DOF calculation

Started Nov 9, 2012 | Discussions thread
jrtrent
Veteran MemberPosts: 3,102
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Re: Reference Viewing Distance for COC Diameters Commonly Used
In reply to Detail Man, Nov 9, 2012

Detail Man wrote:

Here is the information (below) that I have based my assumptions and statements on. Have a look at the related text on the document pages 1 through 4, and let me know how you interpret the text.

As Mr. Conrad points out, the "correct" viewing distance formula he gives is solely for the purpose of vewing the final image with correct perspective, not the distance people would normally view a particular-sized image at.  One site, for example, noted that a 20 X 30 inch print taken with a 24mm lens on a full-frame camera would need a viewing distance of about 20 inches, while the same size print and camera with a 200mm lens would need a viewing distance of about 14 feet.  Mr. Conrad's statement that it is more common for people to view an image at the near distance for distinct vision, which he puts at a bit under 10 inches, also seems counter to personal experience and casual observation at picture galleries.

People tend to view a picture at what seems a comfortable distance from the image based on its size, not its taking lens or the closest distance they can focus at.  The definition of "comfortable" varies, but the closest recommended distance I've seen is at least the diagonal of the image itself; more common is 1.5 times the diagonal, and some put it at 2 times the diagonal.

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