unusual terminology that is attached to it. Below is a small list of terms you will run into when talking with your printer. Although not totally complete, the terms listed below will get you well on your way to understanding your printer and the language that they use.

Bleed – A bleed occurs when your color or image extends off of the printed piece, typically bleeds are created when the printed piece is trimmed.
CMYK – Cyan, Magenta, Yellow and Black are the colors used in 4 color process printing. On the printing press they are run in a specific order. Black, Cyan, Magenta and Yellow, the most transparent of the four and containing the most varnish in the formula is yellow and is laid down last. The most opaque color, black, is laid down first. Following this sequence allows for brighter imaging and better control of color.
Color Densitometer – A piece of equipment used by press personnel to determine the density of the ink color being laid down on the printed sheet. It has a numerical digital read out and the higher the readout on the densitometer, the greater the amount of ink that is being laid down on the sheet. While there is a wide variance in the numbers used, the average range is:

Cyan and Magenta reading around 135 to 145……… Yellow around 105 and Black anywhere from 175 to 210………….. This is only a generalization and the densities that are run should be left up to the press personnel.
Color Density – The amount of ink printed on the sheet.

CTP – Computer to Plate. A process that bypasses the use of film when creating the image that is receptive to ink on the printing plate.

Emboss – Impressing an image by forming the paper using a die that is cast in the shape of the image you want to create. When pressure is applied, the paper takes the form of the die.

Film – A sheet of material that is processed with the image on it. This material will be placed over the printing plate and with the use of light, burning the image into the printing plate, determining the ink receptive areas of the plate.

Halftone – The screening of a continuous tone image, converting the image into different sized, yet, equally spaced dots.

Impression – Each time the sheet passes through the press and is printed, it is an impression. The terminology is useful in production scheduling and estimating because it determines the quantity of the run and the efficiency and speed of the press and the operator.

Large Format – A term that describes the printing of large sized substrates. Printed pieces would include large posters, POP(Point of Purchase) signage and banners. The printers that are used are typically inkjet or IRIS printers. This is an evolutionary segment of the print world and the technology, chemistries and equipment are constantly changing.

Moiré – A pattern that is created from incorrect screen angles seen in the CMYK printing process

Offset – The printing process that uses a blanket to receive the ink from the plate and then impresses it onto a sheet of paper as the paper passes between the blanket and a hard steel cylinder called an Impression Cylinder.

Perfect Bind – A type of binding that combines the cover and the inside pages on the spine with glue. Magazine examples that are perfect bound are Photoshop User, Mac Design, Graphic Arts Monthly and Communication Arts.
Registration – The alignment of dots in relation to each other. When the cyan, magenta, yellow and black plates are aligned and brought into focus, the printed piece is considered to be in register.

RIP – Raster Image Processing………… a computer language that arranges the dots, solids, lines and type in a particular pattern concerning densities and angles. The function of the RIP is to send instructions to the film processor, telling the processor where to place each item and what angle each item is to be placed in relation to the other items on the film or combination of films used in creating the image.

Saddle Stitch – The binding of a book using wire staples on the binding edge to hold the book together. Some magazine and flyer examples are PC Connection, Micro Warehouse and the Java Developers Journal.
Score – A crease that is impressed into the paper. Scoring will allow for exact folding on heavier stocks and helps to eliminate the cracking of some substrates.
Separations – In four color process printing you have a continuous tone image that is separated into four different colors, CMYK, enabling it to be printed. The process begins with scanning an image. The scanned image is then separated into the four process colors. These are processed on film flats with each flat representing a separation.
Sheet Fed Press – A printing press that prints individual sheets of paper as opposed to rolls.

Signature – A parent sheet that consists of 4, 8 or 16 pages depending on the size of the montage that is built for the press it is scheduled to run on. The signature is then folded, collated(depending on how many pages are needed to complete the project), glued or stitched and then trimmed.

Spot Color-PMS-Pantone – Colors that are mixed in batches and are identified by a number. The number can be followed by a C (Coated) or U ( Uncoated). The formula is designed for the type of substrate it is to be printed on taking into consideration the porosity of the paper.
Trapping – The overlay or over printing of dots in relation to each other to compensate for miss-registration on the printing press creating an illusion of tight register.
Web Press – A printing press that prints rolls of paper