Aim: to demonstrate the processing advantages of raw and to put these advantages in perspective.
Ever since I bought my first DSLR I have used the raw option as opposed to JPEG. At first this was because it seemed more ‘professional’ to be shooting in this format and I had read early on that it was a kind of safety-blanket in that it offers more image processing options when uploading it to the computer. However I also realise that raw files are subsequently much larger than JPEGs, due to the unprocessed image information they contain, and they take up much more storage space. Therefore I sometimes wonder if it is always more beneficial to shoot in raw or whether I can give my hard drive some breathing space by uploading slimmer JPEG files. Also since I don’t produce many large prints, would I really see the perceived benefits of improved image quality? Hopefully this exercise will answer these questions.
The image above was taken at the rear of the P&O cruise ship Oriana, docked beside the Greek island of Kefalonia. It was a bright summer day in August, so white balance was set at ‘daylight’ and I used AV mode. The sunny conditions enabled me to use an aperture of f/13. As I have already mentioned before, shooting in raw has always been my favoured file choice, ever since getting my first DSLR. So it was a matter of creating a JPEG version of this image for the purposes of this exercise. For the raw file I increased the exposure slightly to remove the shadow clipping and increased the contrast. Meanwhile the image below is the JPEG version of the scene with the same slight increase in exposure and contrast.
I was surprised to see such a difference in the 2 images, considering I only did a small amount image editing. There is more definition in the highlights and shadows of the raw image. The JPEG image has shadows and white areas that appear to be ‘blocked’ with less gradual changes in tone. The differences in tone are much more graduated in the raw version, whilst the colours in the JPEG look harsher.
The histogram for the raw image shows a broad tonal range with no over or under exposed areas and a slightly greater proportion of shaded areas.
Meanwhile the histogram (left) for the JPEG image shows a higher dynamic range and a spiky graph, indicating missing pixels. There appears to be a greater amount of white wjhich would indicate over-exposed parts of the image.
Both histograms have helped me to understand what is happening in the two images. It is very clear to see that the loss of colour detail and tones in the JPEG has resulted in overexposed areas, where as the raw file has a more compacted graph, with pixels that are next to each other and no gaps.
The image above was taken in a shaded street in Dubrovnik’s old town area. When I opened the raw file in Photoshop there was some shadow around the chairs that lacked detail. I increased the exposure, contrast and saturation to enhance the colour and detail in the foreground.
The JPEG version of the shaded Dubrovnik street had the same processing as for the raw file. Exposure, saturation and contrast were modified slightly. One obvious difference is that the white background on the JPEG appears over exposed with some of the brick detail lost on the wall of the building at the end of the street. The colours also look paler than those in the raw version.
Again the histogram for the raw file shows pixls pushed tight together. The majority are towards the darker side of the histogram.
There is a greater contrast with the JPEG histogram. It has a wider tonal range but the proportion of each pixel is less. There is also a spiky graph produced where pixels are absent. The JPEG histogram also shows at the very brightest end of the graph, which corresponds to the overexposed white areas in the image.
The above image is a long exposure of a street scene taken at night and lit by artificial lights. The highlight clipping warning in Photoshop showed that the centre of the lights on the lamp posts were over exposed, so I increased the recovery and decreased the exposure. I also reduced the amount of shadow to counteract the reduction in exposure.
When editing the JPEG version I found I was limited to less options than in raw. I was unable to make use of the recovery feature so I reduced the brightness and contrast slightly. The raw version appears more defined and brighter, but the difference isn’t as obvious as with the first two examples.
Unlike the previous 2 images the raw file histogram shows a higher dynamic range compared to the JPEG. There is a greater distinction between the darker areas, whilst there is a lack of tonal range in the JPEG.
Reflection: Raw v JPEG
Ever since I had first heard of raw I knew that it produced a higher quality image, but comparing the histograms for both types of image has revealed to me just how different the quality can be. I didn’t realise how the dynamic range can be so different between the two. Shooting in raw enables me to have greater control over the image, using my Mac’s processing power instead of the camera’s. Raw files have a greater richness of detail and colour range. Although Raw files take up more storage space than JPEGs I feel that it is worth it due to the better quality of the image and the safety net of being able to alter more aspects of the image. However I must make it part of my workflow to delete unwanted images to free up memory space taken up by large raw files.