Peter Gomena,

You have a valid point about the time.

But because the image is a step wedge, in terms of "underexposure", it doesn't matter because you can see the curves rise up out of the toe and and reach practical exposure levels.

Rafal,

You have basically created a reciprocity failure study at 0.9 or 1 seconds. You should shorten the time a bit, unless you decide that the reciprocity failure at this time is reasonably close to what you normally shoot.