As I said earlier, DR is only a (small) factor in the explanation of the perceived dynamic range. One other factor of importance, IMHO, is differences in MTF due to sensor array dimensions. A larger sensor array will result in a larger magnification factor of a given FOV on the sensor. A larger magnification will mean that a different part of the MTF response curve is used, a part with potentially a significant higher response. That higher response will allow to discriminate microcontrast that may otherwise result in loss of discrimination due to veiling glare or other optical contributions to the system MTF.
I'm not convinced that such factors are particularly significant to the perception of DR, Bart. It sounds as though you are making excuses for someone who doesn't know what DR is, or doesn't know what he's doing. On the other hand, perhaps it's me who doesn't understand the significance of DR.
I'd like to refer to those extraordinary results from DXO Mark that describe the D3X as having 1.33 stops greater DR than the P65+ (at the pixel level) and 0.68 stops greater DR when both images are downsampled to 8"x12" size for printing.
From the perspective of the practical photographer, this is what I think the results mean. Correct me if I'm wrong.
If I shoot a scene with a high SBR (subject brightness range) using the P65+ and the D3X, using the same focal length of lens with each camera but underexposing the D3X shot by 1 & 1/3rd stops, then both images should be perceived as having the same dynamic range.
Now it's true that the P65 shot will have a wider FoV because it has a bigger sensor and we used the same FL of lens in each case, but we're examining image quality at 100% on screen, not admiring the composition. As long as the full brightness range of the scene is represented in both shots, the different FoV is irrelevant to our purposes. The pixel pitch of the D3X is very close to that of the P65, so the 100% crops that are examined will be about the same size, which makes the comparison easier.
It may be the case that the P65+ shot will be perceived as being slightly crisper due to its lack of an AA filter, but such subtle effects should not change the perception of DR. Even if there's a mismatch of lenses and we use the most expensive Digitar lens with the P65 but an average Nikkor lens with the D3X, the better resolution in the P65 image would be apparent across the entire image and not confined to the shadows. The brain should be able to make allowances, realise that a better quality lens has been used for one of the images, and that the DR of both images is still the same.
In the comparison of images downsampled to 8"x12" size, I understand that equal FoV images would be the source, which perhaps creates a slight problem due to the different aspect ratio of the two cameras. Ignoring this slight mismatch, the DXO results are telling me when the D3X shot (underexposed just 2/3rds of a stop in this instance) and the P65+ shot fully exposed, are downsampled to 8"x12" at 300dpi, thus discarding some resolution from both images, but discarding more resolution from the P65+ image, both images will appear to have the same DR, and presumably the same resolution.
Have I got this right?
A high dynamic range capability in a camera allows for greater exposure latitude. I used to prefer shooting with negative film, rather than transparencies for that reason. I could underexpose one stop and still get acceptable shadows in situations where the subject had a wide brightness range. With slide film one had to be more precise and sometimes risk overexposure. It was widely accepted that B&W film had the highest DR, color negetive film next, and slide film a couple of stops lower.
The DR differences between these types of film was pretty obvious and didn't require endless debate. If camera A has a significantly high DR than camera B, then the shadows in camera A shots will be cleaner, more detailed and of higher quality.
If the DR differences are in the order of 4-6 stops, the cleaner and more detailed shadows from camera A would be so obvious they would smack you in the face. If the DR difference is in the order of 1/4 to 1/2 a stop, then. even with the best intentions, other factors may skew the result and it may not be perfectly clear which camera has the better DR.
Of course, you do have a point about the potential of the MTF of a lens to affect the perception of a camera's DR. This affect would be most obvious in the corners of the image where the MTF response of most lenses is worst. One could use this characteristic of lenses to demonstrate that an APS-C (cropped-format) camera has a higher DR than a FF 35mm.
This is how you would do it. Take a good 35mm format lens that has a reasonably flat MTF response to the corners and virtually no fall-off when used on the APS-C format. Take another FF lens of equivalent focal length for use with the 35mm format camera, but make sure it's a lens with significant MTF fall-off at the corners, as well as severe vignetting. Such a lens could still be impressively sharp in the centre.
Select a scene with a very high brightness range, but arrange the composition so that the shadows are all in the corners of the frame in both shots. Make sure you expose correctly, aiming for an accurate ETTR by bracketing in 1/3rd stop increments.
Display 100% crops of the highlights and mid-tones of both image, demonstrating the superior tonality and resolution of the FF 35mm format and the fact that both shots have received a correct ETTR. Then display 100% crops of the shadows in the corners, lightening the shadows so that one can see clearly the better detail and lower noise in the APS-C shot.
This is an extreme example. I don't think many photographers would be hoodwinked by those results. However, the choice of F stop when comparing different format cameras can certainly skew the results against the smaller format, but I would think that resolution softness can be distinguished from noise.
If you want to exaggerate the resolution advantage of the DB in comparison with the FF 35mm format, then you would use wider apertures for a shallow DoF. For example, if we start with the premise that most lenses are sharpest at F5.6, then we choose F5.6 as the aperture used with the MF format.
In order to equalize DoF in both shots, we then have to use F4 (or even wider) with FF 35mm. But a 35mm lens at F4 is generally not at its sharpest. (Are we testing lenses here, or are we supposed to be testing camera sensor performance?)
If one is aware of such factors, then any serious comparison should include shots of the same scene taken at other apertures. In addition to pairing F5.6 with F4, we need to see F8 on the MFDB and F5.6 on the FF 35mm, or F11 on the MFDB and F8 on the FF 35mm.
I believe it's the case that MFDBs will generally produce noticeably sharper results than FF 35mm DSLRs when a shallow DoF is sought, even when the pixel count is the same. The smaller pixel pitch of the smaller format requires a higher MTF from the lens, not a lower MTF. The MTF at F4 is generally lower than it is at F5.6. However, the MTF is generally higher at F8 than at F11.