Your mother told you never to look at the sun, or you’ll go blind. Whenever some cameras take a picture of a very bright object (like the sun), the light can get so intense that it doesn’t just affect one part of the image. The light streaks out from the light source and creates a supernova like effect that can consume a significant frame. It’s called “blooming,” and in this article, I’ll show you how to stop it.
What causes blooming?
Before I can explain the causes of blooming, you need to know a few things about the way your camera’s image sensor works. An image sensor, or CCD, is an array of photovoltaic cells that convert light into an electrical charge. Each pixel has one of these cells, and when it receives light, that light is converted into an electrical charge. The charge is then converted to a number and stored as an image file on your camera.
If one pixel receives more light, it generates a bigger charge and it gets recorded as being “more bright” than another pixel. CCDs also take information on the wavelength of light to figure out its color. This too, is ultimately converted into a number and stored as an image file.
Blooming happens when a large amount light gets focused to a single point on your camera’s image sensor. This can create so much charge that it actually bleeds from pixel to pixel until it eventually spreads out. Whenever blooming occurs, it has a pretty well-defined boundary. This stands in contrast to lens flares, which can give the entire frame a strange tint.
Most blooming looks like a giant blob of white with pixelated edges. In some cases, light from different wavelengths (blue light or violet light for example) can get so intense that it does the same thing, creating a giant blob of colored light with pixelated edges. The classic case with colored light happens when you point your camera at a colored strobe. The flash is so intense that it causes a colored kind of blooming.
With white light, it usually happens when you point your camera directly at the sun (didn’t your mom tell you not to do this?). The light focuses at a single point on your image sensor, creating a huge charge that bleeds onto the neighboring pixels. You’ll know you’re experiencing blooming when the sun doesn’t even look like the sun. It will look like a pixelated mess, something akin to a phaser blast straight out of Star Wars.
How can you prevent blooming?
For one, listen to your mother. She’s right about a lot of things. Don’t put the sun in the shot. Keep it to the side, and while you’re at it, put a hood on your lens (I swear you’d leave the house naked if someone didn't tell you not to). It will keep stray light from entering your lens and causing a flare, which under certain circumstances can also cause blooming. Think of what happens when the sun reflects off of the chrome on a car, and this should make sense.
There are certain times of day when it’s okay to point your camera at the sun. Mornings and sunsets happen to be one of them. At these times, the light isn’t nearly as intense. It’s also a lot more pretty. But even then, you don’t usually want to point your camera right at the sun. You’d only want to do that if the sun were obscured behind some clouds, turning them bright orange or pink.
Always be careful when you’re thinking about incorporating the sun into your pictures. Looking at the sun through the viewfinder will make you go blind.
You can also increase your camera’s shutter speed to block out some of the light, but this isn’t always effective. Only certain camera makes and models will allow you to do this. Those of you who own digital SLRs, pay heed. Yes, your camera says it can achieve shutter speeds as high as 1/4000 sec, but chances are that it doesn’t do this by using a physical shutter that shuts faster (thus blocking the light). It’s done by modifying the image file after it’s taken. This, while clever, does nothing to stop blooming from happening.
Keep your camera away from the sun; or looking at bright lights; use high shutter speeds, and your blooming problems should be a thing of the past. And if you’re still having issues, leave me a comment below. I’ll help you sort it out.
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