RAW File Processing

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. To find a complete list of cameras supported by the version of MacOS that you have installed on your computer, open System Information.app and, in the left pane, scroll to the bottom. In my Mac, the 3rd item from the bottom is "Raw Support". Click on "Raw Support" to see a full list of cameras supported in the right pane. The fastest way to launch System Information.app is to use Spotlight:  press ⌘+space simultaneously to start a Spotlight search, then start typing "System Information", the first item found is likely to be "System Information.app".  Double click it to start the app.

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 Settings (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

This is used to change the contrast. The default change is 0. If your images are well exposed you should not change the contrast. If your images are badly underexposed and you have boosted the exposure to compensate, a slight increase in contrast might help. If you are worried about blowing out some highlights, a very slight reduction in contrast might help.

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 Settings (see below).

A good way to get starting values for the temperature and tint is to open one of your images in Lightroom or Adobe Camera RAW and adjust the white balance to your liking. Then copy those values to the SLS settings.

Changing Default RAW Settings with Settings

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

Settings that can be changed are:

Exposure

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

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 Settings.

This is used to change the contrast. The default change is 0. If your images are well exposed you should not change the contrast. If your images are badly underexposed and you have boosted the exposure to compensate, a slight increase in contrast might help. If you are worried about blowing out some highlights, a very slight reduction in contrast might help.

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 Settings.

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.

A good way to get starting values for the temperature and tint is to open one of your images in Lightroom or Adobe Camera RAW and adjust the white balance to your liking. Then copy those values to the SLS settings.

Working Profile

This is the color profile used for files that are written. Currently there are two choices ROMM RGB and Adobe RGB 1998. ROMM RGB is the default. (ROMM RGB was previously called ProPhoto RGB.)

Generate 32-bit TIFFs

If you check the box "Generate 32-bit TIFFs" the output files generated will use a 32-bit floating point value to represent each component. The default is to use a 16-bit unsigned integer. This box must be checked before any files are read in order to have effect. Unless you are using a very large number of images (a few hundred), low ISO (e.g., 100 or less) or have a very low noise camera (e.g., Hasselblad) you are unlikely to benefit from 32-bit output at this time. I expect cameras to improve and 32-bit output will become necessary in the future. At this time (late 2025), all Adobe products seem to have a problem with 32-bit TIFFs-- the brightness and contrast are not what I expect nor what I see in apps from other vendors. This is better than last time I checked, but I think Adobe does not yet support 32-bit float TIFFs correctly.

Show Warnings

This section of the Settings  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.

Restore Factory Defaults

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