Yes it does. It uses the center 5+ mega-pixels in the center of the camera. I would use it to gain FOV for a shot where I did have time to change the lens, or did not have a lens with the reach to get the shot, sports, wild-life, etc.
The noise quality with the ISO remains the same since the pixels have not been changed, just reduced.
I use a D700 in DX mode with my 18-200 VR lens when I want VR at short focal lengths coupled with high ISO. This combination at ISO 6400 gives better results, even at 5 megapixels, than my D200 at ISO 800. I'll also use the same combination for "walking around" when results aren't super-critical (which mine seldom are).
"One should photograph objects not only for what they are but for what else they are." -- Minor White
Yes, the D700 has DX capabilities. I frequently switch back & forth from FX to DX using my Tamron 70-200mm f/2.8 (full frame) lens with outstanding results. Some gripe about the 5.1 mp file size in the DX mode, but I find 5.1 mp to be more than adequate for 98 percent of my purposes (especially when I can use Photoshop Elements + Essentials to enlarge pix by 400 percent without losing any resolution). My other special lens is the full frame Nikon 24-85mm f/2.8-4 macro. With the D700's FX/DX options, the lens has an effective focal range of 24mm (wide angle) to 127mm (telephoto) and a great macro mode. That covers a range from a few inches in front of your face to objects at a pretty far distance. The D700's legendary high ISO performance is just as good in DX mode as in FX mode.
I am new to the D700 and have been following this thread. Isn't the DX mode just capturing the center of the sensor, which would be the same as cropping the FX image, but not gaining resolution, ISO or any other benefits except file size? And in FX you may be able to crop more accurately with grab shots that may be off.
You're right, KenL, all DX mode does is crop the image. I would rather shoot in FX mode and have the freedom to crop at will, as you suggest, rather than let the camera do the cropping. That's with an FX lens. While you could shoot with a DX lens in FX mode and crop, it's easier to let the camera do it automatically when you know the image will be vignetted. The exception is a DX lens that will cover the full FX sensor. My Tokina 12-24 covers the full frame from around 17-18mm up, so it's my FX ultrawide while I save my pennies for a 14-24.
John "One should photograph objects not only for what they are but for what else they are." -- Minor White
> same as cropping the FX image, but not gaining resolution, ISO or any other benefits except file size?
You would certainly get the ISO capabilities of the large sensor - DX cropping is identical to the situation where you take an 12mp FX picture, load it into your favorite photo editor and crop out the outside 60% of the frame. Clearly in such a case if the file were captured at ISO 3200 (for example) it would have all of the quality of the FX sensor, right? The only difference is that if you engage DX in camera, you don't capture the outer 60% at all, so you save file space.
_____ Brian... a bicoastal Nikonian and Team Member
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I have found that when using the 18-200DX on my D700, I am often tempted to keep shooting in FX mode. This gives me more control over cropping, but it has one downside. Often I fill the visible frame with an image that is too large to crop without retaining the "vignette" left by the DX lens. Shooting in DX always gives me that good 'ol rectangle (although I often find I like the "peephole" effect of the vignette). So it's more a matter of preference, not of image quality, which stays the same.
I use it often and have one of the front buttons CF'ed to toggle between FX and DX. I use the 70-300 AFS VR for sports and toggle back and forth as needed. I prefer to not spend too much time in PS cropping and what not.