FF + Crop with primes questions...

So I started taking an all prime route for my own reasons on my 5D after selling my zooms.
I just got the sigma 50 and was thinking about the EF 85/1.8 and started thinking... Would it be a bad idea to pick up a 30D/40D later on to have two focal lengths with each prime? The cost of a 85 is about 360ish and a 40D is 400ish.

Would I get the same effect (FOV) as having a 5d + 85 vs 40D + sig 50? (BTW: I know there is a 5mm difference but so close :confused And then continuing the trend with say a 135 and maybe a 24L/35L down the line so that it is like I have two FOV with each prime?

Anyone do this or have reason why this wouldn't work?

For the FOV, yes, same effect.
For the depth of field : you have to multiplicate by 1.6 too : a 135mm at f/2 shot on a 40D gives equivalent of a 200mm f/3.2 shot on FF (but of course with the speed of f/2)
For the bokeh : not really...

Titi

I've got the option and have my primes covered, but I would not be without a good zoom.

I don't care for the 85mm FL on full frame, but I do hang onto it to use more on my 30D. It's a beautiful portrait lens either way but great for headshots on crop. I can't afford a 135L right now so I'm sticking to it for now. I have a 50mm which is great but it stays on the 5D cause I don't like 50mm on crop (I had a Sigma 30mm before, so this replaced it). Keep this in mind- a 135L costs more than a 85mm+40D, something to consider. It's nice having 2 bodies and sensors with different FOV does make it similar to having 2 sets of lenses.

DStanic wrote in post #13352275
I don't care for the 85mm FL on full frame

I do, it's my favourite

I'm looking at this from a different point of view. I can't afford all the lenses I want, but I have a 5D2 and a 7D. So I've currently got a Sigma 30, that only works on the 7D, and my 85. I want 35/85/135. I was going to sell my 70-200 for a 135 and my Sigma for a 28. Now I'm thinking I'll sell both of those and instead of getting the 135, which I have with the 85 on my 7D, and a 28, which I know I'd sell later. I'll sell both, get the 35L and have 35/85 on my 5D2 and 50/135 on my 7D. There will of course be trade offs, but I'm not buying a lens I know I'm going to sell and I'm functionally getting 4 FL's I really want from 2 lenses.