CS2 cache performance vs. onscreen accuracy

FD
Posted By
false_dmitrii
Feb 17, 2006
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132
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1
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Closed
(reposting from comp.graphics.apps.photoshop)

While making some extreme level adjustments with multiple layers to correct large linear negative film scans, I realized that not only was the histogram not keeping up, but the colors and contrast of the displayed image were drifting considerably from the true results of the adjustment layers. Setting the cache level to 1 in Preferences solves this issue, but it also kills performance and disables the handy "auto" and "options" commands in Levels and Curves.

Is there a way to force a cache override to generate an accurate display when desirable without setting the cache level to 1? I know I can duplicate the layered image to a flattened one, but is there a quicker way to the same results? Viewing the large original scans at 100% is not an effective workaround, though I’ve gotten around the slow uncached performance by downscaling a copy of the original, making adjustments, then copying the layers back to the original.

I’m also curious about CS2’s on-the-fly zoom scaling. Paint Shop Pro produces a good-looking image at any zoom percentage and does so with no noticeable performance hit, yet pricey CS2 offers jagged lines, increased noise, and generally inaccurate representations of the image at any zoom that’s not a factor of 1/2. Even 50% zoom is a little tricky to interpret. Is there any trick that will force CS2 to use a slower but better resampling method for on-the-fly zooming?

false_dmitrii
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MH
Mike Hyndman
Feb 17, 2006
wrote in message
(reposting from comp.graphics.apps.photoshop)

While making some extreme level adjustments with multiple layers to correct large linear negative film scans, I realized that not only was the histogram not keeping up, but the colors and contrast of the displayed image were drifting considerably from the true results of the adjustment layers. Setting the cache level to 1 in Preferences solves this issue, but it also kills performance and disables the handy "auto" and "options" commands in Levels and Curves.

Is there a way to force a cache override to generate an accurate display when desirable without setting the cache level to 1? I know I can duplicate the layered image to a flattened one, but is there a quicker way to the same results? Viewing the large original scans at 100% is not an effective workaround, though I’ve gotten around the slow uncached performance by downscaling a copy of the original, making adjustments, then copying the layers back to the original.
I’m also curious about CS2’s on-the-fly zoom scaling. Paint Shop Pro produces a good-looking image at any zoom percentage and does so with no noticeable performance hit, yet pricey CS2 offers jagged lines, increased noise, and generally inaccurate representations of the image at any zoom that’s not a factor of 1/2. Even 50% zoom is a little tricky to interpret. Is there any trick that will force CS2 to use a slower but better resampling method for on-the-fly zooming?

false_dmitrii

Theis sounds like a resource problem, how much ram/scratch disc space do you have?

From the AF, take not of third paragraph re accuracy of cached zoom percentages.

"When you view an image in the document window at anything less than 100% magnification, Photoshop can use down sampled, low-resolution cached versions of the 100% view for speedier redraws. This can be helpful if you constantly work on large images and you need to zoom out frequently. However, it will take longer to open files while Photoshop creates the low-resolution previews.

You can specify the number of cache levels in the Preferences>Image & Memory Cache screen (Figure 4). Needless to say, the higher the number of cache levels, the more resources Photoshop needs to consume. If you have limited RAM, or scratch disk space, you may wish to set the level to 1 or 2; the default is 4 levels. You can go as high as 8 levels, which will give you cached views at 66.67, 50, 33.33, 25, 16.67, 12.5, 8.33, and 6.25%. Setting the cache level to 1 is the same as turning it off because only the current view is cached at that setting

Note: Although the cached views can help with speedier redraws, you’ll do well to remember that any reading that you take based on a cached view will be misleading; for example, when you sample a color or use a cached view to judge the effect of a filter, such as USM, it will not be based on actual pixels. For critical readings, always view the image at 100% magnification (View>Actual Pixels)."

HTH

MH

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