As I have mentioned before, I love photography, and specially a technique called HDR. HDR stands for high dynamic range, and it means the ratio of the "lightness" of the lightest spot in the picture to the darkest.
http://en.wikipedia.org/wiki/High-dynamic-range_imaging
The real purpose of the imaging technique *should* be to increase the tonal range of the picture. Don't you hate it when you look at something that's very beautiful, like a landscape of a sunset, and your camera just cannot take a picture of everything? Either the person shows up in the picture, or the sun but the person is super dark?
This is because the camera has a very limited dynamic range, whereas your eyes have a very wide dynamic range. We are talking in a ratio of a thousand-fold increase!
For photographers, a "stop" is an important measure. Every "stop" is a doubling of the amount of light. Some very good cameras (that cost over 1000 dollars) with large sensors have 10 stops, which means that the maximum light/dark ratio is 2^10 = 1024. By comparison, our eyes have around 2^20 or over a million times the light from the darkest to the lightest spot. It's what allows us to see some bright stars at the same time as we see the details in the moon. Go and try photographing the moon, you either get the details, or you get the stars, but you can't have both.
So, how to go around this? There are various ways. Usually, when you have a landscape such as a prairie and the sunset or the ocean and a sunset, you have a specific "line" where there is a difference between the darkest (the ground) and the lightest (the sun) spots.
This allows you to just use a graduated neutral density filter.
http://photo.net/equipment/filters/ndgrad2.jpg
The picture using the GND filter is much better than the one without. The filter allows light to pass through in the ground area and blocks a certain amount of light in the sky area so that the ratio falls within the limits of the camera.
There are times, though, when a graduated neutral density filter is just not enough. For example, when you have a situation where there is no clear line (one example is a person standing next to a window...).
That's when you use HDR.
When you take a picture in automatic mode, the camera selects an ISO, an aperture, and a shutter speed that, combined, determine the "correct" amount of light to hit the sensor. This is what we will call a "correctly exposed picture". However, this picture is usually a compromise. The camera cannot take ONE picture that has everything, so you end up with a dark silouhette of a person and a washed-out sky.
There is an HDR setting on some cameras. On my camera, a Canon 60D, there's a setting to take three pictures, one after the other. First a "correctly exposed" picture, then a picture underexposed by 3 stops, and a picture overexposed by 3 stops.
I use a program called Photomatix, which is relatively cheap and can be found here:
To combine the pictures into an HDR picture.
Now the picture has 16 stops (10 from the "correctly exposed" plus three on each side of the dynamic range).
However, many people hate the un-natural-looking pictures that photomatix makes.
http://www.hdrsoft.com/images/eiffel/tm.html
I personally don't like that "look"... it can be taken way too far and the results are ugly. For me, you really have mastered the art of HDR when people don't realize it is an HDR picture. It looks natural and unprocessed, as much as possible. Sometimes, I get amazing results, sometimes I don't. It depends.
I have discovered that there is way more to it, like combining in Photomatix first under "combined - average", and then editing the picture using Camera RAW (a program inside Photoshop). Then, adding various fake graduated neutral density filters (exposure and many times color balance), and sometimes using "penciled-in" light and other techniques, I get results that I like.
The drawbacks of HDR are that the subjects don't have to move at all, or you will get ghosting in the image, and it's hard to make the picture look "natural". I still have to experiment with external flashes and fill-light, to avoid HDR, because it can't be used in all occasions. Fill light makes for much more natural-looking pictures, but it's another technique I have to master.
Here are some of my favorite shots using HDR (and showing the process):
"normally exposed": You can see the clouds but some are washed out, the canoe but so dark... Very "boring" picture.
Underexposed (Clouds are clearly visible, canoe barely):
Overexposed (clouds washed out, canoe and trees clearly visible):
Photomatix results (better, but could improve):
Final Results (with some photoshop tweaking, bringing out colors and "shinyness" of the lake):
I want your opinion on the final result... do you like it? What is good? Bad? Could be improved?
Thanks for reading! I am writing about something I am passionate about, if you have something else you are passionate about, please do share!