Tone mapping operators
From OSP Wiki
Please add your experience with the different algorithms into this wiki to help other users to achieve good results in a faster time.
Unless stated otherwise it is assumed that the HDR image is created with the default values, thus only the tone mapping values have to be changed. If you don't like the result of a specific tone mapping operator, please keep in mind that after the tone mapping step you can still use tools like GIMP to post process the resulting image. For example, you can still fix the brightness, change the gamma or the levels, and so on.
For a detailed description of the operators, and things like "Alpha", "beta", "range kernel sigma" and so on refer back to the respective paper's equations.
Contents |
Ashikmin
When to use this algorithm
Pictures can be very high in contrast and very colorful (if all sliders are moved quite far to the left side) or very washed out. The washed out remindes on a mix of water colors and charcoal drawing.
Parameters in detail
Simple (Default not set)
It looks like that using the simple button makes it easier to achieve more realistic pictures. It seems as well that "simple" mode is quite close to "Equation 4" mode if not the simple button is set.
Drago
When to use this algorithm
This algorithm is intended to imitate the human eye's response, and is useful when a true tone result is desired.
Parameters in detail
See the web page at http://www.mpi-inf.mpg.de/resources/tmo/logmap/ for technical details.
The Bias expands or contracts the dynamic range of the tone mapped image. It needs to be smaller if the HDR has a larger dynamic range.
The Beta ratio changes the amount of compression of the dark areas versus the light areas.
Durand
When to use this algorithm
This algorithm produces the most realistic pictures. No extreme effects, but very nice output with lots of details in the picture. This algorithm needs a lot of time to calculate the output.
Parameters in detail
Base Contrast (Default 5)
Found this value usually too high and reduce it between 2 to 3. The lower the value the lower is the contrast, the picture gets darker. This can be important since it seems that light spots are too bright.
Range Kernel Sigma (Default 0.4)
Increasing this value creates a halo around lights, somewhat similar to soft focus filter. Post tone mapping gamma adjustments (Default 1)
The higher the value here the lower the contrast will be. Seems to have a similar effect like the base contrast setting.
Fattal
When to use this algorithm
This algorithm is the one used by most users to produce pictures with a stunning effects. Usually these pictures are not realistic, but can be very impressive. Note that, if your images contain noise (e.g. you took them using a high ISO value), it will be heavily amplified (they are considered details), becoming much more evident. You'd better not to use this algorithm on noise images.
Parameters in detail
Alpha (Default 0.1)
Reducing that parameter quite much makes the picture very colorful. Moreover, lower alpha will make the picture look more realistic (as long as you can call "realistic" the output of this algorithm), while increasing it you will get a drawing-like artistic look.
Beta (Default 0.8)
Increasing this value make the picture very dark, reducing this value give the picture some kind of grain. This grain lookes like a picture from a newpaper which was folded, steped on etc. I rather tend not to change this value.
Color Saturation (Default 1)
As the name says, the color saturation. Increasing this value too much can result into black spots or black coulds of pixels. On the other hand reducing this value can lead to some kind of black and white pictures with some coloured spots, e.g. if you have night shots only the neon signs are coloured the rest of the picture is (almost) b/w. For this b/w effect try a value around 0.27.
Post tone mapping gamma adjustments (Default 1)
Reduce this value to get vivid colours, try 0.36 as a start.
Pattanaik
When to use this algorithm
Parameters in detail
Reinhard 02
When to use this algorithm
The pictures created with this algorithm will have an almost flat histogram, this means you are fully using the (limited) dynamic a standard 8-bit format can offer. The output will look realistic, keeping the details clear at any contrast.
