Aperture Starring

009_CarlsbadFootbridgeLightsThe stars come out at night … in more ways than one.

Most stationary light sources are seen as bright round spots to the naked eye.

But in an expanded moment, lights turn to stars through the eye of the camera.

Aperture openings are not round. They are polygons, constructed by overlapping blades that make up the diaphragm. Where the blades cross, corners are formed. When light passes through the aperture, the rays bend at the corners, and voilà … stars are born.

The number of spikes per star is twice the blade count in the diaphragm, i.e. two spikes per corner.  For an even number of blades, twin spikes may appear as a single spike.

As aperture size decreases, starring spikes become thinner and sharper. As exposure time increases, starring spikes grow longer.

Not all light sources are created equal. Starring of direct light sources is the strongest. Starring of diffused or covered light sources is weaker, and sometimes completely absent.

Starring varies with different lenses. How lens elements bend light plays a significant role in the formation of stars. Experience with a given lens is the best way to know what to expect.

You typically won’t see starring in your monitor or viewfinder. The effect emerges with time.

The recommended aperture setting described in my post aperture settings is a good starting point for Goldilocks starring … not too weak, not too strong.

IMAGE : Footbridge & Lights, Carlsbad, NM

This footbridge has crossed the Pecos River for as long as I can remember. As a kid I ran across it many times. It seemed endless.

I wanted to capture the length of the bridge stretching to the opposite shore. I placed my tripod on top of a nearby bench for a high angle shot. I stood on a step ladder to frame the image through my viewfinder.

This was taken on a clear winter night. The water was perfectly calm so the reflections were as intense as the lights.

The still, dark water made the bridge seem to float in mid air, even though it actually floats on the water.

This image is the result of a 30 second exposure shot at f11 with TMAX 3200 film. This created crisp starring of the light sources and reflections.

The smaller aperture was chosen for a long depth of field. I also shot this at f16 but found the starring to be too strong, overwhelming the importance of the footbridge.

IMAGE TINT : GallerySelenium

In the darkroom a slight Selenium toning creates a purplish tint in the darker tones and cools the highlights. I duplicated this tinting effect to emphasize the look of the starring in the brisk night air.

This B&W image was tinted in Adobe Photoshop with an ICC Profile I generated from my Mac App SuiteProfiler. The Profile was derived from the “GallerySelenium” Color Map created in SuiteProfiler.

Click these buttons to download the ICC Profile and SuiteProfiler Color Map:

EXERCISE : Aperture Starring

Compose an image containing light sources with your favorite lens.

Capture a wonder of stars via multiple bracketing sessions, each with a different aperture setting. Record your exposure information for each shot.

Examine the resulting images to see what amount of starring makes for a balanced image. Pay attention to how starring is affected by exposure time and aperture setting. Take note of what to expect for future image making.

Be sure to review the Safety & Precautions page.

NEXT TIME : “Light Metering”


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4 thoughts on “Aperture Starring

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