Friday, 5 June 2009

Why we need to post-process

The Hut

You don't see the image that hits your retina. Neurons in the eye start processing light (or rather, light's effects on the 'sensor': millions of rods and cones in the retina) into data well before that data reaches the brain and is processed even more into the information the brain uses to construct the image of what's in front of you. And it's that constructed image that the brain sees rather than the real world. And, as I shall be talking about a lot more in future articles, the difference between what you see and what's really there is often quite dramatic. So much so that I'm tempted to put quotes around the words 'what's really there'.

I was very much aware of this as I was walking with a friend through a small village in Surrey, on the way to dinner at my all-time favourite pub. My Canon 40D with its 10.2 megapixel sensor and Digic III processor are far, far more primitive than the human eyes, nervous system and brain. What appears to me as a rich, complex environment of light, shade and colour is transformed by my camera into a small, flat, lifeless pastiche of the original. This is why we post-process our photos just as the brain post-processes the data collected by our eyes.

And this is why the camera doesn't try to second-guess how our individual brains work by doing too much post-processing. Rather it does the absolute minimum: giving us the data as the sensor has produced it if we are shooting RAW, or tweaking the saturation, contrast, colour balance and sharpness to suit our tastes if we're shooting JPEGs.

Of course, we're trained from a very early age to interpret photographs and to decide whether or not a photo accords more or less with 'reality' which, translated, means 'what my brain thinks that it remembers of the way it was back then'. This is why some photographers insist that their small, flat, lifeless images are 'realistic'. It's not that they see the world in that way - I'm sure that, to a large degree, their world is as rich, complex and colourful as mine. It's just that they've learned to interpret photos in that particular way.

So as we walked up the lane to the pub, I knew that my camera couldn't do justice to the scene I saw by the roadside: a simple wooden hut by a field, with the background lit by the glow of the evening sun. But then the camera never can. So I raised it to my eye, metered, composed, and pressed the shutter release, knowing that I could at least tweak it into something that might remind me of what my brain thinks it remembers of what I saw back then.

Imported version

The image above is as it appeared when first imported into Lightroom. Quite a difference, don't you think? Of course, the finished image at the top of this article isn't any more realistic than the starting-point image above; but I have to admit that I like it a lot more.

My first job was to get the lighting the way I wanted it. I tweaked the Exposure, Fill Light and Contrast several times until I got it right. The end result of this stage was: Exposure -1.24, Fill +100, Contrast +100. I usually take care of cropping and straightening right up-front but I forgot this time, so that was my next job and the result of all of this first stage is below.

After exposure, fill, cropping

I'd brought out the detail in the hut quite well and the sunlight on the fences and field in the background was now starting to look good but the sky wasn't as good as I remembered it, so I added a graduated filter with the Brightness set to -75.

Graduated filter added at the top

I often use graduated filters to produce the depth cues of light and shade that can really give a feeling of depth to a photo. With a picture like this one, with a fairly-well-defined horizon line, you can achieve this with graduated filters from the top to the horizon line, and from the bottom to the horizon line. I added a second filter at the bottom with -85 Brightness, -100 Clarity and -100 Sharpness. This has the subtle effect of making detail at the bottom edge less important than the detail at the horizon line.

It was looking a lot better but the overall light wasn't quite right. I went to the Tone Curve and upped the Highlight Tones to +93, the Light Tones to +43 and the Dark Tones to +17, leaving the Shadows untouched at zero. With a smidge of sharpening and a light post-crop vignette, it was almost finished.

Almost done

I could have left it here but, while I'd pulled back a lot of the detail and depth, and balanced the light a lot better, it was still looking a little ordinary. The final touch was to go to Lightroom's Camera Profile section and select the Camera Landscape profile. That really brought out the late-evening blue of the sky and rich warmth of the orange sunlight. The end result is at the top of this post. Quite a bit better than the start image, don't you think?

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