Okay.... here is what I did...
(1) Downloaded the DPR forum OP's "beforeafter","-1", and "-2" jpegs from
http://forums.dpreview.com/forums/read. ... e=35392068 and then cropped the "beforeafter.jpg" in half to create registering 'before', '-1', and '-2' jpeg images, 335x500 pixels each.
(2) Created a symmetrical tone range Mask1 [has the same gradient from a 50% tone to the mask's white (100%) and black (0%) image areas] to be used to blend the 'before' and '-1' images by:
Click on the 'before' image and open the Mask Tool - BrightnessCurve; lower-left Apply Add a StairStep curve=[0,0], [95,0], [95,100], [100,100]; lower-left Apply a Blur=25; and click OK, creating Mask1. Mask1 looks like this:
- SIAmountMask1-200px.jpg (3.19 KiB) Viewed 7901 times
(3) Created an asymmetrical tone range Mask2 [has differing gradients from a 50% tone to the mask white (100%) and to the mask black (0%) image areas] to be used to blend '-2' highlight tones into the the primary blending of the 'before' and '-1' images to retain/provide curtain shear detail by:
Click on the '-2' image and open the Mask Tool - BrightnessCurve; lower-left Apply Add a BrokenLine curve=[0,0], [30,0], [40,100], [100,100]; lower-left Apply a Blur=10; lower-left Apply Subtract a BrokenLine curve=[0,100], [10,100], [30,0], [100,0]; lower-left Apply Feather=-2; lower-left Apply Feather=+2; and click OK, creating Mask2. Mask2 looks like this:
- SIAmountMask2-200px.jpg (6.88 KiB) Viewed 7912 times
(4) Then, click on the 'before' image and open the StackImages transform, leaving individual Curves [PWP5]; Final Shaping Curve [PWP5]; and Density Masks off. Add Input images and Amount masks as follows:
Image 1: Input='before'; Amount mask=Mask1; white=0; black=100
Image 2: Input='-1'; Amount mask=Mask1, white=50; black=0
Image 3: Input='-2'; Amount mask=Mask2, white=25; black=0
Further adjust Amount mask whites and blacks while monitoring an updating Preview to a preference, and then click OK, creating the exposure blended image.
PWP5 users could also adjust the Final Shaping Curve to a preference before clicking OK. Others could use the HSV BrightnessCurve transform.... or Both use a slightly blurred 'contrast mask' and Composite-SoftLight to tone balance image elements brightnesses on the resulting
(4) image.
The only real difference from the above workflow to the DPR OP's method was to better define/form Mask1 and Mask2 for the blending of the exposure images... avoiding halo and tone reversal artifacts.
The mask creations are not necessarily intuitive and are image set specific. The general approach was to primarily blend the properly exposed image areas of the 'before' and '-1' images using a symmetrical tone range mask and secondarily blend the '-2' image highlights using an asymmetrical tone range mask with the corresponding '-1' image areas. The mask Blur amounts are scaled to the 335x500 pixel images but the curves and Feathering would be suitable for full sized images if available.
Anyway... once you have the StackImages transform set up, play with the the black/white Amount slider settings while monitoring an updating Preview...
Cliff... you may prefer the Image 1, Amount mask black=50 or 75 rather than the 100; and/or the Image 2, Amount mask black=5 or 10 rather than then 0 as suggested above....
...Also this is just one possible solution/approach...
Ask if there questions...