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HDR. Useful 3D Photographic Tool

VWTeam

In the last few years the magic tool of HDR is widely used in 3D Industry. Therefore, we wrote this article to help our members familiarize themselves with HDR and even experiment and create their own first Hdri picture. Special thanks to our *Club Member Zbigniew Ratajczak who gave us his HDR images which we used in this article. Enjoy it!

1. Stadium: photography by Zbigniew Ratajczak.
Image Source:  Zedphotos.com

What is.

HDR or HDRI is a set of methods used in photography to capture a greater dynamic range between the lightest and darkest areas of an image. HDR images can represent more accurately the range of intensity levels found in real life, from direct sunlight to faint starlight and is often captured by way of a plurality of differently exposed pictures of the same subject matter.

The human eye can adjust to deep shadows and overly bright light quickly. The perception of the total image includes information from the deep shadows as well as details from the bright highlights. In the early years of photography the problem of dynamic range i.e. the lack of it, was solved by photographers like Ansel Adams in several ways. He used silver based negative glass plates which had a decent dynamic range. This manipulation supplied less light to the shadows and more to the highlights so as to produce a print with great details on both areas.

2. The Bridge: photography by Zbigniew Ratajczak.
Image Source:  Zedphotos.com

Using HDR techniques we are able to create impressive and beautiful images which directly respond to this old problem of not being able to record what our eyes see. HDR overcame this limitation.In photography, dynamic range is measured in EV differences (known as stops) between the brightest and darkest parts of an image.

An increase of one stop is a doubling of the amount of light.If there is plenty of light, some digital cameras can take three photographs at different exposures quick enough to prevent blur without using a tripod. The best information from the highly exposed images is combined in the computer with the well balanced information from the properly exposed highlight areas to produce a photograph that displays all the information you can see with your eyes in real life.

 

As a short history.

1994 – The radiance lighting simulation and rendering system paper is published – Greg Ward.
The first 3D rendering system to use true radiance values (such as the sun example value 10,000,000), Radiance is born. As a result of this new application design a new file format was needed to support this extended data. After a lot of work Greg Ward created an incredible new method of file compression for floating point data. *.hdr is born. 

1996 - Modeling and Rendering Architecture from Photographs – Paul Debevec.
Although this doesn’t directly relate to HDR it was an important project for Paul that led to his next several pieces of work, which are all related.

1997 – Recovering High Dynamic Radiance Maps from Photographs – Paul Debevec.
This is where Photography first made its appearance into the HDR world; Paul developed a method of merging individually developed pictures at different exposures. This was film.

1997 - A Visibility Matching Tone Reproduction Operator for High Dynamic Range Scenes – Greg Ward, Holly Rushmeier and Christine Piatko
Greg develops one of the first modern day Tone Mapping operators that uses the human visual system as a frame for this.

1998 - Rendering with Natural Light – Paul Debevec
Using his new method of capturing environment lighting, Paul extends this method by using Mirrored Balls and captures 360x360 degrees. Now, this allows him to create High Dynamic Range Image Based Lighting (3D rendering system using images as the environment lighting). This method was later used to develop the groundbreaking Matrix effects. 

1998 - LogLuv encoding for full-gamut, high-dynamic range image – Greg Ward
Greg extends his work on High Dynamic Range image file formats by creating the LogLuv Tiff file format.

2000 - Photosphere Application - Greg Ward
Photosphere is Greg Ward HDR application, which was natively developed for Mac users. It allows users to browse, generate and tone map HDR images. In addition, it probably also has the most powerful Panoramic stitching application.

2001 - Real-time High Dynamic Range Texture Mapping – Paul Debevec
"Technique for representing and displaying high dynamic-range texture maps (HDRTMs) using current graphics hardware. Dynamic range in real-world environments often far exceeds the range representable in 8-bit per-channel texture maps. The increased realism afforded by a high-dynamic range representation provides improved fidelity and expressiveness for interactive visualization of image-based models. Our technique allows for real-time rendering of scenes with arbitrary dynamic range, limited only by available texture memory."


2002 - Photographic Tone Reproduction for Digital Images – Erik Reinhard
Erik develops a new method of Tone Mapping Images using a photographic framework.

2002 - A Wide Field, High Dynamic Range, Stereographic Viewer – Greg Ward
Greg presented “a high dynamic range viewer based on the 120- degree field-of-view LEEP stereo optics used in the original NASA virtual reality systems. By combining this optics with an intense backlighting system (20 Kcd/m2) and layered transparencies, we are able to reproduce the absolute luminance levels and full dynamic range of almost any visual environment.”

2002 – Gradient Domain High Dynamic Range Compression – RaananFattal
RaananFattal develops probably the world's most popular Tone Mapping Operator that is used. This has become what many people refer to as the “HDR Look”. 

2004 - Direct HDR Capture of the Sun and Sky – Paul Debevec
Paul expands his work on capturing environment lighting by going for the brightest player in the neighbourhood, the SUN.

2004 - Subband Encoding of High Dynamic Range Imagery – Greg Ward
As always, Greg once again tops himself by proposing an incredible method of embedding HDR data into the JPEG header so that the file is backwards-compatible with any image editor that supports JPEGS.

2004 - High Dynamic Range Display Systems - Greg Ward with Sunnybrook Technologies
Sunnybrook Technologies develops and presents the first HDR display system.

2005 - JPEG-HDR: A Backwards-Compatible, High Dynamic Range Extension to JPEG – Greg Ward

The concept turns into reality with a new addition to the JPEG file format.

2005 - 'Dynamic Range Reduction Inspired by Photoreceptor Physiology – Erik Reinhard

Erik develops a new Tone Mapping operator that uses the Photoreceptor of the human visual system as a framework of its design. 

2005 - High Dynamic Range Imaging: Acquisition, Display, and Image-Based Lighting Book.
High Dynamic Range Imaging: Acquisition, Display, and Image-Based Lighting (The Morgan Kaufmann Series in Computer Graphics) by Erik Reinhard, Greg Ward, SumantaPattanaik, and Paul Debevec 

2006 - MPEG-HDR - BrightSide Technologies Rafal 
Mantiuk

BrightSide Unveils MPEG-HDR Codec at SIGGRAPH 2006. This becomes the very first video file format for HDR imaging. Laying the ground work for developing hardware to support this new format.

Dec 2010 Photoroom Releases first version of HDR - SCI Supporting Computers Inc
Supporting Computers Inc makes their first version of Fhotoroom HDR available to the public. 

 

Conclusion.

HDR is used by 3D designers - Architects - Photographers -Movie Special Effect.
So to sum up for anyone who is still not sure, HDR is a concept, not a process or procedure as you can see, that people have developed many different methods and procedures to acquire or generate high dynamic range images. An accurate HDR image acquires ALL the radiance and irradiance of a scene. The bottom end of HDR is any data that is more than any standard optical device can display, which could mean just one RAW file. Most people prefer the term MDR (Medium Dynamic Range), which is completely acceptable since it doesn't represent the entire range of the environment.

3. Snowy Path: photography by Zbigniew Ratajczak.
Image Source:  Zedphotos.com

 

How to make professional Hdr Images.

 

  • What we need:
  1. A digital camera that allows you to set exposure manually. Even a semi-frame digital camera :)



  2. A sturdytripod.



  3. A subject (i.e. what we are taking the picture of) that does not move.
  4. A computer with Photoshop installed.
  5. A “cable release” if you have a camera that supports it. It is basically a little shutter button that attaches to your camera via a wire so you don't move the camera at all.

 

Step by step creation.

  1. First of all we have to set our camera in Raw mode.The RAW format captures more dynamic range data than is available in the alternative JPEG file. It also gives us a great deal of color temperature latitude meaning we can set the color temperature of all of our photos very easily later.
  2. We need to set our camera to manual exposure mode.
  3. We must put our camera on a tripod so that it doesn't move and then compose the scene we want to shoot. Note that, HDR works better when our subject isn't moving.
  4. Set the ISO Value as low as possible to avoid the noise.
  5. We have to meter our scene and then select the aperture we wish. The critical point here is to bracket our photos (i.e. take a photo of the same scene several times with different shutter speed, automatically or manually). So we only change the shutter speed and not the aperture. The reason being that we don't want our DOF to change between shots since we will be combining several images to make one.
  6. Now we can take our pictures in three or more different EV like the example below.

 

For the aboveprocess we have to follow in order to create a magical HDR Image and a 360 panoramawe found some really interesting and analytic tutorials on the internet.

  1. The keys to panoramic photographs and HDR panoramas by Forrest Tanaka. http://www.youtube.com/watch?v=eJonkmOousA
  2. 360 degree Panorama Photography tips and editing  by Dombowerphoto                    http://www.youtube.com/watch?v=fNJ6jTlADq8
  3. Shooting a 360 Panoramic Photo with a normal lens and tripod by 360Cities  http://www.youtube.com/watch?v=bkownWZmzw0

 

Bibliography.

 
 

Comments.

 
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