Fill the frame refers to the idea of having your subject take up all or nearly all the space in the frame. Doing this makes an image bolder, simpler, cleaner and less complicated for the viewer. As an added bonus, images of potentially dangerous or scary critters that look “too close” can have an added momentary startle or “wow” effect. The “that’s closer than I’d get” response. They don’t have to look for the subject, it’s right there in their face. The idea is to cut the clutter out of the picture. That is, eliminate the extra “stuff” around or near the subject that doesn’t help present the image you want to show. Figure 1, Spotted Moray, is the usual view that divers see when looking at a moray. But, this photo has too much distracting clutter. Figure 2 is the same dive, same moray, same camera and lens, I just moved over a little, turned the camera vertical and got closer with the Nikon 60mm micro lens.
Don’t get carried away with “fill the frame.” Be deliberate about what you keep or crop out of the photo. If the image looks better from farther away, then back up and start to think about where in the frame you want to place the subject and the other elements. For a look at the rule of thirds in photo composition, see the article in the Editing & Printing section of Still Photography.
If you didn’t get close or fill the frame during the dive, you still have a second chance. Using the cropping tool in your image editing software is also a way to “fill the frame.” Enlarge the image and crop away the offending clutter to improve the picture. You can even look at cropping the same picture several different ways. Crop the horizontal to a vertical format or vertical to horizontal. Play with the photo. Find the picture inside the picture. Try different parts of the same photo different ways. Turn the photo to see if it looks better in a different orientation. The folks using film cameras are not totally lost here. They can do these maneuvers too. It just takes a dark room or talking to your photo lab folks or scanning the image into a computer.
On your next photo dive, slow down to compose images, think about the picture you want, and work toward that goal.