When photographing certain subjects or scenes, we want all of the image in focus. This is often the case in product photography and landscape photography. We want sharpness from front to back with no area of the product or landscape out of focus.
This can be tricky to achieve, but there are a number of techniques that can be used to achieve a very large depth of field (the amount of the image in focus).
Something that you might come across when reading camera / lens reviews, or discussions, is talk about equivalent focal length and equivalent aperture. For example, a 50mm f/1.4 lens for a micro four thirds camera might be described as being a 100mm f/2.8 equivalent lens.
But what does this really mean? I have already discussed equivalent focal length in the article Photography Basics – Focal length, though I will cover it again very briefly in this article. But mostly I want to look at the idea of equivalent aperture, and how this relates to depth of field and the amount of light gathered.
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