BetterPhoto Q&A
Category: Problems with Images

Pentagon Shapes in Direct Sun and Moon Shots

	Sunset at Eleven Mile Reservoir Sunset lacking sun Christie E. Kleinert
	Moon at sunset over water best effort at focusing moon Christie E. Kleinert

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December 06, 2001

However, whenever you take photos of a light source, you are never going to get a sharp point. It's always going to flare. (I believe the term is lens flare, but I could be wrong)

I think, though, more likely in your case, it's actually because the sun/moon is way over exposed. Because the surrounding black is so dark, the camera wants to expose the film more, until it has an average of 18% grey on your film. Of course, that means that any bright points are going to be a blurry blob of light.

To avoid this, you need to spot meter from the moon (good luck with the sun! - actually, don't try it. I've heard that it's possible to damage some light meters by pointing them at the sun) The down side of this, of course, is that the rest of the photo will then be pitch black. It's an unavoidable consequence because of the thin exposure latitude of film. (IE, film cannot see both very bright and very dark like the eyes can)

Hope this helps.

Ken.

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December 07, 2001

Christie

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December 07, 2001

Wide open, the aperture is formed by the round lens barrel. As it stops down, these blades form a polygon shaped aperture. Many of the Canon EF lenses for the EOS system have five blades and these form a pentagon shaped aperture at anything but wide open. When a very small and very bright light source (compared to the rest of the image) is within the field of view, the light from it bounces around inside your lens and cause a bright spot in the shape of the lens aperture diaphragm. This is called "aperture flare." Filters won't do anything to eliminate it. In fact, they can make it worse or create additional problems with the added air/glass surfaces for light to reflect from and bounce around inside your lens.

Some lenses are more prone to aperture flare than others; it's a function of lens design related to formulation of the glass elements and groups, anti-reflective optical coating(s) on them, location of the aperture diaphragm inside the lens, and the construction of the lens barrel (placement of light baffles and effectiveness of the "flocking" to reduce internal reflections).

Suggestions:
(1) Take all filters off your lens under these and similar conditions that have very bright small sources of light either in view, or just outside of view but still illuminating the front of the lens. Use a filter *only* if it's a specialty type desired for artistic reasons (e.g., graduated neutral density, "star," multi-image). The desire for the special effect should be strong enough to outweigh the risks created by adding more air/glass surfaces for light to reflect from.
(2) Use a lens hood! This helps keep off-axis light sources outside the field of view from adding to the problem.
(3) Look carefully in your viewfinder for this effect. You won't see the pentagon because your lens is held wide open until you trip the shutter, but you should see a round spot. In the viewfinder, they're very small, dim and easy to miss; not nearly as prominent as they end up in the enlarged photograph. If you spot one and it's objectionable, try recomposing to see if you can eliminate it and still maintain a desirable composition. If it's from a source outside the field of view, and you already have the hood on the lens, use something to shade the lens with to block it. I've used my hand, hat, gray card, a coat hung or propped up on something (or held by a friend), and on one occasion a large maple leaf. Just ensure whatever you use doesn't end up in the field of view!

-- John

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December 09, 2001

For the sunset, wait till the sun is really low on the horizon. Meter from an area next to the sun excluding the sun from the field of view. Set the reading and then recompose your picture.

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December 10, 2001