As I understand it, if you purchase something that is part of your process for producing a product for sale, you can buy it without paying sales tax. So, if your prints are for sale, the printing is part of your "production" process and non-taxable. But, if they are not for sale then you pay sales tax.
There are threads on this under the business section. A lens bought for the business that also gets used for your personal stuff means only a portion can be considered non-taxable--the 'personal' portion is taxable. It gets pretty complex so I tend to pay the tax on everything.
As Don said, your mileage is deductible (along with meals and lodging if that is involved). I just got an accountant this week and he said that everything I do that is business related, get a receipt and keep track of it. As long as it can be considered "reasonable" you can deduct it. (I guess the trick there is figuring out what the IRS considers "reasonable".

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