This morning as I was going to work, the full moon was in the sky and very bright. I could clearly see the dark spots on it. I got my phone out (after stopping) and thought to get a picture, but no matter how I tried to focus the camera, it couldn’t see the moon as anything but a bright ball of light, like looking into a flashlight. Why was it so difficult for my phone to capture this image that my eye could see so clearly?
In: Technology
Your phone camera is trying to set exposure based on the whole sky. It is possible to get a picture of the moon that shows features, but it’s not a simple point and click. You’ll need to adjust the brightness/exposure for the picture.
For an iPhone, here’s a YouTube that shows you how: https://youtu.be/6Gu65xGI_bk
Camera phones are very wide angle, so they can get a selfie shot without needing for you to have 10 foot long arms. That’s not good for long distance things, and the Moon is very far away. Your mind’s ability to focus your gaze on the Moon and ignore all the surrounding black sky is the sort of thing that we’re still not quite able to do in software.
You camera is seeing the whole picture and going “wow, it’s really dark here, I’ll adjust the settings so the picture doesn’t come out too dark”. But, in that context, the Moon becomes a very bright thing that ends up overexposed.
When we use a DSLR/mirrorless we either need to set the exposure manually or set it to ‘spot’ and focus the center of the frame on the moon. By default most smartphone cameras will meter using something called ‘evaluative’, which is to say it will try and see the entire scene and meter based on something called a histogram. This is typically very reliable, but it fails when you have a extreme highlights (the light of the sun reflecting off the moon) contrasted against a super dark shadow – like the night sky. What you get is something called ‘blown highlights’. Digital sensors prefer under-exposure to over-exposure, when you overwhelm a digital sensor with light, all the data basically gets confused. Film was the opposite, under-exposure meant you didn’t have data at all, it could normally go a full ‘stop’ overexposed and still give you a useable image.
If you ever hear a photographer say “expose for the highlights’, this phenomenon is what they are talking about. With photographing the moon, you **must** expose for the highlights. Say I am photographing a couple of people sitting at a table and behind them is a slider door and it is broad daylight, if I expose for the highlights I want to see the background sky nice and blue. Doing this will make the faces nearly black, which is why I use a flashgun to light up the faces and expose for the background. It is why you see photographers use their flash when there seems to be plenty of available light.
Tap on the moon in the screen and your phone camera will adjust its exposure to align to the brightness of the moon so you can see contrast.
Your eye (and your brain) is a product of millions of years of evolution. Having a high dynamic range (being able to see both brightly lit and shadowy things at the same time) can be what allows you to both see the tiger about to jump you and the berries you need to eat.
Your phone camera is a purification of a few decades of development in which keeping costs low, file sizes manageable, and blurring at a minimum.
In short, your camera is pretty cool. But your eyes are awesome.
Believe it or not, millions of years of evolution can result in a pretty good camera and image processor (eye and brain).
Your eyes are essentially ~350Mp cameras with AI light attenuation. Your phone camera is likely around 13Mp, with no AI built in to determine what’s what.
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