Should we process our photographs? Recently, I invited people to give their views and opinion on two images. The first, an unedited RAW image straight out of the camera. The second, an edited copy of the same image.
First of all, photography, like any art form, is subjective. As a result, views and opinions differed. Some preferred the edited version, whilst others liked the unprocessed. Let me begin by saying that there is no right or wrong answer. Everyone is entitled to their opinion, preferences, and tastes.
My aim is not to question individual preferences. I, for instance, do not appreciate cubism. The purpose of this blog is to provide legitimate reasons why post-processing is important.
RAW vs Jpg
For this purpose, let’s first take a look at the difference between RAW and Jpg. Contrary to popular belief, a Jpg is an edited image. Setting the picture quality to Jpg on your camera does the following:
- Compresses and processes the file.
- The camera applies a certain amount of sharpening to the image.
- The camera also adjusts the contrast and saturation of the image.
As a result, you do not need additional software to process images. Although this may seem ideal, there is one major drawback to this. In-camera processing leaves little control in the hands of the photographer.
On the other hand, when set to RAW, the camera does not apply any adjustments whatsoever. Instead, the photographer is left with the task of processing the image. This is great news when you consider some of the shortcomings of DSLR’s. For this reason, RAW images look ‘flat’ when viewed as opposed to Jpg’s
For a more detailed look at the differences between RAW and Jpg read here
The Importance Of Light…..
Although modern DSLR’s are indeed technological marvels, they pale in comparison to the human eye. Ever hear of Pupillary Light Reflex? No? Sure you have. It happens instinctively without us giving it a second thought, and its all got to do with light intensity. In bright light, our pupils constrict (myosis), and conversely dilate (mydriasis) in the absence of light. In other words, our pupils regulate the amount of light entering the eye based on the intensity of light. When our pupils constrict they reduce the amount of light. Conversely, our pupils dilate to allow more light entering the eye.
Now think of the aperture as the cameras’ pupil. It’s either wide open (f/2.8) allowing heaps of light through, narrow at f/22 allowing very little light through, and everything in-between. Unlike our pupils, we have to manually adjust the camera’s aperture based on the available light. For this reason, it is generally a good idea to use a wide aperture when doing astrophotography.
Try this exercise in your living room (preferably during the day)….Sitting in one position look around the room, then out of the window, then back into the room. No problem there, right? Now take your camera and take a shot of the room from the same position including the window. Take a look at the resulting image, and depending on the aperture set:
- The room is evenly lit but the window is totally blown out, or
- The room is dark but the window looks evenly exposed
Our pupils constantly, and instinctively, adjust depending on the intensity of light. Cameras cannot do that…..We need to adjust the settings manually. Sometimes this requires taking multiple shots at different exposure values.
Post-processing gives us the ability to blend bracketed shots seamlessly to produce a more accurate representation of the scene.
How The Camera Measures Light
In most instances, we rely on the cameras light meter to guide us into making our exposure decisions. If you’re shooting in any of the auto modes this might not be something that concerns you…..but it should.
Let’s take a look at how our cameras measure light. Without getting too technical let’s look at what Canon cameras refer to as ‘evaluative’ metering and Nikon calls matrix. In both cases, the camera measures the reflected light in a scene and tries to come up with an exposure value that will balance both the bright and dark areas of that scene. This is great in an evenly lit scene, but can you see the potential issue here?
This becomes problematic when there are objects, or parts of your subject, with different levels of light and intensity. Simply relying on an exposure based on an ‘average’ will, in turn, result in an ‘average’ image. It is impossible to correctly expose for each and every tone within an image in a single shot.
That’s why we shoot in RAW, and why we need post-processing. This allows us to adjust the tones of an image so we can best represent the scene as we saw it.
Chromatic Adaptation
This is how Wikipedia explains the term chromatic adaptation
‘Chromatic adaptation is the human visual system’s ability to adjust to changes in illumination in order to preserve the appearance of object colors. It is responsible for the stable appearance of object colors despite the wide variation of light which might be reflected from an object and observed by our eyes.’
Our eyes may be sensitive to colour, however, our camera sensors are not. The camera only sees tonal values (brightness in a scene). The tonal values range from pure black to pure white with all the different shades of grey in between. Instead, to reproduce colour, the sensor needs a filter array on top of it which will filter out wavelengths of the two other colours.
Familiar with the term RGB (red, green, blue)? The RGB Filter which sits on top of the sensor usually has one red, two green and one blue pixel. Each pixel filters out the wavelengths of the two colours that are not present in that pixel. To put it simply the red pixel filters out the green and blue wavelengths so that the pixel on the sensor can only capture the red wavelength.
Other factors to consider are the imperfections in the optics which can cause colour casts and limited colour ranges.
In Conclusion
Even top-end DSLR’s are unable to match the effectiveness of how the human eye reacts to light and colour. Camera sensors are getting better. Perhaps one day the need to bracket, colour correct, and adjust tonal values in post-processing will no longer be necessary.
But for now, post-processing an image is absolutely critical and should be part of every photographer’s workflow.
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