Pieces of an HDR Image

I just printed and framed this image of the nave at St. John Vianney’s Church on Vashon Island and thought I’d show you the individual images that went into this high dynamic range shot.  This seemed like a good candidate for HDR because there was a lot of strong light coming in from the outside and lots of shadows and details inside.

In the above images “EV” stands for exposure value.  It refers to the number of stops by which the camera increases or decreases exposure for the image.  The 0 (zero) EV image is what the camera thought the most balanced settings would be.  Doesn’t look very good, does it?  That’s because the difference between the brightest and darkest parts of the image was too great for the camera to capture – the dynamic range was too high for a single image.

So I took the -2 EV image to pick up the highlights.  Since it is a darker capture (two full stops below a “balanced” shot), the highlights look a little more normal and not so white.  The +2 EV image was much brighter, but its job was to pick up the darker shadows inside the building.  See, you take a darker image to get the bright stuff and a brighter image to get the dark stuff.  This series of -2 EV, 0 EV and +2 EV is considered the workhorse of HDR imaging, but you can certainly take several more than three images to capture even greater range.

I then exported the three images to my favorite HDR processing application and fussed with the settings a little bit.  The process of blending multiple images together to obtain a single image with higher dynamic range is called tone-mapping and is step 1 in the post-processing.  The three images are combined to create a fourth, and that’s the image we further process until it looks the way we like it.  In this case, I wasn’t going for the super high detailed (sometimes called the grunge look for some reason) look.  The final image is below.

The Nave at St. John Vianney


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