a57 - my first DSLR (t) - long exposure with kitlens

16 mm is noticeably wider than the 18 mm of the kitlens. It would make the kitlens superfluous indeed.

Samyang 14mm is not a fisheye.
Very sharp, but strong distortion makes it less suitable for architecture :-(.
A sony lens supported by A57's lens correction may be wiser.
See http://www.photozone.de/canon_eos_ff/532-samyang14f28eosff

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jvb