I am assuming that the major photographic subjects are the bears, feeding on salmon at at the falls and elsewhere in the park, along with other nature subjects. A few things to remember: it tends to be cloudy so expect low light, you need to hike a mile to the falls so weight is consideration. To fill the frame with the bear head catching a fish, 400mm (600mm on a DSLR) will do, otherwise 200-300mm on a DSLR is plenty long. I used mostly my 80-400mm on my D200 it covered ninty percent of the ranges I needed. I used my 18-200mm for the wider angle shots of the landscape. With these two lenses I covered all I needed. I wished, however, I had a f2.8 long lens. I need to crank up the ISO to 400 for the 80-400, which I prefer not to do in order to keep noise at minimum. Many of the wild life shooters had 400 and 500 mm f2.8 and f4 lenses, many rented their lens, good idea if you need such a lens only once in a while. At the viewing platform you are very close to the bears, elsewhere you see them at some distance and a long lens is very useful then.
In July the light at falls platforms is best after noon and later in the day unless it is overcast then the whole area is like being under a soft box. If the sun is out, between five and eight pm the light is best at the falls. The Ripples platform, the one that is a short distance from the lodge, has the better light in the morning, but good shooting can be accomplished at both platforms during the entire long Alaska days. At the falls the larger bears fish all day and get into conflict with each other, away from the falls a bit, the adolescent bears hang out learning to fish the salmon out of the rushing river. At the lower platform family groups, sows with cubs, adolescents and cub frolic, I found it a more interesting subject.
Between the hours of eleven and four the place is more crowded with day tourist who come to Katmai for the day and crowd the platforms. Before and after their visit is the less crowded time to view the bears.
If you are camping and have no access to electricity, there is no problem with charging batteries, the lodge has several outlets that can be used anytime except at night when the lodge is closed. The cabins have electrical outlets.