What to do with Lens Caps
You want to take some pictures so you take off the lens cap. What do you do with it? This may seem like a simple question, but can you find the cap when you're done shooting? Ah ... not so simple after all now is it?
To begin with of course, you will be holding the lens cap in your hand but that's sure not to last long. One picture, maybe two, three or even several, but sooner or later you're going to want to put that lens cap down somewhere. If you're not thinking clearly, when you pack everything up and head on down the trail it will end up left on a big rock next to where your camera bag was sitting. Not good.
I've seen lens cap tether cords for sale that allow you to keep the cap and the lens tied together even when you're shooting, but I have to say I'm not impressed. I can't think of many things that would be more distracting than having a lens cap swaying back and forth like a pendulum when I'm moving around trying to compose a shot. Especially when shooting near the ground, a lens cap on a string just wouldn't work at least for me.
Dropping the lens cap in your camera bag may work for some people. But in practice I've found that lens caps are small enough to mysteriously work their way down under other things in a camera bag and find their way into places I didn't even know existed. I once lost the cap for a polarizer while shooting on the coast of the Olympic National Park and had to replace the cap when I got back home. Several months later though I was surprised to find the lost cap peeking out from under one of the dividers in my LowePro backpack. I assume it must have been in my bag the whole time but I swear I searched for it thoroughly, more than once, before declaring the cap lost. I had come to accept the idea that it was by now buried in the sand on the beach or washed out to sea perhaps, but somehow there it was, back in my camera bag. Magic, perhaps, but more likely I had just overlooked it somehow. I now have a another spare cap I suppose.
The pockets of your clothing may make a better option, but you have to be careful. With rapidly changing weather here in the Northwest I tend to dress in layers, and that means I start my cold pre-dawn morning out with lots of pockets. My outer layer coat pockets are amazingly convenient, but as the rising sun begins to warm things and I take that layer off it can be all too easy not to take everything out of all its pockets. When I do pack everything up and move on it's amazing how many pockets I can have to search through. Pants pockets generally work better since I rarely take my pants off while out shooting (now there's a sentence I never thought I'd find myself writing).
Many of Nikon's professional lenses have 77mm filter threads. Having a standardized size is a good thing in my book as it means that not only are filters interchangeable but so are lens caps. It's not uncommon for me to put the lens cap from one lens on another when changing lenses, leaving the cap from that other lens in my pocket, snug and warm the whole time. The cap from the first lens goes into my pocket when I start shooting and every time I take a new lens out of my camera bag, the cap from it goes on the lens coming off my camera before it goes back into my bag. At the end of shooting that original cap still in my pocket goes back on the lens currently on my camera, whatever that lens may be. This doesn't work for lenses with non-standard diameters of course, but does cover the majority of focal lengths I need.
Try to pick a clean pocket though. You want to minimize the amount of dust accumulating on your lens that starts out as pocket lint. Especially with a digital camera, the less dust the better. There's a lot of competition for pocket space for the outdoor nature photographer though, so give the subject some thought ahead of time to determine what works best for you. The heat of the moment in the field isn't a good time to be fumbling with lens caps.