Some short shotguns appear to have a pattern not dissimilar to a hyper. Are they interchangeable, especially inside?

My limited understanding is that a shotgun, even a short one, uses an interference tube, making it less directional at low frequencies, and inclined to "boom" inside.

What are the relative merits of short shotguns and hypers?

If you plot frequency response AND direction, you will see that a short shotgun is all over the place once you get off-axis. This means you really should aim it, otherwise the voice sounds weird and it will be difficult to EQ that off. With a hyper, you are more easily able to get away with things like aiming it in between two people (instead of at the person who is speaking at the moment).

2- The other difference is that shotguns sound weird indoors. My explanation would be that the reverb is being picked up weirdly due to the wild off-axis response. And there is the bass explanation. Regardless, they just do sound slightly weird indoors. If you are close with the mic, it mostly goes away. That's what I hear anyways.

See also:
http://www.dv.com/columns/columns_item.php?articleId=23902954

Ty ford has a movie on his site where he demonstrates different types of mics.
http://homepage.mac.com/tyreeford/.Public/Video/Ty%20Ford%20Mic%20Tutorial%20VIdeo.mp4 (Quicktime movie)
http://home.comcast.net/~tyreeford/

Thanks, Glenn. That was my limited understanding. I have watched Ty's video, which is great.

So if short shotguns aren't so useful indoors, when would you use them? When would you use a short shotgun over a long shotgun outside?

Thanks, Glenn. That was my limited understanding. I have watched Ty's video, which is great.

So if short shotguns aren't so useful indoors, when would you use them? When would you use a short shotgun over a long shotgun outside?

Shotguns can be used to good effect indoors on a soundstage or other non-reflective environment as well as outdoors. The choice between long and short 'guns is more based on required working distance - mics have a range of distances where they work optimally, not too close and not too far, and the long gun gives you a more distant working range than the short. The longer guns also have higher directivity so you might choose one where the surrounding noise is more of a problem.

So if short shotguns aren't so useful indoors, when would you use them?

It may be that:
A- They're too much of a PITA since you really have to point em at the speaker. If the lines of dialogue overlap, then you can't do that (which you can say about the short shottie too, but it shouldn't be as bad).
B- If you really have to use the mic indoors (with low ceilings and things like that), the length may be a problem.

I believe short shotguns are typically used more than long shotguns in the field (except on soundstages, which is not in the field). Most of the time people use a short shotgun like the Sennheiser 416, or a hyper like the Schoeps. Some people just use a Schoeps for everything.