What to take? What not to take? What if /insert panic situation here/?
Guilty as charged for overpacking, no matter the occasion. It is usually a symptom of anxiety, brought on by the pressure of having to deliver a product to a customer, or potentially missing out on a great opportunity due to a hardware or software fault. It's a valid concern, "Error 99" on somebody's wedding day without a spare body makes time stop.
A way though this is to try and plan to take the correct equipment for the actual shots (as deemed by your shot plan), plus essential contingency items.
- From the shot list I have developed, what are the lens requirements?
- One wide and one long should cover most standard situations. For example a 24-105 L and 70 - 200 L should be adequate for weddings, sports (mid/short range), candid portraiture etc etc.
- Packing every lens you own for a potential "what if" situation is wasted energy. Pack a third lens that covers the middle band of the focal lengths of your two main lenses.
- It's a given the best body owned will be the prime shooter. This is the biggest show stopper should something go wrong.
- There is no answer to this other than having a second body of suitable standard (works well in low light, excellent noise performance, matching settings & operating functions etc).
- Spare cards.
- Even if the card may seem big enough, space isn't the risk card failure is.
- Spare body batteries.
- Exposure to the cold will shorten the life of a fully charged set of batteries. Add to this a tendency to overshoot & consume more power and you'll have a depleted battery.
And that's the basics. Further items particular to the shoot (speedlights, remote, lens filters etc), can then be loaded in. Having a large bag with many pockets can be a blessing and a curse.
For a long time I would pack the smaller lenses and toys for a just in case moment. Sure it's nice equipment to have in the bag, but on every occasion it gets left untouched. An example is the Canon 40mm pancake. It's a fantastic lens for "happy snapping" & producing sharp 2.8 images but that's not the way to approach a wedding, portrait or landscape shoot. Therefore leave it at home.