Thank you for at last trying to answering the questions that I actually posed. Let me repeat that I am solely interested in the specific comparisons of permanently attached lens vs interchangeable lens
, and have no dispute with the more general idea that _sometimes_, less choice is an advantage. In particular, I agree that when in the field with a camera, some people, some times have perfectly good reasons for preferring to have only a single lens of a single focal length with them.
So the only part of your response that relates to my questions is the last part:
Now, let's address directly the line of reasoning that it "is simply a matter of carrying just a camera with a single prime lens, regardless of whether that lens is permanently attached to the body or not."
The question, in case it is a system with interchangeable lenses, immediately becomes a plethora of choices. Ok, which single prime lens? 28, 35, 50? Let's say you firmly know that it should be 35mm. But which 35? In case of Canon, shall that be 35/2 or 35/1.4?? Or perhaps 35mm with IS? How about Mark II version of the same lens? How about versions from third parties: Sigma, Zeiss, etc. And if Zeiss with C/Y mount, which adapter works best with my camera?
But lets say we've overcome all those hurdles and settled on one lens and we happily go around for years or months snapping with it. How could this be worse than just non-interchangable system. Here is why: the very possibility that you can change that lens will slowly eat you from within. Say you acquired Canon 35/2... but then Canon comes with its IS version, which, at the same time, has oh, so much better MTF reading than your lens. Or the new Sigma 35/1.4 which has oh, so cool bokeh. Choices, choices... and temptations.
You are now (correctly) moving the issue away from what happens when you are out in the field with a camera, to arguing that there is an advantage to:
1) avoiding decisions about which lens to buy
2) avoiding decisions about which of the lenses that you own to take
on a given outing.
Firstly, I suspect that you are by now arguing for the sake of arguing; I doubt that you really suffer such severe decidophobia
as first discussed by the philosopher Walter Kauffmann
in the book Without Guilt and Justice
(see, I can cite academic sources too!)
But if you are serious, I have some bad news for you:
1) Decisions about which single focal length lens to buy
still exist when the lens comes with a camera attached: Sony RX1, Leica X2, Sigma DP1, DP2, DP3 ... ? The addition of further lens purchasing options, in the form of lenses with cameras attached, does not simplify the purchasing choices; it just adds to the options that must be considered. All those upgrade temptations are still there too: have the original Sigma DP1 or DP2, get tempted by the new Merrill versions ...
2) If you succumb to the temptation of owning several lenses (each with body attached) for different outings, like two of those Sigmas for different FOV, then you have to choose which to take
with you. In fact, I am sure that you do indeed already own multiple lenses, so that you already have to decide which lens or lenses to take with you on a given outing. Adding yet another lens, albeit it one with a camera permanently attached to it, will not save you from dealing with your decidophobia. The worst case scenario is that out of indecision, you pack two cameras, and then ....
Maybe you should consider instead putting the price of an RX1 into Energy Psychology therapy!
. But probably these forums provide an adequate support group for all of us with quirky equipment preferences.