[JeffBurns]

K-1 1010 g
K-3 800 g
D810 980 g
D750 840 g

I will need to keep my K-3 for backpacking.

[MadMathMind]

It's the price we pay for it being made from adamantium.

To put this in perspective, the 'worlds lightest' titanium backpacking stove burner is 25g. A Mobius camera is 39g. A Snickers bar is 53g.

If you're making your decision on which camera to carry backpacking, it would be foolish to do it based on so small a weight. A lighter tripod, or leaving just about any small item at home would make up the difference.

[JeffBurns]

The 210 g difference in weight between a K-1 and the K-3 is very significant to a backpacker. This is especially true when the added weight of a full frame lens is considered.

Last summer I spent eleven days backpacking at the Philmont Scout Ranch. I worked very hard to get my equipment weight down so I could take good photographic equipment. 210 g would have been over 1% of my total weight. To keep that in perspective I only took one shirt and it weighed 200 g. For that trip I took the K-3, 18-135 lens, polarizer, 5 batteries, cable release, chest case, and a TrailPix tripod adaptor for my trekking poles. Total weight was about 5 lbs. or 19% of my total gear weight. That is a lot to carry for 100 miles in the mountains!

For my Philmont trip I would have loved to use a 645Z for the landscape shots. When the boys were throwing tomahawks at dusk on a cloudy day a D5 would have been great. Carrying either of these heavy cameras would have been nearly impossible.

I would love to have the K-1, but am disappointed it weighs more than a D810.

I get the 'gram weenie' thing. Anyone who's serious about backpacking has probably spent more money than they'd care to admit to shave off a few grams. It's all about priorities, though. If you're planning to do serious photography, you carry the 'right' gear for it, even if it's heavy. Whether that's the K-1, the K-3, or the D810, a point and shoot, or just your smartphone all depends on what you're planning to shoot.

Leave the battery grip at home. Use a tarp instead of a tent. Carry a smaller fuel canister. There are plenty of ways to cut weight. But realistically, 210g will not slow anyone down.

Of course, if you don't need a full-frame camera or even an APS-C, then don't bring it. If you're willing to spend the time on it you can get the same/better results for landscapes with a narrower AOV lens/smaller sensor and panorama stitching in post--hand held even (if you don't want to carry the tripod either)