RAW File Processing

Last updated March 7, 2021.Applies toStarryLanscapeStacker version 1.9.0 and laterStarry Sky Stacker version 1.4.0 and laterLong Exposure Stacker version 1.5.0 and later

Supported cameras

SLS, SSS and LES use the RAW file conversion libraries that come with MacOS. The cameras that are supported depend on the version of MacOS that you are running.


Tutorial video on RAW file processing.

RAW files vs. TIFF

Starry Landscape Stacker, Starry Sky Stacker and Long Exposure Stacker are all capable of reading RAW files directly. This can save time and reduce errors compared to using a RAW converter, such as Adobe Lightroom or ON1Photo Raw, to first convert your RAW files to TIFFs. Reasons why you might want to use RAW files directly include:

  • save time compared to first loading the images into a RAW converter and then exporting them;

  • reduce the need for temporary file space;

  • reduce the risk of errors such as not synchronizing modifications across all files or applying inappropriate corrections like lens distortion correction which adds artifacts that are enhanced by stacking;

  • avoid overly “helpful” RAW converters (for example Adobe Lightroom always applies lens distortion correction for most mirrorless cameras, but lens distortion correction adds artifacts that are enhanced by stacking and should never be applied before stacking);

  • automatic synchronization of orientation and color balance between dark and light frames.

There are reasons you might prefer to use an external RAW converter;

  • more control is available over the conversion parameters;

  • better results might be achieved for some cameras with an external RAW converter;

  • TIFFs load much faster than RAW files, so if you anticipate reloading some images many times, first converting to TIFF could save time.

Controlling RAW Conversion

For many users, the default setting for RAW conversion will work fine. Whenever you open any RAW files you will be presented with a panel that lets you adjust the RAW conversion settings. If one of the files that you are opening is a master dark, the panel will be populated with the RAW settings used to make that master dark. You should leave the settings alone to ensure synchronization with the master dark (but you can change them if you really want). Otherwise, the panel will be populated with your default values.

Any changes you make will only effect the current set of images. To change your defaults make changes in Preferences (see below). When the settings are what you want, you can click "Done" or you can press the "return" key on the keyboard. Be careful--if you press the return key after entering a setting as a number in one of the boxes, you will be using the current settings. Use the tab key to move through the settings with the keyboard.

Exposure

This is a scale factor applied to the pixel data that changes its brightness. The default is 0--no change. The lower limit, -1, reduces the exposure (darkens the image) by 1 Ev . The upper limit 3, which brightens the image by 3 Ev.

Contrast

The default contrast is 1. If you are not using dark frames, you might consider reducing this to 0.8 for Starry Landscape Stacker and Starry Sky Stacker, to open up a little room at the ends. Use care when making changes to this setting—a little goes a very long way and it is easy to go too far. (The scale is arbitrary and not directly related to Ev). If you are using dark frames you should leave the contrast at 1.

Luminance NR

Luminance noise reduction can be applied during RAW conversion. It defaults to 0, but there may be cases where a little noise reduction helps. This should be 0 if you are making a master dark.

Color NR

Color noise reduction can be applied during RAW conversion. It defaults to 0, but I have been told that for some cameras, the best final result can be achieved by applying a little color noise reduction before stacking, and then do a little more during post processing. This should be 0 if you are making a laster dark.

White Balance

White Balance is a complex topic because the setting must be carefully synchronized across all images, including dark frames. If one of the files you are opening is a master dark, the white balance values used to make the master dark will be the initial values. Otherwise, the initial values will depend on your Preferences (see below).


Changing Default RAW Settings with Preferences

The preferences can be opened with the "Preferences" menu item under the application name or "⌘," on the keyboard.

Preferences that can be set are:

Working Profile

This is the color profile used for files that are written. Currently there are two choices ProPhoto RGB and Adobe RGB 1998. ProPhoto RGB is the default.

Exposure

If you are opening a master dark, the exposure setting used to make the master dark overrides the default value set with preferences.

This is a scale factor applied to the pixel data that changes its brightness. The default is 0--no change. The lower limit, -1, reduces the exposure (darkens the image) by 1 Ev . The upper limit 3, which brightens the image by 3 Ev.

Contrast

If you are opening a master dark, the contrast setting used to make the master dark overrides the default value set with preferences.

The default contrast is 1 (no change). If you are not using dark frames, you might consider reducing this to 0.8 for Starry Landscape Stacker and Starry Sky Stacker, to open up a little room at the ends. Use care when making changes to this setting—a little goes a very long way and it is easy to go too far. (The scale is arbitrary and not directly related to Ev). If you are using dark frames you should leave the contrast at 1.

Luminance NR

Luminance noise reduction can be applied during RAW conversion. It defaults to 0, but there may be cases where a little noise reduction helps.

Color NR

Color noise reduction can be applied during RAW conversion. It defaults to 0, but I have been told that for some cameras, the best final result can be achieved by applying a little color noise reduction before stacking, and a little more during post processing.

White Balance

If you are opening a master dark, the white balance settings used to make the master dark override any defaults set with preferences.

You can choose to have the white balance setting come from either the first RAW file read or from the constants supplied.

If you use manual white balance, and consistently set it correctly, you should have the white balance from the first RAW file in a set applied to all RAW files.

If you use auto white balance, then the situation is more complex. For night images it is probably best to supply a specified white balance because auto white balance is often wrong at night. For day images, it may be best to use the white balance from the first RAW image. The auto white balance is likely to be close and copying it to all RAW files ensures that the same white balance is used for every image.

The default for Starry Landscape Stacker and Starry Sky Stacker is to use the specified values which default to temperature 4800 and tint -20.

The default for Long Exposure Stacker is to use the white balance from the first RAW file. The defaults for the white balance (if you take the option “Use the following…”) are temperature 6500 and tint 0.

Restore Defaults

If you ever have to get back to the original default values, just click “Restore Defaults”..

Show Warnings

This section of the Preferences allows warning to be suppressed, or turned back on. Since the warnings include a check box to suppress them, this section would most likely be used to turn the warnings back on if you turn them off and later decide that you to want to see them.