Revisiting noise reduction

I've already covered noise reduction earlier in the course but I have also covered it recently on my Photoshop course.  

The best way to avoid noise in your images is not to shoot at a high ISO.  However recently I have been shooting indoors a lot in places where flash and tripods are not allowed so I have had to crank up the ISO.  I have noticed that on my D700 I can increase the ISO without getting as much noise as I have with the D90.  

To reduce the amount of noise I have in some of these images I use the Noise reduction sliders in Lightroom.   These are found under the Deatil menu. 

If you want to reduce the colour noise you can drag the Colour slider to the right to reduce it.  

The Detail slider controls how the edges of your image are affected by the noise reduction.  If you drag it too far over you will run the risk of introducing colour speckles so it is best to keep this to a minimum.  

To reduce grain drag the Luminance slider till the noise is greatly reduced.  The Detail slider if dragged too far to the right can make your image more noisy.  It is difficult to have cleanness and detail in a noisy image.  You have to make the decision which to sacrifice.  

I have used this image as an example.  This was shot at ISO 1600.  

If we look a little more closely at the noise we can see that it is a bit grainy.  

Luminance slider increased to 55

We can see that the noise has been reduced significantly.  

Noise can be reduced in RAW images in ACR.  We have the same sliders to work with and they produce the same effects at Lightroom.  

Noise can also be reduced in Photoshop using the Channels Panel.  This type of noise reduction concentrates on reducing noise in colour channels as there is often significantly more noise in a single colour channel than others.  

When you look at the colour channels it is possible to loo at each colour individually.  The blue channel tends to have the most noise.  

Using the Filter menu, select Noise and then Noise Reduction.  In the Advanced option you can reduce thte noise by colour channel.  

I think that the methods that I find work best for me is to use Lightroom or ACR to reduce noise.  I think the Photoshop method would be good for a noisy JPEG but I rarely tend to shoot JPEG only so I don't have this problem.  

I think introducing noise reduce at the processing RAW image stage works best for my workflow.