When opening the photograph and comparing it to the digital file OCA_colourchart_as looks it looked awful!
Chart pre colour cast adjustment |
Chart | 1 | 2 | 3 |
OCA Chart | 17,17,17 H 0,S 0, B 7% | 52,52,52 H 0,S 0, B 20% | 97,97,97 H 0,S 0, B 38% |
400D Chart | 1,3,1 H 120, S 67, B 1% | 57,48,50 H 347, S 16, B 22% | 144,140,140 H 0, S 3, B 56% |
4 | 5 | ||
OCA Chart | 161,161,161 H 0,S 0, B 63% | 243,243,243 H 0,S 0, B 95% | |
400D Chart | 216,217,222 H 230, S 3, B 87% | 249,251.251 H 180, S 1, B 98% |
Due to the colour cast it was recommended that Enhance was used to correct it. As I am using CS4 the menus and techniques are slightly different, I had to refer to the Adobe help website to find out how to do this.
adjusting cast using curves |
Chart after cast adjustment |
Chart | 1 | 2 | 3 |
OCA Chart | 17,17,17 H 0,S 0, B 7% | 52,52,52 H 0,S 0, B 20% | 97,97,97 H 0,S 0, B 38% |
400D Chart | 0,1,0 H 120, S 100, B 1% | 49,52,53 H 195, S 8, B 21% | 134,134,138 H 240, S 3, B 54% |
4 | 5 | ||
OCA Chart | 161,161,161 H 0,S 0, B 63% | 243,243,243 H 0,S 0, B 95% | |
400D Chart | 213,4, 85 H 230, S 3, B 87% | 254,255,255 H 180, S 1, B 100% |
The blacks were registering fairly close to the RGB levels of 0,0,0, that you would expect and the white close to 255,255,255 even at 134,134,138 the grey was not too far off 128,128,128. Not sure what was happening with the Hue,Saturation and Brightness readings though? Maybe I needed to zoom in a little closer due to the uneven tones of the boxes? I think completing this exercise has left me a little confused as to how to interpret the results. I have examined two colour boxes to see if I could figure out the numbers from there....but there didn't seem to be a correlation? There was not more red in them all or more blue....the green box indicated my camera had more R less G and less B which suggested a red cast but then the blue box measured less on all 3? My head hurts :o/ What I have concluded is that adjusting the mid-tones/BW points is something I should be doing as a matter of course even if I have set a custom white balance. I may not be able to fully understand the numbers I am seeing but there was certainly a colour cast to correct. The Saturation and brightness seem to be close but the hues are definately higher.
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