Video: Noise Reduction with Image Stacking

A video tutorial for reducing noise in Milky Way photos with image stacking in Adobe Photoshop CS6 Extended.

Sometimes you just have to accept noisy images for your astrophotos. With astrophotography, you’re typically shooting at high ISO settings, often exceeding ISO 3200. Sometimes this is perfectly acceptable, but depending on your equipment limitations, you may be restricted to lower shutter speeds and smaller apertures where signals are low and noise is high. This video will show you what I do in those situations.

There are a variety of methods for noise reduction including built-in camera settings and noise reduction post processing algorithms such as the ones available in Adobe Lightroom. Let me start by saying that the noise reduction capabilities of Adobe Lightroom and the Nik Dfine 2 plug-in are nothing short of amazing. If you are not already using Lightroom as your RAW processor, you should highly consider it.

 But there are times where your equipment is just too limiting and no matter what you do, the noise just plain terrible. This is where image stacking makes a huge difference in reducing noise in your images. The averaging of even 4 or more separate exposures will do wonders to images that you might have abandoned otherwise. Image stacking is pretty much what all astronomers use for their deep sky images.

Landscape astrophotography presents some challenges with image stacking methods though because we have to deal with relative motion of the stars to the ground. In this video lesson, I show you how I use image stacks of smart objects with a median statistics filter in Adobe Photoshop CS6 to reduce noise in my astrophotos.

74 Replies to “Video: Noise Reduction with Image Stacking”

  1. Hi there! First of all… I really like your video, easy to understand and very effective.

    Last night I shot some photos of a landscape with the night sky by using my EOS 6D @ 35mm, 13sec, f/2.0, ISO 6400… to align them in PS and then use the median filter for reducing noise. Everything worked out pretty well, except one thing;

    Photoshop seems to have huge problems with aligning the stars, when there is only a sky full of stars (with no star trailing and no milky way in the frame). Photoshop isn’t able to align them correctly.

    If the stars are pin-point sharp (like they are with a 35mm and 13sec exposure) – then it won’t work.

    As also pointed out on another site; “Photoshop can’t seem to manage it for these objects. It could be that they are emphasizing linear features too heavily instead of point features”…

    What’s your word on that, Ian? I guess it’s only possible with the milky way in the sky, so that PS’s alignment algorithm has some “structure” to work with…

    thank you & best regards,
    Marco

    1. I find more excessive use of layer masking can help PS line up stars. Ie: I mask out all the darker areas and areas which only have pixel sized stars and noise on each photo. Make sure to leave the same larger stars un-masked on each photo. Now when you auto align the images, PS has an easier time matching up point to point – in my experience anyway. (NB for best results the bright (un-masked) areas should be located in all 4 quadrants of the photos.)

  2. As with everyone before, thanks for the great tutorials. I am having problems with one step, the Auto Align step using Photoshop CC. I mask the foreground as you suggest and when I preform the Auto Align I get an error. Something about not enough overlap. It seems to be trying to make a pano and not simply align the images. How do I get around this?
    Thanks
    Gary

    1. Gary, I’ve found that Photoshop can be inconsistent with this error. Have you tried saving your progress in a .psd , re-opening and re-trying the alignment process?

  3. Great tutorial! I have a question regarding the order you go about editing. Do you stack the images first and then edit the tiff. Or do you edit the individual images, sync, stack and then tweak the tiff? Thanks!

  4. Great site; just found it and have subscribed.
    I tried this technique, but it didn’t work- I think because I don’t have the right version of PS, Shame.

    I have used starstax quite a bit but that is for star trails.
    I was interested in a technique like this for stacking to reduce noise; there are some programs out there that do this, I think. I’m on a mac though, and I think they are all PC.

    Any suggestions I could try? I know LR pretty well, but am a PS novice (have CS5)

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