UKC

I am looking for a 70+ litre bag that can be used as both a climbing and photography bag. I need a big one, as, I will travel and stay in destinations around the world for a couple months each. I will need a massive suitcase and a rucksack for this. If such bags exist, are there any suggestions for good bag models at good prices ?

With space sounding like it's a premium for you, forget dedicated photography bags -- they never have enough space to store anything but the cameras and lenses. Alas, there is unlikely to be a solution that means you have easy access to all your camera kit.  I suggest you get a comfortable climbing bag, and an insert to hold lenses/accessories like this:

https://www.amazon.com/Ciesta-Flexible-Camera-Insert-Partition/dp/B00C0OF9K...

and maybe the camera in a zoomster/shoulder bag? 

https://www.shimodadesigns.com/

A colleague has used one on a recent trip and they are very good indeed. 

We use a Lowepro Whistler BP AW Backpack, works well in climbing, skiing in snow and rain. Just as good at keeping the dust out when we are safari. It’s not cheap and there are bigger versions, but it’s been worth its weight in gold since we got it.

https://www.wexphotovideo.com/lowepro-whistler-bp-350-aw-backpack-1578048/?...

How much camera gear are you looking to take Jim?

I typically travel with an 80L duffel, in which goes my alpine sac (empty) plus tripod, rope, rack, tent etc. Then I have my camera gear, laptop etc in a lowepro mini trekker classic which I carry on flights. You can get a lot of stuff in the classic mini trekker.

I've got an f-stop Satori for my large format kit, but despite being a big bag doesn't leave much room for anything else. And like all the 'proper' camera rucsacs it's over-priced and over-designed.

You can go one of two ways, get a didicated photo bag such as fstopgear /Lowe pro

http://fstopgear.com/products/packs/sukha

Or or you get a climbing pack and use photo  bags/lens pouches stuffed inside.

i still use both options depending on the balance between photography and walking/ climbing. 

Second the minitrekker option. Best size I've found for a dedicated camera bag, which you can actually get a flask and a duvet/waterproof in as well (in the front section). Must sell my Nature Trekker ...

At the moment, I really don't have too much photography gear. I only have 1 DSLR + 3 lenses. I will be adding more to the gear such as more lenses, filters and a tripod. It's just the gear always gets forced into one big pocket meaning it is susceptible to shock and is very cumbersome to sort and take out.

I have one of these https://www.amazon.co.uk/gp/product/B00KT7GKXK/ref=oh_aui_detailpage_o04_s0...

takes a DSLR and two lens 16 - 35mm and 24 - 105mm L series plus some spare batteries and filters. You can put it into any rucksack so is very flexible and doesn't scream "I'm a photographer come and mug me".  Really well made and lots of dividers. 

Anything like Owen's suggestion should work.

My favourite when travelling light is a Lowepro Inverse 100AW. It's sort of a big bumbag with a shoulder strap. Fits in the top of a sac, or very comfy to carry on it's own, built-in rain cover. Low CoG so good for technical terrain. The 200 would fit all your kit but I quite like being forced to go light with the 100.