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Post-processing a high ISO Milky Way photo

There’s always more than one way to skin a cat. Or, to post-process a high ISO Milky Way photo. In this post I’m going to take a look at using Adobe Camera Raw (ACR) to start, and then invoke ACR as a plugin for additional corrections and modifications.

This was a single image, captured at ISO 12,800 with an Olympus OM-D E-M1 Mark III and 7-14mm f/2.8 Pro lens.

Capture of Milky Way images

Here’s just a few quick thoughts about the initial capture of a single Milky Way image. For more on capturing the Milky Way, check out this post.

  • Shoot in RAW so you have the most information with which to work
  • Use Daylight balance
  • DO NOT depend upon the LED screen to determine exposure — that leads to heartbreak. Use your Histogram to determine exposure. It should read like the one below. If you need to increase your ISO to get your Histogram there, do so. Until you find what works for your bracket, bracket, bracket. Then test in post.
  • Consider using a red headlamp to gently paint in the foreground light. This adds interest in the center during exposure.
In general, this would be a good starting point for your Histogram when capturing Milky Way photos. Dark information in the lower third. The smaller lines on the right represent your stars.


I always think of my images as two pieces. This is known as composite Milky Way image processing. You can make an exposure of the foreground and wait for the Milky Way to make that exposure at a later time. In this case, I am increasing my ISO to 12,800 and processing from a single exposure.

Final post-processed high ISO Milky Way photo

Adobe Camera Raw

First stop is Adobe Camera Raw (ACR). This is the time for a once-over of your file information. This is not the time to do heavy lifting of pixel adjustment — that comes in subsequent steps.

Adobe Camera Raw tools panel gives access to lots of adjustments. Red circle indicates access to the ACR Masking panel.

Here’s our plan. Head over to the Basics tab for overall exposure, and use the Optics tab to work on Chromatic Aberration and Profile corrections. Open the file (I open it as a layer). If you want to get back to these settings at any time, you can hold down the Shift key when opening and the image will open as a Smart Object.

Enhancing ACR

Now it’s time for working individual areas. Make a copy of the layer (Cmd + J on Mac; Ctrl + J on PC), and make sure this new layer is highlighted. Then, go to the Filter menu and click on Camera Raw Filter. This takes this layer and allows us to use all the tools in ACR. Then move to the Masking palette. This is a powerful place, as it allows us to process individual areas with beautifully feathered masks.

Select Sky

An initial Select Sky selection. Note there is an area in transition that might need to be removed with a Subtract setting using the Brush. See below.

Masking tools in ACR are versatile. Using Select Sky does a nice job but sometimes needs a little adjustment. If the selection feather is a little much for you, use the subtract tool with the Brush chosen to paint out the extra and tighten up the selection.

Select Sky after Subtract Brush along the horizon.

If you want to make an adjustment to the foreground, a sky selection can also be inverted.

Targeted adjustments

Selection made with a Radial Mask. I use lots of these masks to target various small areas to open shadows or target the Milky Way for sharpness and contrast.

Invoking the Radial Gradient selects specific areas, such as the Galactic Center that need sharpening, or shadow areas needing opening up or bright spaces that need to be toned down or adjusted for color. Each mask is adjusted independently which is what makes this way of processing so incredibly powerful. Add as many as you like.

Photoshop’s Layers palette. Base exposure ACR copy (with mask) was made to add noise reduction.

With high ISO image captures you will note that the stars will tend to not record color in the stars. I don’t think that has hurt this image.

Yours in Creative Photography, Bob

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Rafael Jones

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