A few days ago I found out about High Dynamic Range (HDR) photographs. A short search on the web will bring you lots of information, but somehow I have been living just fine completely oblivious to HDR.
The threory behind HDR is that film (and digital cameras) have a particular dynamic range that they are sensitive to. Light intensity values that fall outside of this range, tend to get smashed together and “washed out”. You can see this easily if you take a picture of someone with the sky behind them, but set the exposure so that you can see their face. The sky will often appear completely white and lack any detail. Similarly, if you take a picture of a room, often the windows will appear completely washed out without being able to see what was outside. The same thing happens on the dark end of the intensity spectrum: dark details will completely disappear into the rest of the black areas.
Since cameras are limited, the way to get a HDR image is to take three (or more) images with varying exposure. You take one that is approximately “right” and you take one that is obviously overexposed, and another obviously underexposed. The interesting thing is that these over and under exposed pictures contain additional details that are not present in the “right” picture. Today, March 11, was a bright and sunny day and we decided we had nothing better to do than take a Sunday drive through the countryside. I took a number of such “multiple exposure” photos.
When I home, I downloaded the free trial version of Photomatix from a company called HDR Soft just to try out this HDR process. Does it really work? Does it make photos that are “better” than normal photos. You can be the judge below.
From my point of view, it is “interesting”. An adjective I normally avoid because of its ambiguity. There is no doubt that you can see more in the picture. There are more details. The colors seem to jump out at you, and I have to admit that when I was standing at the original scene, the color were overwhelming. In some sense the result matches an emotional impression. At the same time, the HDR images look fake and unreal. They look like “art” and not “reality”. Is it just that I am so used to seeing photographs with the limitations that normal photography brings?
To appreciate the process, you need to see the three original photos, and then the combined results. Please note, the result is somewhat grainy, which I assume is because I compressed the originals to JPG before combining. The guides say to use RAW of TIFF mode in the camera, and it makes sense because the JPG smoothing will in certain ways distort the actual colors of the pixels, and then when you compare them across three pictures, there ma be some problems. Next time I will try will RAW mode to avoid problems.
Here are the original three pictures.
These are read into Photomatix and combined into a single HDR image. The image looks funny on the screen until you apply a Tone Mapping. The result is an image that can be saved as a JPG file. IT looks like this:
What do you think? THe free version of the software puts the “watermarks” on the photo, so please ignore those until I decide whether this is a worthwhile process. It is certainly an amazing transformation of the photo. You can see the detail in the wooden siding of the barn, while at the same time the sky appears blue. Sometimes I think the colors are a bit too saturated, but then it was a beautiful day which was constantly impressing the eyes with color.
Here is another picture of some houses in Aromas, California:
And here is the combined photo, which clearly shows the sky at the same time as the trees.
Comments?
Thinking Matters 
Keith,
Those pics are impressive. They also make me homesick for California.
Ken
Wow — lovely result.. do you think it was worth the effort? How hard did you have to work to match the aspect with each shot — or does the software compute minor corrections for angle? Does it actually merge the 3 images, or uses the other two for comparison/brightness only? What happens if your images are, say 1/2 frame, off from eachohter?
>>They look like “art” and not “reality”. Is it
>>just that I am so used to seeing photographs
>>with the limitations that normal photography
>>brings?
This made me laugh, because that was my thought initially too!
Dunno — seems to me you can get similar improvements on a good shot with photoshop — and that way you don’t have to stop and take 3 different exposures for each image…?
Monica
The software comes with the ability to align the photographs before pixel manipulation, but I did not use that.
I put the camera on a tripod and adjusted the exposure very carefully so as not to jiggle it, and I used the timer to take the shot without touching the camera so that the tripod “sprung” back to the same place for every picture. When I reviewed the pictures, I could see that I had succeeded in getting all the pictures positioned correctly.
Clearly, this is a lot more trouble than ‘point and click’. I don’t know if this is worth the trouble or not. But one thing is clear: photoshop manipulation of the original image will not do it. The washed out detail is simply lost in the single picture and can not be recovered.
Right now HDR is clearly at the “hobbyist” phase. If HDR catches on (and I am not sure it will since the pictures are so … interesting) then we could expect to see cameras that simply capture the higher dynamic range using more bits/pixel.
I haven’t used this software, Keith, but it’s not the way I would go. Digital cameras actually have a pretty high dynamic range, but mapping that to screen or paper output washes out detail and contrast at the high and/or low end, as you say. An easier approach (in my view) is to work with one image (rather than 3) and use masks to separate high, low, and possibly mid tones. Then apply your color/contrast manipulations to each masked separation and recombine. I use Picture Window Pro for this — it has great masking and mapping transformations– but those who prefer to use a more familiar tool (although a more complex workflow) can use Photoshop.