There's quite a lot in here, so I'll break it up and even .../cut/... some parts, and if you feel something has been cut inappropriately, just say so.
I think this is a critical point, and possibly the root of the contention of the "DXO DR naysayers." As someone who prints a lot myself, perhaps I can offer some insight.
Assuming you print at native resolution, printing does not average the original amount of information into something less. .../cut/...
Printing is NEVER a pixel > pixel matter, the screening of the print may be at 2400dpi even though you're printing at 300dpi. Otherwise you would need 16 million differently colored inks to get a full hue/tone presentation. Since you "only" have between four and twelve (we have 10-pigment printers, with two neutral densities) possible inks - and in some head models maybe two different ink spot sizes - you need a variation of [16x10^6 / 8] over area, dithered to get a full tone resolution. I set the divisor to eight, as an average of the amount of available individual inks in a modern printer here. How the screening process (dither or a complete image RIP) is done determines how good the printer handles detail per mm or in the equivalent measurement set: MTF per dpi.
There are other problems with DXO calling their rated DR "Print DR", though. Assuming you are using a godly form of paper, such as Innova FibaPrint Gloss, which has a dMax of over 2.7, you might be able to get 7 stops or so from a print. Your average fine art print paper has a dMax randing from around 1.3 to 1.5 on average to 1.75 or so for some of the more recent higher-end fine art papers. That gets you maybe 5-6 stops of DR.
Don't make the mistake of mixing up tone resolution with DR. They are never the same in any practical application. Example:
A certain measurement
has the DR of 10:1 (say a measurement range of 1 to 10), and a resolution of "1" in that range. Ten discrete steps can be clearly differentiated in the original.
A certain presentation
type has the linear output range of 10-20. That gives a DR of only "2" since 20 is only two times as much as 10. But the presentation still has ten discrete levels very clearly distinguishable from each other, meaning that the tone resolution hasn't changed. On a visual inspection, you haven't limited the measurement DR, just shifted the base point (and lowered the detail MTF of course).
So that takes us back to the definition of DR. I'm happy to accept that DXO has a purely mathematical interpretation of DR, the ratio between white point (maximum saturation) and black point (noise floor). Again, though, I am not sure it is a useful or realistic definition of what dynamic range is. When one thinks about the value of dynamic range in digital photography, the first thing that usually comes to mind is the ability to recover useful detail from deep shadows. I say from the shadows, as I think any photographer who uses digital knows that it is critical to preserve the highlights, as once they are clipped, detail is well and truly gone.Realistic;
who knows, at least I can tell a whole lot of things about a camera and the resulting images, and what you can DO with the camera - just by knowing the DR and some other base performance figures. You would get the same answer from any other competent machine vision specialist or optoelectrician.Practical;
Since a camera sensor signal is linear you can move around as you want in it, internal contrast will be constant. This means that I can expose (photometric exposure) maybe one full stop less with a camera with good DR, giving me more "practically usable latitude" in both
highlight and shadow. This is not a very difficult PP operation - I put (in the raw converter) the exposure compensation at +0.5 and make the highlight tone curve a little less harsh in the cutoff knee.
If the DR is good, I can shorten my shutter speeds or get more DoF (stop down) at low ISOs - without loosing any image quality
compared to a low-DR camera used at longer shutter speed or shorter DoF!
More DoF or/and shorter shutter speeds are in most situations something very practical
, wouldn't you say?
The dispute on record here, if I may define it according to my own views as well as that which I've read from other DXO DR naysayers, is this:
What value does DXO PrintDR (the mathematically derived ratio between white point (maximum saturation, FWC) and black point (electronic noise floor)) have in a real-world context?
From the standpoint of simply moving the black point in a downsampled image, the only thing that occurs is shadows become darker. One LOSES information during the process of downsampling, so the primary benefit of having additional DR in the hardware no longer applies. In the context of viewing images on a computer screen, primarily done via the web, having a deeper black point might be valuable. Computer screens generally support a much deeper black point than actual prints on paper (particularly prints on high quality fine art paper), although none actually support 14 stops of DR regardless, and the average consumer screen is only 6-bit, so roughly the same DR as a print.
Firstly - Most cheap laptop (and cheap TN) screens use 6-bit with 240Hz time scale (delta/sigma) dither to get 8 bits of tone resolution. None of my devices (except maybe my phone) use lower than 8 discrete bits, and both my TV and my computer screens are true 8-bit >> 10-bit time-dithered.
Secondly - This tone resolution is quantized in a gamma-corrected
space, usually around gamma>>2.0. If you look at the sRGB gamma the step between the first 14 (of 256) bits is 1/13 of the bit value. This means the linear DR of 8-bit sRGB in the ideal application is 13x255 = 1:3315 or about 11.5 linear bits/Ev. A well calibrated HD-TV will follow ITU-R BT709, and present a step of 4.5 in the lower part of the gamma-curve - giving a linear DR of 4.5 x (235-16) = 1:985 - or slightly less than 10 bits/Ev
8-bit sRGB as a format standard has almost the same DR per pixel as a 1Dx. (!) -But in a nonlinear tone mapping - that's the difference.
When it comes to real print, assuming one is printing at native size, or an upsampled image, original detail is preserved or slightly softened, but none of it is lost due to downsampling. Regardless, assuming one even does significantly downsample a D800 image so they can print at 8x10", even printed on the highest dMax papers on the market with the brightest L* rating, your going to get HALF the DR you should supposedly be getting from DXO's 14.4 stop Print DR rating.
At best, DXO's downsampled DR rating should probably be called Web DR. It is not detail-preserving Photographic DR, as upon downsampling you lose detail. It is definitely not Print DR, since a print is inherently more about color richness and gamut than white-to-black point dynamic range. The depth of blacks sometimes matters in a print, however the deeper your black point in print, the harder it tends to be to actually discern fine shadow detail.
Again, you're comparing DR and tone resolution as if they were the same thing. And the comparison definitely does not seem coherent in how noise in different tone levels (brightness zones?) is perceived in a real print.
Photography is - when broken down to practical discrete steps - a series of [input DR + tone resolution] to [output DR + tone resolution] translations. As long as the tone resolution of the combined DR+TR of the receiving end is larger than the sending end the transformation can be lossless.
1) 3D object space (reality... :-) ) is projected on to a focal plane (sensor or film) through a lens, where you lose DR due to diffraction, haze and flare. Tone resolution is still infinite, limited only by quantum light physics.
2) the image space (the projection) is to be translated into electrical and then digital signals (the sensor and sensor electronics). DR is lost due to noise issues, TR is lost due to noise and quantization issues.
3) the linear readout has to be tone-mapped into a standardized color space, often a gamma corrected 8-bit RGB space. Here the tonemapping and tone curves determine how much DR you lose - if you lose any DR at all. In a camera phone or a cheap compact, sRGB actually has a much greater DR than what the input can provide! Tone resolution is (often) limited to 1:255 (8bits)
4) the standardized image format has to be rasterized to make it printable. DR is limited by the paper white and ink black densities, tone resolution is limited only by the rasterization scheme.
So, it's quite easy to make a 12bit DR deep shadow detail show up as an easily recognizable noise-free detail even in a 7bit (Ev) presentation DR.
So, what is the value of DXO Print DR? Realistically, practically, physcally...what do I actually gain by downsampling my full-detail RAW into a smaller-sized TIFF? For that matter, what value does DXO Print DR have if I save as a compressed JPEG for viewing on the web? Are we really just talking about a DXO weighted score, and nothing more? If so, should it really be called Dynamic Range, or is there a better term DXO could use that wouldn't come off as some kind of sketchy maneuvering (real or simply perceived) of their results in favor of a major monetary contributor?
Trying to redefine a metric that has been used practically, and for very many practical reasons in very many practical circumstances - by thousands upon thousands of signal processing engineers, sensor developers, imaging software developers (including the guys over at Canon DPP development center) and imaging process logic circuit developers is NOT in any way productive, I'd say it's very counterproductive. Especially since the connection between the measurement value and images in reality is so easy to show.
What would help a lot for most people is to understand what DR is, when used and put in the context that it is MEANT to be used. It plays ONE very important part in the most basic breakdown of the individual parameters that is universally used to measure or determine a signal quality - and a signal quality is the base for image quality assessment.
The camera total raw DR does in very large and noticeable amount have an effect on how the complete chain from object space (reality) to print can be realized. A camera with good DR has the (optional!) ability to show a lot more shadow detail (without adding noise!) in the final result, even if the paper/ink combination is pretty poor.