Newsrama hosts the first part of three articles about Time in sequential art written by Joanna Estep. The piece is very well presented, and I like how systematic her analysis is, especially her use of diagrams to push along the theory. It's well worth reading, and I look forward to seeing what her next installments bring.
However, I also want to point out that it makes certain assumptions that are largely passed on from the Eisner/McCloud tradition. Mainly, it holds that "one panel = one moment," which simply isn't the case if you actually look at sequences of images from books (as opposed to just mental theorizing – of which I've been guilty of too). There is nothing about two panels that dictates time is passing – only content that implies temporal succession can yield this result. And, once you see that many panel sequences don't inherently push time along, you realize that problems arise in any linear notions of time across panels.
Following this, it also reinforces the ideas that "spatial distance = temporal distance." I had some thoughts on this like four years ago that I've never really worked into a full-blown paper, but the basic idea is that panel sizes create a rhythmic structure for reading. To really see if this is true I'd need to do eye-tracking studies though…
I'll hopefully be posting an essay I've been working on about Time myself sometime soon, but till then my old essay Visual Syntactic Structures (and book Early Writings...) delves into these things for anyone interested.
Update: I now see that Timing Part 2 is posted too. Again, worth reading, but continues the assuptions in McCloud that "reading time = fictitous (i.e. mental) time." I'm also curious why she includes her "hierarchies within images" as being related to time, since she doesn't measure any increase or decrease thereof. I agree with this: I don't think foregrounding is related to time at all, though I do think its related to distinguishing things like who is the focused actor and who is subsidiary.
Update #2: Timing Part 3 is up now, rounding out the articles. This one is about the integration of text. I'm not sure what real relevance it has for the understanding of Time after stripping away the assumptions I talked about above, but she certainly has some interesting things to say about composition and reading orders. Go read.