The problem then becomes seeing that point clearly.
The nice thing about a Siemens star is that no matter how big it is in the frame, the goal is always to make that soft center circle as small as possible. This is what you’d see when back focusing, although typically that circle would be a bit bigger when viewed through a typical HD camera. That shows the limiting resolution of the process I’ve put this image through in order to post it on this page. Notice how the Siemens star appears to have a soft round circle in the center. I’ve acquired a Siemens star graphic from Wikipedia in order to illustrate my points. The Siemens star is very good at revealing the focus setting at which it is sharpest: just adjust back focus until that blurred circle at the center appears to be the smallest it can be.Īs I am occasionally an idiot I neglected to shoot a Siemens star while testing the DSC charts in this article. The points of the star touch only in the center, but most systems fall short of the resolution necessary to see that point so the loss of resolution causes the lines appear to blur together into a circle around the center. The Siemans star has been the back focus aid of choice for decades.Īccording to Wikipedia, the Siemans star was originally developed to measure the resolution of imaging systems. Now they’ve done it again, but this time for focus.Īs back focus must be set using a lens of short focal length, it can be difficult to find a focus target of appropriate contrast and detail in so wide a shot. The first time I used a DSC Chart for color analysis I was completely blown away by the thought and cleverness that went into designing the Chroma Du Monde.
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