Standard shutter speed increments (1/30, 1/60, 1/125, etc.) are calibrated to admit the same amount of light from speed to speed as the standard f/stops (f/4, f/5.6, f/8, etc.) will, when adjusted from aperture to aperture. In a perfect world, as long as the same amount of light strikes the film, the image will always be the same. However, an image exposed at 2 min./f/32 will exhibit different color values than the same image exposed at 1 sec. @ f/2.8, even though the same amount of light is passing through the lens. There are complex technical reasons for this color shift, but simply put, the longer the exposure, the more "tired" the film gets. This reciprocity failure varies with film type and exposure length. The effect can be minimized by adjusting exposure times and apertures or by use of filters. Sekonic meters will automatically recognize the 1:1 relationship between shutter speed and aperture as you adjust one or the other. Reciprocity failure does not occur with digital cameras the way will, when adjusted from aperture to aperture. In a perfect world, as long as the same amount of light strikes the film, the image will always be the same. However, an image exposed at 2 min./f/32 will exhibit different color values than the same image exposed at 1 sec. @ f/2.8, even though the same amount of light is passing through the lens. There are complex technical reasons for this color shift, but simply put, the longer the exposure, the more "tired" the film gets. This reciprocity failure varies with film type and exposure length. The effect can be minimized by adjusting exposure times and apertures or by use of filters. Sekonic meters will automatically recognize the 1:1 relationship between shutter speed and aperture as you adjust one or the other. Reciprocity failure does not occur with digital cameras the way is does with film, but you will begin to notice increased levels of noise with long exposures.will, when adjusted from aperture to aperture. In a perfect world, as long as the same amount of light strikes the film, the image will always be the same. However, an image exposed at 2 min./f/32 will exhibit different color values than the same image exposed at 1 sec. @ f/2.8, even though the same amount of light is passing through the lens. There are complex technical reasons for this color shift, but simply put, the longer the exposure, the more "tired" the film gets. This reciprocity failure varies with film type and exposure length. The effect can be minimized by adjusting exposure times and apertures or by use of filters. Sekonic meters will automatically recognize the 1:1 relationship between shutter speed and aperture as you adjust one or the other. Reciprocity failure does not occur with digital cameras the way is does with film, but you will begin to notice increased levels of noise with long exposures.exposures.will, when adjusted from aperture to aperture. In a perfect world, as long as the same amount of light strikes the film, the image will always be the same. However, an image exposed at 2 min./f/32 will exhibit different color values than the same image exposed at 1 sec. @ f/2.8, even though the same amount of light is passing through the lens. There are complex technical reasons for this color shift, but simply put, the longer the exposure, the more "tired" the film gets. This reciprocity failure varies with film type and exposure length. The effect can be minimized by adjusting exposure times and apertures or by use of filters. Sekonic meters will automatically recognize the 1:1 relationship between shutter speed and aperture as you adjust one or the other. Reciprocity failure does not occur with digital cameras the way is does with film, but you will begin to notice increased levels of noise with long exposures.