Tag Archives: HDR

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Dynamic range

Human eyes have the fantastic ability of being able to handle a vast dynamic range -possibly well over 20 stops.  Thus a stained glass window can appear stunning to the naked eye with a range from almost clear glass to dark vibrant blue.  Sadly even the best cameras will only capture a small segment of this.

Dominic Price - Positions & Practice Oral Presentation

Each of the ten segments above is separated by 1/3rd of a stop.  It is clear that the white areas become washed out when overexposed by no more than 2 stops, but the blue areas require at least 3 stops more light in order to become visible.

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Multiple Exposure Blending vs High Dynamic Range

Unlike the more consumer-oriented EOS bodies, the Canon EOS 1DX Mark II and its predecessors do not offer an in-camera High Dynamic Range (HDR) feature. As a result, the solution I worked towards in order to capture the high dynamic range found in stained glass windows was Multiple Exposure Blending (MEB).

Which ever process is used, a final image is created from a series of bracketed photographs (bracketing referring to taking a set of photographs in which one setting in the exposure triangle (ISO – Aperture – Shutter Speed) is changed. For each window I photograph, 20 images are captured each with a fixed ISO (50), fixed aperture (f/8.0) and varying shutter speeds (at 1/3rd stop increments).

It is possible to have HDR Software apply an algorithm to blend portions of the mages together through tonal mapping, but I much prefer the manual approach of MEB. By using layers in post production, I am able to select the optimum appearance of each glass element within the stained glass window and merge them together into one ‘optimum’ image. While this method is both time-consuming and skill-intensive, it achieves the most accurate results:

HDR - originalOne of twenty bracketed images, unedited.
HDR - EditedThe final image after Multiple Exposure Blending.

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Man vs. Machine – the merits of HDR software

In light of the nature of this research project, it may seem strange that today was the first time that I have ever tested HDR Exposure Merging within an image editing program.  The test piece is a stained glass window I had recently photographed at Christ Church Cathedral and the images here show a small segment of that panel.  The completed image of this panel (detailed HERE) required just over four hours of editing so I am interested to see what software can achieve in just a matter a moments:

Dominic Price (2019) Panel from Vyner Memorial Window depicting Timothy & Eunice [Edward Burne-Jones, 1871 – Christ Church Cathedral]

DCP_9772 (ec)

Edited by hand

DCP_9771_68_65_62_Detail (HDR crop).jpg

Software-based HDR editing

It is interesting to note that I have opted for slightly greater saturation of colours and higher contrast (no surprise there) – however, this is an image that I have yet to moderate against the original.  The one area in which the software falls down (arguably) is in its handling of the clames, with the lead being represented more three-dimensionally, whereas I have endeavoured to represent the image two dimensionally with the lead being rendered black.

The results are mightily impressive and for occasions when I require a quick, yet imposing solution for social media (or indeed for inclusion as a small part of a printed publication), this could provide a pleasingly simple solution.  Of course, the digital removal of support bars can only be done by hand and that will add one or more hours per bar to the process!