What is HDR? HDR stands for High Dynamic Range. In photos where the sun is bright and the shadows are dark images from cameras lose detail. You will see areas that are too bright like clouds. These areas will be all white with no detail showing. The shadow areas will be all black with no detail showing. This is because cameras have a limit on how bright and how dark they can see. You can adjust your exposure to get the details in dark areas but then you lose more in bright areas or if you adjust for bright areas you lose even more in the dark areas. High end DSLRs can see up to 11 stops where as shots into the sun can be in excess of 20 stops.
HDR photos are the solution to this problem. They look more like paintings because peoples eyes have a higher dynamic range as well as when we look through the scene our eyes adjust automatically to the light in that part of the scene. With special software you can take several images to adjust to all the light conditions throughout the scene. The software uses something called tone mapping to adjust specific parts of the image selecting the right exposure. The software uses all sorts of complex mathematical equations to calculate this. Here is the basics of how a HDR is created without too much detail.
First you need to take several images with different exposures. I have taken three different exposures exposures. You can either take your exposures manually or if you have “exposure bracketing” on your camera it will automatically calculate the exposures for you. I have set mine to exposure bracketing and took three pictures really fast. It is best if you use a tripod but if you don’t have one handy, set your camera to continuous shoot and take three photos holding the camera as still as you can. Software will adjust for really small amounts of movement. The first photo is with normal exposure.
Next is my image is the under exposed image. If you are shooting manually you should start with your darkest exposure. It should be dark enough so that there is no clipping in the highlights (so you can see detail in the brightest part). After that you take an other image exposing it two more stops until the darkest parts are bright enough to be mid tones (So if the darkest part is black your brightest part is 50% gray).
My last image is my over exposed image. It is over exposed by two stops which I specified in my camera settings. Most software can work with exposures up to two stops in difference so each image you take should be two stops different in exposure. I find that usually three images are enough to create a decent HDR image.
After you have these exposures you need to load them into software that creates HDR images. There are ways of creating HDRs with out using special software but it is lots of work and does not turn out the same. There are several settings to align images, exposures, and choices of formulas. Then there are different settings for each type of formula. There are default settings so you don’t really need to know what they mean but you can play with them and experiment to see what results you get.
Here are two versions I have created. One more realistic and the other one more detailed.
The best part of being on campus is the opportunity to capture things like this on a lunch break.
I thought I would take advantage of late night at work.
When leaving work, I stopped and took this 30 second exposure.
[ f6.3, 30 sec., ISO 400 17mm ]
(click on image to view full image)
I always knew there was something different about the people at TRU. Today I learned why.
