You know better than any of us if you are ready for that leap. It sounds as if you are very well-informed about what the differences are. Be aware that you will only have P,A,S, and M modes and none of the cute icons for sports or portraits, etc.
It sounds like you are looking for some validation, which makes me think you are concerned about spending five large on a camers. Did you consider the D300? I have recently written a stock comparison on these two cameras, so I'll put it here for your consideration:
Nikon D3 vs. D300
Here are some references. You will see cross-references to each camera in the other camera's review in Popular Photography and by Ken Rockwell. Be prepared to spend a couple of hours if you really want to read all of this information.
D3: http://www.popphoto.com/cameras/5047/camera-test-nikon-d3.html
D300: http://www.popphoto.com/cameras/4911/camera-test-nikon-d300.html
D3: http://www.kenrockwell.com/nikon/d3.htm
D300: http://www.kenrockwell.com/nikon/d300.htm
See also: http://www.dpreview.com/reviews/compare_post.asp?method=sidebyside&cameras=nikon_d3%2Cnikon_d300&show=all
Obvious differences:
D3 costs three times as much as D300
D3 is full-format sensor and D300 is DX sensor
(864 sq mm vs. 366 sq mm)
D3 goes two stops higher with ISO boost
D3 has faster continuous capture rate of 9/11 fps vs. 6 fps
D300 has built-in pop-up flash and D3 does not
D3 weighs about 50% more and is about 1½" taller
Not-so-obvious differences:
D300 has wider relative tracking area for 51-zone autofocus
For the OCD. I've been meaning to do this anyway...
From the PopPhoto summary charts:
Image Quality at ISO 200-3200
- both are "excellent" and virtually equal on the graph
Image Quality at ISO 6400
- both are "extremely high" and virtually equal on the graph
Resolution ISO 200
- D3 "excellent" at 2320 lines
- D300 "excellent" at 2350 lines
Color Accuracy (Lower Delta E is better)
- D3 "extremely high" at Delta E 7.28
- D300 "extremely high" at Delta E 7.19
Noise levels are generally lower on the D3
- both rate "extremely low" or "very low" through ISO 1600
- D3 generally outscores D300 by around 20-30% on noise levels
except at ISO 800 where the D300 is about 20% better
Highlight/Shadow Detail
- both rated "extremely high"
Contrast
- both rated "slightly high"
Autofocus Speed
- D3 is generally about 2-3/1000th faster at all EV levels
- D3 is notably faster at EV 1 and EV 0 (2/10th and 12/100th sec), but
- D3 and D300 are virtually the same at EV -1 and EV-2
The D3 is obviously Nikon's best-ever pro digital camera. It beats the D300 in all areas of measurable performance, but just barely. If continuous release shutter speed, availability of ultra-high ISO, and full-sized sensor are important to you, the D3 is the winner. If you can live with the "lower" performance of the D300 in these areas - where it still beats pretty much anything ever made prior to now - you can save over $3,000 by buying the D300.
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