About this tutorial: This tutorial is made especially for beginners. The terms have been simplified than they should be in some cases. So, experts, do not complain, they are intended to be "noob-friendly". If you are an advanced user, you can also read through. You might learn something new. Topics are so vast that they deserve to have a standalone tutorial for each of them. So, I recommend you search the internet for more information about the topics to get a clearer idea.
What is HDRI: HDRI stands for High Dynamic Range Imagery. What is dynamic range? Within the context of photography, dynamic range is the range of light, from little to much, that can be measured and recorded, normally by a single exposure. In simple words, it's the ability to "catch" the light in the image. Suppose, you have a cup and a bucket. Your bucket will hold significantly more liquid than your cup. Now apply the concept to photography, normal images hold little data, HDR images hold significantly more. Your eyes are designed to detect very high and very low light, and your eyes will auto adapt to catch the most amount of detail. But cameras cannot do that. See this image below.
As you can see, your camera holds only a "fraction" of the dynamic range. To catch the scene as it is, you will need more than that. That's when HDR images come in. I strongly recommend you read this wikipedia article when you get some free time as it will help you a lot to understand what actually is HDR.
Exposure: It's hard to simplify the concept of "exposure", but let's just say it determines how much light your camera will capture. Cameras shoot at a default 0 EV. Go negative (-1/-2/-3/-4/-5 etc.) and the image will become darker as you are capturing less light. The opposite will happen when you go to positive values (+1/+2/+3/+4/+5 etc.).
Histogram: A histogram graphs the brightness values of individual pixels absorbed by the camera sensor within a digital image. Basically, it displays where all of the brightness levels contained in the scene are found, from the darkest to the brightest. It is basically a graph showing the brightness distribution of an image with pure black on one end, pure white on the other and grey in the middle. You might've noticed this before, but don't know what it means or does. To simplify this concept, see the image below.
If your histogram looks like the left one, your image have lost detail in shadows. If it looks like the right one, then it has lost detail in the highlights. But if it does not touch the left and right edges and stays in the middle (any shape), then the both the highlights and shadows of your image are preserved. Most of the cameras now have the option to show histograms in camera. So, you can take a look at that and adjust your exposure bias to catch the detail.
Bit Depth: This topic is complicated by birth, so we will try to skip the technical factors. Just remember it... the higher the bit depth of an image, the more information about the scene it will hold and therefore, the better. 16-bit images are a lot better than 8-bit ones, and 32-bit HDR images are significantly better than both 16 and 8 bit images. So, try to shoot/work with the maximum bit depth as it will make further editing easier and more flexible.
Tone Mapping: HDR images have very high contrast ratio and thus, cannot be rendered by normal televisions or monitors. You need special HDR monitor to see the file as it is, and they are insanely expensive. How bright is the sun? And how dark is a cave? Just imagine your monitor is rendering a daylight scene where it hurts to look at the bright sun or sky but the shadowed cave is dark and has slightly visible details. An ordinary monitor cannot do that, but an HDR monitor can. Also, printed images do not have the ability to show such high dynamic range. So, there is a technique that reduces the contrast of the HDR image to get the details out but still maintaining an acceptable dynamic range which the monitors or televisions are able to render. This process is called tone mapping. The tone mapped image is basically a low dynamic range image. So, it is a process of converting high dynamic range images to low dynamic range images.
What you need
# A camera (be it point and shoot or DSLR)
# Adobe Photoshop
# Basic knowledge (included above)
# Photoshop basic skill (the higher the better)
You may use either Photoshop or Photomatix or both (I recommend both). If you want to go with only one program, then go with Photoshop as it will make post processing much easier.
You need at least 2 differently exposed images of the same scene (that means at the same time and same point of view). Most of the photographers use 3 differently exposed images. They may be +1/0/-1 EV or +2/0/-2 EV or theoretically any (most photographers prefer +2/0/-2). But try to keep the spacing constant. For example, you may, but should not go with +1.26/0/+2.14 EV. For intense scenes that have both very light and very dark areas, you might need a greater EV spacing (like +3/+2/+1/0/-1/-2/-3) to catch the details precisely. DSLR cameras are perfect for these conditions. Point and shoot cameras do not have much flexibility and only allow to shoot 3 differently exposed images at once. These set of differently exposed images are called bracketed photos/exposures.
How you shoot the bracketed exposures varies depending on your camera. So, it is up to you to find out. Take the help of the camera's user's guide.
Now when you have the bracketed exposures ready, put them in a separate folder (for the sake of arrangement). Then follow one of the two ways below.
Photoshop: I have used Adobe Photoshop CS5 x64 for this tutorial:Photomatix: I have used Photomatix Pro 3.2 for this tutorial:
I have used 5 different exposures for this tutorial. They are -1/0/+1/+2/+3. I have used a normal point and shoot camera. If you have a DSLR, you are likely to get better results.
Although the main objective of HDR images is to bring out the details to make the image look "realistic", some people love more aggressive tone mapping. Some love those overdone images, some hate them. It's your call. If you want it to be realistic, you can do that. But when you decide to exaggerate the image, it will become somewhat artistic. An example will clarify this. Here is the 0 EV photo to the left, realistically tone mapped in the middle and overdone to the right.
Here are a few other examples that you might want to check out as well:
Thank you for reading. I hope you will be able to shoot photos in High Dynamic Range from now on. Whenever you get time, read more about the topics and practice with different scenes. HDR is the future of photography, and you should be prepared.
One example of bracketed exposures is attached with this post for you to experiment with.
You may want to post your comments here if you want.