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Steven Gangstead's profile photoTom Rose's profile photo
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What an interesting effect. I can't figure out why the stamen isn't in focus. The base of it seems to be. Does this lens have macro capabilities?
 
I think the effect is just a surprisingly shallow depth of field at the biggest aperture. The lens comes with a detailed chart of the measurements of the depth of field for each aperture and a range of focus distances. at f/1.4 and focus distance of 18" the depth of field is 1'5-7/8" to 1'6-1/16". That's 3/16 of an inch. At 3 ft focus distance the depth is 1". At 20 ft depth is 4' 2"

It must have taken the most OCD Japanese person ever to fill in this chart, unless these are calculated values.
 
Also, "depth" is subjective the way I understand it. There is a smooth roll-off. I wonder how they define the edge, and I wonder if different mfrs. use different standards. I can't think of a way to even objectively measure focus. Maybe the apparent width of a razor line measured in arc-length?
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