Exercise 10: Colour cast and white balance Part 1 Review.

Sunny Day

The first set of photographs I took were on a sunny day at approximately 2pm, the four different white balance results are shown below :-

 

File temperature read 5650



File temperature read 5150










File temperature read 6750








File temperature read 5850

 

Out of interest I noted down the colour temperature readings on the RAW files and noted that the AWB value was very similar to the Cloudy.

I was surprised that although I can see there is a variation in the colour cast it was not more pronounced. The AWB I feel has represented the truer colours, the daylight setting has added a touch of blue which although makes the sky a lovely shade gives the grass an odd hue. The Shade WB setting is the least satisfactory giving the image a very orange appearance with the Cloudy setting not too bad a result but still a little on the yellow side.

Cloudy Day

The next set were taken on a cloudy day at approximately 3.30pm.

File temperature read 5550

File temperature read 5150



File temperature read 6750




File temperature read 6750



Once again I noted the colour temperatures and the AWB @ 5550 was closest to the Cloudy WB setting @ 5850.

I think that the variations were more noticable under the cloudy conditions. The AWB rendered the image quite well but the image seemed a little flat, while the daylight setting once more gave the image a cold blue cast. The Shade setting made the brickwork much warmer but gave the overall shot an orange/yellow hue, the Cloudy WB seems to have been the best option but is not that disimilar to the AWB.

Open Shade

This set of images were taken in open shade on a sunny day at about 2pm

File temperature read 4500



File temperature read 5150




File temperature read 6750




File temperature read 5850



Noting the file temperatures in RAW once more it was interesting to see just how far out the AWB reading was from the other settings on this occasion.

I felt that the variations were more striking with these shots. The AWB has left the image dark and with a blue cast as has the daylight setting. Once again the Shade setting has given a very warm orange cast with the cloudy also not giving a very true result, erring on the yellow/orange side. The daylight setting seems to have the closest colour representation if I was pushed to choose.

This was an interesting experiment to undertake. A lot of the time when shooting outside I rely quite heavily on the AWB setting due to the changing nature of the weather and therefore the light. From these results I conclude that the AWB setting on my camera performs quite well on most occasions, with the Shade setting giving a very unsatisfactory result even in the shade. This will help with my decision making when shooting outside as far as white balance settings are concerned. I have as yet to experiment with the custom function but I can't see me always carrying a white card about or not always having the time to use it in certain circumstances ;o)

Exercise 10: Colour cast and white balance

The first part of this exercise is to familiarise myself with the exact procedure for altering the white balance in my camera.

On the 400D there is a specific button that allows you to access the cameras white balance settings. There are eight altogether, auto, daylight (approx 5200K), shade, (approx 7000k), cloudy (spprox 6000K), tungsten light, (approx 3200K), white fluorescent light (approx 4000K), flash and custom.

The following settings are recommended  :-

• Sunrise, although you can use AWB it is recommended that if possible use the custom white balance.
• Midday, the Daylight setting is a reliable choice.
• Sunset, the Cloudy white balance setting is a good choice.
• Diffused light, on cloudy or foggy days, awnings etc again Cloudy is a good choice.
• Flash, using the on camrea flash for use indoors or outdoors as a fill-in use the Flash option.
• Tungsten light, this is the light most commonly found in household lights and lamps it produces a yellow/orange cast. Setting the cameras tungsten wb setting retains a hint or the warm colour of the tungsten light while rendering the colours accurately.
• Fluorescent, commonly found in offices and public places this light ranges from a yellow to a blue-gree hue in these instances use the Fluorescent WB setting.
• Other light, other types of lighting include mercury-vapor and sodium vapor found in public arenas and auditoriums, it is recommnded that in these situations you set a custom white balance.

If shooting jpeg only images you can use white balance auto bracketing which captures three images, each with +/-3 one stop differences in colour from the base current white-balance setting. This function is not available with RAW.

If you have a mixed light situation or less-than-perfect light you can set a custom white balance. In doing so you are telling the camera what should appear white in the specific light you are shooting in. As long as you remain shooting in those lighting conditions the custom white balance should render the whites accurately. This saves time that would otherwise be spent correcting colour cast post production.

To set the custom white balance on the 400D :-

1. Position the camera so that a sheet of white paper fills the centre of the view finder, ensuring that it is correctly exposed.
2. Press the menu button.
3. On the Shooting 2 tab, press the down cross key and select Custom WB
4. Press the Set button. Make sure the image displayed is that of the white sheet of paper.
5. Press the Set button again, The camera then imports the white-balance data from the selected image.
6. Lightly press the Shutter button to dismiss the menu, and then press the WB cross key. The White Balance screen will appear.
7. Select Custom White Balance.
8. Lightly press the Shutter button to return to shooting.

Information from the Digital Rebel XTi/400D Digital Field Guide.*

I need to find the four following outdoor lighting situations. Sunlight, Cloudy,Open shade on a sunny day, Auto. For each scene I have to choose a scene or object to photograph and shoot four versions using the four different white balance options.I then need to compare the results.

For the second part of this project I need to find and shoot a mixed-lighting scene. Suggestion made is to shoot a mixed indoor/outdoor shot at dusk. Shoot three versions using the following white-balance settings

• Sunlight
• Tungsten
• Auto

Comparing the results which of the three versions would I choose? Experimenting in RAW find a compromise version that I like.

*refer to Lowrie C K (2007 p26/27 and p86-89) Digital Rebel XTi/400D Digital field Guide