Comparison of HDR techniques

I recently went on a week-long vacation to Trinidad & Tobago(more about the trip later). I took several pictures of the natural beauty that the islands had to offer. I experimented with High Dynamic Range(HDR) as I normally do and ended up with the above picture, a combination of three pictures shot at different light exposure levels and “stitched” together.

I had a couple of friends ask me how I took this picture, how to do HDR and if HDR is possible with just one picture or if the same output can be achieved with one picture made into three with exposure levels altered by post-processing and then stitched together.

The Procedure

I shot the pictures with my Canon EOS Rebel SL1 with Canon EF-S 10-18mm lens. I used Lightroom to edit and manage the pictures and Photomatix Pro for HDR stitching. Photomatix pro does HDR stitching by taking a number of images(three in my case) with different exposure levels. I took these pictures one with normal exposure, one with -2 and one with +2 exposure setting. I always shoot the pictures in RAW format.

Single Image HDR – Under Exposed

underexposed - original
Underexposed – Original
HDR-underexposed
Underexposed – HDR

The comparison shows that tone-mapping or applying HDR techniques to a single underexposed picture will cause a fair bit of noise and incorrect reproduction of colors, as seen around the darker leaves and the lifeguard hut in the background.

Single Image HDR – Normal Exposure

normal exposure
Normal exposure. Original
Normal exposure - HDR
Normal exposure – HDR

The comparison shows that tone-mapping or applying HDR techniques to a single picture(with normal exposure) will cause still cause a tiny bit of noise and a wee bit incorrect reproduction of colors, as seen around the darker leaves and the lifeguard hut in the background. The contrast does seem much lower, hence the water appears less “oh my god the water looks so good” blue, something that can easily be edited in Lightroom or Photoshop.

Single Image HDR – Over Exposed

Over Exposed - Original
Over Exposed – Original
Over Exposed - HDR
Over Exposed – HDR

Tone-mapping an over-exposed image has the least noise of the three and the color reproduction is the best of the three. However the colors seem to ‘pop out’ the least, an issue that can easily be fixed.

Conclusion

HDR with images with different exposure levels gives the best color reproduction, detail while keeping noise at a minimum. But trying to take three pictures without camera shake, or when shooting a moving image could be problematic. In these cases I need to remember to set a higher exposure so that I can still create a decent looking ‘HDR-esque’ image.

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