Thursday, November 19, 2009

Examples of HDRI



HDR Utilities


HDR SHOP
The godfather of all HDR utilities. HDR Combination is very dated, and it does tone mapping only via Plugins. But it has a good amount of editing capabilites, that still make it the swiss army knife in HDR.
HDR MAX
HDRMAX comes in a very professional outfit and fits right in with Adobe's Creative Suite. Tonemapping is powerful, simple to use, and pretty halo-resistant.
HYDRA
$60
Hydra has by far the flashiest interface, a 101% Mac-App. Tight integration with iPhoto, even comes with an Aperture plugin version included. Unique strength is the alignment feature, that will morph and warp each exposure into place based on control points.
PHOTOMATIX
HDR Combination and Tone-Mapping, very user-friendly hence recommended for beginners. Sports ghost removal, RAW decoding with CA compensation and batch processing, which makes it photographer's favorite. Integrates nicely with Photoshop, Lightroom and Aperture.
PICTURENAUT
The new kid on the block, hosted right here. Highly configurable HDR Combination and fastest tone-mapper around. It runs HDRShop plugins, and performs basic conversion tasks. Not quite as many editing features as HDRShop yet, but eventually getting there.

Shooting HDRI's



You'll need a digital SLR camera with interchangeable lenses is the ideal solution, but almost any camera will work if you can lock the aperture, lock the focus, and lock the white balance. Auto-bracketing (AEB) option is convenient.
Wider lenses best. The farther away physically that you are the better because it helps to reduce your reflection in the ball. A zoom lens (i.e.: 70-300mm)
wide angle rectilinear lens over a fisheye
Generally f8 or f11 are the sharpest overall areas within a lens.
Watch out for your feet and clothes!
Shoot RAW or JPEG
shoot in 2 EV increments when shooting Raw and shoot 1 EV increments when shooting in the JPEG format.
3-9 shots depending on your project.
Contrast. Don't shoot on a bright day at noon.


Industry Examples:
Stuart Little used a chrome ball.
Spider Man 2 and 3 used fish eye lens and HDRCAM chirpy to save time and money
843 HDRI's
30,348 exposures

HDR VIDEO CAMERAS
Spheron:
- 20 f-stops of dynamic range
- full HD resolution 1920 x1080
- 24 and 30 fps, possibly up to 60 fps
- saves to fiber coupled storage server
- records 5 hours of EXR frame sequences
Civetta:
faster, cheaper, higher resolution.
The SpherCamHDR uses a single-line CDD in a constant revolution, scanning the full environment as it turns. Especially in low-light situations, that can take a long time, and it's even slower when you max out capture resolution (because it has to turn slower).
The Civetta is built on Canon technology, and snaps fullframe pictures with a 15mm fisheye. That makes it more of a traditional panobot, with all the speed and resolution advantages. If you had the patience and real skills in lathing and milling, you could build such a panobot yourself. Except, it wouldn't look as slick, and it wouldn't be as easy to use.

Light Probe Images



CHROME BALL METHOD
Light probe images are created by taking pictures of a mirrored ball.

Easy learning curve

Glass balls are $10 to $25 each or steel balls

Easier to process and convert to HDR files because it is just a single file

Overall low quality* image (*This can be improved if you shoot 2 or 3 additional angles of the same ball)

Overall, captures accurate color/light information

Not ideal for background plates or reflection maps (unless they will be very out of focus or blurred on purpose)

LATITUDE-LONGITUDE PANORAMIC METHOD

Can be stitched in Photoshop.

Multi-image spherical panoramic HDR


10 spherical panoramas. Each panorama was taken one f-stop of exposure apart in order to capture the full range of light in this scene.

Equipment: digital camera, tripod, panoramic photography pan and tilt head, shutter release cable, Stitching application, HDR Shop.

  1. Photographing the panorama, bracketing each shot
  2. Parsing the files by exposure and renaming them
  3. Stitching one exposure into a panorama then using the same stitching project to render each exposure
  4. Creating a responce curve for the camera
  5. Creating, editing and setting the whitebalance for the HDRI
  6. Conclusion

Multi-image spherical panoramic HDR

Gear is much more expensive and heavy

Exponentially more files are needed, which means more hard drive space, more file management, more retouching, etc….

Bigger time/manpower investment

High quality results can be used for lighting, reflection maps, and background plates. 
(Side note – You generally only need a very low resolution panoramic HDR file for the actual lighting information. You might need a higher or full res version for the reflections or background plates)

Much more "flexible" in that you have a high quality image that you can always make smaller if needed.



History


What is HDRI?

a set of techniques that allow a greater dynamic range of luminances between the lightest and darkest areas of an image.

· This wider dynamic range allows HDR images to represent more accurately the wide range of intensity levels found in real scenes ranging from direct sunlight to faint starlight.

What is it used for?

computer renderings and photography

HISTORY

1850

The idea of using several exposures to fix a too-extreme range of luminance was pioneered as early as the 1850s by Gustave Le Gray


1930

High dynamic range imaging was originally developed in the 1930s and 1940s by Charles Wyckoff. Wyckoff's detailed pictures of nuclear explosions appeared on the cover of Life magazine in the mid 1940s. Wyckoff implemented local neighborhood tone remapping to combine differently exposed film layers into one single image of greater dynamic range.

1980

First practical application of HDRI was by the movie industry in late 1980s and, in 1985, Gregory Ward created the Radiance RGBE image file format which was the first (and still the most commonly used) HDR imaging file format.

1993

Global HDR was first introduced by Steve Mann: different approach, based on making a high-dynamic range luminance or light map using only global image operations (across the entire image), and then tone mapping this result.

1997

Global-HDR technique of combining several differently exposed images to produce a single HDR image was presented to the computer graphics community by Paul Debevec

2005

Photoshop CS2 introduced the Merge to HDR function