Tuesday, August 24, 2010

Photo(s) of the Day: "Merry Christmas!" versus "Merry [NSFW] Xmas"

Another new blog feature: on some days when I'm working on a Photography Case Study, as I now am for Friday, I'll try and post a much abridged version. Today, let's discuss effective flash use, briefly.

Christmas is coming, right? Our first contestant is a rather blah test case with no flash:

Uh, yuk. This image is overexposed. "What?" you say? Indeed. The sky, where it meets the horizon, is blown out. This is an example of something that cannot be fixed, at least without much pixel-on-pixel action, in post processing. Even if you can bring it back, it's still a sad image. (It is also, of course, underexposed, too. Both are possible in the same shot.) I should add both images were taken with Matrix metering adjusted -2/3EV exposure compensation. Even the unassailable Matrix meter is not psychic.

The next image was taken 14 seconds later. I dare anyone to spend 14 hours to bring out the same amount of punch from the above image that I was able to extract below, by popping up my flash and dialing in a few small adjustments, which I'll get to in a minute.

Holy smokes Batman!

So what did I do?

Pop up the flash. That get's you started. But if you only do that, the camera will try to illuminate the scene with flash and you'll get something similarly vapid to the top image. Select slow-sync flash and the camera will only attempt to lighten the dark enough that a short enough exposure is possible to avoid blowing out the horizon. Both images were ISO 200 at f7.1 with the stock D90 18-105 VR kit lens. (Hint: If I recall correctly, the default way to select slow-sync on most Nikons is to hold down the flash button while spinning the front command dial.) The first image was exposed 1/25 sec. and the second 1/60 sec., or less than half as long — saving the horizon and deepening the colors.

Those two things alone are 90% of the change in image. The only other adjustment crucial to getting right in camera is the final lighting variable. I set the flash to -1 EV power. (Hint: most Nikons do this by holding down the flash button and spinning the opposite command dial as the one used to change flash mode. Single command dial cameras - D40/D40x/D50/D60/D3000/D3100/D5000 need a quick trip into the menus.) Without that change, the "Seasons Greetings" banner is too bright... well, why tell when I can show?

That's no good: the banner is too bright, the snow is too bright and the tree is too bright. Subtlety is your friend. You don't want it to be obvious you used flash, note how the illumination evenly fades into the ambient lighting in the middle photo.

The final two adjustments can be made in post, although it's best to do in-camera if you can. (Again, there were :14 elapsed between the top and middle images. Learn you camera well enough to set it by touch in the dark.) I set "Vivid" picture control for additional saturation and vibrancy and adjusted white balance to a warmer setting. That's it!

Something to remember: always use your flash unless you have a reason not to. Such reasons include shooting landscapes beyond the reach of your flash, discretion (hiding in the bushes), and needing a shutter speed above the camera's flash sync speed. There are many times you won't need flash and shouldn't use it, but be sure to think of what those reasons are before you pull the trigger. Flash on should be your default.

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