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PAC-MAN Pizza Parlor
Help PAC-MAN serve hungry customers!
Chicken Invaders 3
Save the Earth from the greatest chicken threat ever!
Hidden Mysteries: Vampire Secrets
Join Claire on a Hidden Mystery!
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What is HDR? HDR stands for High Dynamic Range and it is the next big step in photography. There is a lot about HDR that people don't understand and I often see it being totally misunderstood as some type of a special effect to make photos cartoony. HDR is basically an enhancement to the definition of the image - it adds more detail to the color information of the image than the traditional digital or film photos can store, or our display devices can show.HDR itself doesn't mean that the colors will be surreal or the appearance would be more or less cartoony. In fact, you would be able to process an HDR image in a way that would result in exactly the same look as a traditional "LDR" image. An image with high dynamic range contains a lot more information than an LCD monitor can display but HDR images are not actually meant for displaying. When you see a JPG titled as "HDR photo", what you see is technically a low dynamic range image created based on a HDR source. How to take HDR photos?  Ideally - and I'm sure this will be reality in near future - you would take HDR photos in a single shot, exactly as you shoot any digital photos now. However there are no consumer level cameras available yet with more than 12 bits per pixel (per color component) fixed point precision. In order to have a real HDR image we need at least 16 bits floating point value for each color component. So we can't use a camera to shoot a HDR image, how can we do it? To achieve good deal of dynamic color range to our source image, we need to take multiple photos of the same target using different exposure settings. These images will be stored as regular images (either as JPG with 8 bits per component or RAW with10 or 12 bits per component) and transferred to the computer for further processing. Some cameras can automate the process of taking several photos in series using different settings, while with others you need to shoot a number of times changing settings between each shot. Whatever way you do it, a tripod is definitely for stability. It should also be noted that you can only shoot still targets with this technique. For the best results you should have a fairly high end camera with RAW format support and automated multi-shot function but I've experimented with a Sony DSC-P200 point-and-shoot camera with "ok" results. It's not convenient and the quality is not optimal but at least it gives a chance to go through the steps and learn how things work. The easiest way to combine a set of LDR images into a HDR image is using Photoshop CS2's built in HDR image support. Basically you just choose a series of images and Photoshop composes these into a floating point HDR image. Photoshop CS2 supports 32 bit floating point image buffers so once the image has been loaded you can do processing and save the file without compromising quality. HDR Post Processing  I am familiar with HDR post processing techniques from the next-gen console games I've worked on. Games on the latest generation of game consoles (PS3/Xbox360) often produce images in HDR and then do post processing before tone mapping the image to the screen. When your source image has a high dynamic range, you can do post processing without losing image quality. One of the most popular post processing effects in games is blooming. Bloom can be used to enhance the appearance of bright lights and it can make images feel more "dreamy". You can get similar effect by adjusting exposure levels when taking photos, but it's just much easier to work on such effects after the fact, in Photoshop. Perhaps the most important thing to keep in mind with any effect is - make it subtle! Basically a special effect is well done if the viewer doesn't notice it.Tone mapping  HDR images can't be displayed directly because the color range they contain simply is not displayable on any type of display. Therefore, tone mapping is the last step, which converts your HDR image to a 8 bits per components per pixel fixed point resolution. This is what the common image formats like JPEG use, and this is what the typical LCD monitors can display. In this step you choose how you want the image displayed. Since your source image has a lot of extra precision, you have a lot of freedom here. You can choose to flatten the colorspace to bring out dark colors and tone down the brighter, resulting in a cartoony image which is what most people think of HDR image these days. But equally well you could hide the dark and bring out the lights, other the other way around just like in traditional photography. The difference here is that you have the power to make the choice after the photo has been taken, and you have the ability to look at all the possible variations of the image.HDR photography is still new, and both the tools and the techniques are in their infancy. A lot is to be learned, and the cameras and the software will definitely improve a lot. The images used in this article show the huge potential of HDR images. All of these shots are taken by wili_hybrid, who was very cool to give me permission to use some of his photos as examples of great HDR photography. Click on the images for larger versions. Take a look at more cool classic and HDR photos from Wili at www.rawjay.com! (Note: this link doesn't seem to work in China... if you can't open rawjay.com, try this: www.flickr.com/photos/wili) |
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Here's couple more amazing shots from Wili. To see more, check out his page: www.rawjay.com!  |
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I second that... fascinating indeed. So you're saying I can do that with a pocket camera? I would have thought you need a professional SLR camera and a few thousand $$$? How exactly does it work? I guess I need pro equipment to capture shots like the ones from wili_hybrid? |
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You can do it using a pocket camera but it's a little more work and the quality is not quite as high. Here's a test I made using a Sony DSC-P200, which is a regular 7 megapixel snap and shoot camera. There are two major problems using a camera like this to compose HDR images - first, there is no way to automatically shoot multiple photos using different exposure settings. This means you need to take multiple shots, holding the camera on a surface to make sure it stays very still, and change exposure settings between each shot. Not fun! The second downside is that there is no support for RAW images, so you're limited to 8 bits per pixel color precision which is not quite enough. Above you can see four shots taken at different exposure levels. I took a total of 7 photos going from EV +2.0 to EV -2.0.   Above left is an unmodified photo with EV 0.0 exposure setting. This is basically what a photo would look like if I would just take it as is. Right side is an HDR image before tone mapping (taken as a screen grab from Photoshop's output). I created the HDR image by importing the set of 7 photos to Photoshop CS2 using the new HDR merge function. Since the screen can't display color values brighter than 1.0, a lot of the bright pixels appear over-saturated.   Above left is a result of Photoshop's own tone mapping. The options are quite limited but you are able to control the color curve to get reasonable color reproduction across the image. The colors are not vibrant, but the over-saturation problem is fixed. The right side is an image created using Photomatix tone mapping plugin. Photomatix has a lot more options on contorolling the color and light balance so I was able to get stronger colors. A thumbnail of each of these shots looks "ok", but if you look at the larger version you will notice how the pixel level detail is not there. Part of this is due to the lack of precision in the source images, partly it is because I wasn't able to hold the camera steady enough between the shots. A disclaimer: These are my first ever attempts in the world of HDR photography... take them with a grain of salt! I will post more shots as I learn some more.  |
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   hehe, not bad ya... those are so great pics! But jani's pics seems still need better light. those colors are not so correct anymore. but still it makes lots of sense already!  |
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No need to cry, Jani now has a new camera and a tripod. Check my recent posts or photo album for some new photos. Here's some examples: www.xihalife.com/photosets/513/  |
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