Colour cast and colour balance.

Exercise: Colour cast and colour balance.

This kind of exercise is, for me, particularly challenging as I am 8% colour blind.  This affects specifically my perception of greens.  I can see light and dark but hue is a mystery.  Some shades of, what I am assured are, green I see as grey.

For this exercise I used my Olympus E3 as my Canon lacks the full range of white balance settings required.

I took three full sun sets and two open shade sets.  The weather is too clear for the cloudy set at present.

I chose the two that looked most interesting for the purposes of this exercise.

Full sun set.

The scene is of a white cottage across a green field with surrounding trees and a sky of mid-morning blue with fluffy clouds.

Auto

In this image the camera has almost match the cloud setting.  This has given the image a slight warming which I find quite pleasant.  The whites and greys, as read by the Digital Colour Meter, showed as slight bias towards the red.

                           

Sun.

The colour and tint were as above. The sky looks bluer and  the greens have, to my eye, taken on a lighter look.  Others my see a more acid hue.  The DCM readings are fairly neutral at the whites and greys.  

Full shade.

There is a definite warming here.  The open shade filter is designed to rid a scene of the blue tint given by a clear blue sky that is untempered by the warmth of direct sun.  The effect here is to warm up the image.  The DCM shows a distinct red shift in the whites and greys.

Cloud.

The colour here is close to that in the first image  If there is a difference between the auto version and this one my eyes can't detect it.  The DCM shows a slightly greater bias towards the red than the auto image.

Of these four I found the auto image the most pleasing as it slightly warmed the image without making it too obvious.  

Open shade.

The view is of a street in Deal.  The pale colours of the houses demonstrate the effect of  the colour cast quite neatly.  

Auto.

The auto reading setting for this shot is the same as for the last set.  As in the above set this has given this image a pleasing warm tone.  The DCM when used on the blank white wall demonstrated neutral readings.

Sun.

The effect of this filter is to counter the warming influence of the sun and this can be seen in the DCM reading of the white wall where the blue is raised.

Open shade.

In this image the effect of the filter is the most obvious with the whole picture taking on a yellow cast.  The DCM shows elevated reds.  

Cloud.

The effect here is to give slight warming look to the image.  The DCM showing a slightly elevated red.

Below I have reproduced all twelve images so that the differences can be seen more clearly.  

           Auto                              Sun                      Open shade                   Cloud

A cloudy scene.

I had to wait a couple of days to get the overcast day required.

The scene was similar to the last set but as all was under cloud cover I used the whole street.  The camera was again the Olympus E3.

Auto.

The auto setting has produced an image very close to the cloud setting.  This was confirmed by the DCM.

Sun.

With the sun setting the street now has a very cold look to it with the white walls taking on a blue hue, which was confirmed by the DCM showing the blue was reading high. 

Open shade.

The shade setting was very marked in the way it warmed the image, with the whites taking on a distinct yellow hue.  This was confirmed by the DCM showing reduces blue and raised red.

Cloud.

The cloud setting was pretty much spot on as the DCM displayed even readings across the white and greys.

Conclusion: 

As was postulated at the start of this exercise, the camera's auto setting tried its best to mimic the fixed settings when it read the lighting conditions for each scene.  

I try and use the correct colour setting even though I shoot in RAW.  There are times, however, when the colour setting becomes academic, as in the fair ground picture earlier in the blog.  Getting the colour right in the camera gives me a good chance of getting right in the print.

Mixed source.

To carry out this exercise I was forced to cheat as my house, along with all those around me, have eco-lighting.  This means there are no incandescent bulbs.  My only reasonable access to these bulbs was my pair of old photo-flood.  To make the most of what I had I set three orchids on a windowsill so that the garden and the outside was naturally illuminated and the inside was illuminated by the photofloods.

The day was overcast with thin cloud.  Because of this I took an additional image.

Auto.

The auto setting has tried to resolve the unresolvable.  The wall at the end of the garden is in fact a pale yellow but in this shot it has been reduced to nearer grey.  The warming effect of the tungsten light has been lessened but the whites in the image are still yellow.

Sun.

The sun setting has allowed the outside to retain something close to reality but has done nothing to correct the warming effect of the tungsten light.

Overcast.

This setting has allowed the outside elements to retain their true colours at the expense of the colour cast

caused by the tungsten light.

Tungsten.

The tungsten setting has turned the image an eerie blue.  The rendition of white on the DCM shows a heavy blue bias.  I don't know the temperature of the photofloods but they must be less yellow than normal incandescent bulbs.

Correction.

From Auto.

Above is my attempt to correct the colour of the auto setting.  In altering the colour balance for the inside elements I have pushed the outside elements further into the blue.  The whites in this image are neutral.

From tungsten.

Even the over blue mess of the tungsten filter could be alter sufficiently to obtain neutral whites.  The end result is very similar to the altered auto image.

        Auto                 Sun               Cloud           Tungsten         From auto  From tungsten

Of all the above images the one I prefer is the one that the camera's auto setting has produced.  Although the colours are not perfect in either the outside or inside elements neither do any of them jar the senses by being to distorted.  The sun and cloud settings have warmed the image too much while the tungsten has turned the whole thing a nasty blue.  In altering the auto and tungsten to make the whites truly neutral the outside elements have been given an unpleasant cold blue cast.