Two inline block divs--second one shifted down?

Can anyone explain why this happens? Two inline block divs. Both have fixed width, height 100% of parent. All static positioning. I would expect them to simply stack next to each other with top aligned to parent top. For some reason the second one seems to vertically align its middle to the bottom of the first one??? This only happens when there’s an image in the second div–if they’re just empty divs it works as expected.

In fact they’re not even quite vertical middle-to-bottom aligned. If I try to fix this by setting the position of the second div to relative and shifting it up 50% (of parent height), the result is off by a few px. ???