Colour Calibration

Colour Calibration

If you don't colour manage your devices, your prints will not match what you see on your computer monitor, your camera data won't match your printer, your scanner will not match your beamer, etc., you get the idea. Nothing will match the actual lighting conditions of the scenery. Colour management is inevitable unless you don't care if your images have little to do with what you saw. One device simply doesn't know how another one represents colour. Not to mention that no device knows how you perceive colour. But that's another story.

Colour management is achieved by calibrating and profiling your digital devices so that colour reproduction is consistent for all of them. Colour management is not very complicated in principle but it is confusing. Calibrating means to measure how some well-defined colours are represented by a specific device. Profiling means to create a description (profile) of these colour capabilities. Using these profiles will not only make your colours consistent but also make optimum use of the device capabilities.

The actual example shown below will make things clearer. You'll be amazed what's in your images when you scan and print them with colour management! You don't have to be a "professional" to benefit from colour management!

kiss-of-light offers calibration and profiling of all the devices listed in the table below. We'll also set up your computer for proper colour management and show you how, including soft-proofing etc. We can create simple to very advanced (high accuracy, high bit-depths) printer profiles for all the papers and inks you use, including special profiles for black and white printing. Btw., we also calibrate our photospectrometers...

Contact us for your needs.

Colour Spaces Adobe RGB vs. sRGB - Adobe RGB gamut is larger especially in the greens and blues which is obviously important in nature photography.

What is needed to calibrate what

device  needed  comment 
computer monitor, digital projector (beamer)  photospectrometer for light-emitting device; software to display targets with sample colours, to calibrate and to make profiles (icc, icm)   monitor is most important, also if printing is done somewhere else 
printer  photospectrometer for reflective media (prints); software to print targets, to calibrate and profile   printer is second important; need to calibrate for all paper-ink combinations 
scanner  targets (samples) for reflective (prints) and transparent (negatives and slides) media; software to calibrate and profile  scanner should be calibrated even if manual adjustments are possible using a calibrated monitor 
digital camera  reflective target; software  calibration depends on lighting conditions, not very useful for outdoor photography 

Simple Actual Example

Here we show the actual calibration of a Canon Selphy CP750 "toy" printer. This is a tiny, mobile dye-sublimation printer for 10 X 15 cm (4 X 6 in.) "snapshots". It prints at 300 X 300 dpi with 8 bit per colour (256 shades). The Canon printer driver doesn't even know about colour management (which doesn't mean that we can't colour manage it). It will be interesting to see if such a simple "consumer" product's output can be improved by color management. The image below shows the result of a fast calibration (150 colour patches): The upper triangles show the reference colours as seen on a calibrated monitor, the lower triangles show what the printer made of the reference colours when printing them. Quite different. Part of the difference, however, is due to the fact that the printer has to reproduce the colours on paper which is a reflective medium -- to achieve monitor brilliance from a print one has to illuminate the image very well. The photospectrometer, on the other hand, of course provides it's own calibrated lighting conditions. It is clear, however, that there isn't much variation in the dark tones (lower right) and in the greens (upper left) - the printer cannot reproduce these shades properly.

Canon Selphy CP750 A tiny printer for mobile photo printing. Photo by Canon.

The next image shows the same as the one above, i.e., the difference between printer output and target input colours. You can switch between output and input by simply moving your mouse over the image. The difference becomes even clearer. Move your mouse over the image to see the input and study for example the block of dark shades, these are dark blues and greens. If you can't see this, the monitor you're using might not be properly adjusted -- try here. If that doesn't help buy a real monitor. Now remove your mouse and look at the output for the dark shades -- not exciting. The same is true for the greens which can hardly be distinguished in the output.

After creation of the profile from above calibration measurement, let's see if using the new profile will improve the situation. The next image is also a mouse-over and demonstrates the difference in actual printing: The first image was printed without colour management, the second (when the mouse is over the figure) was printed with profile. We can now clearly distinguish the different dark colours, the greens and also the bright pastels at the very bottom right have improved a lot! Using the printer with a custom-made profile makes a huge difference, the output is vastly improved! (These are calibrated scans of real prints, not soft-proofs or whatever.)

Colour Spaces I Adobe RGB vs. Canon Selphy CP750 - the CP750 can reproduce only a fraction of the Adobe RGB colour space.

OK, great, but what does that mean for real photographs? The next image, also a mouse-over, gives an example: A landscape first printed without profile, then (mouse over figure) with colour management enabled. Just toggle and see the difference in colours, colour dynamics and tonal dynamics (details in bright and dark areas, such as around the sun and in the sand). Remember these two prints were made using the same paper and inks and the same printer driver settings! Using a profile makes all the difference... (again these are calibrated scans from actual prints, calibrated scans means that the scanner was calibrated and the scanner settings were not changed between scans).

Colour Spaces II EPSON R2400 (premium glossy paper) vs. Canon Selphy CP750 - the CP750 has a much smaller gamut.

Finally, here is an example for part of a more advanced calibration done on an EPSON STYLUS PHOTO R2400, one of the best fine art inkjet printers. Shown is the extended grey target for optimal black and white printing -- black and white printing also greatly benefits from profiling.

Colour Spaces III Just to make sure: Adobe RGB vs. EPSON R2400 - of course the printer's gamut is smaller but again it is much larger than the CP750's, for example.

We hope that you enjoyed this excursion into colour calibration and profiling and that we were able to convince you that even a simple printer's output can be greatly enhanced.

Update: Lasersoft's Silverfast Ai IT8 (Studio/Multi-Exposre version) now includes printer calibration without the need for a photospectrometer. Once your scanner is calibrated using a special target (an IT8 target), the scanner becomes the spectrometer. I haven't tried it yet but it sounds very good: Saves the spectrometer and should be much faster!

Contact us if you have any questions or comments or would like to have your equipment set up for colour management.

(Christian Goltz)

EPSON STYLUS PHOTO R2400 One of the best fine art inkjet printers. Photo by EPSON

(C) 2006 - All rights reserved

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