Taking Night Photos, Understanding Focal Lengths, and More

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Have a question about digital photography? Send it to me. I reply to as many as I can--though given the quantity of e-mails that I get, I can't promise a personal reply to each one. I round up the most interesting questions about once a month here in Digital Focus. For more frequently asked questions, read my newsletters from January, February, March, and April.

Taking Great Night Photos

Recently, with all of the storms that have been going through Arkansas, I wanted to shoot lighting. However, when I set my camera to the bulb setting and the ISO to 200, all of the pictures look as though I have shot them on some cloudy afternoon--they are very bright. I have tried using both my 18-55mm and the 55-200mm lens, but to no avail. I'm a very novice photographer having had my camera only about 6 months.
--Layne Yawn, Jonesboro, Arkansas

By setting your camera to Bulb, you're on the right track, Layne. But keep in mind that's not an exposure setting in and of itself; Bulb simply gives you manual control over how long you leave the shutter open. And therein lies your problem: If your pictures are coming out too bright, you're leaving the shutter open too long.

Another important detail is the aperture, which you don't mention. Set your aperture to its smallest opening (which is the largest f/number) and your ISO to its smallest value as well (such as ISO 100, if your camera goes that low). Then take some test shots, experimenting with various shutter speeds. Try 5 seconds, 10 seconds, and 20 seconds, and compare them. In this way, you can find an exposure that'll give you better results for the next storm. For some more help with night photos, check out "Photographing Fireworks: Tips and Tricks."

A Homemade Flash Reflector

Do you have any directions for making a homemade flash reflector? I saw some directions once, but can't remember where I had found them.
--Barry Bowman, Staten Island, New York

Sure thing. A flash reflector--commonly called a bounce card--lets you diffuse the light from your camera's flash to avoid harsh and cold illumination. As I've mentioned before, you can bounce the light off the ceiling or use a bounce card, which diffuses and redirects the light from your flash. You can buy a flash card, but there's no need to. The Web is filled with instructions for free ones you can make yourself. Try, for example, a DIY bounce card at Make. Print the PDF, cut it out, and attach it to your flash with a rubber band. It works great.

Understanding Equivalent Focal Lengths

I am new to digital cameras and I have question that I can't wrap my head around. I have read that the 35mm equivalent focal length of a digital camera is determined by the size of the sensor. For example, in How to Do Everything with Your Digital Camera you state, "if this digital camera were a 35mm camera, its 9.3mm lens would give you the same picture as a 50mm camera." Would you please explain?
--Calvin S. Hall, Springvale, Maine

I'll give you a really simple explanation, Calvin. A lens's focal length is not an absolute measure of the "magnification" it delivers. Instead, the size of the image depends upon both the focal length of the lens and the size of the film or image sensor. For any given focal length, the smaller the image sensor, the higher the relative magnification of the image will be. Most digital camera sensors are smaller than a frame in a roll of 35mm film. So when you use any lens on a digital SLR, it will have a longer effective focal length than how it's marked, as compared to using the lens on a 35mm film camera.

This is why some digital SLRs are advertised as "full frame" models--their sensor is the same size as a frame of 35mm film, and so the lens behaves exactly the same. Of course, this magnification effect can be both good and bad. If you love telephoto photography, you'll like using a digital SLR, because all of your old 35mm lenses automatically have more "reach." But by the same token, it's harder to get the most from a really wide angle lens on a digital camera, because all lenses are somewhat magnified, reducing the wide angle effect. As a result, folks who love fisheye and wide-angle photography tend to gravitate towards the relatively small number of full-frame cameras on the market.

The Water Is Bent!

My wife used a cheap digital camera to take this photo of our daughter-in-law washing her dog. This is how it came out.

So how did water get bent? I'm a professional photographer and I can't figure it out!
--John Brown, Salem, Massachusetts

You've stumbled onto a fascinating glitch that has caused endless confusion for camera phone owners. Inexpensive cameras, particularly camera phones like the iPhone, use something called a rolling shutter. Due to the way the rolling shutter works--capturing the image one row of pixels at a time, sort of like the way an old-fashioned TV would display video--you can get some really funky photos. This photo, which captures spinning airplane blades with an iPhone, is one of the more famous illustrations of this problem.

Generally, you'll see this kind of effect when you take a photo of something that's rotating during the exposure, so its position changes over the course of the short exposure. I can't quite figure out what caused the effect in your photo of the kitchen sink, but it has all the hallmarks of a rolling shutter problem, and so that's how I would diagnose this photo.

When to Crop?

When in your digital workflow should you crop a photo? First? Last? Somewhere in between?
--Alex Rigly, San Diego, California

Typically, I suggest cropping the photo very early in your editing process, Alex. You should definitely crop before you do any color or exposure adjustments. That way, your photo editing software can base any automatic adjustments only on the colors and brightness found in the part of the photo you want to keep, and it can disregard the bits you've cropped away.

Hot Pic of the Week

Get published, get famous! Each week, we select our favorite reader-submitted photo based on creativity, originality, and technique.

Here's how to enter: Send us your photograph in JPEG format, at a resolution no higher than 640 by 480 pixels. Entries at higher resolutions will be immediately disqualified. If necessary, use an image editing program to reduce the file size of your image before e-mailing it to us. Include the title of your photo along with a short description and how you photographed it. Don't forget to send your name, e-mail address, and postal address. Before entering, please read the full description of the contest rules and regulations.

This week's Hot Pic: "Full Moon," by Robert DeMott, Fort Myers, Florida

Robert writes: "On March 19, the moon was closer than it has been to Earth in many years. I got up at 1:30 AM and snapped a few pictures with my new Nikon D7000 and a 300mm telephoto lens. The night I took the picture the moon was so bright that the whole neighborhood was fully illuminated just by moonlight."

This week's runner-up: "A Florida Sunset," by Joan Feldvary, Jackson, Michigan

Joan says that she took this photo with her Pentax K7 while on vacation in Florida.

To see last month's winners, visit our April Hot Pics slide show. Visit the Hot Pics Flickr gallery to browse past winners.

Have a digital photo question? E-mail me your comments, questions, and suggestions about the newsletter itself. And be sure to sign up to have Digital Focus e-mailed to you each week.

This story, "Taking Night Photos, Understanding Focal Lengths, and More" was originally published by PCWorld.

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