If you could only take one prime for your apsc/crop?

Indiana25 wrote:

I recently travelled on business around the world in two weeks stopping off in five nations. Packing for business and multiple climates meant that space and weight was a premium, so I tried to come up with the most versatile two lens combo. (I also had very little time to take pictures as I was on the run all the time)

I am still evaluating, but I took my Sigma 18-35 and my 18-135 STM. The sigma as you know is like having several primes rolled into one and really was useful for indoor photography. My trusty 18-135 gave me some reach particularly outdoors, but in retrospect I did not use it as much as I thought. I probably could have just got by with the Sigma and zoomed with my feet when I needed more reach!

The trouble is the Sigma 18-35 is a beast and I got to thinking about if I wanted to go even lighter and I could take only one lens for my 70D, what would it be? I'm thinking it would be a fast prime so that I can shoot in low light without a flash. Something not too wide, but wide enough to be able to do some group shots. So, with that logic as a framework, I started looking at primes at the 24-30 range and ideally less than $800. My top pick today might be the Sigma 24mm ART, but may experiment with the concept first by trying out the Canon 24mm STM. The Canon is not as fast, but the size and focal length hit my initial mark.

I know some will say why not buy another camera for this kind of money? I might go that route, but I do love and know my 70D. If I can find a lens I like (with the obvious compromises), I think it is worth giving it a serious consideration

So, before I out out out some cash, I'd be interested in what others would do from their experiences... if you could take only one prime lens on an around the world trip for your APSC/crop camera, what would you take for the most versatility?

Thoughts and opinions welcomed...

I know you didn't ask it like this, but honestly, if it were me and I was on crop, I would use the Sigma 18-35mm that you have.  It's super sharp and covers the indoor focal lengths I would want for a prime.   If you dont' want that because of the weight, I wouldn't bother with any of the Art series because you're not gaining that much.  If you really want to lose the weight and have a more portable prime, I would probably look at the 24mm pancake, the Sigma 30mm Art (same art series but much smaller lens made for APS-C) or the Canon 35mm f2 IS.