Zerene Stacker

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stacker:docs:faqlist [2018/07/13 21:33]
rjlittlefield [Are there more FAQs?]
stacker:docs:faqlist [2018/07/31 00:45] (current)
rjlittlefield defect trails
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   * [[#what_is_the_best_way_to_add_files|What is the best way to add files?]]   * [[#what_is_the_best_way_to_add_files|What is the best way to add files?]]
   * [[#my_output_image_has_a_band_of_streaks_on_one_side_why_is_that|My output image has a band of streaks on one side.  Why is that?]]   * [[#my_output_image_has_a_band_of_streaks_on_one_side_why_is_that|My output image has a band of streaks on one side.  Why is that?]]
 +  * [[#my_output_images_have_worm_trails_why_is_that|My output images have worm trails!  Why is that?]]
   * [[#my_colors_changed_a_little_why_is_that|My colors changed a little.  Why is that?]]   * [[#my_colors_changed_a_little_why_is_that|My colors changed a little.  Why is that?]]
   * [[#why_do_my_images_look_noisy_as_soon_as_i_load_them_into_zerene_stacker|Why do my images look noisy as soon as I load them into Zerene Stacker?]]   * [[#why_do_my_images_look_noisy_as_soon_as_i_load_them_into_zerene_stacker|Why do my images look noisy as soon as I load them into Zerene Stacker?]]
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 Edge streaks can also be caused by forcing a stack to be processed starting at the "wide" end, meaning whichever end of the stack has the widest field of view.  In this case the streaks are likely to appear on all four edges, and may extend from the edge of the image to the edge of the narrowest field of view.  With standard settings, Zerene Stacker automatically determines which is the narrow end of the stack and starts there, which completely prevents edge streaks with a well aligned stack.  However, it can be forced to start at either end by de-selecting Options > Preferences > "Automatic order".  Normally we recommend to leave "Automatic order" selected, and set things up when the stack is shot so that everything you care about is contained even within the narrowest frame.  See the tutorial [[http://zerenesystems.com/cms/stacker/docs/tutorials/tutorial002#summaryuse_either_method_but_be_sure_to_check_framing|HERE]] for more information on that point. Edge streaks can also be caused by forcing a stack to be processed starting at the "wide" end, meaning whichever end of the stack has the widest field of view.  In this case the streaks are likely to appear on all four edges, and may extend from the edge of the image to the edge of the narrowest field of view.  With standard settings, Zerene Stacker automatically determines which is the narrow end of the stack and starts there, which completely prevents edge streaks with a well aligned stack.  However, it can be forced to start at either end by de-selecting Options > Preferences > "Automatic order".  Normally we recommend to leave "Automatic order" selected, and set things up when the stack is shot so that everything you care about is contained even within the narrowest frame.  See the tutorial [[http://zerenesystems.com/cms/stacker/docs/tutorials/tutorial002#summaryuse_either_method_but_be_sure_to_check_framing|HERE]] for more information on that point.
 +
 +===== My output images have worm trails!  Why is that? =====
 +
 +That description sounds like what we call "dust trails" or "hot pixel trails", depending on whether the trails are darker or lighter than their surroundings.
 +
 +If you carefully check your source images, you will find that in each of them there are a few individual spots, one spot for each trail in your output.
 +
 +Those spots will occur at exactly the same pixel coordinates in each source image.
 +
 +The reason that trails appear during the stacking process is this:  Due to magnification changes, jitter, or systematic drift in your focus stepping setup, the subject moves slightly left/right/up/down in each frame.  Essentially the subject is moving around with respect to the spots.  In order to make a clean rendering, the focus stacking process must correct for the subject movement, so the subject stays in the same place for each frame.  But then the spots appear to move around with respect to the subject.  To the focus stacking algorithms, the spots look just like sharp detail that should be retained, and so in the final image you see each spot in every position that it ever occupied with respect to the subject.  In combination with the human eye's great ability to pick out linear structures, this causes each spot to become a collection of spots that looks like a straight line, a wiggly trail, or something in between, depending on exactly how the jitter and drift behaved in the first place.
 +
 +In general, these sorts of artifacts can be called "defect trails", because they are trails of small defects in the original images.  The most common form is "dust trails" due to dust on the sensor, producing dark trails on light backgrounds.  Light spots, typically very small, are caused by "warm pixels", in which individual photosites on the camera sensor accumulate charge due to electrical leakage in addition to light exposure.
 +
 +The best cure for these problems is to prevent them in the first place.  Fixing the problem after the stack has been shot inevitably means guessing about what the pixel values should have been, that were hidden by the spots.  So, it's best to clean your sensor and keep it that way.  Warm pixels get worse with long exposures and higher temperatures, so the best way to avoid them is to use short exposures by adding light, typically flash.  It also helps to avoid Live View mode during actual shooting, if possible, because continuous use of the sensor during Live View causes the sensor to get warmer.
 +
 +If you cannot avoid dust or warm pixels in the first place, then the second-best approach is to remove them before stacking, using some technique equivalent to batch mode dust removal.  This can be done using tools such as Lightroom or Photoshop.  You can find a lot of information about this by searching the internet for words like "remove dust from multiple pictures".  Alternatively, it often works great to paint over the trails by retouching, either inside Zerene Stacker using Edit > Retouching, or outside Zerene Stacker using something like Photoshop's healing brush or clone tool.
 +
 ===== My colors changed a little.  Why is that? ===== ===== My colors changed a little.  Why is that? =====
  
stacker/docs/faqlist · Last modified: 2018/07/31 00:45
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