We've called, checked online, and talked to people about this. And parts have recently (in the past month) changed, so read carefully.
You must collect tax on any product (most people understand this). You don't need to collect tax on services UNLESS a product ever comes about from that service. For photographers, that's everything. There is no point in hiring a photographer just to photograph and not see anything from them (it doesn't make much sense). Therefore, at least in Ohio, you (as a photographer) must collect tax on everything you charge for.
The only time I can think of where you wouldn't pay the state its tax on the session is if you only did online proofing and they ended up not purchasing anything. In that case, you could refund the tax to your customer, but it would be such a PITA to do I doubt anyone would care. You'd still have to collect it at the time of the sale.
Collecting tax on everything makes it easy to figure out.

Now for the part that has recently changed. A couple years ago, Ohio changed its tax collection to be for the county of delivery. So, if you bought a washing machine at hhgregg on Sawmill (in Dublin, Franklin County) and had it delivered to your house in Powell (in Delaware County), you would pay Delaware County tax, and hhgregg would have to pay Delaware county that money collected. Even though both Franklin and Delaware counties have the same tax rate at this time.
What this meant for us as photographers is that for every sale that we mailed to an Ohio address, we'd have to look up their tax rate using
The Finder and adjust their total, if necessary. We'd then have to make sure their county received the tax. It's usually something like 80 cents -- really stupid. Luckily we don't have to write separate checks out to each county, we can pay it all at once and let them know where the money goes.
There was a grace period that just passed that you had to start doing it this way.
They've now changed it so that if your annual sales are less than $3 million, you can collect tax based on your location, not the location of delivery. Luckily (or not), our sales are less than that so (I think) we can now go back to collecting for Franklin County only. The reason "I think so" is that if you had started collecting sales tax the "correct" way before the grace period was up, you might have to keep doing it that way. We still need to figure that one out.
I told you it was confusing. And, of course, I'm not a CPA or a lawyer (nor do I play either on TV) so make sure you check it out yourself and don't take my word for it.