First off thanks for the assistance that was previously offered on my previous post regarding the use of telephoto lenses. In fact based upon one of those responses I have the following follow up question. My current lens arrangement includes the following: D3, 200-400, and a 70-200 vrI as my longest glass, instead of going to a 600 vr or a 300-800 would it be more practical to go with a DX (90, 300 or 300s) and stick with my 200-400? I like the idea of the an additional body for backup, video, etc and with the additional crop factor, seems a good alternative when traveling with gear. I have had various tc's but they seem to cause the 200-400 to hunt a little to much to my liking. Am I approaching this correctly?
With a DX camera you'll get extra "reach" because roughly the same number of pixels covers a smaller part of the lens image. What you will lose, however, is the dynamic range offered by the D3. Consider what you shoot and whether or not you can afford to lose one or two stops of dynamic range at any ISO, and then you'll know whether the DX camera is appropriate for you. There's a lot of money involved too.
Which effective focal length will you be using most ? The answer to that will determine which camera will be used most. You may not want the D300s to be your primary camera when you have a D3 sitting idle as a backup.
A final consideration is the difficulty of travelling with a large and heavy lens plus the large tripod and gimbal head needed to go with it. Perhaps not so bad in your own car (unless it is filled with family and luggage) but much harder if you are using public transport.
My recommendation is to take the significantly cheaper DX option unless you know for sure that you will get your moneys worth out of the longer lens. There's little enjoyment to be had from photography when you have too much gear and too little use for it.
