How do you do that?: Properly expose a full moon

Gary Hart Photography, Moonrise, Yosemite

Twilight Moonrise, El Capitan and Half Dome, Yosemite (2014)
Canon Rebel EOS SL1
.4 seconds
Canon is 70-200 f/4L
ISO 100
F11

The problem

Cameras struggle to capture simultaneous detail in bright highlights (the moon) and and dark shadows (the landscape)—capturing one or the other is easy, but both? Not so much. A full moon is daylight bright, but because a full moon rises at sunset and sets at sunrise (more or less, depending on exactly how full the moon is when it rises/sets, and the elevation of the horizon the moon and sun rise/set above), when a full moon is visible, the sky and landscape will be some degree of dark.

The dynamic range problem is compounded by the fact that the darker the sky, the better the moon looks—often by the time a photographer is inspired to pull out a camera to capture the moment, it’s too dark. Additionally, many photographers attempt to photograph a rising full moon on the night it’s at its maximum fullness, which at best provides very little margin for error, and often is just plain too late.

While the advent of digital photography has provided exposure aids like LCD review and a histogram to help us cope with extreme dynamic range, these advances have also caused poor exposure habits. By far the most frequent mistake made by aspiring moon photographers is insisting that the landscape part of their scene as it appears on the LCD look close to what their eyes see, all but ensuring a white blob of moon. Even the trusty histogram lets down moon photographers because the moon is usually too small to register on a histogram—they pat themselves on the back for what appears to be a perfect histogram, completely oblivious to the fact that the moon is hopelessly overexposed.

The solution

One solution to extreme dynamic range is a composite: one image exposed for the moon combined with a second image exposed for the landscape. As tempting as a composite solution seems, my goal is always to capture everything with one click. (But just because we’re doing it with one click doesn’t mean there’s no post-processing required bring out the full range of light my camera captured.) While my technique can work with a jpeg image, you’ll have a much greater chance for success shooting raw. Of course there is a point when the sky and landscape are so dark that a single-click moon/landscape capture becomes impossible and you’ll need to pack up, resort to a composite, or simply stand there and appreciate what you’re witnessing.

Timing

When I plot my moonrises, I look for opportunities in my “lunar sweet spot,” when the sky is dark enough for the moon to stand out in brilliant contrast, but not so dark that I can’t photograph landscape and lunar detail with a single click. That starts around 15 minutes before official (flat-horizon sunrise) and last until about 15 minutes after sunset. That doesn’t mean that I can’t get nice images a little earlier, and squeeze out usable exposures a few minutes longer, but it’s a good rule of thumb.

Getting the full (or nearly full) moon in my “sweet spot” starts with picking the right night—just because your smartphone app tells you the full moon is Sunday night, don’t assume that Sunday night is the best night to photograph it. “Official” sun and moon rise/set always assumes a flat horizon—if you have mountains or hills in the east, you’ll need to wait for the moon to ascend above them, all the while the sky and landscape are growing darker. It helps to know that the moon rises a little less than an hour later each day (this is an average that varies quite a bit with a number of factors)—of the full moon won’t rise above your local horizon until long after the sun is below the horizon, pick an evening one or two days earlier. While the moon is only completely round when it’s full, a day or two earlier will still net you a mostly full moon in much easier light. And if your scene is in the west, your best chance will be a sunrise moonset after the moon is full.

For example, I do a lot of Yosemite moonrise photography, where most of the views are against the eastern sky—depending on where I want to photograph the moon, I may need to be there one, two, or even three evenings before it’s completely full to time its appearance for sunset. In my just completed Yosemite workshop, my group got to photograph moonrise at sunset from four different locations on four different evenings—each evening I found a spot a little higher and farther away from the valley rim so the moon would have to rise quite as high as it did the previous night. On the other hand, in my Death Valley workshop most of our views face west, so we do three or four sunrise moonsets, each one at a spot with a higher horizon than the previous day.

Exposure

The key photographing both the full moon and landscape with detail starts with ignoring the way the picture looks on your LCD because, in a high dynamic range scene, an ideal exposure rarely looks good on the LCD. I repeat: In a high dynamic range scene, an ideal exposure rarely looks good on the LCD.  The key is to make the image as bright as possible without blowing the highlights, then adjust the highlights and shadows in post-processing. In most extreme dynamic range situations the key is to completely trust the image’s histogram, but the moon is such a small part of most images, it rarely registers on the histogram—it’s possible to capture a histogram that looks great and moon that’s hopelessly blown (detail-less white).

So if you can’t trust the image or the histogram, what can you trust? I thought you’d never ask. While the histogram is helpful for the landscape part of the scene, when I photograph a full moon, I monitor the moon’s exposure with my camera’s highlight alert feature (“blinking highlights”). Highlight alert manifests in the post-capture LCD image review (though a mirrorless camera displays a highlight alert before I click, too). When engaged, everything in your frame that’s blown out flashes when you review your image, a helpful reminder that the exposure is broken and needs to be fixed. Every digital camera I’ve ever seen offers highlight alert, though some make you burrow deep into the menu system to turn it on and/or hide it on an obscure image playback screen (I’m looking at you, Nikon). If you don’t know how to find the blinking highlights, pull out your camera and manual, click a frame with blown highlights, and read/experiment until you figure it out (it really isn’t that difficult).

Once you’re confident that your camera’s highlight alert is engaged and you know how to check it, you’re ready for the next full moon. Here’s my process for a sunset moonrise:

  1. Metering in manual mode (because I want complete control of my exposure), I meter the landscape just as I would an ordinary scene. If I can get a good exposure (unclipped histogram) without the moon blinking, I know I’m good for the time being and get to work. Of course for a sunrise moonset, the process is reverse: I subtract light until the moon stops blinking
  2. The moon’s brightness won’t change, but if it’s a moonrise I’m shooting (always at sunset), I know the landscape will continue to darken, so that exposure that was perfect a few minutes ago isn’t quite so perfect now. As the scene darkens, I continue to add light by increasing my shutter speed in 1/3 stop increments (that is, one click at a time). Each time increase the exposure, I check the moon to make sure it’s not blinking.
  3. As soon as the moon starts blinking, I’m done adding light—no matter how much darker the scene becomes, giving it more light will blow out the moon.

The more familiar you are with your camera, the more success you’ll have. Different cameras’ highlight alerts engage at different points, and it’s entirely possible (likely even) that you can add a little more light after the first “blinkies” appear in the moon—on my Sony a7RII, I can usually push my highlights another 2/3 to 1 full stop once I first detect blinking and still recover detail later.

A graduated neutral density filter will subdue the bright moon, allowing you to add more light to the landscape without blowing out the moon. Depending on the location, a GND will add 5 to 15 minutes of productive shooting.

Processing

This is not a processing tutorial; I assume you’re shooting in raw mode and have at least rudimentary Lightroom or Adobe Camera Raw skills (though I’m sure if you’re comfortable with any raw processor you’ll be able to figure it out). I’ll just describe a couple of really quick raw processing moves to get you started.

As with all of my images, I try to do most of my full moon image highlight/shadow recovery in Lightroom. But before doing that, I want to get the white balance right. When I open the image in Lightroom, I drag the Vibrance slider all the way to the right (to exaggerate the color cast), adjust away any unwelcome color cast with the White Balance slider, then return the Vibrance slider to 0 (though I reserve the right to nudge it up or down later, when I’m further along in my raw processing).

With the color temperature right, I pull the Highlights slider all the way to the left, and the Shadows slider all the way to the right. This isn’t likely where they’ll end up, but it gives me a good idea of whether I captured recoverable details. If the moon is still blown, or the shadows are still black, I pull the Exposure slider left or right until the missing detail appears. (Tip: Holding down the Option/Alt key while adjusting any exposure slider reveals exactly what is and isn’t clipped.) If I can’t find the detail with the exposure slider, it’s not there.

This is by no means a complete processing workflow—that will vary with too many factors to cover here (including the conditions and exposure decisions at the time of capture, and your own processing style and preferences). But if you exposed the scene correctly, my suggestions will get your overall exposure to the point where you can start working on the rest of what the image needs.

About this image

My favorite spot to photograph a moonrise in Yosemite Tunnel View, which, in addition to being a fantastic view, is far enough from Half Dome to allow a fairly long telephoto. But for this moonrise in 2014 I realized that the moon would appear just a little too late—I needed to be higher and farther back to get the moon before the sky and landscape were too dark. So instead of Tunnel View, I took my workshop group to a vista on the west side of the Wawona Tunnel. While the view here is missing Bridalveil Fall and the bottom half of El Capitan, for our purposes it was perfect. (For this shoot I used my 1.6 crop body to increase the reach of my 70-200 lens.)

Workshop Schedule


A Full(ish) Moon Gallery

Click an image for a closer look and slide show. Refresh the window to reorder the display.

4 Comments on “How do you do that?: Properly expose a full moon

  1. “It helps to know that the moon rises a little less than an hour later each day” may be a surprising fact for those who (like me) did not pay close attention to astronomical events, accustomed as I was to the sunrise/sunset times changing but a few minutes each day. As you have written before, PhotoPills and The Photographer’s Ephemeris are great tools, and playing with them at home gives insight into the dynamics of sun, moon, and stars.

    • Thanks, George. Yeah, even though this is about exposure, I should probably add a reference to Photo Pills and TPE—they’re excellent tools that enable photographers to make decisions that can make or break their exposure success.

  2. Enjoyed reading how you go about making these incredible photos. My wife and I were just in Yosemite on Friday as part of our honeymoon. We booked one of the tours out of San Francisco for the day to the park. Such a beautiful area! Would love to come back soon and participate in one of your photography workshops. Keep up the great work!

  3. Great photo for the opening spread and at the end Gary. I bought an SL-1 a couple of years to use as a lightweight walk around and it’s a neat little camera. If I weren’t so old (75) I would consider switching over to Sony but I’ve got too much invested in Canon and they still serve my purpose. It’s always nice when you post the EXIF for us amateurs. Have a great Thanksgiving and Christmas.

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