Wednesday 5 November 2008

Wedding Photographer in Kent - Focusing Tips

For further photography-related information check out my compendium of tips.

I've had a couple of readers ask me how I get sharp images in low-light conditions. The following are some points to consider when focusing:
1. Focus on points of good contrast - eyebrows and eyelids for a portrait shot, for example.
2. The central focus point is the most accurate and, with lenses of widest aperture f/2.8 or less, additional sensors come into play (see diagram above). In low-light conditions I use only the central focus point.
3. The outer focus points are fine with good lighting conditions but I find that they are not as reliable in low-light conditions.
4. I tend to avoid focusing and then recomposing at wide apertures. Depth of field (DOF) can be extremely small and recomposing can leave your subject out of focus (see diagram above). This is a judgement call though, since it depends upon the precise aperture, and very significantly, distance to the subject. You need to develop an instinct for judging DOF.
5. As a result, when I encounter tricky conditions, I often 'shoot and crop'. Use the central focus point and take the shot without recomposing. Crop during post-production to adjust composition. The greater resolution of the 5D Mark II will be invaluable for this method.
6. Light levels can drop so low that auto-focus is unable to work. In this case an AF assist beam from a Speedlite or the ST-E2 transmitter is necessary. If your eyesight is very good, you can try manual focus.
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