Over the years I've traded my work for opportunities to be published in books, magazines, on websites, and in all kinds of promotional materials - even a textbook in Singapore. Often times my decision on whether I donate my work (or trade it for a credit) comes down to a few simple things:
1. Are they going to make a profit by using my image?
If someone is looking to use your work in an ad or in any way where they are directly pushing a sale, you should be compensated fairly. The time that went into shooting and editing that image obviously got their attention, and in an advertisement it seems more unlikely that anyone will notice the little photo credit you traded your work for.
2. Do you agree with how your image is being used?
The intent of someone looking to use your photography is incredibly important. Naturally, if you're trading your work for a credit you want to make sure that your image is used in the most flattering way possible.
3. Will this photo credit lead to future work or attract potential business for you?
In some cases trading your work for a credit can be like free advertising for your business. For example, I donated my photography for a 2014 calendar with a local real estate agent and he covered all of the printing costs. I had my logo (which included my web address) on each image, and he had his contact info on the calendar. It was a win-win for both of us, and a situation where the local advertising the calendar brought me was greater than any short term payment I would've received from just the images alone.
Do your research. I've also had lots of businesses and groups come to me with the promise of giving me promotion, but my images were already showing up first in google searches or I personally already had a significantly larger social media following than them. In those cases, it becomes clear that I'm helping them more than they're helping me, and I'd prefer they purchase an image license to use my work.
4. Is the story worth it?
Sometimes the photo credit doesn't matter because the story is worth the trade. Like that Singapore textbook I mentioned above - I just wanted an excuse to say that I've been published in a Singapore textbook.
5. Is the trade portfolio building?
Sometimes the payoff in having someone ask to use your work is about the prestige more than anything else. In these cases you know that the client has more experience or following, etc. than you and you're just happy to be included. Still note the points above, but consider the value of how that credit will look in your portfolio. There's no reason that this couldn't be a paying gig either.
In the end, whether photography is your hobby or your business, realize that the quality work you do has value and giving it away for free sends the impression that it's cheap. There's a reason why people continue to ask for images. They want them! Photography for a credit is only one form of compensation, and the reality is that people are responding to quality creative work now more than ever. It's worth something! Don't be afraid to ask to get paid for your efforts (and throw in the credit too).
Sometimes the payoff in having someone ask to use your work is about the prestige more than anything else. In these cases you know that the client has more experience or following, etc. than you and you're just happy to be included. Still note the points above, but consider the value of how that credit will look in your portfolio. There's no reason that this couldn't be a paying gig either.
In the end, whether photography is your hobby or your business, realize that the quality work you do has value and giving it away for free sends the impression that it's cheap. There's a reason why people continue to ask for images. They want them! Photography for a credit is only one form of compensation, and the reality is that people are responding to quality creative work now more than ever. It's worth something! Don't be afraid to ask to get paid for your efforts (and throw in the credit too).