A Counter-intuitive Tip To Tack Sharp Photos With A Long Lens

The hues of twilight cast offshore sea stacks in a blue glow as waves wash around them, Crescent City, CA
The hues of twilight cast offshore sea stacks in a blue glow as waves wash around them, Crescent City, CA

On my recent trip north up the California coast to photograph redwoods and rhododendrons, I also had an opportunity to shoot sea stacks just offshore in Crescent City, CA. After shooting a bit with my 70-200mm, I really wanted to go for a unique perspective of these rocks and stack them on top of one another. So I grabbed my go-to bird lens, the 800mm f/5.6. Using a Canon 7D with a cropped sensor gave me an equivalent focal length of 1280mm.

I waited until the sun set, giving me photos with the cool blue of dusk, and allowing me to slow my shutter speed to turn the crashing waves into a calming mist. This is the effect I was after – hard, sharp rocks shrouded in a blue fog of moving water. However, as soon as my shutter speed got longer than 1/100th of a second and started creeping toward the 1 and 2 second mark, the results on the back of my LCD were horribly blurry.

In normal shooting conditions with this lens, I never like to let the shutter speed drop below 1/250th of a second, and only if I have a stationary subject do I lock down the gimbal head on my tripod and go for something slower. But usually 1/100th of a second is my slowest usable shutter speed. What to do in this situation? Even by bumping the ISO very high I couldn’t achieve a fast enough shutter speed in these darkening conditions, and doing so would also counteract the effect of the moving water.

The solution seemed counter-intuitive at first. I found that by greatly lengthening my exposures, I was able to achieve much sharper results! The initial blurriness I was seeing was caused by the shutter vibration, amplified by the extremely long focal length (and yes, I was using mirror lockup). When I increased the exposure time, the percentage of time that the mirror shake impacted the overall exposure time was reduced, thus creating a sharper image. Using this principal, I found that by exposing for 30 seconds, I was able to achieve the sharpest results.

A couple things to keep in mind. First, this technique will only work if there is no wind. Even a slight breeze will blow a huge lens like that back and forth, ruining any chance of a long exposure. Second, make sure to check sharpness by zooming in to your resulting photo on the camera’s LCD. Never trust sharpness from a photo displayed 3 inches across – everything looks sharp when it is that small!

So next time you’re out with a giant lens trying to do landscape work (really not a very common combo!), remember to experiment with the slower shutter speeds. You might just find some sharpness in there.