Screen Calibration


1. Introduction - explains the difference between prints and screens and why calibration is desirable
2. Step by step guide - with calibration image
3. Additional notes - for those that want more information
4. Links -  to other calibrators and further information

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#Introduction


This is a simple guide on how to calibrate your screen brightness and contrast for viewing photographs, to closely resemble how they will be seen when printed. This is important because the images on this site are intended to be displayed as prints. Correctly calibrating your screen will not only enable you to see my pictures as I intend them to be viewed, and any images where the photographer has used industry standards to control colour, but in most cases it will also be less of a strain to your eyes and reduce screen power consumption.

This guide does not cover colour management as this requires specialist equipment (see additional notes for more information).

The main difference between a screen and a print is that: 

 

Screens radiate light ~ Prints reflect light!

 

This means that a screen produces white, along with colours and the various shades, by emitting light (i.e. very bright light for white and absence of any light for black). Where as a print allows the paper to be seen through the ink in various degrees with reflected available light (i.e. no ink coverage where pure white is desired, total coverage for deep colours & pure black).

For this reason:
  • Screens can display a much brighter white than the white of any paper.
    • Note: this is especially so if the screen brightness has been turned up for a sunny day and is then used to view images in the evening.
  • Screens can show every subtle dark shade, but in print the darker shades often appear as black in all but the brightest of lighting conditions.
    • Note: new screens are initially calibrated to view all shades of grey in a bright office, but the human eye cannot distinguish the darker shades so easily when relying on reflected light from a print.

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#Step by Step Guide


If you want to get your screen to emulate a printed image as closely as possible, you can do so by adjusting the brightness and contrast of your screen to show darker shades as black and whites as paper white. Following these steps can help...

  1. Warm up your screen for at least 20 minutes, an hour or two is even better. 
  2. Eliminate unnecessary light, especially if falling directly onto the screen, and give your eyes 20 minutes to adjust to the new environment.
  3. Set the screen brightness to 50% and contrast to 75% as a starting point.
  4. Using the image below, adjust the brightness so that the area marked "seen as black when printed" appears black (as per the notes below), this is usually between 25% - 50% but could be more or less according to the brightness of the ambient light and the individual characteristics of your screen.
  5. Adjust the contrast so that the area marked as paper white appears no brighter than white paper.
  6. You may need to fine tune the brightness and contrast until you get the desired result. Also allow time for your eyes to adapt to a darker screen before fine tuning.

Grey Scale Reflection for Calibration Image
Grey scale image for screen calibration - showing how paper affects the print (white being paper with no ink coverage)

Notes:
    • 0% should be absolute black and 100% should be 'paper' white.
    • The darker three gradients 0%, 5% & 10% should appear as a near continuous black block.
      • 5% & 10% should appear the same as 0% black from a distance of over 3ft (90cm), with just barely visible definition between them at 1ft (30cm). 
      • 10% will not quite be as black as 5% when you concentrate your focus on this area, but if you concentrate your focus on the line between 10% & 15%  then the line between 5% & 10% should be much less noticeable ( where as looking at  the line between 90% & 95% you will still be aware of a noticeable difference between 95% & 100%). There should be almost no noticeable difference between 0% & 5% even when looking directly at them.
      • Perfection isn't necessary as eyes can adapt too easily when concentrating on these subtle differences (so they will be even less noticeable when viewing a picture and appreciating its beauty and content).
    • You should now only see a clear definition between between all the gradients from 10% and above.
    • The difference between 10% & 15% should be similar in contrast (but a little less) to the difference between 95% & 100%.
    • 55% should now be mid-grey creating an unbalanced image (try holding a folded sheet of paper over 0% & 5% to rebalance it).
    • When adjusting, especially when fine tuning, think of increasing/reducing contrast as increasing/reducing the gap between white and black (making whites brighter/duller and blacks deeper/lighter); and the brightness adjusts to match the ambient light (especially useful if that changes from room to room or at a different time of day).


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#Additional notes:


  • The gradient percentages represent the amount of brightness in an image on the screen, with 0% being pure black and 100% being pure white. 
  • Many calibration guides will recommend that you adjust your screen so that you can see a clear definition between all the dark shades and white as pure white, but paper is not pure white and the screen will not represent the dark shades as the printed image is seen by the naked eye with reflected light. 
    • Guides that indicate that a clear distinction between all the blacks would work if the print is then sent to a printer that has been manually calibrated to show the dark values in the same way. 
    • Professional printers use calibrators with standardised values, so would not work so well with these guides.
  • Changing the brightness of lighting in a room will affect the way the screen brightness is seen. So, in an ideal world you would recalibrate every time the light changes (daytime/evening, sunny/cloudy, main/side light) or recreate the same lighting conditions.
  • Wearing a bright top or having a white wall reflecting off the screen will make images appear brighter (coloured walls and clothing will also give a slight colour cast), so be sure to make allowances or change your clothing and/or the screen angle.
  • You don't need to be too fussy as there are other variables that come into play such as the type of paper, as they have characteristics that affect tone, contrast and finish (e.g. gloss, matt, fine art, smooth, textured, crystal archive photo paper etc); also where it will be displayed, the amount of natural and artificial light that falls on it, the time of day & year if near window light; what you were looking at moments earlier (your eyes take up to 20 minutes to fully adjust from light to dark or from being in a bright area to entering a dark room); as well as age related fading (for this latter reason, prints tend to be printed with greater depth in all but the brightest tones and our fine art printer inks have a higher fade resistance than standard prints too). Furthermore, I also check I'm happy with the finished print before posting. However, it is good to get the screen calibration close to the printed image so you can get a clearer idea of how I intend it to look.
  • This calibrator does not cover 'colour management' as people rarely change the factory defaults, which are usually fine for general image viewing if brightness and contrast are correctly adjusted. Colour calibration can only be done visually with the help of accurate colour swatches and colour balanced light, but for best results you need to use specialist calibrators - hardware that reads colour values from your screen and creates a profile to display colours correctly and specifically for your screen. I use a Spyder4Elite by Datacolor as it measures the ambient light during calibration, then constantly checks it as I work and warns me if there is a significant change that may affect my work. This is only needed on a professional level, using the screen manufacturers default setting and calibrating your screens brightness and contrast is usually sufficient for general purpose. 
  • As ever, send me an email or call if you have any questions.


#Links

 
http://www.redcliffe.co.uk/fine_art/screen-check.htm recommended reading - a simple but very good guide
http://spyder.datacolor.com/ calibrator hardware manufacturers
http://www.photofriday.com/calibrate.php a useful tool but, it says that the tones immediately lighter than true black should be clearly distinguishable from true black, on my monitor (calibrated using a Spyder4Elite by Datacolor) B is barely distinguishable from A (true black) and it takes several seconds to see the inner most circle. However, C is clearly distinguishable from B. The guide then goes on to say "adjust brightness and contrast until you can 'just start to see' the shapes." Furthermore, this observation is reflected in my test prints.