HDRI < Tonemapping tips

by bob on February 27, 2011

in Dutch Light 360 online shop, Dutch Skies 360° online shop, HDRI, Support

more info soon: still updating this page

One problem with HDR has always been in viewing the images. Typical computer monitors (CRTs, LCDs), prints, and other methods of displaying images only have a limited dynamic range. Thus various methods of converting HDR images into a viewable format have been developed, generally called “tone mapping”.
Early methods of tone mapping were simple. They simply showed a “window” of the entire dynamic range, clipping to set minimum and maximum values. However, more recent methods have attempted to compress the dynamic range into one reproducible by the intended display device. The more complex methods tap into research on how the human eye and visual cortex perceive a scene, trying to show the whole dynamic range while retaining realistic colour and contrast.
Images with too much “HDR” processing have their range over-compressed, creating a surreal low-dynamic-range rendering of a high-dynamic-range scene.

Tonemapping Tools:

There a a lot of tonemapping tools arround. A complete list you can find on the HDRlabs website

If your budget is very minimal the would advice to start with the free tool Picturenaut.

Work here with several commercial tonemapping tools:

1) Photomatix

2) PTGui Pro
3) HDRExpose

Combination:

Found that every HDR Images needs its own specific needs regarding tonemapping and so you can off course mix tonemappings made with one of the tools above together in Photoshop

Solving the 360° seam problem with HDRExpose

When you want to tonemap with HDRExpose then you have a often have seam problem when you want to tonemap 360° HDRI panorama’s.

Made a simple Photoshop action that solves the problem. Here you can download the actions. Instruction are within the zipped file.

Banding problems

Sometimes its possible you ca have some banding problems when post processing HDRI images. Had a quick chat with Christian Bloch about this he will probably put some more info about this very anoying problem (its acomplete riddle why it happens)

It happens actually a lot when you work with HDRIs in compositing, either After Effects or Fusion. When you comp everything in 32 bit, and then just convert it down to 8 bit (instead of tonemapping), this conversion can introduce banding. Doesn’t matter how clean the data is. Not sure why. It goes away when you use Dithering during the conversion. Or add a slight amount of grain

Here did the trick on another way in a new project:

– Tonemapped the HDR’s in HDR Expose and saved them as .EXR
– And then do not alter gamma/ EV in the 3D app think that is causing the banding too or even makes it worse

Some more tips / suggestions

The HDRLabs forum has tons of usefull informations about HDRI. If you might encounter a problem or have any suggestions just post them on that forum.

The High Dynamic Range (HDR) Landscape Photography Tutorial

Shootings HDRI 360 scenes with diff color tempature