I shot a musical performer on spec. The deal was she would get 4 photos of my choosing for free, digital only, no prints, that she could use on her web page. Then I would put up a proofs page from which she could purchase more photos if she wanted to, and I gave her rates, scaled down the more she purchased.
It was a chance to take, then it looked to pay off. The 4 pics I gave her were the best quality live shots that had ever been taken of her, but I made sure to leave some of the very best ones as proofs so she would have incentive to buy. She was excited by the proofs page, and said she was going to purchase some and was going to take the weekend to go through them and make her choices.
Then she and her boyfriend went on a drunken splurge in Vegas and she forgot all about the proofs page. I ended up waiting around, frustrated she hadn't made her picks. I went to one of her performances to remind her about the proofs. (Well, I also enjoy her music.) She determined to finally make her choices and go ahead with the deal.
On spec is tough! Granted, that shoot didn't displace any other paid shoot. I had the evening free and took a chance. I'm thinking of using some kind of incentive to get people to follow through and choose their proofs, something like if you make your choices by such-and-such date, you'll get 3 extra photos for free. I believe this woman is genuinely interested in buying. She just gets distracted by a lot that's going on and then choosing proofs drops down on her priorities.
I'm wondering if anyone here has successfully used incentives to get clients to pick their proofs in a timely manner. Do you use, "Pick your photos by Date X and get Y number of free photos"? Or do you use something else?
It would be different if it hadn't been on spec. I would have required a deposit. On spec is rough, but I have been paid for doing it and it has its uses. Just curious how others have dealt with this.

