Troubleshooting Photos –
About Color Reproduction & Monitor-To-Print Differences
Perhaps the most frustrating aspect of digital photography is what seems to be its half-delivered promise. On your monitor you see that your camera has delivered up a rich and beautiful image, full of lively colors subtly transitioning from one to another. So carefully following your printer's instructions, using paper that seems insanely expensive, you print your photo and patiently wait for it to dry. But when you finally look at it, you see this... this... print – something seemingly little better than the local drug store photo counter used to serve up.
What happened to the rich, translucent color? Where are the subtle transitions? They're back on your computer and that's where they'll stay. It's not magic in the computer display or a flaw in the printing process and it's not that your printer is crummy – contemporary photo printers are astonishingly good for the price you pay for them. And it's probably not your fault. Notwithstanding the existence of this site, it's fairly easy to make reasonably good prints most of the time (it's the rest of the time that will get you tearing your hair). What you are seeing are characteristics of the respective processes that produce images on your computer monitor and on paper. It also needs to be said that, your disappointment notwithstanding, a print made on a high-quality photo printer is more colorful than your monitor, but it's a different order of colorful, and you need to learn to appreciate the difference.
Before we get into an explanation, try this simple demonstration:
- hold a sheet of blank white paper against a white area on your screen – bond or photo, it doesn't matter which, as long as it's thick enough that light doesn't shine through it (or just use several sheets);
- hold a solid black object – a page covered with black ink or a piece of black plastic – against a solid black area of the screen.
Compared with the white of the screen, paper-white looks rather dull, doesn't it? The monitor is transmitting white light directly into your eyes, so naturally it is brighter and more pure-looking than the paper. The paper relies for its brightness on the source light it can reflect, and since some portion of the light is either absorbed or scattered by the paper, its white is necessarily is less bright than a source that transmits light. The same limitation applies to colors. The red, green and blue circles below are transmitted from monitor to eye as brighter, more lively colors than could ever be reflected by a sheet of paper.
On the other hand... compared with the black of ink on paper or a black object, the screen black looks somewhat gray, doesn't it? Screen black is just screen pixels that aren't shining brightly, and by its nature, it never can be a really black black – and this accounts for ink-on-paper's superior ability to show detail in shadow areas.
Monitor color vs. paper color
The differences between monitor color and paper color go beyond their relative ability with lightness and darkness to the way they form colors.
Monitor color, properly known as additive color, is based on the additive primaries of Red, Green and Blue (hence the common name, RGB color). When combined, red, green and blue light combine to form white light. In addition,
- where blue and green overlap, they make cyan;
- where blue and red overlap, they make magenta; and
- where red and green overlap, they produce yellow.
This is a demonstration often done with colored flashlights: where the red, green and blue beams overlap, white light appears – against most viewers' expectations. Take a magnifying glass to your computer screen and you can see how the red, green and blue pixels combine to form various colors. The white areas, of course, have all three set at maximum intensity – but if you've calibrated a monitor, you know that there are many different flavors of white, and all your other colors are affected by that starting point. Use your browser's Reload button to see the animation again.
As you would imagine, minor adjustments in the proportions of red, green and blue not only form the rainbow of colors, they form equally numerous interpretations of "white" on our monitors, depending on the precise balance of red, green and blue. It's important to your color judgment – and your ability to get the colors you want in your photos – to ensure that you have a reasonable "white". Most monitors are very blue when new. Calibrate your monitor – it's really worth the minimal trouble it takes.
Ink-on-paper color, properly known as subtractive color, is so called because its primaries, cyan, magenta and yellow, are formed by subtracting an additive primary color from white light, so:
- white – red = cyan (blue + green);
- white – green = magenta (blue + red); and
- white – blue = yellow (red + green).
Subtractive color proceeds from whatever you're printing on – in this case a simulated white sheet of paper. The ink or dye colors subtract color from the illuminating light; what remains is the color you experience. As you might expect, the color of the illuminating light and the color of the paper profoundly affect the final color. Use your browser's Reload button to see the animation again.
Most inks, pigments and other subtractive colorants are translucent. The light falling on the paper passes through the ink and is reflected back from within the paper. On its passage though the paper and ink, colors are filtered from the white light. The colors not subtracted make the color or combination of colors you see.
In theory, a balance of all three subtractive primaries will filter out all colors, leaving the paper black. In practice, colorants don't do a perfect job, so you end up with a muddy brown. Printers (and printing presses) therefore add a fourth ink, black, to the mix. As an area gets darker and darker, your printer driver swaps out some of the colored ink and substitutes black ink. This gives you a richer black with fewer undertones of the color that was there only to darken the other two.
The three subtractive primaries plus black (Cyan, Magenta, Yellow and blacK or CMYK) work well for commercial printing, as magazines and newspapers are seldom expected to have the richness and color accuracy of a photo print. For photo printing, it's common to have additional inks – photos scanned for this site are printed with a mid-price 6-ink photo printer with CcMmYK inks (where c and m represent lighter versions of cyan and magenta) – and eight colors are increasingly common.
Light reflected from ink on paper inevitably has much less visual impact and color range than light that is transmitted directly into your eyes from a monitor. monitor represents the visible spectrum as displayed on a monitor (and what you see here depends on the quality of your display). photo shows the same range of colors translated into the range achievable by a 6-color photo printer. office shows the same range as produced by a $15,000 laser printer and press shows the range as printed by the type of printing press used for good-quality magazines.
This example shows that ink on paper (reflective color) isn't as good at showing bright, saturated colors as a monitor (transmissive color). What it doesn't show is that ink is good at representing dark colors, which it does with ease because black ink can be a lot blacker than monitor black.
No matter how many inks are used or how bright the paper (or other substrate), the nature of subtractive color means that a substantial portion of the light that falls on the paper is absorbed and cannot carry color to your eye. This means that ink on paper can never convey the same type of visual excitement. This does not means that a print is a lesser object. As mentioned earlier, the nature of subtractive color lends it to rendering complex details in shadow areas, an area where monitors fall flat. Moreover, at the current state of the art, a good photo print can carry a broader range of saturated colors. It also carries much finer detail than a monitor image; you need only to compare type on screen against type on paper to see the difference.
