There are a lot of factors that can cause this type of behavior in corns. I'm no expert, by any means, but I do have several years experience with keeping corns, yellow & black rat snakes, as well as others.
The camera flash could've startled it enough to put it on edge or it could be a number of other things that got it on edge. Breeding season will sometimes do it but this isn't a corn's normal breeding season.
Other factors could be:
Environment changes, like; temp and/or lighting changes, etc...
Feedings
Sudden increase/decrease in frequency of handling
Room activity
And several more; but I'm sure you get the idea.
How long have you had it?
The timing of your post is uncanny because I shipped a 3-ft corn to a fella last week and the corn's been behaving as nice as it did when I had it. That is, up until the yesterday, I think it was. He started "rattling" like you said yours is doing but this corn wasn't striking like yours.
I think the problem with the corn that I shipped is in the increased frequency of handling because me & my son only handled it about every two weeks or so. But yet it was still tame. Now that its being handled just about everyday (which I think is good) its trying to adjust to it and sometimes just wants to be left alone.
Here's what I told the fella that now owns my old corn:
Sometimes when they do that (rattle their tail) I'll leave 'em alone for a few hours or so and sometimes I'll go ahead and pick them up. Depends on how I feel, or, how much I think they're trying to bully or intimidate me. If I think they just want to be left alone for awhile I'll leave 'em be. If I think he's trying to be Mr. Tough Guy I'll pcik 'em up and gently handle them for just a few minutes. I handle 'em just enough to show 'em that I'm boss and they don't scare me but not so much that I tick 'em off. To me, it builds trust and overcomes fear, for both the owner & snake.
Like someone here already said, a corn's bite doesn't hurt and sometimes I feel its neccessary to take the chance in order to work out the problem. My 8-yr old son is practically impervious to a corn's bite. The main thing is not to jerk back when they do strike/bite. Could hurt snake and make actual bite worse.
And like was mentioned earlier, corns don't bite everytime they rattle or show agression and usually calm down once in hand.
Take care!
Mike
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It is said that 1 out of every 4 people are mentally unbalanced. Think of your 3 closest friends, if they're normal, then it's you.