Cross With Purpose

This Article Features Photo Zoom

Cross-polarization improves the rendition of this lustrous piece of petrified wood by removing reflections that mask true color and detail. In the first image [above], captured with two flashes and a 100mm macro lens, glare hides the complexity of color in the wood. In the second image [below right], cross-polarization of the light sources and lens reveals color and detail. No Photoshop enhancement was used. Canon EOS 5D Mark III and two Canon Speedlite 580EX flashes.

Reflecting On Reflections
Many exciting nature subjects come with a built-in photographic challenge: reflections that mask color and detail. It's a particular problem with minerals, shiny flower and leaf surfaces, or anything that's wet or moist, such as tide pool denizens. In the studio, controlling reflections is a factor when photographing jewelry, coins and crystals. No, you can't just fix it in Photoshop—at least, not yet. But there's an excellent solution to the problem: cross-polarization.

A single polarizing filter is a common photographic tool used to darken skies, improve color saturation and eliminate reflections when photographing through glass or plastic. More control is gained when the light source and lens are cross-polarized; that is, polarizing material is placed over the light source(s) and a polarizing filter is placed over the lens and aligned in such a way that nearly all divergent light rays from the subject and the light source are kept from entering the lens. The technique doesn't get every reflection on a multifaceted subject because to do that would be to cut out all light from every direction. But cross-polarization does eliminate nearly all reflections and enhances the discernable colors and detail in the subject.

I first used this technique years ago when I was involved with art conservation photography. I was shooting large-format images of art for museums, either to document them or for use in exhibition catalogs. Oil paintings with lots of varnish have reflections that are normally impossible to eliminate with standard lighting. I used two large studio flashes covered with polarizing material along with a polarizer over the camera lens; the combination amazingly cut through the glare, revealing all the color and none of the brushstroke reflections. I then applied the technique to nature subjects, such as wet specimens, minerals like quartz and shiny black beetles.

You'll need two (one will work, but not as well) electronic flashes (a large hot-shoe type is adequate), a circular polarizer for the lens and polarized material in sheets, available from www.Polarization.com and Edmund Optics at www.edmundoptics.com/optics/polarizers/linear-polarizers/visible-linear-polarizing-laminated-film/1912.

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Place the polarizing material over the flashes, making sure they're positioned to match each other and are aligned horizontally. Place the polarizer on the lens, and look through the camera into a mirror. While looking through the viewfinder, rotate the lens polarizer until you see the flash polarizers go black. Mark that position on the lens polarizer so the next time the setup will be easier to adjust for maximum cross-polarization without the need for a mirror.

Use a TTL flash exposure and check the results on the camera's LCD. Be aware that you'll be losing from three to five stops of light. The increased clarity and color you'll achieve are well worth the investment and effort involved in cross-polarization.

The Triggertrap App
A new app has surfaced that turns your smartphone into a sophisticated DSLR controller. As I write this, Triggertrap is available only for the iPhone, but my bet is that by the time you read this column, Triggertrap also will work with Android phones.

The Triggertrap app could actually save you money—really!—over the cost of buying your DSLR manufacturers' accessories to accomplish the same functions. In order to use it with your cameras, you'll need the mobile app at $9.99. The app by itself will do many things using your iPhone camera, but we serious photographers want to use it with our DSLRs. To make the connection between the phone and your particular camera, you'll need a dongle and cable, ordered for $19.99 from Triggertrap's website (triggertrap.com).

So what great things will this app accomplish? More than you thought possible. Here's what the Triggertrap is capable of doing with your DSLR attached to your iPhone:

Cable Release. You can use it as a simple release, or place the camera on Bulb and control it for long exposures.

Sound Trigger. Set the phone to a preset sound level; when the phone hears a sound above that, it fires the camera.

Time-Lapse. This is a sophisticated intervalometer. Select the number of images over a set time, or set the camera to go off at intervals of your choosing.

Eased Time-Lapse. Your time-lapse can ease in, then accelerate, then ease out again.

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Distance-Lapse. The camera will fire after traveling a set distance. Point it out the car and it fires every time you travel a preset distance; slowing down or speeding up won't affect the interval of pictures. This could be fun!

Seismic. Movement of the phone sets off your camera.

Peekaboo. Using the iPhone's face-recognition capability, you can set off your camera whenever there are faces seen by the iPhone. You even select how many faces before it triggers. Not sure how I'll use this one, unless it recognizes animal faces.

Star Trails. Take a lot of long exposures with a short gap between them. I could have used this a number of times.

HDR. Setting your camera to Bulb, you can take HDRs under low light at a number of settings.

HDR Time-Lapse. This needs to be long-exposure HDRs because your camera has to be set to Bulb.

Tesla. This has something to do with magnetism. If a magnet is moved next to the phone, the camera is set off. Think of a situation like a burglar alarm where when a door is opened, the camera goes off. I didn't know my iPhone had a magnetometer in it.

Motion Detector. The camera in the iPhone takes a picture of the background. When the picture changes a set amount (you set the amount of change), the DSLR takes a picture. How crazy is that?

As you can imagine, this company has been overrun with geeky photographers/iPhone users wanting to combine the two "tools" to accomplish weird photography. I bought into it in a heartbeat! That's a lot of things to do with your iPhone and camera for little additional investment. As an example, if you want to do time-lapse photography with your Canon DSLR, you need an intervalometer (currently $135.99 at B&H). See, I told you the Triggertrap would save you money—really!

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Stacked Converters

Q At a recent seminar, you mentioned using the 1.4X and 2X Canon tele-extenders together. I'm assuming that's done with an extension tube between them, or am I missing something?
J. Studwell
Via the Internet

A Different camera systems combine accessories in different ways. The method of stacking two tele-extenders together in the Canon camera system has changed over time. The original Canon EF tele-extenders wouldn't stack (mate), and a 12mm tube was placed between them to facilitate the technique. Interestingly, long teles like the Canon 300mm ƒ/2.8, 400mm ƒ/2.8, 500mm ƒ/4 and 600mm ƒ/4 would still focus to infinity with the 12mm tube in the light path. Then Canon came out with the improved 1.4X II and 2X II, which would stack without the need of the 12mm extension tube. Now Canon has made available the III series of tele-extenders, and they won't stack without the 12mm tube between them.

If you have trouble mating tele-extenders on other camera systems, try the extension tube. Be cautious, as pins on Nikon lens connections can be damaged when using extension tubes. I always carry a 12mm and a 25mm extension tube in my camera bag for closer focus and to use when certain combinations don't match due to a protruding rear element.

Autofocus At F/8

Q Will the new Canon EOS 5D Mark III autofocus through the full range of the EF 100-400mm f/4.5-5.6L zoom lens with the Canon EF 1.4X tele-extender?
G. King
Via the Internet

A All of the Canon "consumer-level" cameras (and, as awesome as it is, the 5D Mark III is included in this category) will autofocus only when the maximum aperture of the lens combination is ƒ/5.6 or larger (meaningƒ/5.6, ƒ/4, ƒ/3.5, ƒ/2.8 and so on). The professional cameras with the EOS-1 designation will autofocus up to an ƒ-stop of ƒ/8, except that the new Canon EOS-1D X won't autofocus to ƒ/8 and is regulated to ƒ/5.6 and larger.

The Canon EF 100-400mm ƒ/4.5-5.6L, 1.4X tele-extender and 5D Mark III combination won't autofocus because the 1.4X loses an ƒ-stop of light, making the maximum aperture of the 100-400mm zoom ƒ/6.3.

For information about upcoming seminars and digital-imaging workshops, visit www.georgelepp.com. If you have any tips or questions, address them to: OUTDOOR PHOTOGRAPHER, Dept. TT, George Lepp, 12121 Wilshire Blvd., Suite 1200, Los Angeles, CA 90025-1176 or online at www.georgelepp.com.