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dudler’s latest blog : thinking about it

dudler's latest blog : art, snap or reportage

Thinking about it

28 Mar 2021 10:35AM  
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Many years ago, I reported to a maths graduate from Cambridge University at work. He is one of the most straightforward people I’ve ever met, and I learned a lot from him, professionally and generally. He believed in thinking about problems, carefully, ruthlessly, and checking every fact and assumption. When I left our mutual employer, I brought home a few outdated documents he’d written, and they are models of clarity and also of intellectual honesty.

What’s this got to do with photography, you may ask. Well, it’s the fact that Mike believed that it is always possible to solve a problem by getting sufficient data about it, and thinking hard. Actually, you begin by thinking, so that you can gather data that is likely to be relevant; and later on you may conclude that you need more data before you can continue with the thinking.

So, if you want to solve a photographic problem – shall we say, decide the likely correct exposure for the moon – you start from what you know. What light source is illuminating the moon? Yes – the sun. And you already know a lot about the strength of sunlight 93 million miles from the sun. Combining this with the fact that the moon is made of rock, a first approximation for exposure would, therefore, be 1/125 second at somewhere between f/11 and f/16 at 100 ISO.

At this point, more data – try it and see what happens. In practice, you will need a shorter shutter speed with a very long lens, but you can either open the aperture or raise the ISO to compensate. And then you can fine-tune things.

How about that phenomenon called ‘rolling shutter’ that you’re supposed to get when you use an electronic shutter – the ‘silent shutter’ mode that many mirrorless cameras have. I was wondering about it as I went for my morning walk yesterday, and decided that step 1 was to get real data for myself, by taking a picture of a moving object with an electronic shutter.

So I engaged silent mode on my camera, and got the result you see at the top. Definitely noticeable distortion (this with the car moving at around 30mph, and a shutter speed of 1/400), uneven across the frame, so that a simple skew correction won’t sort it, which surprised me (anyone who can explain why, please do so!)

I wonder if turning the camera upside down would make the car lean forward in a Looney Toons sort of a way? I don’t do enough action photography to be very interested in taking this further, and shutter noise isn’t relevant to motorsport: but if I photographed wildlife, I’d be doing more experiments in very short order, and possibly queuing up for Sony’s new Alpha 1, which apparently minimises the effect, as well as offering 30fps. As one frame every couple of seconds will do for what I shoot, you can have my place in the queue.

So, if there’s a particular photographic issue worrying you, think about it. Decide whether there are any practical experiments you can carry out to get more data. And consider looking in a traditional photographic textbook, as well as on the interwebs… Or ask here at EPZ – though you’d be well advised to do as Mike would have done, and check the thinking behind anything other people tell you. Even me.


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