Picture This: Crank it Up
Opportunities expand for shooting in low light.
By Earl Nottingham
Back in the olden days of photographic film, one of the first things I was told as a cub photographer was that to obtain the sharpest photo possible, a serious photographer needed to use a film that had a low ASA (American Standards Association) number — referring to the sensitivity of that particular film to light, also known as film “speed.”
A low ASA number meant low speed and low sensitivity; a high number meant high speed and high sensitivity. The sharpness of the lower speed film is due to smaller grains of silver salts in the film emulsion. Conversely, faster films have larger and clumpier grains of silver that make them more sensitive to light. Faster films allow photos to be made in lower light situations but result in a granular or “grainy” appearance in the final image. Typically, films in the 25–125 ASA range were considered low speed, with anything over 400 classified as high.
The trade-off was apparent. You could shoot a slow film and get very sharp images, but that might require you to use a tripod because of the longer exposures. You could use a faster film for faster exposures, but the result might be a grainier image. As film emulsions improved over the years, manufacturers could increase ASA speeds yet keep grain down.
Beginning in the 1980s, the ASA standard was superseded by ISO (International Organization for Standardization). Both standards still referenced the sensitivity/speed of a film. As digital sensors replaced traditional film, ISO speeds remained as a useful measurement of sensitivity to light. The difference is that while a film is limited to one ISO speed, the digital sensor can be set to a wide variety of ISOs, ranging from very low to extremely high, opening a new world of possibilities for creative photography. You can now have the equivalent of an unlimited number of traditional film emulsions available in one digital camera.
This black-and-white film negative shows the coarse grain pattern inherent in high-speed film emulsions.
With digital images, film grain has now been replaced by its electronic equivalent — digital noise — which has an uncanny resemblance to grain. While digital noise increases as the camera is set to higher ISOs, it doesn’t approach the degraded resolution of a high ISO film. This means that the photographer can now venture to ISOs from 100 to roughly 12,000 (and higher) and still get good image quality. The quality increases with each new camera model that comes out. (Photographers shooting in automatic modes may not be aware that the camera is changing ISO speeds behind the scenes.)
Despite the ability of digital cameras to shoot at higher ISOs, many photographers are still reluctant to embrace the higher speeds for various reasons. Many traditionalists still cling to the idea that “low is best,” not realizing that images from a typical newer camera using an ISO of, for example, 400 are as noise-free as those recorded by previous models shooting at 100.
On my previous camera, for instance, I wouldn’t venture past ISO 3,200 due to noise. Now, I find that ISO 12,800 is my acceptable limit. That type of sensitivity makes photographers rethink the limits of what can be considered good shooting light. Every starlit sky, moonlit night or candlelit room becomes a backdrop for a potential masterpiece. You will need to test your own camera at various ISOs to see where noise becomes unacceptable. The bottom line is that shooting at a high ISO is no longer a barrier to getting sharp images.
There will always be instances (such as portraiture and daylight landscape photography) where shooting at a low ISO is still preferable. However, once you have ventured into the hours of waning light, cranked up that ISO and seen the photographic possibilities that exist on the dark side, you may never go back.
Please send questions and comments to Earl at email@example.com. For more tips on outdoor photography, visit the magazine’s photography page at www.tpwmagazine.com/photography.
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