I am looking into producing images for submission to Science Photo Library and was wondering if there are any contributors here who work with this agency.

In particular I am interested in what kind of (annual) RPI is typical and what kind of portfolio size is needed to achieve sizeable returns (i.e. $1,000 per month). I will of course need to upgrade my camera as I believe they require images to be at least 12 megapixels uninterpolated.

I have a background in science so have some idea of the types of images that could be submitted.

Isn't (or wasn't) SPL some sort of BBC enterprise from their nature/science output?

It's a trad library where you should get a good return when you sell something but sales may be few and far between. But I think it is the market leader in its niche, which is good.

If I'm not mistaken they only do Exclusive representation (check the contract PDF on their site).

Okay guys, I will describe my own short experience of work with Science Photo Library, may be it will be useful for somebody. I like to draw 3D illustrations of microbes. Mainly I sell my images and video clips through Shutterstock and Fotolia. I also tried 123rf and Depositphotos but they gave so low earning that finally I stopped spending time on them. At the end of last year I decided to try SPL too (thanks to this forum!). I was ready to draw some exclusive images and although I did not have many, I decided to try.
They proposed two types of contracts - exclusive for new images (according to it I will get 50% from sales) and non-exclusive for my old images (with 40%). With video clips the same. They wanted that I upload all my Shutterstock portfolio as soon as possible but the main limiation for me was the size of images - I made 3000*2000 px for Shutterstock but they wanted 4 times bigger (6000*4000 or 5000*5000) and I had to rerender them, so uploaded overall near 40 exclusive and 70 non-exclusive.
I was given my own photo editor and video editor, they check now my submissions and guide me. At beginning all my submission were very fastly uploaded on-site (I was really impressed because Shutterstock takes 2 weeks to upload my clips). But then they started to work rather slow, and I am not so happy with this. My latest submissions from beginning of February are still not uploaded to site.

To summarise, what I like:
1) I can sell there my non-exclusive images from Shutterstock also,
2) my photo and video editors give me useful suggestions regarding what else is good to draw,
3) images/clips of other artists are really interesting and studying them gives me lot of new ideas,
4) they send my works also to Alamy and other agencies.

What I don't like:
1) they work too slow, when submissions are checked for several months I really loose interest,
2) for the first 2 months my earnings are rather low. Only few my exclusive images were sold at the lowest resolution, so I even don't know whether there is a sence to spend time on sending non-exclusive images,
3) my computor is not so potent and large size of images which they request slow down all my work.
At beginning I was so impressed and excited that was going to spend all my next efforts on SPL but now, I am still going to continue to submit some images and clips, however, main my efforts I am again directing on Shutterstock and Fotolia.

I will keep posting my next impressions as well