Tuesday, 10 July 2012

Exercise: Colour cast and white balance

This exercise is fairly straightforward, and its aim is to show us the difference in using various white balance options. I always shoot RAW now, so I can edit this in post-processing, but do find (particularly when shooting under artificial lighting) that it makes a difference to how the image displays on the camera and thus the 'feel' of the image, so it does pay to get the WB right for the scene, or at least close to the scene.

The Exercise:
I have undertaken this exercise in the backyard, with simple props to maintain some constency between the images to hopefully see clear results. I photographed a similar scene under the three different lighting conditions; Sunny, Cloudy & Open shade on a sunny day. For each, I used a tripod, and used each of the four white balance options; Auto, Sunlight, Shade and Cloudy. All images were taken using ISO 200, 50mm lens, f/3.5 with varying shutter speed for the different light conditions.

The Images:
I have grouped them according to the three lighting conditions:

Sunny Day:
Sunny day images, with varied WB options
Slight differences are observed in the colours on the car, and on the green grass in particular. In this case it's really just a matter of slight preference, but the sunlight white balance and auto white balance have both done a good job.

Cloudy Day:
Cloudy day images, with varied WB options
Again, there are only slight differences between the colours in the car and grass. In this case any of the images are acceptable, with a slight preference for the cloudy option.

Open Shade on Sunny Day:
Open shade on sunny day images, with varied WB options
None of these images are particularly good actually, which is a bit surprising! I had thought the shady option would do a better job that what it has in this case.

Second Part of Exercise:
This part of the exercise called for a mixed-lighting scene.

These indoor shots were taken at sunrise at Caloundra, with a lamp on inside. The light levels were roughly similar between outside and inside as recommended in the course notes.  ISO was set at 400, and I have used my Canon S95 for this exercise, and would expect the results from my 30D to be very similar.

Indoor view to outdoors (mixed lighting), with varied WB options

In this situation, if I had to choose between AWB, Sunlight and Tungsten, I think the AWB does the best job, though it is close with Tungsten. The Sunlight version is much too yellow inside.

The AWB does a reasonable job mostly, but in general I choose the correct ISO for the conditions, and shoot RAW anyway.

No comments:

Post a Comment