Scratch Test: Difference between revisions

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==Methods==

General: It is helpful to do a deep and thorough clean of your projector before a scratch test.

===General===

It is helpful to do a deep and thorough clean of your projector before a scratch test.

If evaluating for scratches on screen, use a full aperture lens and plate so that the maximum possible image area (including the soundtrack) is visible.

If evaluating for scratches on screen, use a full aperture lens and plate so that the maximum possible image area (including the soundtrack) is visible. It's best to have a second projectionist to observe from the auditorium.

Because film behaves differently when running at full speed, advancing a scratch test by hand is not sufficient. Advancing by hand may be useful in determining if a roller is scratching film, but not so much for determining if your lower loop is hitting the bottom of your intermittent casing, for example.

If your scratch test passes, you can save your film to use again.

===Loop Method===

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===Reel-to-Reel Method===

Prepare 50-100' of test film on a house reel. Project as normal, rewind, and repeat several times (50-100 is ideal, 10-15 may be more practical). Check for scratching on screen and/or on the bench when rewinding. Keep track of base and emulsion side so you can evaluate if anything shows up.

Prepare 50-100' of test film on a house reel. Project as normal, rewind to maintain the same orientation, and repeat several times (50-100 is ideal, 10-15 may be more practical). Check for scratching on screen and/or on the bench when rewinding. Keep track of base and emulsion side so you can evaluate if anything shows up.

This method is most useful for evaluating vertical scratching.

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===Visual Evaluation of Film Path===

Because the above tests do not take into consideration running a full reel of film, and it would be impractical to use 2000' of expensive film stock to run a scratch test several dozen times, a careful and thorough check of a known good test reel should conclude the scratch testing process. Run a full reel of film and examine the film path as it plays: Are all rollers turning? Are the arms aligned so that the film is completely clear through the entire reel? Is the film entering the projector evenly? Look for any new scratches or other issues on your test reel.

==Diagnosis==

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Some examples:

If a straight vertical scratch appears near the center of the frame, the film is likely being scratched in the gate. Check that the lateral guide rollers are turning freely and that the studio guides are not too tight and are not pinching the film inwards.

*If a straight vertical scratch appears near the center of the frame, the film is likely being scratched in the gate. Check that the lateral guide rollers are turning freely and that the studio guides are not too tight and are not pinching the film inwards.

If vertical scratches on the far edge of the image and soundtrack appear, check that pad rollers are turning freely and are not pinching the film.

*If vertical scratches on the far edge of the image and soundtrack appear, check that pad rollers are turning freely and are not pinching the film.

If random "dancing" vertical scratches appear across the entire frame, check that the flywheel is spinning freely.

*If random "dancing" vertical scratches appear across the entire frame, check that the flywheel is spinning freely.

==Related Pages==

*[[Test film]]

==Resources==

@@ Line 7: / Line 7: @@
 ==Methods==
-General: It is helpful to do a deep and thorough clean of your projector before a scratch test.
+===General===
+It is helpful to do a deep and thorough clean of your projector before a scratch test.
-If evaluating for scratches on screen, use a full aperture lens and plate so that the maximum possible image area (including the soundtrack) is visible.
+If evaluating for scratches on screen, use a full aperture lens and plate so that the maximum possible image area (including the soundtrack) is visible. It's best to have a second projectionist to observe from the auditorium.
 Because film behaves differently when running at full speed, advancing a scratch test by hand is not sufficient. Advancing by hand may be useful in determining if a roller is scratching film, but not so much for determining if your lower loop is hitting the bottom of your intermittent casing, for example.
 If your scratch test passes, you can save your film to use again.
 ===Loop Method===
@@ Line 23: / Line 24: @@
 ===Reel-to-Reel Method===
-Prepare 50-100' of test film on a house reel. Project as normal, rewind, and repeat several times (50-100 is ideal, 10-15 may be more practical). Check for scratching on screen and/or on the bench when rewinding. Keep track of base and emulsion side so you can evaluate if anything shows up.
+Prepare 50-100' of test film on a house reel. Project as normal, rewind to maintain the same orientation, and repeat several times (50-100 is ideal, 10-15 may be more practical). Check for scratching on screen and/or on the bench when rewinding. Keep track of base and emulsion side so you can evaluate if anything shows up.
 This method is most useful for evaluating vertical scratching.
@@ Line 31: / Line 32: @@
 ===Visual Evaluation of Film Path===
 Because the above tests do not take into consideration running a full reel of film, and it would be impractical to use 2000' of expensive film stock to run a scratch test several dozen times, a careful and thorough check of a known good test reel should conclude the scratch testing process. Run a full reel of film and examine the film path as it plays: Are all rollers turning? Are the arms aligned so that the film is completely clear through the entire reel? Is the film entering the projector evenly? Look for any new scratches or other issues on your test reel.
 ==Diagnosis==
@@ Line 43: / Line 44: @@
 Some examples:
-If a straight vertical scratch appears near the center of the frame, the film is likely being scratched in the gate. Check that the lateral guide rollers are turning freely and that the studio guides are not too tight and are not pinching the film inwards.
+*If a straight vertical scratch appears near the center of the frame, the film is likely being scratched in the gate. Check that the lateral guide rollers are turning freely and that the studio guides are not too tight and are not pinching the film inwards.
-If vertical scratches on the far edge of the image and soundtrack appear, check that pad rollers are turning freely and are not pinching the film.
+*If vertical scratches on the far edge of the image and soundtrack appear, check that pad rollers are turning freely and are not pinching the film.
-If random "dancing" vertical scratches appear across the entire frame, check that the flywheel is spinning freely.
+*If random "dancing" vertical scratches appear across the entire frame, check that the flywheel is spinning freely.
 ==Related Pages==
+*[[Test film]]
 ==Resources==