Exercise 31: Control the strength of colour

For this exercise I set my camera for 5 frame bracketing with a 0.7 stop interval. The other I could have opted for 0.3 stop intervals, but I decided that the 0.7 interval would show more pronounced results. The mode was set to shutter priority with a shutter speed of 1/200 sec. I used high speed continuous shooting so that the setup time was minimal and there would be little change in the cloud conditions. The lens was set at 170 mm

I used the boot of my wife’s car, which is ‘Chilli Red’. 

 1/200 sec, f/7.1

This is 1.4 stops under-exposed. The image shows a lighter red than the actual colour. There also seems to be a slightly yellow cast to the image – this could of course be attributed to screen calibration, but that was only calibrated two days ago, so it’s not very likely. The HSB readings in Photoshop are 353^o, 79% and 100% respectively – the paleness can be attributed to the lower saturation.

 1/200 sec, f/9.0

 

This is 0.7 stop under-exposed. The image is still a lighter red than the actual colour, but the yellow cast is not so pronounced. So it doesn’t look as though the screen calibration is to blame for the first image. The HSB readings in Photoshop are 350^o, 95% and 100% respectively – the paleness can be attributed to the lower saturation. The slightly lower hue could be due to my targeting of the colour in Photoshop.

 1/200 sec, f/13

This is where the camera automatic exposure was set. The colour looks right to me. The HSB readings in Photoshop are 352^o, 100% and 86% respectively – the hue is about the same as the previous two images, but it is now fully saturated with some reduction in brightness. 

 1/200 sec, f/14

This is 0.7 stop over-exposed. It’s obviously a darker red than actual. The HSB readings in Photoshop are 353^o, 100% and 73% respectively – the hue and saturation are steady, but the brightness has reduced.

 1/200 sec, f/18

This is 1.4 stops over-exposed. It’s obviously darker again and it seems to have acquired a blue cast – the cast could be due to the blue from the sky, or the sampling point in Photoshop. The HSB readings in Photoshop are 350^o, 100% and 49% respectively – the hue and saturation are steady, but the brightness has further reduced.

The changes of perceived colour can be effected by so many criteria, including what the mind expects to see, so the slight variations in hue could be purely imagined. The difference in perceived colour cast, particularly in images 2 and 5, are not borne out by the Hue temperature in the Photoshop information, so it’s got to be down to saturation and brightness only. It seems that the increased exposure makes the colour stronger by firstly increasing the saturation then reducing the brightness.