Overlooking the obvious.

Recently I’ve been looking at shooting images against everyday backgrounds but blurring out the background. A pretty straightforward photographic technique used extensively by photographers everywhere and one that I think gives a good look, particularly with black and white images.

It is a technique that does require some photographic knowledge but nothing beyond the realms of most photographers who are able to use a camera with manual settings and an understanding of the principles of how to set up a camera to produce a shallow depth of field. In simple terms, the way to do this is to set your camera lens on as wide an aperture as possible or, open its eye as wide as possible. However by doing this you need to make other adjustments to compensate for the extra light entering the camera and in bright conditions it isn’t always possible to easily compensate for the extra light entering the camera.

My way round this in the studio was to add a neutral density filter to the front of the lens, basically adding sunglasses to the camera. As this reduces the amount of light entering the camera, the “eye” of the lens has to be opened more to get a correctly exposed image and this will give you the conditions needed to achieve a more shallow depth of field. In simple terms, the image will be in focus for a shorter distance in front and behind the subject.

All very simple you might think, and so did I until I looked at some of my recent images enlarged and discovered that a few were not as sharp as I would have liked. I blamed the filter, which was a reasonably inexpensive one, but then a chance conversation with another photographer highlighted another possibility.

When photographing people the general rule is to focus on the eye, making sure the nearest eye to the camera is in focus. With modern cameras it is fairly common to use its built in autofocus system with very good results in most conditions but by trying to get a shallow depth of field I had potentially created a problem for myself. Focusing as normal, I had focused on my models eye, locked the focus and then recomposed the shot by making slight movements of the camera. All fairly standard stuff but this is where there was a potential problem that I just hadn’t thought about. Normally, recomposing an image is not a problem but when you are trying to achieve a shallow depth of field you are trying to reduce the distance that is in focus in front and behind the point of focus and in some cases this can be reduced to a few centimetres. Even a slight movement of the camera to recompose an image will result it the distance to your focus point changing and under these conditions that change of distance could be enough to render your focus point out of focus.

Fortunately there was no major harm done. The shoot had been arranged to test my ideas, most of my images were usable and I had highlighted something that I had simply not thought about before. Sometimes you just overlook the obvious.

Was it the quality of the filter or was it my focusing technique? That’s for the next shoot but it just shows how sometimes it is so easy to overlook the obvious. So, we move on, these problems will be eliminated but I’m sure there will be more to come because I am looking at new ideas, trying to improve my photography and if you don’t try new ideas and make a few mistakes along the way, how are you going to improve?

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