11-19-2011, 03:20 PM
Taking some portaits of kids last weekend I found it quite difficult to get tack-sharp focus on their eyes... that's partly due to the autofocus (back-focus) problems I've been having with my D7000, which is now with Nikon for calibration.
That got me wondering about calculating depth of field. I know there's a depth of field scale on my 85 f/1.8D but it's the only one of my lenses that does have, and I don't know if it's accurate when using with DX sensor... is the depth of field the same?
When it's stated that the depth of field of this lens wide open (f/1.8) is equivalent to f/2.8, is it because a 130mm focal length lens at f/2.8 has the same depth of field as an 85mm lens at f/1.8? How is the aperture equivalence calculated?
Back to the portraits: how do I calculate what aperture will give me a 30cm / 1 ft depth of field for different lenses (50mm, 85mm) at different distances, used on a DX sensor?
That got me wondering about calculating depth of field. I know there's a depth of field scale on my 85 f/1.8D but it's the only one of my lenses that does have, and I don't know if it's accurate when using with DX sensor... is the depth of field the same?
When it's stated that the depth of field of this lens wide open (f/1.8) is equivalent to f/2.8, is it because a 130mm focal length lens at f/2.8 has the same depth of field as an 85mm lens at f/1.8? How is the aperture equivalence calculated?
Back to the portraits: how do I calculate what aperture will give me a 30cm / 1 ft depth of field for different lenses (50mm, 85mm) at different distances, used on a DX sensor?