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An LR view of the Stouffer wedge - Evaluating the Wedge in LR

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An LR view of the Stouffer wedge
Evaluating the Wedge in LR
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Evaluating the Wedge in LR
Using a "raw converter" to evaluate a raw images is not really optimal, I'm trying to develop a tool for analyzing the wedge in linear (gamma =  1) space. I did some preliminary studies using LR.
Lets look at shadow detail:

This shows the lower part of the wedge. Exposure was increased 2EV in LR to make the steps more visible. It is not easy to say which steps are clearly visible but is seem reasonable to assume that step 35 or 36 is the first really discernible step. The assumption is based on alternatives views with higher exposures and extensive fill light.

 

It's quite interesting to study the histogram:

What we can see here is noise and signal. Noise is the continuum (grey mass) on the left side of the diagram. Going to the right, that is with increasing exposure, we start to see peaking. The peaks correspond to individual steps on the wedge. We can see that on the left side we have much noise and little signal while on the right side we only see signal (that is peaks).

The higlight screendump below was made with -1.5 Ev exposure correction in Lightroom.

In this image we can see step 5 as clearly visible. This really indicates that we have about 1.5 stops of headroom.

There seems to be a color shift in the recovered highlight area. I'm not sure it is for real. The Stouffer wedge may not be neutral gray. In the higlights we may see the color of the light table used for exposure but on the higher density areas we may see the color of the wedge.

 

Dynamic range

It is hard to exactly tell the dynamic range from this test. it seems that the highest discernible field is 36 and the lowest 5. This would give us 36-5 = 31 step. The wedge has 0.1 density steps, corresponding to 1/3 stop. So the dynamic range is about 10 stops.

 



Last Updated on Thursday, 01 September 2011 05:34  

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