HDR light probes for cheap

Wednesday, 3 May 2023

TL;DR: A Ricoh Theta S can be had for under $60 on eBay. Combined with pfstools, you can easily capture HDRI environment maps and merge them into OpenEXR images.

The Ricoh Theta S is Ricoh’s cheapest 360-degree camera that has automatic bracketing functionality. I bought mine for about $60 on eBay second-hand. The image quality certainly isn’t as good as the flagship Ricoh Theta Z1 ($1,050) but it does the job.

Honestly, I haven’t seen the camera in any color other than black or white.

The automatic bracketing is easy to set up in the app and when run will take each shot in sequence with a few seconds of thinking in between.

Automatic bracketing wasn’t added until firmware v01.82, so if you don’t see it in the app, make sure your firmware is up-to-date.

In the Ricoh Theta app, go into the camera settings and choose “multi-exposure”. The first time you use it you will need to manually add each shot’s settings.

Note the limitations of the Theta S: no RAW captures, only JPEG, and it’s not particularly fast. The output resolution is 5376×2688 pixels but that’s the stretched equirectangular image. (The camera specs claim 12MP x2.) Also, it’s usually impossible to underexpose the sun even with the fastest shutter (1/6400) and slowest ISO (100), which might mean manually editing the HDR image afterwards.

JPEG preview of an OpenEXR image I shot in a nearby park. Note the defects: purple fringing and visible tripod mount.

After you’ve captured a series of images, you can merge them easily with Photoshop or pfstools:

pfsinme image001.jpg image002.jpg image003.jpg ... | pfshdrcalibrate -v | pfsout output_image.exr
Test render using the above HDR environment map, showing highlights and shadows true to the sun’s direction.

Written By
Eric Jiang

The entry 'HDR light probes for cheap' was posted on May 3rd, 2023 at 20:50 and last modified on May 3rd, 2023 at 21:06, and is filed under Graphics. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

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