Removing Image Capture Noise in Composite RGB in Photoshop

Some images have lots of noise on all the channels. Usually these images are just as effectively worked on in the composite RGB mode rather than on individual channels. Here you will work on the composite RGB channel to remove noise:

1. Open and make a duplicate copy of the PolyChrome Alpineglow_RGB image.
2. Using the Channels palette, look through the three channels to view the noise in each one. You will notice that, unlike the Palm Sunset image in the previous example, there is significant noise in all three channels. Note that this type of high noise across all three channels is typical of images shot in low-light conditions with high ISO values.


3. Activate the RGB composite image in the Channels palette. To mitigate some of this noise and retain some of the image sharpness, you can apply the Reduce Noise filter. Choose Filter --> Noise --> Reduce Noise. The Reduce Noise dialog box appears. Note: This filter’s name is deceiving, because it is both a noise reduction tool and a sharpening tool. You will note that there are two modes, Basic and Advanced. The Advanced mode allows you to work on individual channels. Here, because all the channels are very noisy, you will need to work with only the Basic mode. There is a Remove JPEG Artifact check box and four fields to assign; the Details fields are sharpening functions:
   Strength This softens luminance-based noise (noise that is symmetrically distributed on all three channels).
   Preserve Details This sharpens luminance-based details (details that have been smoothed on all three channels).
   Reduce Color Noise This removes color-based noise (noise that is distributed asymmetrically on the various channels).
   Sharpen Details This sharpens color-based details (details that have been smoothed on all three channels).
4. Begin by zooming in on a key portion of the image. In this example, zoom in on a view that shows the sky and the mountain ridge. You can use the sky to judge the noise removal, and the mountain ridge to evaluate the sharpening. To control your zoom, you can use the + and – symbols at the bottom of the Reduce Noise dialog box or control magnification by pressing spacebar+F/Ctrl while clicking and dragging. Use F/Ctrl++ and F/Ctrl+– to zoom the image view itself behind the dialog box.
5. Enable the Preview check box to preview the effects of your settings on the actual image.
6. If you were working with a JPEG, here you’d enable the Remove JPEG Artifact option and view the results. You will find that this will remove minor JPEG artifacts but not major ones.
7. With the four noise reduction and sharpening fields available in this dialog box, you could chase your digital tail by randomly applying values. The best way to start is to apply 0 to all of the fields.
8. The next step is to configure the top two luminance-based values. Increase the value (1–10) until the noise pattern softens enough. You can push this image all the way to 10, but for many images this is too much.
9. Now raise the Preserve Details values (%) until the sharpness of the high-contrast ridgeline edge improves. Keep raising the value until the noise begins to reappear in the sky, and then back off a bit. Try in the 50%–60% range.
10. Now zoom in even more on a highly colored rich portion of the image. There really isn’t a super color-rich area in this image, but try the color gradient in the sky or water.
11. Apply some Reduce Color Noise values while carefully viewing the preview. Repeat the same procedure as with the Luminance values earlier. In this image, the color noise has little impact, so you need not make any adjustments. This means that most of the noise is luminance-based. With this noise reduction tool, you are able to view and separate luminance noise from color noise and adjust your image accordingly.