Chaos Terminal

Now that I have gotten a little bit better with photography, I have started looking for solutions to some of the problems I have come across. One of the major problems is getting the exposure right on a scene with a broad range of lighting. A good example of this would be an area in bright light and an area in shade, a landscape toward the sun or indoors with a lighted window. The average camera can only process so much contrast and is definitely not as good as the human eye.



The more I investigated this issue, the more I uncovered and ultimately found out that improving this is called dynamic range. The solutions all require more than one picture. This limitation removes many possible subjects, especially moving subjects. The basic technique is to take a picture that properly exposes the dark areas then take a picture that properly exposes the light areas without moving the camera. Basically, this should not be attempted without a tripod as the slightest movement will cause items in the frame to move, removing the ability to overlap the correctly exposed dark areas with the correctly exposed light areas.



The combination techniques work for just about any image editing software. The two basic techniques are to either cut and paste the correctly exposed light areas over the dark exposure or to paste the entire light scene over the dark scene and use transparency on both exposures to average out to a good picture. There are tools out there to do this automatically: Fred Miranda DRI Pro Plugin uses the selective cut and paste technique and Bill's Dynamic Range Action uses the transparency blending technique.



I decided to test both out. Bill's is free and Fred's was $20. $20 is a small price to pay to perform this analysis for my faithful readers! All three of you. My test subject was a landscape with a very dark foreground and a very strong light source in the background, the sun. I will perform a more reasonable test at a later date. Here is the series of images I took to get a baseline:


































So as you can see, this is an extreme example. Even at the quickest shutter speed, the area around the sun still just shows up as pure white. At slower speeds, the light of the sun streaks into the darker foreground. I know I will not get a good picture out of this set but it will give a good idea of the technique.


These tools take two images as input and give you a single image as output. I started out with two relatively extreme images:






Here are the results:

Program	Adjustments	Image
Bill's Dynamic Range	None
Bill's Dynamic Range	Levels
FM DRI	None
FM DRI	Levels

Both programs created completely unreasonable shots as the sun basically looks like an exploding nuclear bomb. Additionally, the FM DRI plugin created a band of near-white all long the top of the image. Unacceptable.


I decided to move on to more moderate images:






Here are the results:

Program	Adjustments	Image
Bill's Dynamic Range	None
FM DRI	None

Both shots are much more reasonable. The sun isn't completely blown out and everything is visible. The FM plugin did not cause a band of white this time. As for which result is better, the FM kept more of the blown highlights while Bill's has better overall range. This round goes to Bill again..


For a final test, I did a merge of five different images:










Here are the results:

Program	Adjustments	Image
Bill's Dynamic Range	None
Bill's Dynamic Range	Levels
FM DRI	None
FM DRI	Levels

Again, FM has blown out the highlights. The rest of the image is quite comparable to Bills.


So, what is my final conclusion? The direct comparisons between FM DRI and Bill's Dynamic range for each technique have shown Bill's to be better, FOR THIS EXAMPLE. I will do a test with a more reasonable baseline later. Which technique is best? Obviously the high/low merge is out of the running. The highlights are blown and the overall tone is still of very bright highlights and underexposed foregrounds. Between the mid merge and the five image merge, the five image merge is brighter overall without removing information from the highlights. It is about five times as much work with Photoshop, but it's only about 2 extra minutes. It also requires additional images, but if you have taken the time to setup a tripod, taking five pictures versus taking two pictures is practically no additional work.


The bottom line is, use Bill's FREE Dynamic Range Action with more than two images to produce the best results!

Posted by Mike on Apr 22, 2005 at 11:42 AM | Permalink