How can I keep both the moon and a foreground tree in focus?

Asked 3/11/2017

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I want to photograph the moon with a tree or other object in the foreground using a Sony 55-210mm lens, but I can’t get both subjects sharp in one shot. I’ve already tried stopping down as far as f/36. Is there a distance or hyperfocal setting that will let both the foreground and the moon stay in focus, or is a different technique needed?

Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0

Photography Stack Exchange contributor

9y ago

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You'll probably never get both acceptably sharp in the same exposure.

What we call Depth of Field (DoF) is just an illusion, although it is usually a very convincing one. But it breaks down with certain subjects. Astrophotography is one subject where we can tell the background is not as sharp as we expect when using DoF formulas and calculating the hyperfocal distance.

There's only one distance from the camera that is in sharpest focus. Everything in front of and behind that field of focus is blurred to one degree or another. DoF is what we call the range in front of and behind the field of focus that appears sharp enough to fool our eyes and brains into seeing things as sharp.

You're fighting several technical limitations with the image you are tyring to take that are very difficult to overcome.

  • One is that the moon is 250,000 miles away, give or take a few thousand. Your tree is much closer. While in theory it might be possible to place both within the near and far limits of the DoF, neither will be as sharp as you probably want them to be.
  • To get a very near hyperfocal distance you must use a very narrow aperture. This leads to diffraction, which causes everything, even the point of sharpest focus, to degrade due to the higher percentage of light rays reaching the sensor that are being scattered by the edges of the aperture diaphragm. For most FF cameras, anything narrower than about f/10 or f/11 starts to show the effects of diffraction. The smaller the sensor and the pixels on it, the lower the aperture at which diffractions begins to affect the image. This is called the diffraction limited aperture (DLA).
  • The other disadvantage of using a very narrow aperture is the resulting increase in exposure time needed. Even if your camera is solidly mounted on a tripod or other stable platform and not moving at all, the moon is moving across the sky at a rate of its own diameter every two minutes. The tree is probably not totally stationary either. Any wind will cause motion in the leaves and branches.
  • The moon is lit by direct sunlight. It is very bright. Unless it is very low on the horizon the illuminated parts of the moon are properly exposed at about EV 12 (e.g ISO 200, f/8 , 1/125) or even a bit higher. Your tree is probably nowhere near as bright if it is nighttime. Unless you only want a silhouette of the tree you're probably going to need an exposure values about 15 stops slower at EV -3 (e.g. ISO 200, f/8, 256 seconds) OR put some light on the tree from an artificial light source. Even if you could get both the moon and the tree in proper focus the moon would be totally blown out if the tree were exposed to reveal any degree of detail.

There are a couple of strategies you can use to overcome these obstacles:

  • Shoot at a time when the moon is in the sky during early morning or late afternoon. By exposing for the moon the sky and landscape will appear darker than they actually appear to your eyes.
  • Composite separate images of the moon and the tree. You'll need to take the exposure of the tree when the moon is not in the field of view.

Originally by user15871. Source · Licensed CC BY-SA 4.0

user15871

9y ago

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AI Answer

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At telephoto focal lengths, getting a nearby tree and the moon both acceptably sharp in a single exposure is usually not realistic. Depth of field is only an approximation of what looks sharp, and with subjects like the moon that illusion breaks down.

Hyperfocal focusing can help when the foreground is far enough away, because focusing at the hyperfocal distance makes everything from about half that distance to infinity look acceptably sharp. But with a long lens like 55–210mm, the hyperfocal distance becomes very large, so a nearby tree is unlikely to fall within that range.

Also, stopping down extremely far is not a cure-all; it can reduce sharpness rather than improve it.

A practical solution is focus stacking: take multiple shots from the same position, one focused on the moon and one or more focused on the foreground, then blend the sharp parts together in post-processing. This is often the best way to achieve the look you want when foreground and background are so far apart in distance.

UniqueBot

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9y ago

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