hdr tone mapping

     To begin this tutorial it is assumed that you have a basic understanding of what HDR images are and their importance. If not, please read What is HDR tutorial. To learn how to merge LDR (JPG's, TIFF or RAW files) images into a single HDR, go to Creating HDRi Files.  

Tone Mapping Operator are like filters but what they do is compress HDR data (also known as 32bit images) LDR data (also known as 8bit and 16bit images simply put jpg's and tiff's). Since there are virtual an infinite number of ways to compress the data, different Tone Mapping Operators have different options that perform different functions. Fhotoroom offers 2 built-in tone mapping operators called Dramatic and Natural and each of these produce a different results. Dramatic is a complex operator that is slower than Display but it produces that commonly referred to result as "HDR cartoonish". Although it can produce results that are almost cartoonish it can be applied very subtly so that it also produces very natural results. Natural like it's name implies produces very natural results with a touch of dramatic detail. 

The tone mapping interface is consistent regardless of the tone mapping operator selected, but not all options are available to all operators. The interface breaks down into 6 specific areas the Preview options located at the top above the picture, and the rest (Presets, Detail, Colors, Exposure, and Extra) are all located to the left of the preview picture.

Undo Button - This option allows users to undo the tone mapping settings to their 
previous values.

Redo Button - This option allows users to redo the tone mapping settings to their previous undo values.

Dropdown List - This lists all of the tone mapping saves that have been saved.

Delete Button - This option deletes your tone mapping setting in a xmp file.

Preview Samples - Allows users to create different samples before deciding your final effect.

Local Controls - is a group of three sliders that control local functions such as detail and sometimes the overall strength of the tone mapping operator.

Exposure - These are global functions that control the overall look of the image such as brightness.

Color Balance - These are global functions that control the overall look of the image such as brightness.

Levels & Histogram - This allows users to make final corrections (usually after the tone mapping settings have been set) to the image before outputting the results. The Histogram (vertical Blue Lines) displays what the distribution of data looks like for the image shown in the right hand side preview window. 

First try to bring in as much data to the center of the Histogram which is illustrated by the red, green and blue lines, and the second is to try to make sure that distribution between the dark and bright areas of the image are even.

Using Levels offer a new way of working with the Highlights and Shadows (H&S) of an image. The key difference between the Levels H&S options and the tone mapping options, is that the tone mapping options only work on data that is on the bottom or top half of the histogram while Levels works across the entire image data set. So using the H&S options in Levels tool can increase/decrease the overall brightness of an image.

Now if you want to reset the values of the Levels options. The "Reset" button is located at the upper right hand corner of the Histogram. This option is different than using the "Undo" settings button located at the top. 

At the very bottom of the Tone Mapping window are several additional options that can be used to determine the type of image you are using and how you would like the output to be.


Noise Reduction - Some tone mapping operators can produce to much noise in the final result and even though this can be controlled by using a Details option, it will also change the overall appearance of your image. The Auto Noise Reduction option on the other hand will will automatically reduce the amount of noise in your results while preserving the overall effect created by the Details option.

Vignette Effect - This option controls the amount of Vignette effect is applied.

Panoramic x360 - These options have been added to allow users to tone map their panoramic images. Since not all panoramic images are the full 360x360 degrees these option were separated (unlike most competitors that only handle 360x360 or 360x panoramas) so that users can tone map their nadir and zenith fisheye images. This helps ensure that when your hdr panoramas are unwrapped or wrapped they will produce seamless results.

Output - Depending on the intended final use of your tone mapped hdr image, user can select to out their images as 8/16 or 32bit.

Auto Save Default Settings - Users sometimes want to be able to reset the default values of each tone mapping operator, the auto default option will save your settings as the new default values when you click apply. This option is very useful when dealing with very similar hdr images that work with the same setting values.

Save Settings with File - Users can now save their tone mapping settings in the same location as their final image file for reuse at future date. Loading the settings file is done by selecting the Load Settings... option in the Drop Down List at the very top.

Preview Options

Since each tone mapping operator takes a different amount of time to process and the results can vary slightly based on image size, Fhotoroom has 4 Preview Styles; Very Fast & Low Detail, Fast, Balanced and Slow & Detailed. A good practice is to use one of the lower Styles for setting your values and once you are happy with your results, it is good practice to make sure that the results still look good on the Slow & Detailed style. This will help ensure that what you see is what you get.

Show Out of Range Pixels - When this option is select it shows which pixels are either over or under exposed by displaying them as red and blue colors. This doesn't affect the final results cause it is only for information purposes. 

Original photo belongs flickr user: cammyjams > flickr.com/photos/36113180@N00/