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On Screen Troubleshooting: Difference between revisions
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These are some examples of common on screen issues, and their potential causes and remedies. | These are some examples of common on screen issues, and their potential causes and remedies. | ||
=Contrast | =Contrast degradation= | ||
Signs of contrast degradation are a washed out image with pale colors and milky blacks. | Signs of contrast degradation are a washed out image with pale colors and milky blacks. | ||
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=Focus= | =Focus= | ||
==Focus | ==Focus drift== | ||
The unpleasant phenomenon of [[focus]] drifting over the course of a reel, or "pulsing" in and out of focus. This is most commonly caused by warped film. A film with a minor amount of warping may require only a few small adjustments throughout the reel to stay in focus, but a reel with severe warping will require constant attention, and often it will only be possible to keep the center of the image in focus. Warped prints tend to play better on projectors with curved gates, which help bend the film back into position. | The unpleasant phenomenon of [[focus]] drifting over the course of a reel, or "pulsing" in and out of focus. This is most commonly caused by warped film. A film with a minor amount of warping may require only a few small adjustments throughout the reel to stay in focus, but a reel with severe warping will require constant attention, and often it will only be possible to keep the center of the image in focus. Warped prints tend to play better on projectors with curved gates, which help bend the film back into position. | ||
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Polyester film should maintain nearly perfect focus and not warp, so if Focus Drift is observed on a polyester film or test loop it is a good indication of a mechanical issue. | Polyester film should maintain nearly perfect focus and not warp, so if Focus Drift is observed on a polyester film or test loop it is a good indication of a mechanical issue. | ||
==Focus | ==Focus uniformity== | ||
Focus uniformity is the overall evenness of focus across the entire image. If examining focus uniformity using a test film, it is not uncommon for the far edges of the frame to be slightly softer than the center. More problematic is when one side or area of the image is less in focus than another. | Focus uniformity is the overall evenness of focus across the entire image. If examining focus uniformity using a test film, it is not uncommon for the far edges of the frame to be slightly softer than the center. More problematic is when one side or area of the image is less in focus than another. | ||
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Lateral (side to side) movement. The most common mechanical cause is worn, dirty, or damaged [[lateral guide rollers]], or acetate film that has been trimmed or beveled to remove edge tears. Less common is excessive play in the Starwheel Shaft Thrust Collar, which would cause the intermittent sprocket to move from side to side during projection. Weave can also be caused by film [[shrinkage]], and can also be printed in. | Lateral (side to side) movement. The most common mechanical cause is worn, dirty, or damaged [[lateral guide rollers]], or acetate film that has been trimmed or beveled to remove edge tears. Less common is excessive play in the Starwheel Shaft Thrust Collar, which would cause the intermittent sprocket to move from side to side during projection. Weave can also be caused by film [[shrinkage]], and can also be printed in. | ||
=Visible | =Visible negative splices= | ||
[[File:Negative Splice.jpg|right|thumb|700px|Negative splices in MAME (Gene Saks, 1974, left) and I STILL KNOW WHAT YOU DID LAST SUMMER (Danny Cannon, 1998, right). In anamorphic projection, a poorly made negative splice may be visible on screen if the film isn’t perfectly framed or the projector’s aperture plate is over cut.]] | [[File:Negative Splice.jpg|right|thumb|700px|Negative splices in MAME (Gene Saks, 1974, left) and I STILL KNOW WHAT YOU DID LAST SUMMER (Danny Cannon, 1998, right). In anamorphic projection, a poorly made negative splice may be visible on screen if the film isn’t perfectly framed or the projector’s aperture plate is over cut.]] | ||