This is the process that I use to reduce space noise. By this I mean reduce the noise in the parts of your image that don't contain features such as stars and nebulae. I'll introduce the problem, discuss the components we need to improve our images, and then we'll assemble the components into a process. In this way I hope that you'll better understand what is happening at each step in the process. I will then demo the process in Photoshop and then finally I'll demo my free astro action that automates the process so that you don't have to remember it. Space noise is associated with the darker parts of the image. This is because the signal is very low and the noise in an image is generally the same level across the whole image. And therefore the signal to noise ratio in the darker parts of the image are very low. Our process needs to reduce the noise in the darker parts of the image without affecting the brighter parts. And we need to ensure that we preserve the details. Now we understand what we want to do. Let's look at some of the underlying techniques we'll need. Our images can have multiple layers. How those layers interact depends on the layer mode. The default layer mode is called normal. This replaces the layer below with the layer on top. Layer modes change how the layer interacts with the layers below. For example, darker and allows darker pixels from layers below to pass through the layer. And lighten does the opposite, allowing lighter areas of the image to pass through the layer. The layer mode we're going to use is called soft light and it requires a bit of explanation. It's supposed to mimic soft lighting conditions. So let's delve into what this layer mode does as it plays an important part in our process. First let's simplify the graph. The horizontal axis indicates the colour of the pixel in the lower layer. The colour of the line indicates the colour of the corresponding pixel in the upper layer. Here I'm only showing a line for mid-gray. This is the midpoint between black and white. The vertical axis represents the colour of the corresponding pixel when soft light is used. So if we have a mid-gray pixel in the upper layer, we can read the graph to find the corresponding result. And you can see from this, if the upper layer is mid-gray, that the soft light mode has no effect on the final image, each colour in the lower layer translates to the same colour in the resultant image. Now let's consider what happens if the upper layer pixel is black. If the lower layer pixel is black, the resultant pixel remains black. And the same applies if the lower layer is white. The result is also white. But in between you can see that the result is always darker than the underlying layer. You might also notice that dark colours are darkened more than the lighter colours. We see the opposite effect when the upper layer is white. The colour of the lower layer is brightened, but the effect is still larger for pixels that are darker in the lower layer. Adding some intermediate grays into the graph, we can see that overall if the upper layer is darker than mid-gray, the result is a darker image. If it is lighter than mid-gray, the result is a lighter image. And that the effect is most prominent when the lower layer pixels are dark. We'll look at how we can apply this later in the video. Now let us quickly discuss masks. Without masks, the whole layer would be affected by the layer mode. masks allow us to define at a pixel level which pixels would be affected by the mask. If the mask pixel is black, the corresponding pixel is completely transparent. So the underlying pixel is shown unaffected. If the mask pixel is white, the layer mode has the full effect on the corresponding pixel. And all shades of grey in between effectively change the transparency. That's therefore work a little bit like the opacity slider, but on an individual pixel level. The final thing we need to understand is the median filter. The median filter takes the median of the pixels in a specified radius around a target pixel and replaces the target pixel with that value. Medium filters are good at reducing noise but at the expense of losing detail. Generally, medium filters will remove detail smaller than the radius of the filter. Okay, so that's all the components of the space noise filter. Let's look at how we combine these layer effects, masks and filters to reduce space noise. First, we duplicate our image as a new layer. We then create a mask for the new layer using an inverse of the image. Remember the darker the mask, the less impact the layer mode will have on the resultant image. So by using an inverse of the image, we are protecting the brighter parts of the image. Incidentally, masks can be edited just like images, so you can edit the mask to make the layer more or less transparent or to enhance or reduce specific parts of the image. However, we don't need to do this for our space noise filter. We now apply a medium blur on the new layer but not the mask. You can see that this reduces the noise significantly but it is not selective and our faint galaxy has also been unacceptably blurred. Now we change the layer mode to soft light. The darks are darkened and the blurred image works as a map to smooth the effect, whilst the mask protects the galaxy. Here are some before and after shots. Here is an image of a supernova in NGC3643. Click the in video link to watch a video on how I fix the oval stars in this image. This is M1, the crab nebula, which is a supernova remnant. And here is a colour image of the Eskimo nebula. Now I will demonstrate the process in Photoshop. Here is an image of the heart and soul maybe a little. The first thing we are going to do is duplicate the layer. I create a mask for the layer. I will select all the copy and the copy and go to the mask. Now I will go to the mask and go to the mask. I will go to the mask and go to the mask and go to the mask. I will go to the mask and go to the mask and go to the mask. Now I will check the layer mode to soft light. And that is the result. So that soft light and soft light makes it a lot more punchy. And then just how much of the effect you want. I will turn the opacity of the layer to the mask. Now I will go to the mask and go to the mask and go to the mask. I will go to the mask and go to the mask and go to the mask. I will go to the mask and go to the mask and go to the mask. I will go to the mask and go to the mask and go to the mask. I will suggest you to try to look how they look.DRSA's important. A little bit easier to recover from. continue Done Now I can still adjust the level of the effect If I don't get it out of like it It's all done off Six different days It's at easy You can download the action from the link in the description Then from inside Photoshop Select the load actions option from the actions menu And you'll be able to install it Thanks for watching If you enjoyed this video please click the thumbs up If you'd like to see more videos like this please click subscribe I'll see you in the next video