Help picking out a DSLR body/lens for my dad's 50th birthday

The D700 is an excellent choice....but.... Yes, it will automatically use a smaller portion of the sensor with DX lenses, and if you think he's likely going to want to hang onto all those DX lenses, you may want to consider a D300S which would also give him HD video capabilities, and will actually render arguably better performance with a DX lens (the sensor offers more pixels in that area than the cropped sensor of a D700 if I'm not mistaken...they'd be pretty close though). If you go with a D700 he will likely want to sell off all his DX lenses and get more appropriate lenses to take advantage of the full frame capabilities of the that camera. The D700 does not have the HD Video feature. I guess it depends how much he's got invested in DX lenses at this point, and how important the advantages of full frame may be to him.

I'd second the D300s.

Full frame lenses can be a tremendous investment. If your dad has lots of dough, that's fine, but for an advanced amateur, the D300s is all the camera he will ever need.

The main advantage of the full frame sensor is low light. The D300s performs well in low light too, especially with f/1.4 primes. I would get him a camera body that he can use without chucking his whole lens kit.

Best to let him make the decision whether he wants to start over again with FF. If it was me and someone gave me a D700, I would return it and get the D300 and another lens.

It really depends on what he enjoys using the camera for. What does he like to shoot and what does he do with the images? The D300S is probably overall more versatile, and would suit 80% of the most serious shooters out there, and gives you HD video to boot (which I'm sure will be the next feature added to the likes of the next D700 encarnation since Canon has offered that in their new 5D). Bigshot makes a good point - the D700's low-light performance is excellent (of the best out there in small-format digital)...I would clarify that it excels at high-ISO low-noise output that the D300s cannot match. The fast (read: expensive) lenses, like 1.4 primes, will only get you so far and also, of course, limit DOF at their wide openings as well as not be as sharp at those openings (though I do love using them that way myself). A file shot at EI 1600 or 3200 with both bodies will reveal quite a bit of visual difference in noise with the D700 pulling cleanly away from the DX camera. You can probably search the web for some examples of this on review sites. One other advantage I find with the full frame sensor is that the wide angle lenses available occur to me as sharper and with less distortions. All that said, I'd still say the D300S is currently the more appealing for most shooters, especially those with a collection of DX lenses. If money is not an issue, and he's really serious about just still shooting, then by all means, go for the D700. I'm betting the next generation is not far off though, which means the price would drop a few hundred or more.

Here's just one comparison of the high-ISO noise rendered by D700 vs 5D vs D300. There are probably others as it's an obvious point of contention in making a decision like yours, and is otherwise a big issue in digital shooting. I also thought to mention that the current crop of VR lenses are very effective in allowing you to hand-hold a camera at much lower shutter speeds than ever before. This is especially appealing in the longer lenses like the astoundingly sharp 70-210 2.8 VR. The only downside of them is that you MUST remember to switch the VR off when the camera is put on a tripod (or you will get soft images). I would steer you and your dad away from buying the cheaper lenses in either DX or FX lineup as the construction is often not very good (lots more plastic used), and more importantly the autofocucus is lagging behind, as is overall performance. Of course you pay for the performance, but the point I'm making is that you get what you pay for if you are using this stuff on a regular basis, and or it's important to you to not compromise those qualities. The quality of the optics of some of the best zoom lenses now meets and sometimes even exceeds primes. The zoom has always been tremendously versatile tool, but has been hampered by less than prime optical performance. Lenses like the 70-210 I mentioned, and my other favorite, the Nikon 14-24mm 2.8 (an FX lens), offer astoundingly great performance throughout their range. They don't come cheap though.

One other note regarding using DX lenses on a D700 body - the finder does not reduce to show the actual crop, but instead a dim frame-line appears that indicates where the crop will occur. It is very easy to not pay attention to that line and miss the crop in shooting. It's not like the bright lines of a Leica M series body, for instance, which are more difficult to ignore. Further reflection reinforces what I've already said - the D300S is better if he's going to use those DX lenses, and it will certainly resolve more than the D700 with a DX crop.

it's a total waste of money to get a full frame camera and not use the full frame. But if he's into the idea, it's a great camera. I would take a D700 over a D300 or a 5Dmkii because I love what good high iso performance lets me do. With the d700 you almost never need to use flash.

Only professionals who need to be sure their lenses can take a few knocks and are sealed against dust and dirt should be 'steering away' from the 'lesser' lenses in Nikon's and Canon's ranges.

Even if the idea is to use the gear regularly, you don't have to drop thousands of dollars on pro glass when you're not actually making the same demands on your gear as a pro! The all-metal bodies might be strong but they also weigh a lot more, and easy-to-handle cameras are more fun to use.

It's important to keep the low light capabilities of the D700 in perspective. The difference in price between the D300 and D700 is basically the difference of two f stops. The low light capabilities of the D300s is WAY beyond film and is a couple of stops better than the camera your father has now.

Camera bodies are a matter of taste anyway, too many arguments either way.

So to get back to this simpler question, everybody needs a 50, especially if they turn 50 , and a 1.4 is always a good idea. All Nikon 50mm primes are made for FX, so you can pick based on budget. The new AF-S 50 is sweet though, and not that expensive.

Never "invest" in a camera body, as they tend to depreciate like a new car off the sales lot. If you have the budget to buy a D700, I'd suggest you to get a nice lens instead.

If he likes taking landscapes and architectures, get him an ultra-wide angle. Something like the AF-S 10-24mm f/3.5-4.5G or the AF-S 12-24 f/4G.

If he likes taking portraits and anything between 6-20 feet, get him a nice midrange zoom. AF-S 17-55mm f/2.8G DX or the AF-S 24-70mm f/2.8G works. Note that the 24-70 works on DX as well, effectively 36-105mm but it cost a lot more.

If he likes taking pictures of birds and little critters then get him a telephoto. An used AF-S 70-200mm f/2.8G VR is by far the best bang for buck (don't get the new VR2).

Get any of those lenses mentioned above and you still have enough change to get a fast prime. :P

I would argue that the main advantage of the D700 is its comparatively huge viewfinder. I shoot film regularly now, and the D200 has become a relative chore to use given its tunnel-like finder. I still agree, though, that the D700 makes little sense unless the OP's father owns or is willing to purchase a solid collection of full-frame lenses (might I recommend manual focus AI primes?).

The difference between the D300 and D700's low light abilities is profound in actual practice, make no mistake about that. It is a tremendous asset to have in a digital camera, though not a make or break feature in the OP's debate IMO.

To say the abilities of any small-format camera is way beyond film is misleading. It is like saying the abilities of high-resolution digital files are way beyond vinyl playback. Tonal subtleties and gradations are still dominated by film. To actually consider using film vs digital at this point is silly even for a pro. Only the esoteric perfectionist would be drawn to continue to use film. Digital is certainly more convenient by far and leaves film in the dust that way. I would agree though, that for low-light use, the better digital cameras have surpassed film in terms of noise vs film grain in that specific use. But, again, tonal subtleties and color gradations have not been surpassed in the small-format world of digital pro and prosumer cameras. Yes, I've seen the comparisons online by various pundits, but in actual use, film still wins in my book. Getting film processed well is becoming a greater challenge, even in bigger metropolitan areas. Here in Seattle both of the major labs have closed their doors for good, and one smaller lab is running E-6 daily. Better in NY and LA, but still, not what it used to be. That's not necessarily a bad thing, it just is.

Manual-focus AI primes don't play nice with Nikon's excellent strobe lighting options like the SB900 speedlight, as well as the on-board flash (sucks in comparison to the 900) on the D700. AI manual focus optics are also not optimized for use with a DX sensor. They will work fine, but the optics themselves are designed for film and not digital. Otherwise they can be had inexpensively and are well-built lenses.