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An LR view of the Stouffer wedge

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An LR view of the Stouffer wedge
Evaluating the Wedge in LR
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Photography is not about technicalities, but understanding the physics and math behind photography makes it easier to maximally utilize the tools that we have.

Also, putting the tools that we have to best advantage may enable us to achieve results that we hope we could attain with more expensive equipment.


That said, optimization has it's limits. We can make best use of the equipment we have, but the same principles could also be applied to the "better equipment" we feel we cannot really afford.


I recently acquired a 41 step Stouffer Transmission wedge. The intention was to use it to compare dynamic range of negative film with DSLRs, but just studying how it works with Lightroom and DSLRs is quite fun, and may gleen some insights on how LR handles a subject with wide dynamic range.


Original DMG images are here: Sony Alpha 900 and Sony Alpha 55


The equipment I used is what I have. The cameras represent two generation of Sony Exmoor sensors.  The Alpha 900 is three years old and uses a sensor very much like the one in the Nikon D3X, although Nikon seems to make better use of it. The Sony Alpha 55 shares sensor design with the Nikon D7000 and the Pentax K5. I have only written about the Alpha 900 image, but may possibly fill in with info on the A55 later on.

About the wedge

The wedge I have is a 41 step transmissive target. It's Dmax is 4.1 meaning and is stepped in 0.1 density steps. We can translate this into photographics stops directly. A stop means a factor of two, pretty exactly 0.3 change in density. So our D-max of 4.1 translates into 13.7 stops.  Another way to put it is a contrast range 1:12500.


Looking at ETTR

Michael Reichmann, the man behind "Luminous Landscape", introduced the term ETTR (Expose To The Right). The idea is to achieve maximum exposure without clipping nonspecular highlights. Maximum exposure is a good thing. The problem is that we base ETTR on in camera histograms and they are a bit conservative. One of the objectives with the recent experiment was to find out how conservative?
What the wedge look like? Cannot be shown easily because of it's excessive dynamic range!

Exposing the wedge

I have chosen to base my exposure on step number 10 of the wedge. This was exposed so that "blinking highlights" indication was not shown. The idea was to find out what headroom was available. To achieve this the upper nine steps of the wedge were covered, and exposured increased until "blinking highlighst" were shown on step 10, after that exposure was reduced 1/3 step.


Last Updated on Thursday, 01 September 2011 05:34  


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