A Tip for Long Exposures

 Submitted by Sheila Reeves

You are standing in front of a beautiful scene with rippling water, moving colorful clouds and a great composition of hills and trees. You think to yourself, “This would make a great long exposure.” You attach an ND filter (maybe a 6 stop or 10 stop) to reduce the light entering your camera. You dial in a low ISO to avoid a noisy image. You think you will need about a 2 minute exposure, so you put your camera on bulb mode and take the picture keeping the shutter open for 2 minutes. Oh no! You calculated the exposure time wrong. The image is way too dark or way to light!

Well here is a tip to determine if you calculation is correct without having to wait those 2 minutes.

Change your ISO by 6 stops. If you are shooting at ISO 100, change it to 6400. That is six stops. If you are shooting at ISO 64, change is to 4000. 

Then substitute seconds for minutes of exposure time: 2 seconds for 2 minutes, 3 seconds for 3 minutes, 4.5 seconds for 4.5 minutes, etc. If that gives you a good exposure, reset your ISO and take the shot for the original exposure time. If it does not, you can adjust the time up or down to get a good exposure without having to wait minutes between attempts.