Pictures from the new Nikon D3X are effectively double the resolution (42 percent linear) of the otherwise identical D3. 24 Million pixels against 12 million for the other full frame sensor as used by Nikons D3 and D700 cameras.

This means an approximate 42% bigger image. The problem is that every time you increase pixel density (double in this case) you also increase noise markedly, slow down the camera, see less depth of field on screen at 100 percent and have double the data for every file if all else remains equal.

I was hoping for a D700x or whatever they decide to call it, but after this little experiment and looking at real world lens performance I am not so sure its a good idea for anything other than extreme studio use..

Look here for e.g. at a few lenses, remember that to see a real 12 million pixel resolution the lens has to be able to deliver that.  The Nyquist line in the fancy interactive graph in the link below represents 12 million pixel sensor resolution. That is the MAXIMUM resolution it can record. Never mind the 24+ million pixel sensors we are talking about here! Even a good 50mm Prime struggles at 12 million pixels over much of its area or possible F stop settings. Most lenses do very much worse, especially zooms.  Slide the little wheels around and have a look.  This Good Prime can beat a 12mp sensors resolution at certain apertures but not all over especially the edges.  Most lenses cant get close. What's the point of a sensor that can resolve more detail than a lens can provide? We are going to need better lenses if 24 million pixels becomes normal - and better technique!  Check out some consumer lenses like the 18-200!  Here is the 50mm f1.4 Nikon Prime.  http://www.dpreview.com/lensreviews/nikon_50_1p4_n15/page5.asp 

More sensor resolution can only give more photo resolution if the lens can deliver it to the sensor after all. Otherwise just like 5 million pixel phones all you get is a huge file!

So it will never be a shoot in the dark fast D3 (or D700) due to the smaller photo sites on the sensor but at low ISO noise should not be an issue. This camera is really for absolute expert critical studio and landscape use on a tripod with only the best possible lenses set to the best aperture for sharpness in each case. Because  MOST lenses other than the really expensive ones cannot actually resolve this level of detail at all!

At which point the D3X gives more noise than the D3 or D700 and bigger files with no gains to be had. A simple experiment shown below shows this reasonably clearly even using Nikons own "best case" images from its own publicity site http://imaging.nikon.com/products/imaging/lineup/digitalcamera/slr/d3x/sample.htm ...

In the images below I take a Nikon JPG from the promotional web site (not the raw) and resize it to the same dimensions and pixel count as the D3 and D700 so it gets reduced from 24.5 million pixels down to 12 million. So now its the same as if taken by a D3...  It also goes from the D3X image size of 6048 x 4032 down to the D3 and D700 image size of  4256 x 2832 pixels.  Now its a "low res" D700 sized image! But that's enough to capture the detail the lens provided!

Then it is resized in one go in Pain Shop Pro 12.5 back to the same D3X image size of 6048 x 4032 as it started. Both these resizing steps reduce image quality further...  But its needed to compare size for size.

I printed both these samples below at full A4 page size. I cant see any difference at all. Maybe its me. Maybe it just this image. So I will do the same with some of the other images from Nikons web site examples. I doubt it will make any difference though.

So it has effectively been reduced to the same photo that you could have taken with either of the other 2 full frame 12 million pixel cameras, and upsized (using default algo) to match the very expensive D3X!  Now remember that resizing up and down both reduce image quality and sharpness. Especially how I did this! There are better ways and better programs dedicated to resizing images. 

So you would expect that the original D3X file JPG from Raw from Nikons site would be massively better than the roughly resized and then resized back up one that I did!   Well there is "some" slight difference. But remember that at 100 percent this is a 6 foot+ wide image on my screen at least! So if that was on your wall it would be viewed from about 6 feet away, not with your nose to a monitor.  Go 3 feet away and tell me you can see any difference.

Original 24.5 million pixel image with best case scenario and very good lens as seen on Nikons site is image 1

Resample image down to 12 million pixels and to the D3 and D700 image size of 4256 x 2832 pixels. And then resampled back up again to compare directly to the originals...  Remember this is what you would get if you shot the same exact image through the D700 / D3 with the same lens and the same settings as the D3X...  This effectively shows what is gained by going to the D3X over the D3 or D700 in extra resolution for an enormous price hike! -- it does not show what you lose in low light or high ISO ability speed, or huge files though.

Original JPG from Nikons site (100 percent crop)

Below:

The original full JPG reduced to D700 / D3 size or resolution, and then up sized with Paint Shop Pro to match the D3X sized image.  There are better ways and "cleaner" ways to do this but this just proves the point adequately enough.

This resized 12 million pixel image could easily have been directly from a D3 or D700 and just upsized to D3X dimensions. This image does show some small change in quality (mostly from the type of resizing chosen) but remember this is a crop, the full image is about 6 feet or 2 meters wide!

Below. A better easier to see difference... A "Mouse Over" image swap. When you run your mouse over the image below it swaps the first two images. Remember that the first one is a direct 100 percent crop from Nikons own D3X 24 million pixel photo. The other image is the SAME crop after first  reducing the file to D3 or D700 size and resolution. In other words it was reduced to 4256 wide x 2382 high. It is now effectively a D700 or D3 sized image. Then it was resized back to D3X size and cropped. I see barely any difference. And you need a good monitor to see ANY difference!  The D3X image is the one you see before the mouse is over it. The resized (UP-SAMPLED) 12 MEGAPIXEL image is the one you see when the mouse is on the image.

Is this difference (if you can see any) worth a slower noisier and much more expensive camera unless you are using very good lenses and a studio in controlled conditions? In 99 percent of normal images the difference will be absolutely and completely undetectable, or even less sharp due to lens, focus error, or movement as higher ISO settings are more limiting.

Try this yourself and you may do a better job of it than I did!  Photoshop offers better up and downsizing options than Paint Shop Pro and undoubtedly can do a better job still. It all makes 24 million pixels seem a step further than the lenses can manage.  Remember this is one of the images Nikon chose to showcase their new camera, chosen from the best they could do with the best lenses and under the best conditions to show the 24 million pixel advantage.

Had they chose a less expensive lens or in slightly darker conditions meaning slower shutter or higher ISO as in more real world conditions then the D700 or the D3 both with with much less noise would undoubtedly have been the better performer.  Seems a high price to pay for the improvements you see above (if you can) under studio/controlled conditions when printing really huge images.