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Ishihara Test Patterns Results • If you see 45 and 56 you are probably good • If you see 56 but not 45 you may be Red/Green deficient (protanopia) See a qualified ophthalmologist or optician if you have any concerns about your vision or eyesight What you see is what you get? Doubtful! by Robin Palmer T he colour you see is not necessarily the same colour experienced by someone else looking at the same thing. It all depends on the viewer and the viewing conditions as well as the actual colour of the thing. In some professions having perfect colour vision is a matter of safety as in the case of airline pilots and those in railway signalling. People involved in broadcast, video editing and movie colour grading are probably unlikely to have been subjected to a compulsory Ishihara colour vision test. And yet as many as 8% of white males can be affected with red/ green colour deficiencies which can cause confusion in colour recognition. Protanopia is the most common form of this so-called colour-blindness but there are others. True colour-blindness is actually very rare so the average sufferer will still see a full spectrum of colour and yet make mistakes in recognising certain hues and tints. For genetic reasons, females are rarely affected with colour vision problems. The problem in recognition comes from the red/green/blue colour science where the intensity of each primary creates the sensation of colour. Where there is a mixture of all three making a hue like beige, sensitivity to each component is not the same as for a normal vision-abled person. Beige could look greenish even though a deep pure red could easily be distinguished from a solid bright green. Even people with perfect colour vision can be confused. The eyes are very susceptible to ambient viewing conditions. If the ambient lighting has even a slight colour cast, then the delicate relative balance of red/ green/blue sensitivities can be affected causing problems in the perception of subtle hues. For this reason, colour grading is done in darkened studios. Also the screen GUI graphics of the editing interfaces tend to avoid any bright colours that could disturb the operator’s colour balance abilities. Since no two people can really have exactly the same colour experience, colour grading is as much a specialised craft as a science. In the grading suite vectorscopes and waveform monitors are a common aid but can be difficult to interpret under some circumstances because the differences in RGB or HLS from one colour to another can be very slight. Then there is the display monitor itself and its state of colour calibration. Even with grade 1 picture monitors, the setup needs to be carefully maintained to ensure it is showing the right balance. Ordinary LCD monitors cannot be trusted for colour rendition; this is a whole big topic in itself. Pixel-Scope is a new software tool from Cel-Soft to help colour recognition and matching for people with or without perfect vision. This low cost application for Windows aids any other software, editor or colour grading kit. It provides detailed colour analysis and image inspection to any part of the target application output window. It does this by opening a sampling region and analysing the active pixels it finds. The sampled region can also be magnified on a sliding zoom for close visual inspection. Pixel colours can be reported in real time as numerical values and as words. Actual hues are translated into plain English as well as either RAL or Pantone colour values and into other languages such as French, German, Spanish and Dutch. Colour matching tools aid the user when comparing, for example, still photos or documents and live video. Robin Palmer is Managing Director of Cel-Soft and is usefully involved with solutions for 3D & TV quality control and measurement technology.Stand K1 at BVE 2013. 54 | TV-BAY MAGAZINE TV-BAY074FEB13.indd 54 11/02/2013 16:53 343