DHJ: Not much. I use what's there. I often use friends in photographs, and I do make a point of photographing a range of people, different ages, men and women, black and white and in between. I do that because it's a good thing to do, and it makes business sense too. There is a need for more images of women scientists, African scientists, etc. I have found it can help a picture if a person has a distinctive appearance rather than a traditionally handsome or pretty face. But science photography is not fashion; it's not fixated on appearance.

Question: How do you know from day to day what to photograph so that your images sell?

DHJ: It's a combination of what the photographer wants to photograph, what the agency wants, and the photographer's research and hunches about the kinds of subjects and types of images that are going to be needed.

Question: Do you suggest studying images that are out there?

DHJ: Yes, more for technique than subject matter. Any image that is in a weekly or monthly magazine was taken some time ago. Unless the images were specially commissioned (which isn't going to happen to an unknown), they were probably on file long before the article was written. That means the photographer and agency had a good idea that those images were going to sell. The agency might even have had an active role in encouraging the magazine to write about that subject.

Question: But how do you know what will sell? Where do you get your hunches from?

DHJ: My own experience tells me to ignore the daily newspapers because what's in the papers isn't news once it's published. You have to be ahead of the news. As far as science is concerned, daily newspapers so often report on themes that have been simmering for a while, and then suddenly they are able to hook into them. If you're a science photographer, it's useful to know what is happening in university research departments. Keep an eye on those departments, find out what's important to them. I have followed subjects very closely for years. If you're lucky, the research will become newsworthy and your photographs will be on file waiting to be published.

Question: Isn't it difficult convincing a picture editor that your images are important months ahead of them being published?

DHJ: Yes and no. Sometimes you'll follow dead ends and go nowhere. At the same time as you're following dead ends, you'll be doing your routine photo work of improving your portfolio, following leads and hunches that are happening now. Then you'll spot something you are convinced is going to be important and you'll argue your case. If the pictures look good and are captioned well, they will be accepted onto file.

Question: You mention captions. How important are they?

DHJ: In a specialist subject like mine, captions are essential. You can't just label a photograph, "Scientist releasing a ballon", you have to describe the type of balloon, the payload (ie, the instruments it is carrying), why the experiments are important.

Question: That information does not fit on a 35mm slide.

DHJ: No. You give each slide a number code and you write a caption on paper or disk detailing what the picture is about. It's important to be accurate and specific. Check your facts!

Question: How do you recommend choosing subjects to photograph?

DHJ: I suggest starting out with what you know and like. If you are an ornithologist, I suggest immersing yourself in the subject and trying to find ways of taking the kinds of images that aren't published. There are too many pictures of birds doing nothing, perching on sticks, so my inclination with birds would be to go for movement and behaviour and interaction with other species. Then I'd follow that approach until it started to bring results.

Question: The photographer needs to be patient, is that what you're saying?

DHJ: Yes, patient about taking pictures and patient about selling. It can take years to take good photos and it can take years to sell them. If you are lucky, you can reduce the years to months. And as you get better and understand your subject in detail, you'll shorten the time lag between taking the picture and the picture selling.

Question: Hang on to your day job in other words?

DHJ: It depends on your priorities and expectations. It would take a long time, ie forever, to bring in a significant income, a few hundred thousand dollars a year -- unless of course you can routinely come up with unique images that would interest an international audience.

If you're a part-time park ranger earning $15,000 a year, it would not take too long to bring in an equivalent income from good photographs. You can usually combine stock photography with another job; it's probably a good idea to do so, especially if they are related. I often wish I were a research scientist with unlimited access to cutting-edge astrophysics projects.

Question: What is wrong with imitating photographs that are already being published?

DHJ: You can certainly improve your craft that way, but if the image is to sell, it has to be much better than the ones on file. It has to be stronger, more graphic, better composed, have more distinctive looking people in it, have stronger colors, etc, etc. It's not impossible to improve on what's out there but it's a tough route to take.

Question: Does a stock photographer need to travel a lot?

DHJ: Not at all. There is usually enough going on within 20 miles of your home, and that's the case if you're in the sticks, on a farm, in a little village. It's not just about living in big cities. There are always subjects to photograph in depth. Traveling is often a  way of running away from the need to commit where you are.

Question: Does luck play a part in getting good results?

DHJ: I am not sure what luck is. The unexpected? Something for nothing? What I have found is that if you do your research, are well prepared and serious about your work; if you are able to show clients you are serious, then good luck comes to you. I have an example: I spent months and months trying to gain access to a research center in northern Scandinavia. It wasn't coming together but I didn't give up. I kept writing and calling, trying not to be a pest but I guess I was. One day, after a week of calling and emailing, I was invited to photograph a project but was told there was only a 50-50% chance of anything interesting happening. That made me wonder whether it was worth driving the 100 miles on winter roads to get there, but I took a chance. I arrived, the picture opportunities were great, and that day the year's Nobel Prize winner in physics, Frank Wilczek, was visiting. He didn't mind being photographed. A perfect day in other words. Perfectly lucky!

Question: Does it help being able to write?

DHJ: Yes, without a doubt. For example, if your subject is botany, say tropical plants, an ideal scenario would be to get a degree in that subject, do some creative writing or attend journalism classes, get photography experience -- in other words, adopt an all-round approach. A person with a Phd in botany, credits in writing and with published work, plus photography experience, classes and diplomas even, that person is going to be a very strong candidate for success.

Question: And if one is not academically inclined?

DHJ: Then you make the most of what you've got. Hard work, social skills, contacts, ability to take good photographs, willingness to learn, those things.

Fotonic: How long should you give it before you know whether you are going to make it or not?

DHJ: You might never know, but generally, three to five years is a good span. If you haven't made any inroads by that time, it might be worth having a plan B. Most folks haven't the dogged determination to endure five years without success, and we all have bills to pay. You might have to work a couple of jobs in the beginning. After five years of consistently submitting good images, you should be selling a lot of photographs. It might not mean big bucks, but you should be in plenty of publications by then.

Question: What's the basic equipment you need, the absolute minimum you can work and earn with?

DHJ: I'd need a camera body, ie my EOS3, a good lens suitable for the work I do -- in my case it'd be a wide angle, say a 20/2.8 -- and a flash. That would do. At a pinch, I could do without the flash. I have long lenses but I rarely use them. I have studio lights; they are very useful for lighting big spaces. I have a macro, a 100/2.8, which has made me a lot of money. A 17-35 lens would be good to have, as would a longer zoom, something in the range of 70-200 mm.

Question: Are there any good rules of thumb you can think of, stuff that you apply in your work?

DHJ: "Get close" is a good one, as close as you possibly can. I am often in people's faces, up their noses; I move them around, ask them to do this or that. I always aim to be polite and cooperative and am sometimes told to step back. "Use diagonals" is another good rule for adding impact. "Think about the light" is a third, ie don't shoot everything on automatic but really think about what you want to say with the picture and expose accordingly. But, if things are happening quicker than you can think, use the cameras automatic settings to help you out. What else? "Don't be shy", that's a good one. I am very shy, so I've had to work at overcoming it. Oh, "Simplify" is a good rule for stock photography: let the writer tell the story; the image is there to accompany the words, to convey an overall idea or to whack you with impact. Don't clutter your images!