Sunday, 12 August 2012


The advantages of using RAW for image capture are generally accepted to be the ability to carry out non destructive and post acquisition editing which allows us to hold the image quality until a later stage of the image processing cycle.

This exercise is to put in to perspective how noticeable this  benefit actually is in real terms.

I have captured three images with different lighting set-ups. Each image has been captured as a RAW file as well as a JPEG (at highest quality). On my camera I am able to do this simultaneously, so both files will have identical lighting etc. To minimise the amount of post processing, I have set the camera up to give the best possible image at the time of shooting, i.e. white balance, exposure etc.

The first two images were taken in a local church yard. Very little tweaking was required on the RAW file. A little more was required for the jpeg as there was still a slight colour and brightness difference compared to the RAW version.

Jpeg from RAW file.
Edited Jpeg.
Comparing the two images at all stages I noticed the following. As previously mentioned the jpg file was slightly different to the RAW, straight out of the camera. The jpeg was darker and colder than the RAW. Some adjustment to the brightness, contrast and colour curves brought the two images into line.

After this work I examined both images at 100%. I checked for the presence of fringing around the edges of shapes and noise in the darker areas of the image. This image has a very shallow depth of field which allowed me to examine both sharp and soft area's.

An examination at 100% did not really reveal anything that I would worry about. There was no fringing and the noise in the darker areas was no worse than in the RAW version of the file. In the two images above you are able to see the slight difference in the colour tone but as both pictures have been converted to Jpeg, it is naturally not possible to see the differences between RAW and Jpeg. In this lighting situation the dynamic range of both shots is the same.

Image pair number two were shot in artificial light. For this I used a two flash-gun set-up with the main light to the left of the camera through a shoot through umbrella and the second flash to the right with no modifier except the flip down diffuser on the front of the flash. The camera was set to flash white balance and tripod mounted.

Again there were differences to the Jpeg and RAW files as they came from the camera. The Jpeg was again a flatter image and needed a bit more adjustment to brightness and contrast. In my images there was very little tolerance when adjusting the contrast. There was very little adjustment to be had between the highlight clipping warning and the shadow clipping warning. This was apparent in the white of the flowers and the black of background.

Again an examination at 100% showed very little to be concerned about with regards to the image quality. I paid particular attention to the edges of the white flower petals against the black background. It will be interesting to see if this is the case with the last two images!

RAW Conversion.
Edited Jpeg.
There are two more images needed to complete this exercise, which will be high contrast.