Does deferring admissions to PhD affect future (post-PhD) career path? I'm currently in my final year of undergraduate study, and will be applying to physics PhD programs (for condensed matter theory) soon. Without going into details, I am convinced that deferring my admission for a year, i.e. taking a "gap year", would be beneficial for me personally, and it is my understanding that most schools permit a one-year deferral. I would most likely work in the tech industry for this time. 

I am not worried about my physics/math abilities atrophying; I plan on actively keeping up with my studies independently during this time. 

Assuming I am permitted to defer for a year, are there any negative perceptions related to time off before graduate school that might affect my future academic career, after the PhD?

Will some people in the community look down on me for taking time away from academia, or is this considered a fine thing to do? Could this hinder me in the future when applying for postdocs (both the year away from academia and the fact that I am probably finishing my PhD a year later than I otherwise would)?

I am asking about the general perception of a gap year as it pertains to and affects a career path, not about how a gap year impacts a PhD application (which is addressed in this question).
In general, there is very little effect from taking a year off between undergraduate and doctoral studies, so long as you complete your graduate studies in a "normal" manner. The primary concern is how you did as a graduate student on your particular project; after you've received the PhD, the particulars of how you got there are much less important in determining your future career path. There may be some people who are prejudiced against people who deviated from what they consider a "normal" trajectory, but I wouldn't expect this to be a major fraction of potential employers. (And more to the point, you probably wouldn't want to work for such an individual anyways.)