I have been asked the question many times before: why does my photography/image look so flat when i convert RGB to CMYK color?
Well, the answer is science.
RGB is additive color theory. Red, green and blue light when combined produce white light. When red, green and blue light are turned off, there is no color therefore resulting in black. This is how your monitor and television function.
CMYK is subtractive color theory. Cyan, magenta and yellow ink act as filters to absorb and reflect light that is reflected off paper. When light reflects off paper where no ink is applied, this is white. When light reflects where all three colors are present, no light reflects back resulting in black. Cyan ink absorbs red light; magenta absorbs green light; and yellow absorbs blue light. This is the basic theory of subtractive color.
It’s important to note that a fourth ink (black) is used to create more contrast and deeper blacks/shadows in images. The amount of black ink is dependent on the conversion process that is used, for example medium GCR (Gray Component Replacement).
RGB color uses projected light which is much more brighter than light reflecting off a substrate with CMYK color. The additive light (RGB) creates a color gamut that is much larger than subtractive (CMYK) color gamut.
Does this explain RGB to CMYK conversion for you? Please place your comments below…
[learn_more caption=”Transcript of Video” state=”open”]
Hi. This is Rick Rys from HiDefColor.com. Today we are going to discuss the conversion from the RGB color space into the CMYK color space.
[0:14] RGB is an additive color space meaning that red, green, and blue light together will create white. When red, green, and blue light are off, they will be black when it is projected onto screen, or onto a monitor.
[0:31] CMYK is the subtractive color theory meaning that the cyan, magenta, and yellow inks act as filters. As light bounces off of the paper, it reflects up through the cyan, magenta, and yellow inks, which in turn will either absorb or reflect different color wavelengths.
[0:52] The opposite of red is cyan, the opposite of green is magenta, and the opposite of blue is yellow. The subtractive colors are the gray components of the additive colors meaning that when they’re put together, they create gray, or black, or white.
[1:07] The LAB color model–let me turn this off here–is a 3-axis color system, and the LAB colors are absolute meaning that the color is identical. It’s across what’s called a device-independent, meaning that the LAB color space is the only way for you to communicate different colors across different devices.
[1:35] Now, it is a 3-axis system. The first axis, the L-channel, or lightness goes up and down the 3-D color model, and it consists of white to black, and all of your gray colors will be exactly right down the center.
[1:49] All your neutral colors will be relatively in the center of this axis. The A-axis goes from a cyan/blue color across to a magenta/red color, and the B-axis goes from blue to yellow.
[2:07] Within this area, we’re going to plot our visual or reproducible colors based on the gamut or the profile of the device we have. I’m going to turn on the sRGB color profile. Most monitors display in sRGB; sRGB is preferred for any type of Internet or Web application.
[2:27] And look at this thing spinning here. And you can see the volume of the colors that you can reproduce from this additive color model. Obviously, since it’s dealing with projecting light, they’re very bright colors and they’re very saturated.
[2:44] Now when we bring in and display the CMYK GRACoL color profile, you’ll notice when I turn it on the sRGB encompasses the whole CMYK color gamut beside this area of cyan and greens through here.
[3:03] If you look down on the color model, you’ll notice that the circumference of the model is projected along the bottom here. You can see the outside perimeter of the sRGB color profile.
[3:17] The brighter colors are just not capable of being reproduced with the CMYK color gamut. You can see what happens when you get these real dark blues. There’s no blue for you to hit in a CMYK color model.
[3:30] What I’m going to do is I’m going to take our sRGB color profile, and I changed the opacity, so you can see the difference that we’re dealing with here. As you can see the volume of color on the RGB color profile is nowhere near what can be reproduced in a CMYK color profile.
[3:53] So what we have to do is we have to do our best job of remapping these colors, or what is known as tonal compression, to bring this sRGB color model into the CMYK color space.
[4:06] This is why–I’ll stop right here–when you look at a blue sky, you may always be disappointed with the results you get because when the photograph is in RGB, you’ve got all these deep bright blues and more of the colors you see in the horizon.
[4:30] When they’re converted to CMYK – you’ll notice when I change opacity, all those bright blues have to be condensed into this little area here of the blue hue that’s reproducible in CMYK.
[4:42] There’s a sacrifice there, and that’s where you get into using either relative rendering intent, or the perceptual color intent. That will help you resolve some of issues you have with converting your dark blues into the CMYK color space.
[4:58] Let’s turn this opacity back up, and you’ll get an idea, again, of what we’re dealing with here. We need to take all of this color and condense it into this little area right here.
[5:12] And this is the GRACoL color profile. The GRACoL color profile has more colors than the SWOP profile, so we’re going to get a better representation of some of those more juicier RGB colors when they’re converted to CMYK.
[5:27] So let’s bring this up again and show you the difference of converting all of this into this little area here. This is why color management is so important and knowing what profiles you’re dealing with.
[5:41] Your safest bet is using the sRGB color space and converting into the coded GRACoL profile. Keep in mind that dealing with your print provider, they will produce, or they will provide the correct color profile based on their printing condition.
[5:58] A profile is a recipe, or the characteristics of a particular printing condition. Based on the press, the inks, and the paper that they use that will produce a profile.
[6:10] Well thanks again for tuning in. I hope this clears some things up. If you have any questions, please feel free to leave a comment on the blog. And we will see you next time.
The fact that an image is in CMYK does not mean the color will be correct for a printing press.
CMYK is a ‘device dependent’ color space, meaning that the CMYK data will print differently from one CMYK device to another. Every CMYK device has it’s own color profile. Knowing which CMYK color profile to convert to from RGB is very important to the success of color quality.
A CMYK printer profile is the characteristic or behavior of a printing condition or process.
Today we will demonstrate the differences between the GRACoL (general requirements for applications in commercial offset lithography) and SWOP (specification for web offset printing) CMYK color gamuts, or CMYK printer profiles. The GRACoL printing specification has a larger CMYK color gamut than the SWOP printing specification.
This VIDEO demonstration shows the GRACoL and SWOP CMYK color gamuts in a three-dimensional wireframe. The color wireframes are plotted in the LAB color space. Create an even larger CMYK color gamut by printing with FM/stochastic screening!
The LAB color space is ‘device indepedent’, meaning that LAB color data is absolute. LAB is a universal color space and is the best way to communicate the appearance of color.
Which color profile looks better to you? Please leave your comments below…
[learn_more caption=”Transcript of Video” state=”open”] Hi. This is Rick Rys from HiDefColor.com.
00:04 Today we’re going to talk about the CMYK color space and the two most common CMYK color printer profiles. It’s important to note that a color printer profile is the behavior or the characteristics of a printing condition. It’s important to note that when dealing with your commercial printer to ask them which color printer profile or which color specification they print to and use that profile. Here at HiDefColor.com, we support the GRACoL color specification.
00:40 The important thing to note is we’re going to be – you’re actually looking at CMYK color model is plotted in the LAB color space. The LAB color space is a three axis determination of what a color is going to be, so it’s absolute.
01:00 The first axis is the L channel or the lightness which goes from white to black. Now that is going from top to bottom and it’s also important to note that along this axis is where your grays are going to be; your gray balance here, fifty percent gray, seventy five, twenty five and so-on are going to be down the center of that axis.
01:22 The second axis, the A axis goes from a cyan/green over to magenta/red color and the B axis goes from blue to yellow. So within this area here is where we’re going to plot all of our colors.
01:38 We’re going to go from our lightest colors up here, to our darker colors down here. So in the center is where all your neutral colors are going to be. We’ll start with our first color printer profile, that will be the SWOP color printer profile.
01:51 When we turn that on, you can see we’ve generated a three-dimensional wire frame of that color model. You go from our paper-white, down to our shadows, and then across from our primary colors our reds, our blues, greens, to our subtractive primaries our yellow, cyan and magenta. And from the top down – looking straight down – you can see that we plotted the outside circumference of our color space, so you can see our color a little better, along with our three-dimensional wireframe.
02:27 The second option is the GRACoL color printer profile. Now, i’m going to bring that in. You will notice that when i click this on, that the GRACoL color printer profile completely engulfs the SWOP color printer profile.
02:41 Looking down here at the bottom – follow the cursor – you’ll notice from the top down the shadow, or the circumference, is much larger than the SWOP color gamut, meaning that you have more color that’s accessible when you convert from RGB to CMYK. You’re going to get a larger color gamut and this is displaying graphically what the larger color gamut is with the GRACoL color profile.
03:04 It’s important to note that you can’t just choose a profile. You have to understand what profile or what specifications your printer is running to. So if you convert to a SWOP profile and you’re printing GRACoL, there’s going to different results.
03:19 So again, what I want to do here is i’m going to change the opacity of the GRACoL so you can see better how much more color is available resulting in a larger color gamut.
03:31 We’ll get this spinning here so you can look around the different colors and look at the top down and also look at the wireframe to see how much more color. There’s more volume of color for you to work with to get a better reproduction in CMYK when you convert from RGB.[/learn_more]
HiDefColor.com is proud to be part of G7 Master Printer network!
The G7 Master Printer Certification is a qualification program that identifies printing companies that have been trained to print to G7 Neutral Print Density Curves ensuring gray balance across the tonal range. The advantage to facilitating a G7 workflow guarantees print buyer expectations of the closest color match from proof to press and across other methods of printing from offset to digital to large format products. Although all methods of printing (offset, digital, large format) have their own color gamuts, the effect of printing to neutral density print curves results in a visual color match of each different product to the human eye.
The result is your branded identity will have a visual color match from different locations and different printing devices.
The G7 Master Printer Certification also means we use modern colorimetry technology and employ G7 process controls to guarantee color quality.
HiDefColor.com is one of the few online printers who are G7 Master Printers. The G7 Master Printer status is audited and renewed on a yearly basis.
How many times have you sat in those marketing meetings trying to think of a clever, unique way of creating marketing pieces? A new innovative and inexpensive printing method is digital dimensional printing. Digital dimensional printing is a raised, high gloss, spot coating that creates an additional sensory feel to your marketing pieces. This raised or 3-D effect helps your communications stand out in a crowded marketplace.
Images and photographs that look like they have a textural feel are perfect images to start with since the reader will already have a mental thought of what the image will feel like. Images that are highly detailed are also a great selection to use digital dimensional printing
One particular case study is from a residential commercial roofing company. Their marketing challenge was two-fold: one, how to produce marketing samples that accurately reproduce the many different colors of their roofing shingles and two, create the sensory effect of a shingle.
The solution? Digital dimensional printing.
The individual colored shingles were scanned, not photographed, and brought into Adobe Photoshop for color correction. The colors were accurately matched using a spectrophotometer and cross-referenced with LAB values on screen and readings from the actual shingle. Once the LAB color corrected images were approved, the images were converted to our GRACoL CMYK color profile for printing on Nexpress.
The selection for the texture was made by cross-referencing the various color channels and manipulating curves to create a high contrast selection of individual pebbles in the shingle. The marketing campaign results were incredible and great ROI.
Digital dimensional printing is a great alternative to raised UV coating and less expensive. It is completely recyclable and does not require any special de-inking process and uses no VOCs (volatile organic compounds) to the environment.
What are your thoughts on creative ways to use digital dimensional printing?
This has to be one of the best videos I’ve ever seen. Please take a few minutes out of your day and watch this video. It’s great to see the passion people take with their jobs to produce the best color possible.
Our business truly is a craft run by passionate people who genuinely care about their work.
If you have an appreciation for Art, you will truly enjoy this video.
What could be more important to producing great color on press than ink?
Tip: View this at ‘1080’ full screen for best results. Press pause, let it spool up and enjoy…
FM, AM, XM, Hybrid, Staccatto, Segundo, stochastic, conventional, 200 lpi, 175 lpi, 20 micron, 10 micron, first order, second order…What does this all mean?
NOTE: Screening is the process after rasterizing PDF files in the RIP (raster image processor) during prepress. Halftone screening is done through software and creates very small dots, or cells, that are imaged onto a printing plate. The tiny dots create the illusion of continuous tone photographs when printed on press.
Advantages to printing with FM screening versus AM screening:
Continuous tone photograph reproduction
Produces a larger CMYK color gamut on press
Renders greater detail
Eliminates moire patterns
Reduces ink consumption by as much as 10% – notice the ‘pooling’ of ink in conventional dot
Produces smoother gradients
More consistency in color throughout pressrun
Faster ink drying
Conventional screening (150 lpi, 175 lpi, 200 lpi) refers to AM screens, or amplitude modulation. This refers to halftone dots that are fixed on a grid, angled in 30 degree increments (except yellow: 15 degrees) and grow in size based on tonal value.
LPI = lines per inch
Stochastic screening (Staccato) refers to FM screens, or frequency modulation. This refers to micro-dots (20 micron, 10 micron) that are FIXED in size and tone values increase by adding more dots. The dots are rendered in a psuedo-random algorithm making them ideal for high definition details in photography and artwork. The micro-dots are rendered in a ‘weave’ to create very smooth tonal transitions.
Micron =1/1,000,000 of a meter
It’s important to note that FM screens produce a larger CMYK color gamut than AM screens. This occurs because light reflecting off the paper is filtered more efficiently, resulting in less ‘whiteness’ from the paper reflecting into the eye.
Also, reprints are less likely because of the stability in controlling color on press. FM screens are much less likely to be impacted by ink density variations on press. The ink film on press is much thinner and less likely to be affected. Notice in the enlargement photo above the ‘pooling’ of ink in the conventional halftone dots. This causes the press to use more ink than is necessary.
HiDefColor.com utilizes 20 micron Staccato screening for all color printing.
Have you ever seen printing with FM/stochastic screening? Please leave your comments below…
I’m sure everyone has seen it before: highly saturated digital photography (RGB image), however the sky blue prints purple on press. The resulting color is a product of the color gamut your commercial printer prints to or the profile of your inkjet printer.
The rich, blue hue of the sky looks very surreal on screen because of a polarizing filter or just using a wide color gamut such as Adobe RGB. However, when these rich images get converted into a smaller CMYK color gamut, such as SWOP, the rich blue prints purple because those colors are not available in this particular CMYK gamut.
A better solution is to work with a commercial printer that prints to a higher standard CMYK color gamut. HiDefColor.com prints to the GRACoL color standard, which contains more shades of blue for the rich RGB image to get converted into, especially Adobe RGB.