Apr 152011
 

Light drops off by the square of the distance and why should you care?

Were you ever in a stadium with thousands of fans, and most of them are a quarter of a mile from the action and some great thing happens on the field and flashes pop all over the place?  I’ve been with friends who’ve done it, and tried to explain that the tiny flash on their p/s or even their dslr is just not going to make it to the pitcher’s mound.

Or you’re in a crowd, New Years Eve, and the subject that you want to capture is eight city blocks away, and you’re shooting with a not-so-smart phone or any camera.  And midnight hits and flashes go off like fireworks.

Well, I don’t care if you’ve got a powerful off-camera flash, it’s just not going to do anything for you if you’re ten blocks away.

In fact, the odds are that you’ll overlight the people in the foreground.  But anyway, the rule is very simple.  Let’s say that you can properly expose an object with your flash on high power at 10 feet, f2.8 and 1/60th of a second.  If you double the distance, and move to 20 feet, you’ll need to open up two stops.  If you double the distance again, you’ll need to open up another two stops.

The automatic everything camera doesn’t care much about this, but sees that it’s dark, maybe it makes itself more sensitive, but the tiny flash is just not going to reach ten blocks.

On the other hand, when you are in a small room with your friends and take their picture and the flash is the overwhelming light you will get all sorts of problems.  You may have had enough light to shoot without flash.

Anyway – that’s my pet peeve for the day.  I ended up shooting these shots by putting them on a monopod and holding it above everyone’s head.

If my flash had fired, I wouldn’t have had the effect of all the LCD lights.  I realize that not everyone is going to bring a monopod with them but at least experimenting with what (if anything) you can get at night if you set the ASA as high as it can go, and maybe find something to steady the camera on.  Just don’t expect your flash to illuminate Times Square (already bright enough) with flash from n number of blocks away.  And if you can – wow.  That’s a heck of a flash.

  3 Responses to “When Camera Flash Is Useless”

  1. Hi- So was the IR filter on the flash made of glass then? Does it still emit enough light for the camera to freeze motion, etc.? Where can I get these gels/filters?

  2. It was a special plastic, and it emited lots of light. Tons of light. It never overheated. And I still have it and plan to use it again.

  3. It’s beyond visible (you’ll see link at bottom of this post)
    http://www.beckermanphoto.com/blog/photography-with-an-infrared-flash/

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