Canon’s Auto Exposure Bracketing Explained

EOS 50D Auto Exposure BracketingCanon has made serious improvements in the Auto Exposure Bracketing in the EOS 50D / 60D / 7D and 5D2 although they still lack the ability to take more than three bracketed exposures at a time. Today, only the much more expensive EOS 1D Series cameras allow for more than three bracketed exposures. In these newer EOS models, Canon has combined Auto Exposure Bracketing with Exposure Compensation in a way that should make photographers working with HDR (high dynamic range) techniques very happy.

As you can see in this image, photographers can now use this feature to easily shoot a series of bracketed exposures covering the histogram from -4 EV to +4 EV in increments as fine as 1/3rd stop. For my own architectural HDR work I generally use the following series of nine exposures to provide the maximum dynamic range. I can take four continuous bursts of three bracketed exposures (I generally delete the three duplicate exposures) in less than 10 seconds.

Many of the latest EOS models have a new “function” button that can be set to display the EC/AEB settings as shown above. Once the EC/AEB settings are displayed I take the first set of three bracketed exposures with the camera set on continuous burst (high) with EC set at +2 EV. The three bracketed exposures take less than 1 second.

I then change the exposure compensation to +1 EV using the Quick Control Dial, hit the set button and take the next set of 3 bracketed exposures. Again, this takes less than 1 second. I continue this process two more times at -1 EV and -2 EV and end up with 12 exposures taken in less than 10 seconds. Its not as automated as using a Nikon D3 or D300 but it works fine for me.

EC Value  |  AEB Amount
+2 EV  |  +/- 2 EV = +4 EV, +2 EV, 0 EV
+1 EV  |  +/- 2 EV = +3 EV, +1 EV, -1 EV
-2 EV  |  +/- 2 EV = -4 EV, -2 EV, 0 EV
-1 EV  |   +/- 2 EV = -3 EV, -1 Ev, +1 EV

Results
-4 EV, -3 EV, -2 Ev, -1 EV, 0 EV, +1 EV, +2 EV, +3 EV, +4 EV

Do I really need nine exposures for my HDR work? Probably not, but I’ve yet to find an architectural situation where nine exposures didn’t adequately cover the entire dynamic range,  so for me this technique works perfectly. Its one more reason why the newer EOS cameras are a welcome upgrade from the previous models.

My basic HDR setup is fairly standard.
1) Camera on tripod, lens with AF on, IS off.
2) Set the AF point to ONE point, not “auto”.
3) Focus on the subject and set the lens’ AF to off (manual focus)
4) Take the bracketed exposures.
5) Review the histograms to make sure the entire dynamic range is covered.
6) Process in Photomatix Pro.

Sitting Pretty

Here’s another shot taken in 2008 at the Wings Over Houston air show, processed as a three-shot HDR merge using Photomatix Pro. I took all three shots hand-held using a High Speed HDR technique I learned a few years back.

Sitting Pretty

Sitting Pretty – Houston, Texas
Copyright © 2008 Jeff Lynch Photography
Shot taken with a Canon EOS 40D set on aperture priority (Av) using an EF-S 17-85mm f/4-5.6 IS USM lens hand-held. The three exposures used for this HDR image were taken at 17mm and f11 at ISO 200 using a B&W circular polarizer. All post capture processing was done in Adobe’s Lightroom 3 Beta & Photomatix Pro. Click on the image above for a larger version.

Urban Photography – High Dynamic Range

UPDATE: I reprocessed and re-cropped this image and fixed the issue with the clouds “ghosting” in Photomatix Pro. I think this looks much better. I also think it will make a nice gallery print at 16″ x 20″.

fountain print

Fountain Gallery Print
Copyright © 2009 Jeff Lynch Photography

Urban settings are a great place to practice HDR capture techniques. I love the variety of textures to capture from steel and glass to bricks and granite. This fountain made a wonderful subject with the waster cascading down in the background and the texture of the arches in the foreground.

Fountain HDR

Fountain HDR
Copyright © 2009 Jeff Lynch Photography
Shots taken with a Canon EOS 50D tripod mounted, EF 24-105mm f/4 L IS USM at 47mm at ISO 100 on SanDisk digital film. Post capture processing was done in Photomatix Pro, Lightroom, Photoshop Elements and finished in Noise Ninja. Click on the image above for a larger version.

Camera Setup
I’ve found the two most important aspects of setting up my camera for HDR captures are using aperture priority (Av) mode and manual focus. The idea is to make sure the focus and depth of field don’t change during the series of exposures. Since my eyes are not what they used to be, auto focus was initially used but then turned to “MF” to prevent the camera from refocusing between exposures. This was an eight exposure series with exposure compensation set from -4 EV to +3 EV in 1 EV increments (-4, -3, -2, -1, 0, +1, +2, +3) to provide the fullest possible histogram. My 50D was tripod mounted and all exposures were taken using a cable release to prevent camera shake as much as possible. Image stabilization was turned off since the camera was tripod mounted.

Post Capture Processing
I processed these eight raw exposures in Photomatix to create an 8-bit TIFF that was then processed in Photoshop Elements using the techniques explained in Jeff Revell’s Grunge Tutorial. I was surprised how much detail this double processing brought out in the bricks, concrete columns and water. The image turned out great with the exception of the clouds. It was fairly windy when I took these exposures and as you can see, Photomatix had some trouble dealing with this in the HDR image.

Landscape Photography – High Dynamic Range Sunset

Have you ever taken a photograph of a beautiful sunset and then gotten home to review the shot, just to find that the wonderful light and colors you “saw” in your viewfinder are nowhere to be found in your image? Welcome to the club!

The human eye is an incredible device, capable of recording dynamic range and color depth far beyond what the most expensive CMOS sensor can ever hope to. We can “see” detail in shadows where our camera can record only black. We can “see” variations in extreme highlights where our camera is virtually blinded by the light. This is why capturing what we “see” on digital film is so difficult at times and why HDR (high dynamic range) workflow is so alluring for photographers today.

Prairie Sunset HDR

Another Prairie Sunset
Copyright © 2008 Jeff Lynch Photography
Shots taken with a Canon EOS 50D tripod mounted, EF-S 10-22mm f/3.5-4.5 USM at 22mm, f/9.5 at ISO 100 on Lexar Professional (UDMA) digital film. All post capture processing was done in Photomatix Pro 3.1, Lightroom 2 and Noise Ninja. Click on the image above for a larger version.

Last evening I sat down with my Macbook and watched Matt Kloskowski’s new online training class at Kelby Training called Real World HDR. Matt does a great job of explaining how to setup your camera for HDR as well as how to use Photomatix Pro to create great looking HDR images that look incredibly detailed, rich and vibrant. Images that really capture the essence of what we “see” when we look through the camera’s viewfinder.

If you’ve never looked into a subscription a Kelby Training, now would be a great time. Matt’s Lightroom and Photoshop CS4 courses are really well done, as are all the courses I’ve viewed from folks like Joe McNally, Laurie Excell, Moose Peterson and Scott Kelby himself.

Canon 50D – High Dynamic Range Photography

The new Canon EOS 50D is especially well suited for high dynamic range (HDR) photography with its 15.1 MP sensor, its Highlight Tone Priority mode and an array of very sharp lenses like the EF-S 10-22mm f/3.5-4.5 USM.

Bracketing / Exposure CompensationI wanted this image to display as much detail as possible in the church’s beautiful exterior clapboard siding and scalloped trim. Merging three exposures (-1.5 EV, 0 EV, +1.5 EV) and tone-mapping in Photomatix Pro brought out a lot of hidden detail and converting the image to grayscale in Lightroom finished it off very nicely.

Metering a bright white structure against a cloudy sky was a challenge for the camera’s meter so I took several bracketed sets using various levels of exposure compensation until I got just the right three histograms. Exposure compensation and auto-exposure bracketing can now be set using the same screen on the EOS 50D, allowing a quick check of the overall exposure when combining both as I had.

Catholic Church in Wallis, Texas

Catholic Church in Wallis, Texas
Copyright © 2008 Jeff Lynch Photography
Shots taken with a Canon EOS 50D tripod mounted, EF-S 10-22mm f/3.5-4.5 USM at 11mm, f/8 at ISO 200 on Lexar Professional (UDMA) digital film. All post capture processing was done in Photomatix Pro 3.1 and Lightroom 2. Click on the image above for a (much) larger version.