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stacker:docs:faqlist [2019/05/15 00:41]
rjlittlefield "Use preset contrast threshold"
stacker:docs:faqlist [2019/06/07 23:12] (current)
rjlittlefield [Are there more FAQs?]
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 When DMap pauses for you to Set Contrast Selection, you're supposed to move the slider until out-of-focus background goes black in the preview image, while your subject retains most of its natural colors.  What you're doing is using your human judgment to mark "can't tell" regions where you want the program to emphasize smoothness rather than getting misled by pixel noise that might look like detail but isn't. When DMap pauses for you to Set Contrast Selection, you're supposed to move the slider until out-of-focus background goes black in the preview image, while your subject retains most of its natural colors.  What you're doing is using your human judgment to mark "can't tell" regions where you want the program to emphasize smoothness rather than getting misled by pixel noise that might look like detail but isn't.
  
-When you use the slider, you are actually setting two numbers: the //percentile// which says what fraction of pixels ended up getting set to "black in preview" (that is, contrast of details is below threshold), and the //level// which describes the strength of detail at the break between "black in preview" and normal colors.  The numeric value of level is not meaningful to a human, beyond the understanding that the values will be larger in areas that show sharp detail with high contrast, and smaller in areas where there is less detail to be seen.+When you use the slider, you are actually setting two numbers: the //percentile// which says what fraction of pixels ended up getting shown as "black in preview" (that is, contrast of details is below threshold), and the //level// which describes the strength of detail at the break between "black in preview" and normal colors.  The numeric value of level is not meaningful to a human, beyond the understanding that the values will be larger in areas that show sharp detail with high contrast, and smaller in areas where there is less detail to be seen.
  
 Usually it is best to set the slider interactively on every stack.  However, for batch operations where you have a bunch of stacks with similar appearance, you can checkmark the option to "Use preset contrast threshold".  That prevents the slider and preview image from being shown, so that multiple DMap operations can be done with no user interaction.  In that case, you must also select to either use the value of Level that was left over from the last interactive setting of the slider, or compute a new threshold for each stack based on specified Percentile and the image contents of that stack. Usually it is best to set the slider interactively on every stack.  However, for batch operations where you have a bunch of stacks with similar appearance, you can checkmark the option to "Use preset contrast threshold".  That prevents the slider and preview image from being shown, so that multiple DMap operations can be done with no user interaction.  In that case, you must also select to either use the value of Level that was left over from the last interactive setting of the slider, or compute a new threshold for each stack based on specified Percentile and the image contents of that stack.
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 +VPS
  
stacker/docs/faqlist.1557880910.gz · Last modified: 2019/05/15 00:41
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