Digital Light & Color

Hi, I'm trying the Stack Images transformation for the first time. I'm confused as to the method of working out in the field when shooting. I've created curves from a Q13 target using normal, two stop over and two stop under. Then when out shooting I'm supposed to shoot three bracketed exposures of the scene using normal, two over and two under. My question is about the choice of normal. Let's say I'm shooting a landscape as the sun is coming up (or going down). The land can be very dark while the sky can be very bright. There won't be a mid-tone in the image, only dark shadows and bright highlights. So what constitutes a normal exposure value?
Thanks
Anthony

In a scene like that you may not need a normal exposure, but in any case the idea is to set the over and under exposed images so they show some detail in the shadow and highlight areas respectively. The normal image would then be in the middle of the two.

If in doubt, maybe try shooting a sequence such as -4, 3, -2, -1, 0, +1, +2, +3, +4 -- then you can decide which three image to use later based on how they look.

Thanks for that. I'm thinking back to PWP version 4 which I'm pretty sure had a similar control which I used to use sometimes. The difference was that there wasn't any need to build curves using the Q13 target. You simply chose two images and set the curve for each one to decide what parts of each image were included in the output image.
Using this latest tool it looks like I can do exactly the same, basically choosing for myself what curves to use for the brightness curve, density mask and final curve. So what's the advantage of building the curves beforehand based on the Q13 target image? Certainly the curves thus produced are very different to what I might have naively chosen myself (I'd probably just choose straight lines with opposite gradients for the density mask of my two under/over input images).
Anthony

Curves computed from the Q13 combine the individual images, shifting them as necessary to get the brightness values to line up where they overlap, so you end up with a single, lower contrast image that covers the entire tonal range. If you do it manually, you run the risk of introducing kinks into the final tone curve. The use of the Q13 is optional.