As speakers slowly come to realize the power of using strong visuals in their presentation slides, the issue of giving proper credits comes up. Most of the time, you will be using someone else's photos, so of course you should be making sure that you are using those photos under a proper license, i.e. either pay for the right to use it or comply with the photo's license, e.g. a Creative Commons license. With the latter, a lot of people seem to think that giving credit to the photographer means that they actually have to put the name inside the photo or at least on the same slide.
However, that - to the best of my knowledge (disclaimer: I am not a lawyer) - is not what the Creative Commons licenses require. The license asks for proper credits - yes. But nowhere does it say that the credit has to appear on or even near the works.
Again, I'm all for credit where credit is due. Photographers who make their works available under a Creative Commons license should of course be credited. It's the least we, the users of that photo, can do.
My argument against putting the credits on the photo is purely for the effect it will have: When you bring up a slide and it contains text - any text, anywhere in the photo - the viewer will immediately be drawn to that text and will try to read it. Try it for yourself.
What I'm saying is that putting credits on the photo will lessen the impact that you were hoping to make with that photo in the first place. I.e. it will weaken your point. This - and not disrespect for the work of the artist - is why I'm against having credits on photos (and slides). The less the audience is being distracted the better for your message.
So, how do you give proper credits? Actually, I don't think there's a good way to properly give credits during a presentation. You could of course make a "credits" slide, but it will contain too much information and nobody will read it anyway. But if you make your slides available online, such a "credits" slide is a must!
What do I do? I usually prepare a "credits" slide as the very last slide of my presentation but don't show it. That way I don't forget to add it later :) Also, I do usually link the photos on the slides to the source, e.g. the photo's Flickr page. When exported to PDF, the link is still there and if you're viewing my slides, the original photo is only a click away.
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