Please take some time to address and check out the attached spreadsheet w/ its two tables and graphs.

Only 1 number per table is entered (black, bold, framed). All the rest calculates from cell to cell.

I encourage interested readers to open Peter's spreadsheet and PDF. Exposure adjustment in PV2010 involves scaling by a factor; a +1 EV involves multiplying all values by 2. As Peter's documents show, one can perform the multiplication on the gamma 1.0 raw file or the rendered gamma 2.2 file.

George Jardine's and Andrew's step wedges are not produced by photographing an actual step wedge and rendering the raw file, but synthetically in Photoshop. The steps are perceptually uniform and are evenly spaced in the gamma 2.2 space.

As Peter explains, gamma 2.2 compresses the highlight tones. Therefore, the steps in the raw file are larger in the shadows than the highlights. This can be demonstrated in Photoshop by converting to a profile with a gamma of 1.0, as shown below.

Alternatively, one can calculate the raw values, which would be proportional to the luminances of a photographed wedge. The calculation involves applying the inverse gamma function. The calculations demonstrated here are for sRGB (approximately gamma 2.2). The steps in the shadows are very small.

For the purpose of demonstrating the visual effects of adjusting the exposure in the raw converter, the perceptually uniform wedge that the DigitalDog and George Jardine used in their tutorials is preferable to the Stouffer wedge that I had been using and was used by Charles Cramer in his excellent post here on LuLa. As George explains in his tutorial, editing of the synthetic step wedge TIFF in ACR/LR is not exactly the same as editing a raw file in these programs.

Adjustment of exposure in PV2012 simply moves the histogram to the left or right without changing their spacing (this is what I would expect, but I have not actually tested it). With PV2012, increasing the exposure rolls off the highlights as clipping is approached, and the steps move closer together in the highlights and the contrast decreases as can be seen by looking at the slope of the characteristic curve.

Bill