Selecting an acceptable shutter speed for long telephoto wildlife photography in order to deal with possible motion blur is sure to evoke diverging opinions. On the one side, there are those who claim that only a very high shutter speed can be relied on to compensate for motion blur and produce acceptable wildlife images, even if it means resorting to exceedingly high, noise inducing ISO settings. And, they are correct when the subject is in constant motion -- there is no substitute for high shutter speeds to stop action.
But, what about ostensibly stationary subjects? Some contend that even motionless subjects, perched birds, alert wildlife and the like, require high shutter speeds because no wild animal is ever completely still. Yet, is that necessarily the case? Can slow(er) shutter speeds produce useful results, albeit with possibly a reduced percentage of keepers, when used to photograph perched birds, for instance? It seems clear that in good light, the above debate is mooted by the availability of high shutter speeds and low ISO settings. After all, “sunny sixteen” implies the following choices:
But what about poor lighting, for example when photographing small passerines in the understory on a cloudy day? One can't have both low ISOs and high shutter speeds, particularly when using teleconverters, a frequent occurrence with small song birds at significant distances. Something has to give, and once the lens hits maximum aperture there are only two choices left, increase ISO or or reduce shutter speed – or a mix of both.
Gear and Situations
Undoubtedly, circumstances vary, as well as individuals' approaches to handling them. I can only speak from my own experience, but I side with those who occasionally resort to very slow shutter speeds, even with long telephotos, to get the image. This whole shutter speed vs sharp vs not sharp isn’t an absolute; it comes down to percentage of keepers relative to what one finds acceptable – and for what uses. I routinely shoot sparrows, warblers and finches at 30+ feet in the deep understory, and I get enough printably sharp images to make it worthwhile. Setup: EOS 1DX MkII, EF 600mm f4L IS II, 2X III (1200mm) at f11 (for depth of field primarily, although image quality is also a bit better than wide open at f8), carbon fiber tripod, gimbal head, flash on raised flash arm and Fresnel flash range extender -- flash usually set to -1 2/3 compensation, give or take – I don’t care for the look that results from flash as main light.
On top of that, I prefer not to shoot this type of subject with full sun. The sun doesn’t illuminate subjects in the deep understory anyway, but it does create a dappled effect in the background, with far too many out-of-focus hot spots to yield pleasing images – as well as possible shadows across the subject. So, I go out on mildly overcast days, with little or no wind, to take advantage of the resulting diffused light and calm conditions.
For image quality, I prefer to be below ISO 3200, although I’ll take 6400 in really poor conditions – and shutter speed gets traded off with ISO in trying to find the best balance. A quick glance at Canon’s MTFs, or at The-Digital-Picture image quality test charts, shows that the 600 with 2X does not yield the absolute pinnacle in image quality – and my technique isn’t flawless either. Further, small passerines tend to not stay perched for very long. Heck, it’s hard enough to acquire them at 1200mm before they’ve flown again. Depending on the perch, there may be some left-over motion from the bird’s touchdown. Also, they tend to be in constant motion, looking all around, possibly keeping a watch for any predators that might be nearby. And, in a few seconds they are gone.
How Well Does It Work?
All of which is to say that opportunities are limited and the ceiling of what can be accomplished is not high. I’m often in the 1/160th to 1/320th range, simply because there isn’t enough light to do more with the ISOs I’m willing to use. Nevertheless, for small enlargements I find there are enough satisfactory results to be more than acceptable for my use. I’ve gotten printable images as low as 1/60th of a second, although obviously that’s not preferable and the percentage of keepers at that shutter speed is understandably low. Note that image stabilization is crucial to success in these circumstances. When I owned the first generation Canon image stabilized 600mm (advertised 2 stops of stabilization) I could see my heartbeat in the viewfinder; with the version II (advertised 4 stops) I don’t. The net effect is an increased percentage of keepers. And, it surely helps that I never print large, typically 7x10” -- the preference is to create wall size montages composed of many images, of a wide variety of subjects, including landscapes, travel, portraits, sports, architecture, wildlife and all manner of birds -- including passerines in the deep understory.
Of course, the larger the print, the more critical every parameter becomes, and what works for small prints works less well for larger ones – perhaps even to the point of being completely unacceptable. (Regrettably, there are people in Internet land whose standard response to any posted image is, “That’s not sharp” – even if you could spit a hair on the detail. These people are simply "I know it all" egotists and are best ignored; it’s none of their business what another individual considers acceptable.) I do grade images at 100% on the screen during post processing, and if it isn’t as sharp at that magnification as the optics permit, then it is a reject.
There is a hidden assumption in the scenario discussed above. That assumption is that there will be plenty of opportunities; thus failure in one does not matter so much in the long run. This assumption breaks down in situations where opportunities are severely limited and not likely to be repeated. In such cases, one must think very carefully about the decisions and compromises one makes so as to not come away with nothing. The above approach works for my circumstances, but perhaps not for others. In the end, each photographer has to work out their own process.
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