Inexplicably the HM 100 does not have a histogram. I can't figure out any explanation for this oversight, and it's a pretty glaring one for anyone interested in precise control of exposure. It could be that JVC doesn't want to cannibalize sales of their more expensive models, but it's hard then to imagine why they have incorporated some pro-level features and yet not others so basic as this one. Not a show-stopper, but a real disappointment.
I don't think that a true live histogram is very common in digital camcorders? I'm not familiar will all pro and prosumer camcorders, but I know that high end Canons don't offer a live histogram, only on the play back of still images.
I agree it would be very useful, but in all fairness the HM100 DOES have the traditional zebra stripe pattern for indicating over exposure and can be set by IRE level. I wouldn't classify the omission of a true live histogram a "glaring oversight" or a "real disappointment".