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Sunday 24th August


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Exactly what is photographic exposure and why does it matter?

Exposure is a massive massive subject. Ultimately it encompasses the whole world of photography and is relevant to everything in it. Photography is interested ONLY in light photons and how they hit the world and bounce off objects and how we can use science to display it on a recordable medium of choice. Wood, skin, film, cloth, digital sensor etc.

When we talk of exposure in camera, and in a more everyday sense, it can be described as being the amount of light intensity that falls on your cameras sensor or film. The camera sensor in your DSLR is a fingernail sized plate which is made of millions of tiny electrical diodes called photosites, which receive a greater or lesser amount of exposure to light, according to the scene that is being shot. Those photosites receiving a stronger light intensity will be interpreted in the final picture as the lighter areas of the picture, and also those receiving less light intensity be interpreted in the final picture of those areas which are dark. Sensors are likened to solar energy cells. The light energy produced is converted into an electrical charge which is then read by the cameras computer.

If a camera sensor contains for example 10,000,000 tiny light-sensitive photosites it can be said to be a 10 megapixel sensor and of course the greater number of megapixels the camera has, the greater its ability to produce a smooth diffused greyscale tone from pure white to pure black. A smooth transition of the these 255 possible shades will produce a clearer, smoother, better picture with increased print quality. Throw in colours on top and you have millions of possibilities. Of course the trick is to get exactly the right amount of light in the way you want it.

1.There is no such thing as a ‘ correct' exposure. There is only a 'good or bad' exposure relative to your own vision of the shot of you are taking. As in all artistic or creative pursuits there are only opportunities, choices and outcomes.

2.Editing software is just great. But there is NO better policy than attempting to get exposure spot on or damn near to what you wanted in camera first. It improves your eye no end, your artistry is affirmed by knowing you are seeing the world photographically and you are in less danger of swinging curves about in photoshop and damaging the image.

3.A shot does not have to be technically perfect to be ‘correct’. There is many an interesting shot that breaks all the rules. Bring it on ! But if you're going to be Picasso - learn to be Turner first. You can only credibly break the rules when you know what the rules are in the first place.

4.You are NOT GOD ! What ever your take on God might be, he’s not going to give you any concessions on psychics, universal laws, theories of relativity, inverse square laws, you name it. So you are bound by the limitations of light and camera.You cannot do the impossible with your camera, so to learn trickery and deception is what its all about.

5.Think VISION. Your vision of the shot. Take your time, if there is some spare. Work it out. Get it in place in your mind. SEE the possibilities. What type of shot do you want it to be. narrow depth of field?, wide landscape?, blurry busy market place? and adjust in your mind the options your camera gives. A thought out exposure is a better exposure.

6.That means you have to really know your camera knobs and dials. Initially understand how exposure is dependent on how much light and for how long. But after that, it’s every man for himself as far as creativity is concerned. The more your camera and lens have in terms of choices will dramatically effect your ability to expose how you wish. If you leave it all to auto, you’ll be sorely disappointed. Maybe not today, but definitely tomorrow. The camera has no soul. It is not your friend, it is a tool.

7.The HISTOGRAM however on the SLD on the back of your camera, is your friend. ( sort of ) Get to know its graph, its strange looks and shapes and understand you are looking at the nuts and bolts structure of your image. Start to think of your images not just as the picture you want to print or post, but as a mesh of pixels of mathematical information. Clinical yes, but the romance comes later at the champagne gallery viewing; for now think science and precision.

8.The photosites on your cameras sensor can only react to a finite amount of light. Once the limit is reached it cannot go any higher, resulting in a total white ‘bunch up’ to the right of your histogram. The same is true of the blacks on the left, where conversely, no information is recorded. Learn to READ the histogram and make adjustments accordingly.

9.Be a CONTROL FREAK. Use your F stops with aperture, your time with the shutter, the sensor sensitivity with the ISO, Add in some exposure compensation, some external light source, some high dynamic range and a host of other ways to manipulate your light as it enters your camera, and hey presto, you're a master of exposure.

9½. Obviously each one of these points is a huge subject in itself, and we are going to explore them all and many many more over the weeks in my blog.

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