Stars and stripes

A technical post today—after all, this is a technical learning blog.

When you see a picture with details like this (from my Mac’s background picture)…
…then you know that a small aperture was used for this photo.

The only way to get the sharp star shape you see here, you see, is to use a small lens opening. Meaning a small aperture (“aperture” means “opening”). Meaning a high “f-number”. In this case, I used an aperture of f/22. The reflection is from my flash, which was aimed straight at the car.

I have other clues. Other detail in the picture includes:
That is at least proof that the lens was not wide open. If it had been, the polygon at the top would have been not a polygon, but a circle.

Other notable facts: the lines (there’s your stripes) all converge where the sun is. And finally, the lens is probably an expensive one: the polygon has seven sides. Most have five or six sides. The more sides, the more the lens approaches the ideal, a circle. That ideal gives you great bokeh.


THE TERM BOKEH, by the way, when used correctly, is used to describe the quality of the fuzzy background. “I want bokeh” is not a correct term: when people say this, they usually just mean “I want a blurry background”.

Correct usage: A lens that has great, beautiful bokeh is a lens whose blurry background is wonderfully smooth and evenly creamy. A cheap lens, on the other hand, has bokeh (especially “fully open” bokeh) that is more like clotted cream: much less smooth, more uneven. I can tell a cheap lens from an expensive one immediately, and I bet you can, too, when you see them side by side.

And that concludes today’s lesson. For more, attend one of my many upcoming workshops: scroll down to read more.


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