Over the years, I've been asked what the MINIMUM CAMERA EQUIPMENT was needed for a trip. The answer really depends on the trip, the goals & purpose of the trip, and type of shooting you are planning to do. Ultimately, the answer is ENOUGH & A BACKUP!

Remember, the camera YOU HAVE & KNOW HOW TO USE is better than nothing. If it is just for fun... take your main camera, and consider a back up camera - even if just a point & shoot (that uses AA batteries), just in case. If it's for money - a paying gig, then you really should have a quality back up... which hopefully you'll never need. 

Ultimately, most of photography is being in the right place and the right time, especially when you are outdoors. But it's meaningless if you can't quickly change your camera settings to accommodate the rapidly changing surroundings, and new opportunities. Having a working camera available is the starting point. Knowing how to use it in a variety of situations is the second vital point. But being fully prepared for the 'what-ifs' is something that comes with experience, practice, and learning that Murphy's Law really does exist, but far less for those prepared!

But for those that like more information, here are some of MY list:

BASICS: At least 2 or 3 extra battery sets, at least 1 or 2 extra memory cards, ability to add light (either on camera or off camera flash, preferably the latter if you know flash photography will be required... but on camera & a good flashlight can work in a pinch)... both wide angle and telephoto option (at least 35 to 200mm minimum). Ultimately, it depends on WHO & WHAT you will be shooting. More landscape and portrait type stuff, means you'll need a wider angle lens; whereas, less ability to move around and get close to the subject means a further reaching telephoto, potentially up to 400 or even 800mm, depending on the subject and project. Remember, lower light projects will require either wider aperture ('faster') glass or more light (maybe both... again, depending on the topic/subject).

BATTERIES: The purpose of extra batteries is understanding that you won't always or conveniently be able to recharge the battery currently being used by your camera, for a variety of reasons. And, the sad reality is that sometimes batteries wear out, fail, have other issues, or are accidently not charged fully after their last use. If the batteries aren't common, then finding extras isn't likely to happen outside a mega electronics store or the internet. So, GET EXTRAS before any trip or major event! Figure out how many photos you usually get out of your camera, in HOW YOU ACTUALLY USE IT. Some cameras are lucky to get 200 images on a set of batteries, some will take over 1000. Personally, I seldom ever use the LCD view finder on the back, which nearly doubles the life of my batteries on virtually any camera I'm using.

Knowing what your equipment needs, uses, and requires is key to making wise choices. Personally, I usually take 2 sets of batteries PER DAY I plan on shooting, 3 or 4 sets if I'm not sure I'll have access to power, which has happened a few times over the years. Few things suck worse than having a camera that requires proprietary batteries that can't be purchased at stores ready to use... and not have any way to charge the battery(ies) you have. I try to take both an AC & DC charger, and if I'm backpacking or really away from power I'll take a solar charger & USB Battery Pack with a 12-volt outlet to recharge batteries with. 

MEMORY CARDS: Though modern memory cards tend to not be a problem, there are times that they really do 'go bad' (for whatever reason). Non-mechanical cards, like CF (compact flash) or SD (secure digital) seldom have issues, but seldom still happens. So, always have an extra... and know exactly what your devices limits are, how many images will fit on what size of a card... and consider just how many images you're likely to take during your trip. For example, I have some cameras that won't allow any cards above 32Gig, others that will take any size up to at least 256 Gigabytes. My 20 megapixel cameras save images at file sizes in RAW format around 15 to 20 megabytes each, even larger if you save to TIFF and smaller (but less color detail & flexibility in post) if you save to JPG format. Don't forget HD video can take up a pile of space.  So, factor what and how you shoot, and leave yourself some room... some extra stuff you just might need, as you'll never know when you have that once in a life time opportunity... and need for extra memory to save your creative captures to. Understanding the write speed of your current camera is also important. Faster cards allow faster writing, but if your camera won't write that fast, there is little sense in spending the extra money on a card that is 2, 3, 10 times faster than your camera... unless you're planning to upgrade soon to a camera that uses that same type of memory card. 32G cards are really cheap these days... it's wise to have at least 2 to 3 times more than your projections think you MIGHT NEED. And remember, when you download the images to your computer, verify they arrived... back up the card, and RE FORMAT IT! So you're starting with a fresh card. (But don't do it until you verified you have the images on your computer, AND backed up).

GLASS (aka Lens): Obviously, if you have a fixed lens camera, you don't have to think or worry about this; though most of your good fixed lens cameras do have the ability to add filters, adapter lenses (tele-converters and wide angles) which can be extremely useful and add power & flexibility to your images. But with dSLRs becoming so inexpensive, new & used, lens options are something many need to consider. Pick carefully, and wisely, because once you get started investing in glass, you're a tad stuff with a brand and style. While I personally prefer L glass (the weather resistant professional glass that is almost always faster than the kit options, and definitely tougher), there are times I'll pack a kit lens just because it weights about a third of what the L version weighs, and the likelihood I won't 'need' it for the majority of the shoot. If I'm going on a shoot that will be MOSTLY telephoto work, and I'm cramped for space or weight, I'll toss in an 18-55... because it works well, and can work in most wide angle situations; plus with the reverse lens option (an EF 'mount' - that screws on the to front end of the lens, like a filter, allowing you flip the lens around backwards on your camera, which can create amazing super macro lens). It's not as great as the 16-35 or 24-105, but smaller and lighter. If I know I'm going on a wide angle shoot, then I'll usually pack one of my tele lens, like the 50-135 or 55-250 just in case. If I'm limited to JUST ONE lens, I'll pick either the 28-300 or 35-350 EVERY SINGLE TIME! (And usually toss in a 1.4 extender. Those are my 'backpacking' and long hike, kayaking, lens.) Knowing WHAT you'll be shooting is vital... a 70-200 would be very limited on an African Safari, and a 100-400 or 150-600 would be pretty useless for a basket ball game (but potentially perfect for Track, Football, most equine events, and that African Safari). The more you know about where you'll be shooting, the better your choices and options should be. And remember, you can always RENT if the trip is a 'once in a lifetime' and you really want to use something you don't have, and it's usually a fraction of even the used cost... and always in top notch shape, ready for you to capture moments & memories.

BACKUP: The other HUGE benefit to having a 'like minded body' for a backup... one body for telephoto lens (images), and the other body for wide angle stuff. Same batteries, same memory cards, same lens. More importantly, when you have similar bodies, you don't have to mess with any lens changes in the rain, dirt, pollen, dust, pollution, or any other potential air born issues. But for the average person, packing two like kind bodies isn't likely, or common, because they just don't have them. It took me a couple years to learn I really needed to have an extra quality camera, especially when I began shooting professionally - once in a life time type of events. If you're a two body shooter, then you'll want a third body, in case something happens to one of your other two bodies (but you usually don't take the third body with you, and it can be a model or two below what you're using now). However, another fundamental concept is that it is better to have two less expensive good bodies, just so you have that back up, than to have just one awesome camera body. Because when a body hits the floor, gets messed up, or has problems, which will invariably happen, you'll be unable to shoot without either borrowing, renting, or buying another body... until that one is repaired. Also, virtually all beginning to intermediate photographers, it's better to invest in great glass THEN good to great bodies, not the other way around. Get the best you can afford, and start saving up to get another (backup) as soon as you can.

STABILITY: I try hard to take at least a monopod, if I don't have room for a tripod. The stability a stick or tripod can offer is really helpful, but some places don't allow them to be used. However, the monopod I use is a actually a video monopod - with small movable feet, and a fluid head. (It also makes a great walking stick, opens high angle opportunity with a remote shutter, and keeps pesky snakes and critters away in a pinch). There are a couple really cool tripods that allow one leg to 'come off' to become a monopod. A couple of my friends have them and love them, I don't... because they are too short (I'm tall), and they usually have a weak ball head (won't deal with a large telephoto lens and full size dSLR). But, if you are under about 5'8" and don't mind working with the ball head... they are worth looking into.

FILTERS: realistically, a CP (Circular Polarizer) is the most important outdoor filter anyone can carry (or have). Think of it as expensive sunglasses for your camera. The two other filters one might consider, and are really cool when you can use them right... the Variable ND, and Gradient ND. Unless you are on a pro shot, or have a specific reason... or shooting using film, not digital... there is little to no reason for any other filters, if you're packing light.

CLOTHING & STUFF: Some type of hat if you're going to be outdoors, proper clothing that allows the necessary range of motion, comfortable shoes, a rain jacket for your camera (just in case), and I've found a pocket mosquito head & shoulder net to be real helpful at times, especially if you'll be in areas there are a lot of mosquitoes or bees.

GUIDES & ADVICE: If you are unfamiliar with an area, do some research. If it's common, popular, and public... be careful and consider bringing a friend or family member that is used to that area - or type of area, and knows a bit about the plants, wildlife, and terrain. If neither you or your friend is, then consider a guide - especially if it is remote or dangerous. Your photos are meaningless if you are severely injured or dead.

WATER STUFF: You need to know the depth you'll be shooting, so you can determine the housing requirements... there are three basic options, each benefiting from a red filter and some variety of auxilliary lighting when under water more than a few feet. One is a 'soft case' which is generally good to about 15 feet below... great for boating, rafting, kayaking, even basic snorkeling. These cases are usually like a heavy clear flexible PVC plastic, pliable, foldable, light weight, easy to travel with... and is certified to varying depths (usually 30 to 100+ feet). Then there is the basic hard case, usually good to at least 130 feet, which is the deepest most recreational scuba divers are supposed to go. These cases are usually hard, your camera fits inside... and o-rings seals out the water. They generally double the size of your camera... and absolutely specific to the make & model of your camera, and will take up space in your gear. The big pro underwater setups, well they are usually in big pelican box of their own, weigh a lot, and saved for those that aren't concerned about extra bags, cost, and  plan on some serious bottom time.

TECHNICAL STUFF: Know your gear... understand the limitations, and how to work around things when necessary. Consider YOUR GOALS & what you most want (need) to shoot, and preapre for that, plan for it... and be prepared to adapt, overcome, and relax, YOU CAN DO IT!

You understand the exposure triangle, the manual settings, and how to employ extra lighting when necessary. If you don't, then learn... practice, and experiment BEFORE YOUR BIG TRIP. Whether the trip is for fun or money, or if you're lucky, both, know that what you see, what you capture, what you choose to show others is totally up to you! And capturing one amazing image that really stands out is the goal most photographers have, the rest are just icing!