Image Sharpness and Telephoto Lenses: Tips and Tricks

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I recently had the chance of meeting a guy named Jay, who had taken some photographs of birds.  After photographing the birds, Jay realized that the images were too grainy and not very sharp.  So Jay asked me what he could do to save the images.

Image Sharpness and Telephoto Lenses

Jay had the kindness to show me some of his work shortly after we talked about the photos in question.  His other examples were crisp, sharp photographs of wildlife.  He was shooting with a Sigma 50-500mm f/4.5-6.3 APO DG OS HSM telephoto zoom – a strong performer where Sigma telephoto lenses are concerned.

Hindsight, as they say, is 20-20.  And even though we all know it, you should prepare yourself adequately before going out into the field.  Not only should you be thinking about gear, but also how you will take photographs as you see them.  

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Knowing how to react makes you a better photographer.  The answer doesn’t have to be all about the technology.  This image was taken using the poor man’s macro technique.

A lot of our photography education seems to be centered around the technology, and I’m all for some of that.  But another part of our education should be how to react in given situations.

Jay did right by packing a 50-500 mm lens.  For wildlife photography, you can’t get much better.  And the f/4.5-5.6 wasn’t amiss because he was shooting in broad daylight.  But there are some extra things Jay could have done to improve his shots while he was photographing.

First off, image sharpness and telephoto lenses have a rocky relationship.  A lot of times photographers see sample images online and think This lens took these pictures!, while what they should be thinking is that the lens, coupled with some other key factors like stabilization, light, and distance, probably contributed a great deal to the resulting image quality, as well.

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Taken with a Tamron 55-200 mm manual focus lens, without a tripod.  It helped that I laid in the grass to take this.

Another pitfall for those of a technical inclination is to buy into the idea of image stabilization (in the lens Jay was using, this corresponds to Sigma’s OS designation – optical stabilization).  I won’t bore you to death with the science of it, but suffice to say that image stabilization (IS) is a combination of moving glass, motors, sensors, and springs, that attempts to cut down on lens vibration.  It handheld situations, IS can be incredibly useful.  With a tripod, IS is actually counterproductive, and result in not-so-sharp or even downright blurry images.

If you’re shooting as Jay was, turn off IS (most lenses have a switch for this), and use stabilization.  If you have a tripod, use it.  If you don’t have a tripod, use anything.  Use a rock or a tree, a fence post, a park bench, even the roof of your car.  Put sturdy items beneath the lens (like a bipod on a machine gun) to increase your angle without losing stabilization.  These are tricks I’ve used that actually work folks.  Gear can be a great help, but you should never find yourself limited by it.

Secondly, you need light.  This can be tricky, and when it comes to image sharpness and telephoto lenses, it is usually a trade off.  After you’ve brought your shutter speed down as low as you can reasonably go, and after you’ve selected the minimum aperture, your only option left is to jack up the ISO.  Doing so can result in noisier images, so knowing your camera well – and it’s tolerances will go a long way here.

Thirdly, alter the distance.  Photographers the world over have been blessed with things called legs that actually pre-date the zoom lens.

I know.  It’s astounding.

But let’s face it – even though the manufacturers want you to drool over that 500 mm lens, the 500 mm focal length within it’s zoom range is probably not the focal length for optimal sharpness.  Every lens has an optimal focal length – a “sweet spot” – where things just seem better.  There are people out there who test lenses for this.  Go find them.  They will love the fact that someone actually cares.

At any rate, getting closer in can be a challenge.  Too close and you’ve spooked the wildlife.  How do you go about it?  Photography – especially wildlife photography – is very akin to hunting.  You have to take your time, and you have to be intelligent about it.  Move slowly, move quietly.  If an animal is looking at you, don’t approach it.  If an animal has reacted once to your movements, don’t approach it.  And if at all possible, stay upwind from the animal you want to shoot.  These tricks can help you photograph something without spooking it.

Okay, so you’re not a big game hunter, and it is pretty difficult to stay upwind from birds.  I’ll admit these things.  What I won’t admit is that there isn’t a solution to the problem of being too far away.

On the technical side of things, there are ungodly zoom lenses that you can buy, provided you have money to spend on them.  Or you can look into converters for your lens, although they do decrease image sharpness all on their own, and exponentially if more than one is used.

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This image is the result of a 50-60% crop.  It was taken with a Nikon 50 mm f/1.8 E Series lens.  More detail here.

Another option?  Old, manual-focus prime lenses that were made for film lenses.  With these puppies, image sharpness and telephoto lenses seem to go hand in hand.  Some will mount with your digital camera and some will not.  Some may even meter with your camera, but most (the vast majority) will never auto focus on your camera.  Gearheads may not want to hear about the advantages of using old glass and throwing all the modern gimmicks out the window, but I’m approaching this from a tried-and-true standpoint, and this particular remedy is easy, cheap, and effective.  Can’t get any closer to your subject?  Crop in post-production.  You’ll still get incredibly sharp results, even if it is considered “wrong” by most photography forums out there.

But what can Jay do now that the moment to photograph these birds is gone?

Software exists – with varying opinions about its effectiveness – that can remove some grain from photos and sharpen them up a bit.  Does this the troubles with image sharpness and telephoto lenses are over?  I doubt it.  Software companies love to show you testimonials of great experiences, but there are usually people with lackluster experiences too.

Another alternative is finding a digital lab that retouch your files.  Such places do exist, though I have never used them and cannot speak of their performance.


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