HDR Images #2


posted on 9th of june, 2009

© Bogdan (Help)
© Bogdan (Help)
© Bogdan (Help)
© Bogdan (Help)
My interest in HDR photography is growing. I started venturing into this field at the end of last year, and the first experiments were reported in a previous blog post (link). Since then I have managed to sharpen my technique and managed to produce sell-able results, much to my initial surprise.
I use Photomatix software for HDR processing. As my camera limits the number of bracketing exposure to 3, I am only using 3 differently exposed images in generation the HDR file. To decide upon the exposure compensation difference between the 3 shots, I analyze the histogram of the normally exposed photo: if the tones are spread, I am using a higher exposure compensation difference. However, I am still experimenting with different settings...
© Bogdan (Help)
© Bogdan (Help)
© Bogdan (Help)
As for the settings in HDR post-processing, I still decide them based on trial and error technique. However, as the quality of the final file cannot be previewed, I have learned that extreme processing values generate a lot of noise and color aberations, not to mention an unrealistic result.

© Bogdan (Help)
As one can observe when zooming in into the right-side image, previous versions of Photomatix (used to render the image in question) had problems dealing with movement. When combining 3 exposures, even and specially if themselves do not contain any motion blur, a moving object will not overlap perfectly, and causing the HDR script to fail blending them locally. The defect was somehow overlooked by the reviewers in this particular and unique case. The same problem appears with moving foliage or water reflections. This "bug" kept me away from day-time HDR photography for a while. However, the newest version of Photomatix has some scripts to identify and isolate such cases. Although not functioning perfectly, a moving object, foliage or water reflection is now combined much better. I suppose the areas are identified and information is selected only from one of the exposures. When the script fails to find a solution, a specific defect is created - white and/or black zones with rough edges. However, they can be spotted and corrected manually later on.

© Bogdan (Help)
© Bogdan (Help)
© Bogdan (Help)
As a result, I have managed to obtain some good quality HDR during day-light with moving crowds of people as the below image of Isle Palace in Annecy, France. Please note that I needed to crop it a little to avoid any recognisable faces, but one could still see that the crowds on the canal's edge are rendered without defects (zoom in to see the details). Water reflections and foliage are rendered in stock-like quality as well. One should note that these problems do not appear in long exposures, due to motion blue, hence night photography can be generated in HDR much more easily.

© Bogdan (Help)
In the end, I would like to mention that due to a fortunate turn of events, I had the opportunity to upgrade my fairly-new Canon 450D to the newest model in the line Canon 500D. My future additions will have maximum 15MP (in contrast to 12MP), better contrast and color, due to the same image processor as Canon 50D, to mention only a few traits of the new equipment. I have to say that I love the high resolution display - the images look amazing when previewed on the camera. I was so excited just after my first shooting session with the camera, just to be the same as disapointed when I've got home and opened the images on the computer, where the quality difference in comparison with the old model was much more realistic... Just two HDR images (one of them on the right) uploaded from the new Canon 500D, but a few more are on the pending line.

As last time, please find all my HDR experiments in the following light box: HDR images. I am looking forward to your comments and sharing of HDR experiences.

-Bogdan

Comments (9)

Comment by Bogdan on June 30, 2011