I am getting noisy tone mapping results. Is there a way to avoid this?
The Tone Mapping method "Details Enhancer" enhances local details a lot. If the local details of your HDR image are noisy (you can easily see that in the HDR viewer), then the noise will be enhanced as well, unfortunately.
Applying a noise removal tool to the tone mapped image is often the best solution. You may still avoid having to do that with the recommendations below:
Case 1: Motionless scene (i.e. without moving objects) In this case, it should be possible to avoid noise in the HDR image if the differently exposed photos cover the whole dynamic range of the scene. That is, making sure that at least one photo correctly exposes the deepest shadows and one photo correctly exposes the highlights (see above). It is particularly important that your bracketed shots include an image taken with a sufficiently long exposure time to make the darkest parts of the scene visible.
There are some situations (e.g. low-light outdoor scenes) where correctly exposing the darkest part might not be possible. Make sure in this case to enable the noise reduction function of your camera if there is one. You may also try taking several images at long exposure times and stack them together in Photomatix using the "Average" combination. Then, generate the HDR image with the result of the stacking at each exposure.
Also, it may be a good idea to lower the exposure spacing, for instance to one-EV increments instead of two. This is especially recommended if you are using a compact camera.
Case 2: Scene with motion If you have a high-quality camera able to keep very low levels of noise at high ISO settings, then you can limit the number of bracketed shots to just two, each taken at high ISO with very short exposure times. The tone mapping tool is really good at retrieving shadow details from underexposed shots, so you don't need to expose more if your camera has an outstanding signal-to-noise ratio. In this case, you may also try with just one shot taken in RAW mode and convert it into a "pseudo" HDR image in Photomatix to tone map it.
If you don't have such a camera, then you may still try with a limited number of images taken at high ISO settings, and then apply a noise reduction tool to the tone mapped image.
If you are applying the Tone Mapping tool to a single RAW instead of differently exposed images, then the chance of getting noisy results is higher, unfortunately. In this case, we recommend exposing for the shadows by slightly overexposing your shot.
In any case, the problem of noise made more visible with Tone Mapping only applies to the Details Enhancer method. You can still avoid it by using the Tone Compressor method instead.
