With a typical mid-tone placement, traditionally 18% gray (18% reflectance), in practice often a bit lower, like 13%, the 1% gray level is about four stops below the midtones. To be pedantic, it is 4 stops below 16% gray.
That level of "fours stops below midtones" is what is the zone system describes as providing only vague textural information, not real subject detail, which typically ends 3 stops below mid-tones. To give you an idea of how dark 1% gray looks, it is below the reflectance of the purest black of most or all photographic printing papers. Also, four stops below mid-tones is the level at which the ISO definition of film speed requires signal to be just barely above the "noise level" of "film-base plus fog", so more or less the floor for useful "signal" with film used at its rated ISO speed.
So yes, I would say that 1% gray is deep shadow.
P. S. Here is some information on the related topic of albedo, the percentage reflectance of sunlight, which seems a natural measure for daylight photography
http://en.wikipedia.org/wiki/Albedo
One highlight:
"Albedos of typical materials in visible light range from up to 0.9 for fresh snow, to about 0.04 for charcoal, one of the darkest substances."
So 1% gray is two stops blacker than charcoal, and this real-world reflectivity range from fresh snow to charcoal (critical when photographing snowmen!) is about 23:1, or 4.5 stops.
BJL,
What an excellent justification for not needing a better camera than a Point & Shoot, as regards SNR and dynamic range.
However, some of us, notwithstanding the reflectivity of charcoal, wish for lower noise and better detail in the shadows than a P&S or even an Olympus 4/3rds can provide. Some of us even feel the need to merge different exposures to HDR in order to get a better SNR in the shadows.
Comparing the SNR on the log scale at 1% input for various cameras at base ISO, I find that the Canon G12 manages an SNR of about 19 dB, The Olypus E-620 only 18dB, the Canon 50D 21dB, the Canon 60D 22dB and the D7000 26dB.
We can argue all day about subjective impressions of what may be considered a moderately deep shadow, a deep shadow or a very deep shadow, but a degree of shadow in which a P&S has slightly lower noise than the Olympus E-620 does not seem particularly deep to me.
What you've written above also appears to be at variance with DXOMark's own explanations of the meaning of their results.
I invite you to look at the following extract from their 'insights' articles at
http://www.dxomark.com/index.php/en/Our-publications/DxOMark-Insights/Noise-characterization/SummaryAs a consequence, the SNR also has three regimes:
Shadows: the SNR increases 6dB for every EV and loses 6dB for each doubling of the ISO setting.
Midtones: the SNR increases 3dB for every EV and decreases by 3dB for each doubling of the ISO setting.
Highlights: the SNR is constant and does not depend on the ISO.
Now it so happens the SNR graphs for the D7000 lend themselves admirably to demonstrate these DXO statements, because, as you know, the D7000 can be used for all purposes at base ISO. The loss in SNR due to doubling ISO is the same as reducing exposure by one stop at base ISO
In light of the above, we can make some reasonable deductions as to what point along the x-axis of the DXO graphs the midtones and the shadows lie.
If we examine the graph for SNR at 18% grey, for the D7000, we find that there is indeed a loss of approximately 3dB for each doubling of the ISO setting.
If we search for the point along the x-axis on the Full SNR graph where a doubling of ISO produces a fall of approximately 3dB in SNR, ie. the point where 18% grey would lie, we find it's about midway between 100% and 10% on the x-axis. That point represents the midtones, approximately the tonal range of skin tones in a portrait.
If we examine the fall in SNR with each doubling of ISO at the 1% point on the x-axis, which you describe as the deep shadows, we see that between ISO 100 and ISO 6400, the SNR has fallen from 26dB to 4dB with a total change of 6 EV in exposure.
22/6=3.7dB. I hardly think this constitutes the deep shadows, an increased drop in SNR of just 0.7dB compared to the rate of fall in the midtones of 3dB.
If we examine the fall in SNR at the 0.1% point on the x-axis, which I would describe as the point where the deep shadows begin, we find there's a fall of approximately 14dB between ISO 100 and ISO 800, or 4.7dB with each doubling of ISO setting, which is still short of the 6dB mentioned by DXO.
The graphs below show the Full SNR details for the D7000, and specifically the SNR at 18% grey.
Draw your own conclusions, but I know what my eyes tell me and I've taken the trouble to shoot tests with the D7000 to demonstrate the improvement in SNR in the shadows, and the consequent imrovement in visible detail compared with other cameras in identical circumstances.