Reduce Noise in HDR Images with Multiple Layers
Tone mapped high dynamic range (HDR) images don’t always come out of your favorite HDR application looking perfect. Some images have too much noise (a common problem with HDR) in general. The pinnacle of noise reduction methodology is to apply tailored noise reduction levels to specific areas of the image by using multiple layers and masks (in Photoshop) or the Eraser (in Elements).
Although that sounds complicated, the most you’ll ever need is two levels of noise reduction, possibly three. If you see other parts of the image you want to try different levels of noise reduction on, duplicate the last un-noise-reduced layer you have and apply a different amount of noise reduction to the newly duplicated layer.
This figure shows three noise reduction layers being finished. Apply the noise reduction first; then delete what you don’t need out of each layer. Remember, the three layers have different noise reduction strength. More for the ceiling, less for the walls, and just a bit for the floor.
Arrange the noise reduction layers so the areas you have applied the noise reduction to are visible and don’t conflict with each other. In this figure, the three areas don’t overlap. Notice that when all the noise reduction layers are on, there are still quite a few transparent areas. That’s because those areas have no noise reduction at all.
After you get your noise reduction layers finalized, turn on the Background layer (or the next layer underneath) and create a merged copy to lock the adjustments onto one layer.