frog garden figure in snow

The Proper Exposure of Raw Images Results in Noise Reduction

In this blog I am going to avoid the many intricate details of using photo software. There are so many Photoshop / Lightroom gurus out there who seemingly spend every waking hour studying these and other programs that any effort I made would be superfluous. However, there is a need, I believe, to comment on some general guiding principles which are lesser known.

One area I often see where misconceptions arise is the exposure of raw images in-camera. Even some professionals believe they should “protect the highlights” as they used to do when exposing film, and clip the highlights, instead of  “exposing to the right” in your histogram as I did in this “froggy” shot. Half the raw file tonal levels your camera can record are in the brightest stop! Your camera is simply counting photons in a linear fashion at this stage, with no application of a gamma factor (unlike film). So as we progress towards the shadow end, each “stop” of data is being halved, leaving far fewer brightness levels assigned to darker tones. So capture the maximum highlight tones to start.

A related area of confusion for some concerns “Picture Styles” as they are called in general. These are settings you make in-camera and can be somewhat misunderstood. Because photographers in general know that raw files are “developed” in software settings/sliders for output to some other final file format (TIFF, PSD, JPEG) it is understood that the raw file remains intact and untouched by these software settings or as Canon calls them in DPP 4 “recipes.”

However, because sliders are set to zero when raw files come into processing software, one could be forgiven for thinking nothing has been done to the raw files as yet. However, we are looking at a jpeg representation of the raw file at this stage, and even before in camera, as Bruce Fraser explains. The crucial point being that the “Picture Style” that was set in camera is a manufacturer specific set of patented instructions or “recipes” if you will, which are ALREADY baked into the jpeg representation of the file. These include the colour science I referred to in my previous blog, gamma, noise reduction, lens correction etc. So the various “Picture Styles” (Landscape, Portrait, Neutral etc.) have already set up a definite look before you even start post-processing. This can be helpful or a hindrance depending on what your final processing goal is. For instance “Landscape” will have more contrast and sharpening and strongly saturated greens and blues, but “Portrait” softens contrast / sharpening and ramps up reds for more pleasing skin tones.

A related point re: jpeg representation of the raw file being baked in, is that Bruce Fraser told us that this usually involves a strong “S curve” being applied to the raw data. A consequence of this means that your jpeg may show the highlights as being blown when they actually may have 1/2 to a full stop of “headroom” – the highlights in the raw file are not really blown. So depending on the brightness range of the scene, there may be more room for an exposure boost to capture every possible brightness level in the original “linear” raw file capture. If the brightness range of the original scene is below eleven or so f-stops (the average brightness range capture today for most modern cameras), there is likely present some extra potential for more exposure. The point being that capturing the maximum amount of brightness levels will produce a file with less noise and more detail (tonal levels) in the shadow areas.


Re: my reference to Bruce Fraser – my first edition of this post had a link to a paper by the well known late raw file guru Bruce Fraser in which he explained the raw file, and some would say for the first time. However, the link disappeared. It was originally on Adobe’s website. If you can find it by all means have a look, as I did. The info in this blog is straight from Bruce Fraser who I read years ago, but in far less detail.