#1. "RE: London today and rain." | In response to Reply # 0
Either is going to do the job, both have excellent high ISO ability,
Take the D700 if you are looking for something lighter
I used to have a photographic memory but never got it developed
#2. "RE: London today and rain." | In response to Reply # 0
Having lived in London for three years, my observation is that both the D3 and D700 are well-made and well-weather sealed. That said, I would treat either with due care and keep them as dry as possible, including drying them off whenever possible. I think the proper term is "weather resistant" vice "weather proof."
Waterloo, IL, USA
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#3. "RE: London today and rain." | In response to Reply # 2
A simple thought, and I hope I don't seem too annoying with simple ideas. Have a small umbrella with your kit. I love to have my d700 right in the weather. I love poor weather. I've been to London twice and we get rain/fog here, especially often on the coast. Maybe have insurance.