Photo Safaris By Region AFRICA - Botswana Wildlife - Madagascar - Masai Mara Wildlife Reserve, Kenya ANTARCTICA - Ultimate Antarctica ASIA - Essential China—Iconic Landmarks & Landscapes - India—Rajasthan & Puskar Fair - Japan's Winter Wildlife - Laos & Vietnam - Mongolia—The Golden Eagle Festival EUROPE - Best of the Greek Isles - Eclectic Holland - Finland's Arctic Wildlife - Turkey—Continental Crossroads - Tuscany - White Horses of France's Camargue NORTH AMERICA - Alaska Overland - Aurora Borealis—Fairbanks, Alaska - Bald Eagles of the Chilkat River, Alaska - Bosque del Apache & White Sands, New Mexico - Brown Bears of Katmai National Park in Summer - Brown Bears of Katmai National Park in Autumn - Colorado Fall Colors - Denali National Park in Autumn - Exploring Lake Powell - Florida Birds—Best of the West - Grand Canyon at Havasu Falls - Great Smoky Mountains - Horses & Icons of the Wild West - Humpback Whales of Alaska's Inside Passage - Mexico's Colonial Heartland - Monument Valley & Slot Canyons - Nova Scotia—Photo Tour for Women - Olympic National Park, Washington - Predatory Animals of North America - Springtime in Callaway Gardens, Georgia - Ultimate Wolves - Ultimate Yellowstone - Washington's Palouse Country - World's Best Raptor Shoot - Yellowstone & Grand Tetons in Autumn - Nature & Digital Photography Seminars with John Shaw PACIFICA - Midway Atoll SOUTH & CENTRAL AMERICA - Galápagos - Patagonia's Mountain Landscapes - Ultimate Dolphins Wildlife Models Shoot - Wildlife of Brazil's Pantanal Photo Safaris By Date JANUARY - Ultimate Wolves - Nature & Digital Photography Seminars with John Shaw, Dallas, TX & Raleigh, NC - Ultimate Yellowstone FEBRUARY - Japan's Winter Wildlife MARCH - Florida Birds—Best of the West - Nature & Digital Photography Seminars with John Shaw, Phoenix, AZ & Boston, MA - Midway Atoll - Aurora Borealis—Fairbanks, Alaska - Monument Valley & Slot Canyons - White Horses of France's Camargue APRIL - Springtime in Callaway Gardens, Georgia - Galápagos - Finland's Arctic Wildlife - Patagonia's Mountain Landscapes - Eclectic Holland - Great Smoky Mountains - Grand Canyon at Havasu Falls - Mexico's Colonial Heartland MAY - Wildlife of Brazil's Pantanal - Turkey—Continental Crossroads - Ultimate Dolphins Wildlife Models Shoot - Best of the Greek Isles - Tuscany JUNE - Washington's Palouse Country - Predatory Animals of North America JULY - Brown Bears of Katmai National Park in Summer - Olympic National Park, Washington AUGUST - Washington's Palouse Country - Humpback Whales of Alaska's Inside Passage SEPTEMBER - Masai Mara Wildlife Reserve, Kenya - Denali National Park in Autumn - Alaska Overland - Essential China—Iconic Landmarks & Landscapes - Brown Bears of Katmai National Park in Autumn - Madagascar - Yellowstone & Grand Tetons in Autumn - Botswana Wildlife - Colorado Fall Colors - Predatory Animals of North America - Horses & Icons of the Wild West - Mongolia—The Golden Eagle Festival OCTOBER - Exploring Lake Powell - World's Best Raptor Shoot - Nova Scotia—Photo Tour for Women - India—Rajasthan & Puskar Fair NOVEMBER - Laos & Vietnam - Ultimate Antarctica - Bald Eagles of the Chilkat River, Alaska DECEMBER - Bosque del Apache & White Sands, New Mexico

		John Shaw Nature & Digital Photography Workshops Click here for locations and dates Mexico's Colonial Heartland March 17–24, 2007 Horses and Icons of the Wild West August 26–September 1, 2007 Masai Mara Wildlife Reserve, Kenya September 7–21, 2007 Australia Wildlife November 1–20, 2007 Teleconverters are optical magnifiers which multiply by their power whatever you put in front of them. They go between the camera body and the lens, and while they superficially look like extension tubes, they have optics in them, whereas tubes are only hollow spacers. You might hear them referred to by all sorts of names: teleconverters, tele-extenders, multipliers, converters, or (inaccurately) doublers. I've often thought of them as multipliers because that's what they really do; they multiply whatever you put in front of them from the same working distance. Teleconverters are available in 1.4X power, 2X power and even 3X from a few sources. (Don't even think about buying a 3X converter — the results are terrible.) When a teleconverter is mounted behind a lens, it multiplies both the focal length and f-stops of the lens by the power of the converter. For example, a 2X converter doubles the focal length of whatever lens it's used on and at the same time it changes all marked f-stops by two. A 300mm f/4 becomes a 600mm f/8 when a 2X is added. The optical quality of teleconverters has improved over the last 20 years with computer-aided design and better glass. Still, not all converters are equal. Basically there are two types on the market. Dedicated units are available from the major camera manufacturers and are designed specifically to match with certain lenses. For example, Nikon has the TC-E converters designed specifically for their latest AF-S lenses. While these converters might possibly fit other lenses, they are designed for optimum optical performance with those lenses only. The other style of converter is the universal model from accessory manufacturers such as Tamron, Tokina and Sigma. These aftermarket converters will work on any lens on which they can be mounted, but they are not designed for any one particular lens. Think of these as a "one size fits all" product versus the exact fit of the dedicated models. Here's the difference between using a lens all by itself, in this case a 500mm, and then adding a 1.4X teleconverter to the lens. Both pictures are taken from the same location. Converters are an excellent way of increasing image size without having to get closer to your subject. Basically this comes down to two modes of working. Either you want to make a long focal length lens into an even longer focal length, or you want to increase magnification when you're doing a close-up. Here are some conclusions I've made about their use. For best results, use the dedicated converters with long lenses. As a general statement, the special-model-dedicated teleconverters from Nikon, Canon and other camera manufacturers will give you the best results if you want to add a converter to a long telephoto lens. These converters have the best glass and the best coatings; hence they preserve color fidelity without softening the image through lowered contrast or added flare. Of course, these camera-brand teleconverters are quite a bit more expensive than the universal models, but you will see a distinct advantage on film when shooting with your prime lens wide open. Why worry about wide-open results? Well, you primarily use long telephotos close to wide open, especially when you're photographing birds and mammals. Usually you're at maximum aperture or just a stop or two down from it. Use the fastest lens you can. I just said you need lens speed. Start out with a lens that's f/5.6 wide open, add a 2X converter, and suddenly you're at f/11. Unless you're working at high noon, you can hardly see through the lens, let alone hit sharp focus. No autofocus system today will function at this maximum f-stop since so little light is coming through the lens. An f/11 lens is totally useless for natural-light bird and mammal work since you're forced into such long exposure times. Animals are active early and late in the day when light levels are already low, hence you need all the lens speed you can have. Use the best prime lens you can. The highest quality teleconverter used on a mediocre lens will yield mediocre results. Converters magnify whatever is put in front of them, so you want the best possible starting point. All converters magnify defects, optical aberrations and lack of sharpness. Use a lens that already has these traits and you'll just get more of them. Use the best photographic technique you can. Remember that you're creating a much longer lens and you have to treat it as such. Let's say you have a 300mm lens and you add a 2X converter to make a 600mm lens. Compared to a normal 50mm, the 300mm is a six-power optic, but the 600mm is a twelve-power optic. You have to be that much better, that much more careful, and that much more aware of image-degrading factors than you were before adding the converter. If you have a tripod that's barely adequate for a 300mm lens, it definitely isn't enough for a 600mm. If you absolutely must hand-hold a photograph, remember that you need a considerably faster minimum shutter speed for sharp results since you're now using a much longer lens. For the most part, avoid using zoom lenses. Zoom lenses are already optically complex with many elements in the light path. Start adding more elements with a converter and image quality quickly falls apart. There are some exceptions, specifically the Canon 70-200mm f/2.8 EOS lens used with Canon's EF teleconverters and Nikon's 80-200mm f/2.8 AF-S lens mated with the TC-E converters. You might note, however, that these two lenses are top-of-the-line zooms with big maximum apertures and price tags to match. I would certainly test other zooms that you might own, but most of the results I've seen are not encouraging. Of course you must define what "quality" in an image means to you. Just getting a recognizable image of any sort might be enough, or perhaps you demand absolute sharpness. The only answer is personal testing of equipment combinations, mounted on heavy tripods and used with immaculate photo technique. Use a 1.4X converter in preference to a 2X. When making long lenses into longer lenses, the 1.4X teleconverters are by far a better choice in that image integrity is better maintained. All converters degrade the final image on film, but the lower the power, the less you lose. You sacrifice some image size for considerably more quality. This loss of image resolution also suggests that you should always start with the best film you can use under the circumstances — but you should be doing that at all times. Part of the reason that a 1.4X converter gives better results than a 2X is that it only changes the light hitting the film by one stop. Consequently you can photograph using one faster shutter speed than with a 2X, which in turn helps stop both camera and subject movement. You may not have as much focal length, but you'll get sharper photos. By the way, ever wonder about that odd 1.4 number? It's because of the f-stop progression. Have you noticed that going from one f-stop to another changes the f-number by a power of 1.4? Each number is 1.4 times the preceding one: 2 times 1.4 =2.8; 2.8 times 1.4 = 4; 4 times 1.4 = 5.6; etc. Let's assume you're adding a 1.4X tele-extender to different lenses. A 300mm f/4 becomes a 420mm f/5.6; a 400mm f/5.6 becomes a 560mm f/8; a 500mm f/4 ends up as a 700mm f/5.6; and a 600mm f/4 is an 840mm f/5.6. When focal length is multiplied by 1.4, the aperture changes by one stop. You get the depth of field of the "new" lens. I've heard it said that when you use a teleconverter you get the depth of field of the original f-stop of the lens without converter. Not true. Suppose you have a 300mm f/4 with a 2X converter. If the lens' aperture is set wide open, do you have the depth of field of f/4, the aperture at which the lens itself is set, or of f/8, the aperture created by the converter? If you remember that f-stops are a mathematical ratio between the optical hole in the lens and the focal length, you should know the answer. Since the size of the aperture doesn't change when you add a teleconverter but the focal length does, the lens becomes slower. It is an f/8 lens wide open with the depth of field of f/8 at this aperture. Depth of field depends on the f-stop you're using, not how you get to that effective f-stop. Minimum focusing distance of the prime lens does not change. This is one of the major advantages to using a teleconverter. If your prime lens focuses to eight feet, the lens plus teleconverter still focuses to the exact same distance. Really long focal lengths, such as 500mm or 600mm, focus down to about 15 feet minimum. Almost all 300mm lenses, however, will focus without added extension tubes to roughly 8 feet. Use a 2X tele-extender and you have a 600mm with the same 8 feet minimum focusing distance. Autofocus may or may not work correctly. You'll have to check your teleconverter-lens combination to determine if the autofocus provision of your camera does indeed work. The slower the aperture of the final combination, the less likely AF is functional. Most camera systems cut off autofocus at f/5.6 or f/8. Early Canon EOS equipment would not autofocus at any aperture less than f/5.6; the cameras were programmed to bypass any AF function at speeds slower than this. Canon made a 500mm f/4.5 lens, but with an added 1.4X converter you ended up with a 700mm f/6.3 lens. That extra stop — from f/5.6 to f/6.3 — disabled the autofocus feature. In response to many requests for a 500mm lens usable with AF converters, Canon brought out an f/4 version of the 500mm plus camera bodies with AF software functioning at slower maximum apertures. The exposure readout in the camera may or may not work correctly. Most teleconverters permit correct meter readings without any correction factors needed. Here's how to check. Mount a long lens on a tripod and meter the wall of your office without a converter on the lens. You don't need to focus the lens to do this, so working distance is of no concern. Now add your converter and see if it changes the meter readout by the correct amount, one stop for 1.4X converters, two stops for 2X ones. Do this in all the exposure modes you normally use. The exposure will probably be correct, especially if your camera offers an analogue meter display. However, the actual numbers may not be right. Teleconverters are not just for critter shots. This was taken with a 300mm lens plus a 2X converter, a 600mm equivalent. The long focal length gave me the big sun image. For example, if I mount the current Tamron 2X AF converter on my 300mm f/2.8 lens it shows the exposure does change two stops from a meter reading without the converter. However, the digital readout of the f-stop in use does not change. If the lens were set wide open at f/2.8, the display still reads f/2.8 with the converter added. If I do the same test using my Nikon TC-E 2X converter, both the meter reading and the display are correct. The f-stop display shows f/5.6, the effective f-stop created by mounting the converter. I mention this possible discrepancy in case you ever use a hand meter for exposure evaluation. If the meter says "1/125 second at f/5.6", just where and how do you set this exposure on your camera? You need to check your equipment before a shooting opportunity comes along. Teleconverters give you focal length choices. My longest lens is the Nikon 500mm f/4 AF-S. Add the 1.4X Nikon TC-E and I have a 700mm f/5.6 which maintains autofocus while adding only one inch in length and seven ounces in weight. If I use my 2X TC-E I end up with a 1000mm f/8 lens, I lose the AF feature, and I have a combination that's two inches longer than the prime lens alone and twelve ounces heavier. I effectively have two more lenses with me but they add little bulk or weight to my camera bag. Even though these converters are pricey, they cost many dollars less than actually purchasing the equivalent focal lengths. A combination that's very useful is a high quality 300mm f/2.8 AF lens, the best you can buy, and both 1.4X and 2X AF teleconverters matched to the lens. Actually a 300mm f/2.8 is about the only lens on which I feel comfortable in using a 2X converter. These lenses are so superb optically that, properly handled, you can get good results. Since f/2.8 is quite fast to begin with, you don't lose autofocus even with the 2X teleconverter. You have a fast 300mm f/2.8 for low light or close work, a medium length 420mm f/4 for normal telephoto use, and a long 600mm f/5.6 when you really need some reach. Teleconverters let you try out focal lengths you don't own. There's one time I would consider adding a generic 2X teleconverter to a zoom lens and that's when you're trying to decide if you should buy a long focal length lens. Quality long lenses aren't cheap; they are extremely expensive costing well into the thousands of dollars. If you think you need a 500/600mm lens I would first try to borrow one for a few days. If none are available, consider spending about $100 to add a decent universal 2X to your 70-300mm zoom lens. Now go out and shoot some pictures. How often did you actually use that long focal length? Do you see shots where you need a 500mm lens or are you pulled back to the shorter end of the zoom? You might discover that you love the long focal length. OK, now spend the bucks and buy a good lens. On the other hand, you might find out that you rarely see images with such a lens, or that the quality yielded by converter plus zoom is good enough for you. Teleconverter, extender, multiplier...call them what you will. But don't leave home without one! Questions and Answers John Shaw will occasionally answer readers' questions in his bi-monthly column regarding equipment and photography techniques in the field. He can be contacted via e-mail at this address: johnshaw@photosafaris.com. Due to the anticipated volume of inquiries John cannot answer questions individually.

	Joseph Van Os Photo Safaris, Inc. P.O. Box 655, Vashon Island, Washington USA 98070 Phone: (206) 463-5383   Fax: (206) 463-5484    Email: info@photosafaris.com Copyright © 2008, Joseph Van Os Photo Safaris, Inc.