Nerd Notes: Preventing Light Leak and Loss of Contrast in Digital Long Exposure Photographs

From a purely technical perspective, the learning curve for most aspects of photography (especially digital photography) is not particularly steep.  In fact, if one is simply curious or foolish enough to keep experimenting with new approaches, experience – the sheer act of doing – is generally a better teacher than most technical photography workshops.  That said, I’ve always appreciated folks who are more than willing to volunteer tips here and there to help shorten the learning curve for others.  So, every now and then I thought I’d share a Nerd Note that others may find useful.  Today’s tip is brought to you by the letter, “L”.  As in Light Leaks during Long Exposure Photographs.  For the sake of brevity, this post will focus on digital long exposures.

If you’ve had the opportunity to experiment with either day- or nighttime long exposure photography, it’s possible that you’ve discovered new levels of frustration in your life (I can talk about making the actual exposure in a future post).  What makes long exposure photography particularly frustrating is the variable effect of light over time and the relatively low margin for error: after you’ve waited x number of seconds, minutes, or even hours with the shutter open, you go back to inspect your image only to find that it was slightly off focus, grossly under exposed, way over exposed, or marred by a pink/blue haze and low contrast.  With so many ways to screw it up, one might be tempted to give up too easily.  But a very simple tip to improve your long exposure results is to wrap your lens (and the lens mount) in a dark cloth:


The behind-the-scenes image above was an in-progress long exposure of about 90 seconds using a 10-stop neutral density filter on a 28mm tilt-shift lens.  The black cloth (in this case a strip of canvas purchased from a fabric store; but I also often just use a scarf) is somewhat tightly wrapped around the barrel of the lens and the lens mount.  It’s important to double and triple check your focus, as the act of wrapping the cloth around the lens barrel sometimes moves the focus ring.  It’s also worth noting that light can even leak through the viewfinder itself.  For this reason, I cover the viewfinder (some cameras, such as this one, come with a removable viewfinder cover, or you can just wrap it in the same cloth) and shoot my architectural images using only the LCD and a HoodMan loupe for detail magnification.  Anyway, if you successfully wrap your camera you may look funny to passersby, but hopefully your final images retain their dynamic range and contrast, just as you planned.  Happy shooting.