Continuous Lighting and High ISO

Today’s Post by Joe Farace

Everybody knows that higher ISO settings produce more noise but that threshold is a constantly moving target. In my original Shutterbug review of the Nikon D800 I shot images at ISO 12,800 and said, “Being able to shoot (high quality) images at high ISO setting opens a gateway into the use of small LED light sources…”

I could have added “fluorescent” but all light sources, like Flashpoint’s 13-inch Fluorescent Dimmable Ring Light, which I featured in last Monday’s post, obey the same inverse square law, which says that the intensity of illumination is proportional to the inverse square of the distance from the light source. This means an object that’s twice the distance from a light receives a quarter of the illumination. When you move a light from five feet to 10 feet away from a subject, you’ll need four times the amount of light to produce the same exposure.

Flashpoint’s Ring Light is rated at 70 Watts at 4500 Lumens. (For more on understanding Lumens please read my post “The Maze Runner.”) There are no Guide Numbers for the ring light—on any continuous lighting source—if only because standard formulas ignore the effect of shutter speed on the total amount of light striking the sensor. For this session I tended to shoot at higher than normal ISO settings trying to use a hand holdable shutter speed that would produce the least subject motion and a modest enough aperture to maintain some semblance of depth-of-field, while providing acceptable low noise levels.

The bottom line is that there is no perfect ISO setting for every photograph, so you need to make tests using your own camera. When shooting Flashpoint’s 13-inch Fluorescent Dimmable Ring Light, I occasionally had to dip into higher ISO settings but at no point did I feel that was I trading image quality for lighting results. The portrait of a delightfully retro Pamela Simpson was made with a Panasonic Lumix GH3 with a G Vario 14-140mm f/3.5-5.6 Asph. Power O.I.S. lens (at 41mm) and an exposure of 1/15 sec at f/5.3 and ISO 1000.

If you’re interested in shooting portraits, please pick up a copy of “Studio Lighting Anywhere” which is available from your favorite book or camera stores as well as Amazon.com, where your purchase helps this blog.