We probably all know by now that the DR of the D7000 at base ISO (together with that of the Pentax K-5) trumps every other digital camera on the market, whatever the format.
The P65+ is a laggard and under-achiever compared to the tiny format D7000, as regards DR.
But before you go purple in the face with rising blood pressure, and release yourself into an explosion of expletives directed against DXO, let's consider for a moment what the DXOMark rankings really mean.
I think many of you may have bravely ventured beyond the single-figure rankings, and dared to examine the individual graphs comparing one sensor with another of your choice.
If you have, you will likely have noticed on the top left corner immediately above the graphs, there's a (screen-print) option.
When you toggle between these two options, you should notice a substantial change in the results, on the graphs.
With the option 'screen', you are comparing the qualities of one pixel with another (for example, a D7000 pixel with a P65+ pixel).
What the DXO results tell us, is that the P65+ pixel is pretty much the same as the D7000 pixel with regard to SNR at 18% grey, tonal range and color sensitivity, at base ISO. Above base ISO, all bets are off. We sink into the abyss and the P65+ flounders.
However, most images are composed of all, or most, of the pixels on the sensor, depending on the degree of cropping. If we want to know what the comparative image quality would be like, if we were to downsample the P65+ image to the same file size as the D7000, for example, then hit the 'print' option.
You should see a significant jump in the image quality parameters for the P65+. The D7000 still retains its DR supremacy, but takes a dive in all other qualities (SNR, tonal range, color sensitivity).
Now, at this point, I think some further explanation is required about the 'normalisation' size in 'print' mode. It's specified at only 8mp which represents a print size of 8x12 at 300 dpi.
That seems a bit on the small side. I don't imagine that P65+ owners will often make prints that small. Is that size relevant?
Well, yes it is. DXO have chosen that small size in order not to exclude too many camera models. Any image consisting of fewer than 8mp would have to be interpolated.
Here's what DXO have to say on the matter.
Original measurements are useful to help gauge the actual image quality when viewed at 100%, but they do not predict how printed images will compare. In order to give a better prediction of how prints compare, a normalized version is more reliable and is provided based on 8Mpix
And this is what they have to say about the 'single-figure' rankings.
Sensor Overall Score is normalized for a defined printing scenarioó8Mpix printed on 8Ēx12Ē (20cmx30cm) at 300dpi resolution. Any other normalization, even with higher resolution, would lead to the same ranking, given that any camera that could not deliver the chosen resolution would be eliminated from the comparison.
In other words, whether a P65+ image is downsampled to the 8mp of the Canon 20D, the 24mp of the D3X, or the 16mp of the D7000, the ranking is unchanged.
So we should bear in mind that DXO do not offer rankings for small format cameras uprezzed to the higher pixel-count size of larger formats. This seems to me to be at the hub of the confusion.
I think perhaps DXOMark should place a big sign above their single-figure rankings, such as:
These rankings apply only to images that have been downsized to the native print size at 300 dpi, whatever that may be according the pixel count of the smallest camera in the comparison.
Okay! Now to the issue at hand. It seems that some cameras are extremely good at high-ISO performance, but average at low-ISO performance, such as the Nikon D3s.
The D7000 seems to be very good at low-ISO performance, DR-wise, but pretty average at high-ISO. It seems we can't have everything, although we may want everything.
With regard to every parameter that DXO test, except DR, the P65+ is streets ahead. No question.
So what is the significance and the benefit of such high DR, at base ISO, I ask myself? How does it translate to improved image quality?
I found it surprisingly difficult to find any comparisons on the internet that address this issue. But after some searching I did come across a few images that might provide some indication of this extraordinary DR of the D7000.
I'm assuming here that for editorial purposes I am not infringing any copyright. If I am, Michael will probably send me a PM.
The images are from http://robertbromfield.com/nikon-d7000-review-and-impressions/
The image I've selected is a shot at F8 with the Nikkor 14-24/2.8 at 14mm, which becomes 21mm on the DX format.
Robert complains that the image seems less sharp than the same lens on the D700. Does he not know that the 14-24/2.8, at 14mm, is sharper at F2.8 than at F8, as well as being sharper at F4 and F5.6, than at F8?
To compare the D7000 with the D700 using this lens, one should be comparing the D7000 at F8 with the D700 at F12.
Okay! To the nitty gritty. If the D7000 really does have such fantastic DR, then the shadows in Robert's night shot should be relatively clean.
We don't have comparisons with the P65+, or any other camera, so this exercise fails at that level. Can't be helped!
But at least I hope I have successfully defined the issues. The D7000 shot at night without flash, really does seem to show a remarkable amount of detail in the dark shadows, which is precisely what a high DR means.
Here are the images. First, the full jpeg unaltered; second the same image lightened in Photoshop using shadows/highlight tool; third a crop of the bottom left corner after lightening the shadows; fourth, a 100% crop showing the shadow cut-off point where all values are the same.
I'm not a particularly technical sort of guy, compared with others on this forum, such as BJL, but I've read that Nikon have a habit of clipping black levels at a certain point to obliterate objectionable banding and noise, unlike Canon who reveal such banding. Astronomers prefer Canon for this reason. Sometimes, very degraded detail is better than no detail, but probably not for most practicing photographers.
If the next iteration of the D7000 gives us 16 EV of DR, then those grey/black patches should reveal some detail.