Tripods and long lenses

Well we've covered a few things that tripods are good for. Most of them involve giving yourself a slow shutter speed to deliberately create blur in your picture, increase your depth-of-field or sometimes even both. We also talked about using them at night when you would otherwise have shutter speeds well beyond the realm of anything handholdable.

But there's another situation where you could maybe get away without using one but you are often better to dig it out. That's long lens photography. And with the ever-increasing zoom capabilities of many point-and-shoot cameras this lesson goes for those of you with simple cameras as well as SLRs.

The old general rule for handholding a camera was to put 1 over the focal length of the lens and that was the slowest shutter speed at which you could handhold the camera without getting hand shake in there. So if you had a 50mm lens, the theory went that you could handhold it down to about 1/60 second before things started getting blurry.

Extrapolating that idea further you can see that the longer your lens, the faster a shutter speed you need before you have to have some sort of support ie our trusty tripod. A 300mm lens would require a shutter speed of roughly 1/250 second, a 400m up to a 1/500 second. This was all based on 35mm film photography so if you have a compact camera, or a digital SLR you need to convert the focal length of your lens to its eqivalent in 35mm film.

So a 70mm lens on a film camera could be held down to about 1/60 second but when you stick it on a crop digital camera it's the equivalent of a 105mm lens and you'll need 1/100 second to prevent things getting blurry.

Now before we start with the macho churpings of 'Yeah but I can handhold my camera this slow', yes you maybe can but the pictures won't be anywhere near as sharp as they would be if you had the camera on a tripod. And the rule has changed slightly with Image Stabilisation techniques as well.

That being said, putting your long lens on a tripod is just a good idea. It saves you sitting there holding a whopping great lens for hours on end waiting for a little critter to come into your field of view. The shot above was taken with a 400mm lens with a 1.4 x converter on it. I'd tell you the f stop and shutter speed but it was shot on film so I have no idea! I would say it was taken at about f5.6 and the film was definitely ISO 100 which means my shutter speed on that cloudy day would definitely have been too dodgy to handhold.

When I use my long lens on a tripod I have my right hand on the shutter button (or cable release button if I'm using a release) and I place my left hand on top of the lens at the point where the lens is connected to the tripod (usually a tripod collar ring). This helps dampen any shutter vibrations that might further help to give me a less than sharp picture.

Well that's about it for the types of pictures that a tripod will help you take. I hope it's been of some value. For my last post tomorrow I'll talk a little about how to look for a good tripod and the kind of features that will come in handy.