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Subtraction Mode Help ?
HI – I recently shot some high gain video of the stars on a clear night. I have successfully removed most of the random noise by averaging the frames together. The last step is to subtract dark frame noise from the remaining frames. This noise is constant in each frame and was captured immediately afterwords with the lens cap on. How do I subtract this constant noise layer from the averaged layer?
Thanks.
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3 Replies
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Have you tried using AE 6.5’s “remove grain” effect on the clip?
If you place the lens cap shot at the head of the clip, you might get the constant-denoising results you want, but the effect should clean up the clip without doing that.
I used to do demos for Grain Surgery, but they might have tweaked the effect since then.
Steve -
In theory, the CCD-noise layer, applied with the “difference” layer-mode should do the trick.
Especially on a frame with such a dark background.Alternatively the trick I use in Photoshop to get rid of static CCD noise is this:
– duplicate your main image, do a median high enough, so the noise is gone, don’t worry about the loss of detail. (you can do that with a precomp in AE)
– Do a channel-mixer on your CCD-noise-layer: monochrome, and with R,G & B all set to 100%
– Use that Greyscale image as the Mask (Luma Matte) to your Median Layer.
– Fine tune the levels of your mask.Now you’re doing a median, only where there’s static CCD noise.
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Thanks for the tip . Difference mode seems to work pretty well. I may have to use both methods as there’s still residual speckles left over after difference alone though.
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