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Getting Sharp Telephoto Images

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You want to know what the most common cause of photographer disappointment is? Absolutely, positively the most common? Its the photographer who just came back from a special trip — a safari, a wildlife adventure, birding, maybe even whale watching — with 762 blurry telephoto pictures. We talk to someone at least once every week with just this scenario. They took a great telephoto lens with them, spending good money to do so, and they got horrible pictures.

The reason is pretty simple: people who have gotten pretty good at shooting at normal range think those skills will translate well into shooting telephoto images. So they simply think “how long of a focal length do I need to get the shot” without realizing that longer focal length requires an entirely new set of photographic techniques (and sometimes accessories) to get sharp images. Getting a good telephoto lens will get you the image on the left, below. Learning a bit about telephoto technique will let you use the same equipment to get the image on the right.

The Problems with Telephoto Lenses

The problem is simple: vibration causing blur. If you already really understand why that is more of a problem with telephoto lenses, skip on down to the how to solve it sections. But I’ll warn you — 75% of the people who call us with telephoto questions do NOT really understand why this is a problem with telephoto lenses and what things make it worse. So I’d suggest at least skimming this section.

The severity of blur for a given vibration is proportional to the focal length of the lens.

Lets say when I handhold a camera I get a tiny bit of motion at the front of my lens, maybe moving the camera 0.1 degree of arc during the time the shutter is exposing (this would be pretty good actually). If I’m shooting a 50mm lens on a full frame camera, the field-of-view of my image is 39 degrees, so I would blur the image about 0.1 / 39 or .02% — a very small amount. If I blur the image the same amount (0.1 degree of arc) with a 500mm lens, which has a field of view of 4 degrees, I would blur the image 2.5%. So for the same amount of motion while handholding, the 500mm image would appear to be blurred more than 10 times as much as a 50mm lens. (As is usual when I write, there’s a ton of math and physics left out. What I said here is a pretty accurate illustration that ignores about half a page of trigonometry.)

Telephoto lenses are big and heavy

The vibration/movement problem is compounded because a 500mm lens is much bigger and heavier than a 50mm lens. There’s no way I can handhold it as still as I would a 50mm lens, so in reality I’ll get MORE blur when shooting a telephoto lens than I would with a standard sized lens.

Telephoto lenses have narrower apertures

Everyone knows that a wide aperture lens is bigger and heavier than a narrow aperture lens. The situation increase exponentially when you get to telephoto lenses. If the lens gets much longer or wider in aperture after 300mm it about doubles in size. A 300 f4 lens is generally about 4 inches in diameter and weighs a bit over 2 pounds. A 300 f2.8 lens is generally about 8 inches in diameter and weighs about 7 or 8 pounds. A 400mm f2.8 lens is generally about 10 inches in diameter and weighs 10 pounds. To make a telephoto reasonably small enough to hand hold, the aperture at the telephoto end is usually f5.6 or f6.3 for telephoto zooms of 400 to 500mm length. The narrow aperture means longer exposure times, resulting in (you guessed it) more vibration and movement while the shot is being exposed.

Teleconverters make the aperture even narrower, and soften the image

If you haven’t read about teleconverters, you’ll find all you want to know HERE
But the important thing is adding a teleconverter will reduce the aperture by 1 or 2 stops. And it may soften the image (particularly if you’re shooting with a telephoto zoom lens) so that you actually need to close the aperture an additional stop to restore sharpness. Pretty soon you’re shooting at f11 and that causes an additional set of problems.

How to get sharp images, despite the problems

Obviously it can be done. We’ve all seen jaw-dropping, hush-my-mouth sharp images taken at 800mm or more. Most telephoto lenses made today are very sharp under good conditions, sharper than wide angle lenses for certain, and generally sharper than standard range lenses. If you look at MTF charts you’ll find that for almost every manufacturer, their telephoto prime lenses are the sharpest ones they make.

So how do we get those sharp images? Well in two different ways, depending on the type of shooting we’ll be doing. In many cases, we can shoot long lenses hand-held by keeping the shutter speed short. So first we’ll discuss how to maximize shutter speed to try to shoot our telephoto lens without a tripod. In other case, that’s just not possible: we’re going to have to deal with a longer shutter speed. In these cases we’ll need a tripod, but also a few other techniques to maximize sharpness even on the tripod.

Hand-held telephoto sharpness requires fast shutter speeds

If there is one key to a sharp telephoto image, this is it. A fast shutter speed takes the picture so quickly that the vibration and blur that camera-lens movement causes is ‘frozen’. The shutter opens and closes before the camera movement or vibration that’s occurring can blur the image. How fast does the shutter speed need to be? The simple (and not sufficient) rule is 1 / effective focal length. For a full-frame camera shooting a 400mm lens, therefore, you need a shutter speed of 1/400 second (or shorter) to get a sharp image handheld. Remember that a crop-sensor camera has a angle-of-view that’s smaller than a full frame, so the effective focal length is the crop multiplier (1.6 for Canon, 1.5 for most other brands) times the lens focal length. The same 400mm lens shot on a crop sensor camera has and effective focal length of 600mm (1.5 X 400mm) so you’d need a shutter speed of 1/600 second or shorter for a sharp image.

Remember, this is a ‘best case’ scenario. Some of us can’t handhold as well as others. Sometimes there’s a breeze hitting that big lens causing even more motion. Some very experienced photographers suggest that whenever possible you should try to shoot at 1 / (2 X effective focal length). So that 400mm lens should, if possible, have a shutter speed of 1/800 second or less on a full frame camera (1/1,200 second on a crop frame). And if you decide to add a teleconverter, you multiply again by the magnification of a teleconverter.

Fast shutter speeds can be difficult to get

The bottom line of all this is good sunlight is your friend. There’s no way to get these type of shutter speeds indoors, at dusk, or even on a heavily overcast day. A wide aperture helps, too, but for many people this is impractical. They aren’t willing or able to take a huge (and hugely expensive) 400mm f2.8 lens so they have to get by with a 400m f5.6 lens. An aperture of f5.6 is two stops slower than f2.8. Shutter speed is going to double for each f-stop of light, so an f5.6 is going to require a shutter speed 4 times longer than an f2.8 lens. Adding a 1.4x teleconverter doubles shutter speed yet again, while a 2X converter (which takes 2 f-stops of light) doubles shutter speed twice. The bottom line is we usually need to do everything we can to keep our shutter speeds fast.

  • Shoot at the highest ISO that’s acceptable. ISO 800 is good on almost every modern SLR and most can handle ISO 1600 with no problem. Only a few cameras can go higher without loss of image quality, but some can go to ISO 6400 (or even higher if you don’t mind a lot of noise in the image). This is the reason, though, that we sometimes recommend someone consider a newer camera when trying to shoot long-range telephoto shots. New cameras can often handle much higher ISOs than older cameras. But remember: just because your camera can be set at ISO 3200 or 6400, doesn’t mean its a good idea. Some cameras can really do it, others simply have that setting for marketing purposes — its useless in the real world.
  • Avoid Circular Polarizing filters unless you really need them. Polarizers rob you of some light, 1/2 stop or a bit more, that you may really need to get a sharp image. It might be better to have a washed-out sky or a bit of snow glare than a blurry image.
  • Take the teleconverter off if you need to. Taking off the converter does three positive things: it increases the aperture (which reduces the exposure time), it shortens the focal length (which reduces the amount of blur from camera movement), and in many cases makes the image a bit sharper. Its often better to have a small, sharp image than a big blurry blob.

Image stabilization (AKA vibration reduction) can make a huge difference.

If you are shooting at very fast shutter speeds, Image Stabilized lenses don’t make a huge difference. But in reality, its rare that we are able to get shutter speeds so fast that we’re clearly exposing less than the 1 / twice the focal length formula. Vibration reduction can help us get some of that back. To decide how much help we’ll get make sure you know how many f-stops the vibration reduction on your lens (or camera if your camera has an in-body system) gets. For every stop of Vibration Reduction (or Image Stabiization, or whatever term your lens uses) you can double your shutter speed requirement, at least in theory. But remember, the amount of stabilization varies from 1.5 stops (on some of the older designed telephoto zooms) to perhaps 4 stops (on the very newest designed telephoto primes).

Lets say we’re shooting a 400mm lens on a crop frame camera, so we know we need at least 1/600 second exposures and we’d like 1/1,200. If your lens has two stops of Image stabilization then we can double that exposure twice (once for each stop of IS, VR, VC or whatever that manufacturer calls it). So instead of 1/1,200 we can possibly get a sharp image at 1/300 of a second. Notice I said possibly.

But always remember, the manufacturer is going to be pretty generous with their estimates of how many ‘f-stops’ of stabilization their system gets. You can usually subtract 1 from their number and be comfortable, so if they claim 4 stops, then best plan for 3 stops. Also, vibration reduction isn’t perfectly consistent. Several professionals have made it very clear that vibration reduction is inconsistent: shoot the exact same shot 10 times and sometimes the VR does a great job of stabilizing the image, sometimes not so great. Very respected photographers have said it works perfectly from 50% to 70% of the time ( 1. )

Good technique and ‘cheating’ help a lot

I have one customer who constantly gets great images shooting a Canon 500 f4 (a very large lens) handheld at 1/200 shutter speeds, sometimes even a bit slower. He also is an ex-Marine marksman and has amazingly good technique – with his lens arm in close against his chest, shooting after slowly exhaling his breath, he even times his shots with his pulse. Anyone can improve their technique with practice, although probably not to his skill level. There are lots of good ‘cheats’ that can help stabilize our handheld shots a bit. Resting your ‘lens arm’ elbow on a fencepost or tree branch can make a huge difference. Even leaning your shoulder against a tree or building can provide a nice degree of stabilization. Some people recommend the ‘string tripod’ — a cord tied around the lens’ tripod foot with the other end tied to a stick at the proper length. You step on the stick and pull the lens tight against the cord, providing tension that helps stabilize the lens.

In many cases, its just not possible to hand-hold a telephoto lens for the shot you want

In many situations there’s no way to get a shutter speed fast enough to hand-hold the lens. Even under great conditions, shooting at 800 or 1,000mm almost certainly means there is no way to get the shot hand-held. If lighting is less than ideal, even 400mm may be too much to get a hand-held shot. In these cases, obviously, a good tripod is the key. For a big lens this usually means a solid sturdy tripod and good ballhead. A big lens on a cheap, lightweight tripod may have almost as much vibration as it would hand-held.

A monopod may be enough help

I’ve never seen anyone quantitate how much stability a monopod can give so all I can use is my own experience. I’m comfortable that a monopod at least lets me double the acceptable exposure time, and I think perhaps triple it. My personal rule is if I’m going to take hundreds of shots (like sportshooting) a monopod will help me increase my keeper rate significantly, especially with a heavier lens. But if I’m going to get just a few opportunities to get the shot I want (say waiting by a nest for a rare bird to appear) I may want a better set up.

A good tripod is the key

We’ve discussed choosing tripods in another article . The key with big telephoto lenses (by this I mean 500 f4 and larger) is a sturdy, heavy tripod. The lightweight models can still allow vibration to be a problem (1 , 2 ). If at all possible, do NOT extend the center column, this has been shown to dramatically increase the amount of vibration with a heavy lens on board, and also to magnify movement caused by the wind blowing against the lens ( 2 ). In fact, to minimize vibration as much as possible the head should be mounted directly to the legs with the center column removed (or on a tripod designed without a center column).

There has been enough discussion online to show that different tripods have different vibration dampening abilities, but it is NOT clear which particular ones are best with which lenses. Hanging a weight from the tripod certainly helps (4 ), and putting the tripod feet in soft ground rather than a hard rocky surface has also been recommended. When a hard surface is unavoidable, vibration pads can be placed under the tripod feet — I’m not sure how much they help (never tried it myself), but some recommend them.

While I wouldn’t state its totally proven, the few people who’ve done comparisons seem to conclude the head involved has less effect on vibration than the tripod itself does (5 , 6 ). This assumes a heavy duty, high quality head that is rated well above the weight of the camera and lens involved. I’ve found no information that claims a gimbal head, like the Wimberley II, has more or less dampening effect than a good ballhead so my recommendation is to choose the type of head based on the lens and type of shooting, not because one should be better than another at minimizing vibration.

Mirror slap, pushing buttons, and other telescopic trauma

With a telephoto lens mounted on a good tripod, the 1 / focal length rule no longer is limiting. As long as the subject is reasonably still much longer exposures are possible. But when we get into longer exposures (anywhere from 1/250 second to a full second) other sources of vibration become significant. First among these is depressing the shutter button. When your finger pushes that button the entire camera vibrates significantly just from the mechanical action of your hand pushing down on the camera (7 , 8 ). This can be overcome by using the camera’s built-in self timer (not very practical unless the subject is perfectly still) or by using a remote shutter release. Remote shutter releases are available as inexpensive cables or slightly more expensive infra-red or radio transmitter units. Note that the remote release will be fairly camera-specific. Each brand of camera has a proprietary shutter release port, and sometimes the port changes for different cameras within a brand. Canon’s consumer cameras, for example, have a different port than their ‘pro’ series bodies, and older Nikon bodies have different ports than the newer ones.

The final source of vibration we can do something about is mirror slap . The focusing mirror has to be pulled up in a fraction of a second which is actually a rather violent event (you can see a video of it HERE ). The vibration caused by mirror slap lasts about 1/20 to 1/50 of a second ( 3 ) meaning on an exposure of this duration, the camera is vibration the entire time. Reverberations from the mirror slap, while not as severe, may continue for up to half a second if the tripod is inadequate. Most cameras have a mirror lock up feature that will lift the mirror, wait a half second or so for the vibration to die down, and then take the picture. Most allow you to raise the mirror when the remote shutter release is pressed once, and then actually take the picture with a second press of the remote shutter button. This allows you to get ready to take the shot so that there isn’t a delay (during which the subject flies or walks away) when you take the shot.

Shooting conditions

Some things you can’t do anything about except plan around them. Long distance shots are going to present a couple of problems. One is haze or smog. You can do some contrast and color enhancements in post processing to help some, but overall there’s not much you can do to get a good shoot of something several hundred yards away in hazy conditions. Waiting for better weather conditions is about all that you can do. One of the reasons the second moon shot above is much better than the first is that it was shot in winter on a cool clear night with now humidity. The first one was shot in fall on a rather muggy night.

Another thing that can really affect long telephoto lenses are heat waves. Blacktop, roof shingles, and concrete cause amazing heat waves that will horridly distort your images if you try to shoot through the air over them during a hot day. Even open areas of sand or dirt can do it on a sunny summer day. The only solution is to avoid man made objects between you and your subject, shoot early in the day before heat is a factor, of shoot on overcast days when there isn’t sunlight baking down on the objects.

Practice make’s perfect

I share this part from the heart. The moon shots I showed above are reasonable demonstration. The first time I decided to do a moon shot I loaded my gear up and drove out to the country. Setting up a telephoto and tripod for the first time in the pitch dark can lead to dropping things. Just thought I’d mention that. Planning on using a cable release and trying to find out where to plug it in for the first time in the dark is difficult. You find out your ballhead isn’t sufficiently strong and drifts downward slowly if you decide to use the 10 second self timer because you’re too cheap to get the cable release after the 4th or 5th image that doesn’t have the moon in it because 10 seconds is enough time for the lens to slowly drift downwards, but you can’t see it in the dark. Etc. etc.

Anyway after about the third night of frustrating myself doing something as simple as taking a 400mm picture of the moon, I’d finally learned my lesson, practiced setting things up beforehand and got some decent shots. With a little more practice I got much better shots. Now I can set up the equipment blindfolded and get several great shots in a few minutes. The first time I tried it, I got almost nothing usable out of several evenings of shooting.

If you’re shooting a big telephoto for the first time, plan on having at least a couple of days practice before you go heading out for the money shot.

Roger Cicala
Lensrentals.com
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One Response to “Getting Sharp Telephoto Images”

Ian Carter said:

Excellent advice and examples.
All excellent advice and good examples
There is just one more factor that I've noticed when watching other photographers. Some people, when they've pressed the button and "got the shot", relax, visibly. They relax their grip and stance and take their eye from the viewfinder to look at the subject unobstructed. (looking for fall-of-shot?) Sometimes they appear to begin relaxing their stance right at the moment of release, causing a loss of stability after the mirror rises, but during the actual exposure phase.
Follow through.
Wait till you see the subject again in the viewfinder after the mirror returns before you say, "Got it!" You might see a change that occurred during that visual interruption; another player entering the field of vision to negate the great move you've just captured and you still have your camera steadied to grab the action.

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