Ask a National Geographic Photographer

Q: I am just beginning to take digital photos, and file type is one of my main concerns. What do you shoot: JPEG, TIFF, RAW, etc.?

A: At National Geographic we shoot RAW files and submit them to the picture editors that way. We don't do any conversions to TIFF or JPEG. Here is a rundown on file formats:

RAW: This file format is best for archiving because no compression has been applied. It is the purest format available. Every bit of information collected from a camera's sensor has been preserved. The drawback to saving images in RAW format is that the file size can be monstrously large, easily upwards of 10MB to 15MB per photo with today's large megapixel cameras. Professional photographers are often the only ones with enough space to dedicate to such oversized files. Once a RAW image has been manipulated, a copy has to be saved in another form, such as a TIFF or JPEG.

TIFF: This file format is ideal for editing because it still retains a large amount of image information, but not as much as RAW. TIFF is especially good for retaining color information because it is uncompressed, unlike JPEG. Depending on the resolution of your camera, you could easily end up with TIFF files in the 6MB-to-30MB range.

JPEG: JPEG has become the standard for most smaller cameras because it has the highest compression. In other words, it squeezes the information from your photo into a smaller file size than other formats. One drawback to saving photos as JPEGs is that the images will degrade each time you save them. This is known as a "lossy" type of compression. That's why it's important to save a high-quality original and then edit copies of that file.

You can also save your JPEG as a different file type using photo editing software. The TIFF photo file format is "lossless," meaning that no matter how many times you save the image, it will not degrade. If this format is an option within the software you're using, it's ideal for archiving high-quality copies of your photos.

Question submitted by Glenn in Colorado Springs, Colorado

Q: I am interested in taking color pictures with infrared film. I have heard that you can only get these pictures developed as slides. Is this true?

A: Alas, as of March 2008, there is no current color infrared film available for consumers. Citing lack of enough demand and in the middle of a corporate transformation to a mostly digital company, Kodak unceremoniously dropped Kodak EIR Infrared Ektachrome at the end of 2007, and all existing stock quickly ran out.

Question submitted by Greg in Brighton, Colorado

Q: I've taken many lightning photos for my freelance photography, but when the lightning is during daylight or dusk hours, the settings I use overexpose the photo and it turns out bright white. What are the correct camera settings for taking that perfect lightning photo?

A: Lightning is easy to catch at night because you can leave the shutter open for several seconds and let the lightning strikes be recorded. The problem with shooting lightning during the day is your shutter can only be open a fraction of a second or your images will be overexposed. It's nearly impossible to capture lightning strikes using these higher shutter speeds. Besides, lightning looks better at night. It stands out against the dark surroundings.

If you aren't content shooting at night, you can try a lightning trigger (www.lightningtrigger.com). This fits on the hot shoe of your camera and trips it when it detects the earliest stages of a lightning strike. It's expensive but might be worth it for you.

Question submitted by Crystal in Apache Junction, Arizona

Q: How do you shoot the motion of flowing water (or other moving objects) without overexposing the rest of the composition?

A: To get that "silky water" effect when shooting a waterfall, you need to set your camera to a shutter speed of one second or slower. The problem is you often can't close down the aperture far enough to compensate for the longer shutter speed. The result is an overexposed picture. The secret is to use a neutral density filter. Think of it as sunglasses for your camera. It will knock down the light by several stops and let you achieve properly exposed images at slow shutter speeds in broad daylight. They come in many different densities.

Question submitted by Mimi in Hong Kong

Q: I am a travel photographer and many times I unavoidably end up visiting a place of interest in the middle of the day when the light is really harsh. Can you give me any tips for minimizing the effects of the strong overhead sunlight on my subject?

A: One way to deal with harsh, middle-of-the-day sunlight is to use a fill flash. The key in using a fill flash outdoors is to dial it down so it just fills in the shadows and nothing more. A mistake I often see is fill flash that is too overpowering, meaning it's too strong and ruins the mood of the scene. Set your fill flash on automatic TTL and dial it down to -1 or -2 depending on your situation. As the lighting changes in your scene your fill flash will automatically adjust.

Another method of dealing with bad light is to work with it. Look for ways to include dark shadows or openings, like doorways, into your scene. Also look for open shade. Watch the light. See how the bright light reflects off a wall and makes soft, nice light in the open shade across the street.

Question submitted by Maggie in Hyderabad, Andhra Pradesh, India

Q: What type of camera will provide clearer images: digital or film? Is higher megapixels really important? What are your minimum requirements for a digital camera?

A: Digital photography has come a long way and is just as good as film if not better in many situations. The higher the megapixel count the more resolution the digital camera has. This means you can make bigger enlargements. As a rule of thumb: a 6-megapixel camera is sufficient up to 8x10, an 8-megapixel camera is sufficient up to 16x20. Remember this is without cropping. If you want to crop your image then you are tossing away megapixels. In general it's best to get the highest resolution (megapixel) camera you can afford.

Question submitted by Dennis in Paranaque City, Philippines

Q: I would like to know what exactly polarizer filters do and where and when should I use one?

A: First of all, it can darken blue skies, turning them a deep, rich blue. Polarizing filters are also great for removing reflections in water. So if you're shooting a river scene and you want to see detail in the water or on the river bottom, a polarizer will reduce the reflections. They're also good with foliage, making leaves and such less shiny (again, cutting down on reflections). Color saturation is enhanced with almost any subject. It has a moveable outer ring that you twist to find the maximum point of polarization. There are a few disadvantages you should be aware of. The main side effect of the polarizing filter is that it absorbs 1.5 stop of light. So, if you shoot at 1/180th of a second and then add the filter, you will find yourself at 1/60th of a second. This happens whatever the orientation for a polarizer. In low-light situations, some type of camera support, such as a tripod, will be needed. Some autofocus mechanisms are thrown off by polarizing filters. Make sure you use a circular polarizer to avoid these problems.

Question submitted by Saber in Tehran, Iran

Q: What is white balance? How is it adjusted in different situations?

A: All light has a color, which casts a tint, also known as color temperature, over what you see. Early morning and late afternoon light tend to cast a yellow tint, and your average indoor house light has an orange glow. Although our eyes adjust to this color and we don't notice it, the sensor in a digital camera will record it and give us pictures that have a color cast.

The purpose of the white balance adjustment is to compensate for the color temperature of the prevailing light source so that your image will have accurate color. Your camera is probably set to auto white balance by default. The means the camera attempts to determine the color temperature of the light and automatically adjusts for that color temperature. Many people just leave the camera set to auto white balance all the time.

Many cameras come with preset white balance settings. Look for icons representing; clouds, sun, shade, light bulb, and fluorescent light. These provide reasonable color accuracy when the light source matches one of the preset white balance options. It's also a good solution when there is a lot of one color in the scene or the photographer does not want the camera to automatically make adjustments for the color of the light.

Question submitted by Subhasis in Kolkata, West Bengal, India

Q: How do you take photographs of a skyline with the sunset in the background? I have tried it many times with standard point-and-shoot cameras but it has not come out well. Can you suggest ideal ISO settings, shutter speed, etc?

A: A sunset skyline picture can be tricky to photograph because the lighting conditions are such that it can fool your camera meter. Your camera's meter doesn't know if it should expose for the sunset, which is really bright, or the skyline, which is really dark. If your camera lets you set the exposure manually, try adjusting the shutter speed and aperture to shoot images lighter and darker than what your meter says.

If you camera has only automatic exposure, take lighter and darker exposures by adjusting the exposure compensation. Look for a +- icon. If you press it you should be able to adjust it from -2 to +2. This means that your camera will bias the automatic exposure by the amount you have adjusted. -2 means two stops underexposed and +2 means two stops overexposed.

Question submitted by Sidharth in Mumbai, India

Q: Is there a way to take a good photo of a hummingbird with my digital camera? The photos I have taken so far show a blurry bird even after I try to "fix" them with Photoshop.

A: A hummingbird's wings can beat up to 80 times per second. To your eye and your camera the wings are just a blur. You could set your camera on a high shutter speed but it won't be fast enough to freeze the wings. Instead you need to use a flash that has a flash duration of 1/5,000 to 1/20,000 of a second. At full power a typical flash that fits on your camera has a flash duration of 1/750 to 1/1,000 of a second, which is too slow to capture a hummingbird's wings.

Many of today's strobes have variable power so they can be dialed down. As you decrease the power, the flash duration also decreases, roughly in line with the power. The lowest setting can stop action at 1/10,000 of a second—fast enough to freeze the wings of the fastest hummingbird. The downside is that you need to move the strobe in very close since you decreased the power.

Question submitted by Debbie in Southbury, Connecticut