Mar. 2000
President's
Message
Portrait of Patsy Costis
Article: Q&A Forum
Question & Answer Forum
- Erik Kissa
The following questions were submitted to
Erik Kissa as a result of his recent offer to answer general photographic
puzzlements. Erik kindly offers to answer any questions, excluding digital
photography and manipulations at (302) 478-6737 or ekissa@
aol.com.
Last Slide Night I saw a frontal shot of a horse jumping a hurdle. The film used was Fuji 50. How can one use a slow film to shoot a rapidly moving subject and get it tack sharp? I thought the rule was fast film for fast motion.
A slow film requires a fast glass. On a sunny day a typical exposure for ISO 50 film is 1/50 sec. at f/16 (sunny rule), or 1/500 sec. at f/5.6 and 1/1000 sec. at f/4. To stop the motion of a jumping horse from a frontal position requires at least 1/500 sec. With fast lenses, such as 300 f/4, 300 f/2.8 or 400 f/2.8 adequately fast shutter speeds are available. Advantage of using a wide aperture: Out of focus background due to a narrow depth of field. To stop the motion of racing horses requires 1/1000 sec. However, slower shutter speeds can be used by panning the camera - turning the camera in the direction of motion, to keep the moving object within the viewfinder. Advantage: A blurred background suggesting motion. I do not see any compelling reasons for using a ISO 50 film for action shots. Modern ISO 100 films are excellent, Fuji Provia 100F has the finest grain of all color slide films and can be pushed to 200 or 400 speed. Ektachrome Pro E200 is a fine film designed to be pushed. Velvia, the Fuji ISO 50 film, has a slightly but not significantly better resolution than Provia 100F. The main difference is the exaggerated punchy color gamut of Velvia which many photographers like.
How is the push process used? Does pushing ISO to 200 or 400 affect the grain?
Pushing means a modified film development to increase the effective film speed. Set the meter at a higher ISO and tell the photo lab how many stops to push. The film speed cannot be changed in mid-roll, of course. Yes, pushing increases the grain size but fast films are grainier. Fuji people have told me that Provia 100F pushed to 400 has a much finer grain than that of Provia (Sensia) 400. I have ordered Provia 100F and will test it soon. Prepaid mailers for push processing are not available. Local processing plus pushing (Buckley charges $3.35 extra) almost doubles the mail order cost per roll.
Two of my slides have white spots. Processing of film is not at fault. What is the cause?
Streaks, spots, circles, or hexagonals, colorless or colored, are caused by internal reflections. Since most cameras are well baffled and blackened, internal reflections in the lens are the cause. Zoom lenses are especially vulnerable to ghosting by light shining on the front element. A lens hood is a must, but an effective shielding of a zoom lens is difficult because the view angle varies when zooming. Telescoping hoods (folding rubber hoods or bellows) are available but require adjustment when zooming. Light reflected on filters causes flare (loss of contrast with the appearance of overexposure) but not spots.