Manual Exposure Blending

We saw a nice scene where the sun was shining brightly in deep blue sky and colourful flowers in the foreground contrasting beautifully with the buildings in the background. We took a shot and what we got was a well exposed building with overly dark flowers in deep shadows and a pale featureless white sky. A total letdown!  The beautiful high contrast scene was not represented on the photo we took so we became frustrated and disappointed with our camera. The problem is the tonal and contrast range of the scene is too large for the imaging sensor in the camera to capture.


We had the same situation when we were at the Western Courtyard of The Curve mall.  In the center we had natural sunlight streaming in from the top of the open courtyard surrounded by a darkened but clearly visible dining area, leading towards the courtyard were rows of hanging incandescent lamps in beautiful orange glow. However it was all lost with the photo we took - only the beautiful pillars in the courtyard looked nicely exposed whereas the surrounding was in dark shadows and the rows of incandescent lamps looked like some white and yellow plastic bulbs hanging from the ceiling.

Normal exposure of Western Courtyard of The Curve Shopping Mall
The Western Courtyard of The Curve Mall challenge most digital camera in capturing it's full contrast and tonal range check out the exposure-blend image next. -- Camera: Olympus Pen E-P1, Lens: Olympus OM Zuiko 135mm F/2.8 telephoto lens. Exposure setting f/4.0, 1/60 sec ISO 200.

Though at an advanced technology stage digital camera is still a long way in matching human eyes in handling high contrast scenes. However there are ways to overcome these shortcomings of camera sensor. One is the use of Graduated Neutral Density filter which is very popular with landscape and film photographers. However this is not feasible with our courtyard scenes. Other methods to control contrast include using fill-flash or multiple fill-flashes at the shadow area, also HDRi or High Dynamic Range imaging and Exposure Blending technique some referred it as Contrast Blending.

3 bracketed Exposure Blend of the Western Courtyard of The Curve Shopping Mall
Exposure Blending improved the high contrast scenes of the Western Courtyard at The Curve Mall it display more details and colour compare to the previous image straight out of the camera. -- Camera: Olympus Pen E-P1, Lens: Olympus OM Zuiko 135mm F/2.8 telephoto lens, exposure setting f/4.0 and ISO 200. Three bracketed shot with shutter speed of 1/30, 1/60 and 1/125 sec each.

We are going to use manual Exposure Blending technique for the photograph of the Western Courtyard at The Curve. Our aim is to create a photo of how the Western Courtyard looked in our eyes while we were there.

A set of 3 images was taken with the Olympus Pen E-P1 on a table-top tripod. The camera was set to continuous drive or sequential shooting mode, Aperture priority and 3 frames AE bracketing. We had one normal exposed image, one +1 EV stop overexposed image and another -1 EV stop underexposed image in each set of 3 photos. I took several sets of 3 images with a table-top tripod resting on a couch's armrest and some with the table-top tripod pressed firmly against a side wall.

A full size tripod will be more stable but my reason for Olympus Pen camera is about portability and informal. A full size tripod is not as portable or comfortable to lug around and looked too serious for a day out not fully dedicated to photography. Images taken with table-top tripod are not in perfect registration but it can be easily aligned manually on The Gimp. Even so the table top tripod delivered good enough results and better keeper rate from our set of images than handheld bracketing.

Western Courtyard The Curve shopping Mall
Photo of the Western courtyard of The Curve this normal exposed image straight out of the camera show washout highlight and dark featureless shadow area. -- Camera: Olympus Pen E-P1, Lens: M.Zuiko Digital 14-42mm F/3.5-5.6 II standard zoom lens. Camera setting lens zoom at 31mm, f/4.9, 1/30 sec and ISO 200.

The set of  images is opened in The Gimp in three layers with the normal exposed image as the background layer. The +1 EV stop overexposed images opened as the second layer and the -1 EV stop underexposed image as the top layer. The horizontal level on the three images are then carefully level adjusted. The two upper layers are subsequently manually aligned to be in exact registration with the background layer by setting the layer opacity so we can see the selected top layer superimposing on the background layer.

After the alignment the opacity is reset to 100% and layer masks are added to the 2 upper layers. Layer mask shows or hides portion of the images that it is connected to. A black mask hides the current layer and allows images from the lower layer to show through, while a white mask shows what is on the current layer and blocks the images from the lower layer.

Exposure Blend of Western Courtyard of The Curve Shopping Mall
Three layer Exposure Blend of the previous images this one show more colour and tonal details in the highlight and shadow area an overall better image than the previous photo. -- Camera: Olympus Pen E-P1, Lens: M.Zuiko Digital 14-42mm F/3.5-5.6 II standard zoom. Camera setting at 31mm f/4.9 ISO 200, 3 bracketed shot with shutter speed of 1/15, 1/30 and 1/60 seconds each.

In the +1 EV overexposed layer the clipped highlight and overexposed area are masked out by painting the mask black.  We kept only the shadow portion of the images.  For the -1 EV underexposed layer, the clipped shadow and dark area in the layer mask are painted black;  we show only the lamps and the courtyard on this layer. We want the properly exposed shadow area from the overexposed layer and the correctly exposed highlight area from the underexposed layer to blend in with the normal exposed images on the background layer. Gaussian blur with a radius of 35 is added to the two layer mask to soften edges for smoother blending. The layer mask and the opacity of the layers can now be adjusted for the best results in the final images.

Manual Exposure Blending may seem primitive to some but there are reasons for the exercises.  The point in experimenting with manual exposure blending instead of using software script is in control and for learning. In doing the manual exposure blending we are in control every step of the way and we see the result building up as we progress and in turn understand the fundamental principles of exposure blending. Because of the understanding of the rudimentary we feel the methods can be improvised and simplified to a two layer blending instead of three. We are checking out a 2 layers approach so a "Take 2" of Manual Exposure Blending is coming up next.

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