Liquid Dark wrote in post #16288782
David, I can get the 17mm now if that is indeed the right choice
it might seem to be the best idea to most to just go with the 17mm if can afford it. However, I put up with lower quality IQ lenses in the past because I HAD to, now I try my best to only buy the best IQ lenses or not at all.
In other words, if the 17mm is great for WHAT it can do indoors, but suffers IQ wise compared to the 24mm then I want to know that now, not after I buy it.
Again, thanks all for the wonderful advice!
IQ-wise they're both fantastic. The 24 II is better, but windpig's characterization is exactly they way I would put it. Putting the 1.4x on the 17mm absolutely works, but then you are going to lose a bit of sharpness; your IQ will suffer in comparison to the lens without the extender.
Making a recommendation is a real toughy for me. Compositionally and IQ-wise I prefer the 24. With respect to architecture, a 17mm lens is such a wide angle that some people are disturbed/annoyed by the "perspective distortion", whereas a 24mm view looks and feels better. I only shoot with the 17 when I can't pull my scene in with the 24 (small/tight rooms, buildings where you don't have room to pull the camera back, etc.) because the framing/composition is just going to look better. Problem is, I frequently find the 17mm useful.
I have shot shifted panos with the 24 to compensate for its narrower FOV, it's a nice workaround, but there are more limitations in doing that for architecture than for landscapes. For instance, if you're using the shift in the up/down direction to maintain vertical lines (the primary reason for having a tilt-shift for architecture), and you want to do a left-to-right pano, then you're out of luck.
If you can make an order from a retailer with an excellent return policy, then you can buy the lens you think is right for you and return it if you are disatisfied. For instance, you could order then 17mm and do your own tests with the 1.4x to see if you can live with the loss of sharpness.
What I did was start with the 24. If I knew then what I know now (from experience), I would have still started with the 24. But, it's a hard decision and I don't know if you can make a mistake either way.