The image above was originally selected to illustrate this post from last year, but for obvious reasons I decided on the image that now resides there (or whatever it is that photos attached to posts actually do.) But I keep running across it in my blog folder, and always stopping to look at it. So now I’m going to make you do it ;-)
This is not in any way an altered, ‘shopped, or tricked out image – this is a grab shot with a pretty outdated digital camera (a whopping 2.6 megapixels) as the moon rose one night. You can’t trust a camera’s meter to get the correct exposure of a bright object surrounded by darkness, so you resort to either calculating the exposure based on relative brightnesses, or in this case, knowing what it should be and bracketing the exposure. “Bracketing” means that you shoot a few frames, in a range of exposure on either side of what you think it should be – generally, one of them will give you what you want, if the camera is even capable of that.
That’s a key phrase right there – film and digital sensors cannot capture the wide range of light levels that we see with our eyes, and thus will let areas too bright bleach out into pure white, or areas too dark will become black, or both. Dealing with this increased contrast can be tricky, and there are lots of photographers’ tricks, including waiting on more even light levels, filling in the shadows with a flash or reflector, or resorting to something called High Dynamic Range editing.
HDR basically means taking multiple images of the same subject at various exposure levels (a tripod is necessary, unless you like serious headaches) and taking the areas of correct exposure from each image and combining them into one. What I find most amusing about it is, this is exactly the kind of editing that makes most people scream and whine, “Photoshopped!” yet it is now considered a legitimate digital technique, at least among some photographers. I’ve played with it myself, but consider it digital compositing (which it is,) and thus the same kind of shenanigans as painting over trash or inserting, I dunno, a moon into an image that had no moon to begin with. There may be artistic reasons to composite images, but these are digitally-altered images, and should be considered differently from images taken with the conditions “as is.”
Before digital, photographers dealt with the limitations of film emulsions in countless ways, and this was all part of being a photographer. You sought the right light conditions and angles, chose film with appropriate properties, and knew that some images were simply not going to be captured. Sometimes, photographers resorted to something called “graduated neutral density” filters, basically a fancy name for those sunglasses from the eighties that were darker on top than at the bottom, so the too-bright sky was reduced in light while the foreground at bottom was unaffected. But I’ll tell you a little secret, too: experienced photographers, and photo editors and art directors and similar, can spot both HDR images and graduated filters instantly, because they know what light does, and it doesn’t do that. Everyone has their own tastes and preferences, and I mess with digital editing from time to time, but it’s not exactly challenging, or says anything about your skill as a photographer.
I mentioned knowing what exposure I should be using, above, and then left you hanging – sorry about that. If you’ve heard of the “Sunny 16” rule, you know how to apply this, but instead think “Moony 11.” The Sunny 16 rule is a shortcut for estimating exposure when the camera meter isn’t an option, and means, on bright sunny days, set aperture for f16, and your shutter speed should then match your ISO (reasonably closely.) So, if you’re shooting at ISO 100, your shutter speed gets set to 1/100 (1/90 or 1/125 is fine,) your aperture to f16, and voila, you have the correct exposure without using any kind of exposure meter at all. The full moon itself is actually lit by direct sunlight, and is pretty medium-toned, so Sunny 16 applies just fine – but most people don’t like a grey moon, but want it to appear brighter like it seems to us at night, so you use f11 instead, same shutter speed setting, to increase the exposure a bit.
This applies only to a full moon well up into the sky – as the moon gets less full (and thus the sunlight less direct and reflecting back to us obliquely rather than directly) or is lower in the sky and cutting through more atmospheric haze, this changes significantly. A half moon (“quarter”) for instance, only reflects 1/4 as much light as a full moon – yes, that’s the way it works. The easiest thing to do is resort to Keith’s excellent moon photography page, since he’s taken the time to lay it all out in detail. You’ll find the exposures are related slightly differently from the way I did above, but they produce virtually the same result.
For the image above, some atmospheric haze provided just enough reflected light to silhouette the surrounding branches – a clear night would not have allowed this. The exposure of 1/25 second at f8, ISO 50 tells you that the moon being lower in the sky and dimmed by haze required some compensation, being two stops dimmer than the guidelines called for. It can be tricky, so experiment!