Digital camera trekking discussion
Thinking about buying or upgrading for your trek? Do!
Also carefully consider how the camera will be used afterwards.
Intro
It is essential to understand digital photography is a medium. Although many people think you are duplicating what you see in real life; you are not. Our eyes can see more colours, handle far greater variations of light and many other subtleties far better than film or digital; nothing is perfect, luckily nothing is the same a real life. Consider photography a (usually lightly) stylized interpretation of what we see, water colours are another interpretation...
Reviews
Getting serious about comparing cameras? Go to dpreview.com, by far the most comprehensive and unbiased site. If you are overwhelmed just take a look at their conclusion at the end of a camera/lens review and read carefully.
Camera types
Essentially there are five types of cameras:
SLR
ie interchangeable lenses, often also called digital SLR's or dSLR's, these do everything and are wonderful to use, are the most versatile but not pocketable. Really think carefully about whether you want to take something this big trekking; the results are fantastic though. You must plan your carrying system carefully. The greatest advantages of SLR's is the optical viewfinder, and the ability to change lenses. See DPReview's dSLR buying guide.
There are a number of sub-groups, the biggest and best are the full frame (FX) format cameras, but these are heavy and expensive. The DX (and Canon's equivalent) format which have smaller sensors and overall are lighter but still produce excellent results, and lastly the 4/3rds system which is smaller still with only a few sacrifices.
(Mirrorless) Interchangeable Lens Camera
Like an SLR but more compact, but still not pocketable. These are mostly based on the micro-4/3rds system and have no mirror inside, instead use electronic viewfinders, or just the back screen for composition, just like compact cameras.
Semi-compact "travel zooms"
Smaller do-almost-everything cameras, and these are what most people trek with. The advantage of these is some have good zooms, say 35-140mm (35mm equivalent) or more. The superzooms are now in the range of 28-400+mm! The size of these cameras is still an issue, few fit into a pocket without being noticeable, but in a trekking situation with a nice case that attaches to the hip belt area of your pack, they are convenient. None use optical viewfinders (the best for composition), they are all LCD-based, most having an LCD viewfinder and also an LCD screen. Image stabilization (called different names by different manufacturers) is essential.
Super-compacts
The size of a packet of cigarettes, fit in a pocket almost unnoticeably. They are also good for trekking, although less zoom and so slightly less versatile than the above styles. Canon and Panasonic Lumix are the best brands but do read reviews carefully and consider what sort of shooter you are, your end result use. A small case can go on your pack shoulder strap area even. A few of the Canons have an optical viewfinder AND an LCD screen, the rest of them just use a large LCD screen.
Camera phones
These are getting better and better, and for sharing photos they are unbeatable. The downsides are it is hard to compose in bright sun and a very limited zoom.
Brands
Arguably Canon are the leaders in every camera category and you can't go wrong with them. In the SLR category Nikon are chasing hard, sometimes even on top but their compact cameras are ordinary, in general. Sony, Panasonic Lumix and Olympus compete well in several niches, at least in features. Sony makes the best high end compacts.
For SLR cameras the lenses are perhaps the most important factor - choose your lens or lenses first, and that might even decide the manufacturer for you.
Batteries
A good SLR battery used carefully will last around a week, sometimes longer if you are frugal, but all of our treks are longer than that. On our expeditions and some treks we have solar power, 230v and all plug types, and so you can recharge. On other treks the best way is simply to buy some extra batteries. Original batteries are expensive but on eBay no-brand batteries are less than $20 each, and 2 to 3 extra will cover you for a trek - no guarantees though. This is a better solution than looking at solar panels etc. In general original batteries significantly out-perform copy batteries in colder weather.
For best performance buy in advance and use three times, charging and discharging them fully, and this will push the Lithium Ion battery to give the longest life on subsequent uses. It is not necessary or useful to discharge them fully after this, just charge when the opportunity arises.
Memory cards
Professionals all shoot "RAW" format, which makes big file sizes. If you are an aspiring photographer willing to spend time adjusting photos then definitely shoot RAW but mostly it is more practical is to shoot JPEG's, even though it is a setting designed for screens and so printed pictures sometimes look 'flat' compared to RAW (or film). Memory is cheap enough now that you can also shoot RAW+JPEG and get the best of both.
Which JPEG setting? I strongly suggest shoot the highest resolution with the finest setting, regardless of camera.
Compact camera protection
You want your camera instantly handy while trekking - consider carefully what case will work. The whole range of Lowe Pro camera bags and cases are available in Kathmandu so it is a convenient place to buy. One that can attach to the shoulder strap of your pack can be perfect.
SLR camera protection
For SLRs I recommend a neoprene soft cover (Zing), and then you can keep the camera out most of the time using the shoulder strap for carrying.
For a Canon 5D III/IV with 16-35L or 24-105L, 24-70L II, 50L with hood, the large size for zoom lens 4-7 inches is perfect, but will not fit other longer lenses (eg 70-200L f4), whatever the packaging says. The large size standard cover will only take lenses such as the 50mm f1.4/f1.8.

2006: Jamie's brand new Canon 5D was buried for several days in this tent directly under the snow they are clearing, it survived - Jamie
Camera settings
There are endless settings you can adjust. Other than setting the image to jpeg, size and quality to maximum, be wary of changing anything else unless you have tested on a computer. Experiment with snow and snow mountain shots, a third of a stop down (-0.3eV) is often better; don't go more than -1eV / -1 stop.
Do shade the lens in strong sun. Using extra in-camera sharpening or vivid colours looks good in the viewfinder but often looks overdone once on a computer screen or when printed.
Shooting techniques
Providing you are covered for batteries shoot lots, try several different approaches to a scene and experiment, wide vs tightly cropped etc, you can always review and delete. Some people have a better eye than others and shoot only a few shots, keeping every one of them.
Panoramas, ie photos stitched together, often look stunning. You must fix the exposure though. Compacts may have a panorama setting; for others shoot on manual exposure, exposing for the brightest image in the sequence.
In general don't use the digital zoom, results don't look good. Rather, crop the shot later.
On an SLR if you have a polarizer use it sparingly; DON'T leave it on the camera the whole time.
Software
Your camera will come with software good enough for at least basic use. There are some good alternatives though, for looking thru pictures and making quick adjustments. Serious users mostly use Adobe's Lightroom, which is the best for cataloging and reviewing RAW files and is also a classy editor.