Monday, March 28, 2011

Mirror Lockup (back by popular demand)

Nikon D300, Nikon 70-300 ED, f/11, 1/10, ISO 200

I shot this image last summer during a mountaineering trip in the North Cascades.  This image was shot about 25 miles from the nearest road head.  Along with carrying camera equipment we had to carry, ropes, crampons, ice axes, and all necessary food and camping gear for six days.  Thus I was very limited in the photo equipment I was willing to carry on my back.  So I opted to carry a Nikon 16-85 VR, and Nikon 70-300 ED (not the VR version), and my two pound waste high Gitzo carbon fiber tripod. 

Despite the non-pro glass I ended up coming home with several stellar images, including the one above.  Often I am asked by photographers why images shot with their $2000 70-200 zoom lens are not coming out sharp, while I can get good images out of a $150 70-300.  Unknowingly they are asking two separate questions in there statement.  First while at f/4.5 my 70-300 ED is very weak, at f/8 or f/11 it rivals the sharpness of the $2000 lens.  Thus I try to shoot this lens at as close to f/8 as possible to pull out the sharpness.

The second and more important question is "why can't I get sharp images from my 70-200 f/2.8".  The real issue here is not the lens at all, but rather the technique.  While the 70-200's of today are truly amazing, no lens will come out sharp at slower shutter speeds unless it is absolutely rock solid.  But "I have it on a tripod" you may say... Well that is a good step, but it doesn't eliminate the last remaining source of vibration in the system.  It may seem trivial, but at slower shutter speeds when the mirror slaps up right before the shutter opens it sends a vibration through the camera/lens and makes it nearly impossible to capture a sharp image.  While each camera, lens, and tripod combination are slightly different a good rule of thumb is any shutter speed less than about 1/125 down to about 1 second will have this issue.

So if you have been wondering why you don't seem to be getting the image quality you were expecting from your investment at slower shutter speeds, try using the mirror lock up feature on your camera.  Mirror lock-up is one of the most expensive features to include in a camera, but most higher end digital cameras now come with this as a  standard feature.  If your camera does not have this feature you can still hedge your bet by using a solid tripod, a cable release, and trying to avoid the "danger" shutter speeds when possible.  If you must shoot at these slower speeds make several exposures and hopefully one might come out sharper than the rest.  Like everything in photography it is a balance of what we want vs. what we can get away with.