Big Glass on Display
Recently I was in the birding in the Everglades with my wife and a friend. The day was mostly cloudy, and the wind blew and gusted regularly, a lousy day for photography, but I tried just the same. At Mrazek Pond I was probably more distracted by the gear the several other photographers rolled out than the feeding antics of American White Pelicans and Roseate Spoonbills. The 500 mm and 600 mm lenses mounted on their spindly pedestals of aluminum tubing bristled with the aura of professionalism. But on this perfunctory day, it was more a show of big glass. One guy actually had a smaller lens and camera clamped to the same tripod head as his big outfit. Now that seemed useless, but flexibility is part of this treatise.
On an empty West Lake a monstrous lens was keeping imperious watch for what we’ll never know. I looked over the photographer’s opportunities and decided he was in for an interminable wait, or he really had no clue what he was doing. But he had big glass, and for wildlife photographers such gear is the price of admission to a select group.
What is this 500, 600 thing anyway? Well it probably doesn’t hurt to go back and look at focal length. When we use the term ‘normal’ we are talking about a lens which projects on the film format an image with the composition in the same perspective as we view it with the naked eye. Everything in the picture is in its proper relationship to each other. This focal length is about equal to the diagonal of the film format. In large format photography using 4 X 5 inch or 8 X 10 inch sheet film, that lens will be 6 or even 12 inches from the objective lens element to the film plane in order to cover the entire frame. With the smaller 6 cm X 6 cm, or 2-1/4 inch square that same normal lens is about 3 inches, or more commonly, 80 mm. With the small 35 mm format the average normal lens is 45 - 50mm.
Now that we have this established, so what? Well if normal is 50mm in 35mm lexicon, then a lens twice as long, 100mm, would have half the angle of view and would be considered 2 X normal. A 300mm lens is 6 X normal and these monuments we are discussing above are 10 and 12 X normal, with a very narrow angle of view. More importantly, with every increase in ‘power’ each tiny vibration of the lens is magnified ever larger and causes the image to blur. The more power the more carefully they must be handled, and the successful shot ratio drops accordingly.
Add to this the fact that current image sensors, often referred to as DX for digital, are only 2/3 the size of a 35 mm frame. So a normal lens in this format is 30 – 35mm, which means that that every lens in your bag has increased focal length by a factor of 1.5. Now the big glass is a really big, as a 750 mm or 900 mm lens rendering an image 15 to 18 X normal. Vibration is now a significant issue. Still, I rarely see one of these lenses properly supported and dampened. In today’s digital photography cropping an image for composition is as common as adjusting exposure. If you shoot birds and other small wildlife as I do, you probably crop over 75% of your images. I am intent on the eye of the bird, the wing and head of the butterfly. If they are in focus everything else is probably okay. Keeping equipment vibration to zero is of paramount importance in achieving that goal.
Bird photographers, me included, have an in-bred tendency to reach too far. When we do that with these long lenses we are inadvertently bringing in the background as well. This compressed perspective is an effect of telephoto lenses. Distant subject also often have backgrounds that are less out of focus, and poor ‘bokeh’. Other than the vibration issue, nothing detracts more from an image than a busy background. In seminars I have given my mantra is often “watch your background”. Contrast is also an issue, particularly with off-brand big glass. Finally those distant shots you thought you wanted to make will likely never resolve on the details of your subject to your satisfaction. Looking back on my portfolio of over 1000 images of wildlife and scenics, I can count pretty quickly the truly distant shots I have been satisfied enough to keep.
So is big glass a waste of money for wildlife photographers? Certainly not if used in the proper context of distant shots not requiring an immense amount of subject detail. Can they deliver detail? Yes, but with far less frequency that you would like. It goes without saying that they are all but immobile except from a vehicle window clamp, and then we are back to the issue of vibration. Only one of them has anti-shake technology built in to it.
One solution is a 200-400mm f/4 zoom lens with IS/VR technology, still a very pricey and professional piece of equipment at $5000. It is smaller (14 inches vs. 16 inches for a 500), only slightly lighter because of the zoom elements, focuses much closer (6ft vs.15ft) and is easier packed and transported in a reasonable sized camera bag. By all accounts it is also well matched to the standard Gitzo 1300 series tripods. Yet with teleconverters and the DX chip you can still reach the equivalent of 840 mm (17-20X) to 1200 mm (24-28X) both of which are farther than I need to go for the reasons I mentioned above. Add to that the composing capabilities the zoom permits and you may be able to find that small warbler in the view finder after all. However, be aware that you will likely never be asked to join the select group with really 'big glass'.