D-Max shootout

[Larry Gebhardt]

Tim, what is your definition of dynamic range in this context? We may be speaking about different things, so here is my interpetation on scanning and printing.

On a hypothetical black and white negative the dMin may be .2 and the dMax may be 1.45. This gives a dRange of 1.25. When you scan this you invert the image and interpret this range from say almost black to almost white. A curve can be used to make this look correct. Printing on paper does the same thing, with paper grades defining the curve and the black and white points.

A transparency has a much higher dRange. The dMin may be .02 where as a the dMax may be 3.0 or more. When you scan this it still needs to be mapped to the same almost white to almost black, but does not need to be inverted. Printing this needs to be compressed to the paper's smaller range.

The big difference is that transparencies need to be viewable as the final result, so they need to have a high dMax to give a good black. Negatives don't because they are only an intermediate step. When you scan either one you map the materials range to your output range.

The different printing methods effectively constrain how black your black can be. Thus on siver you can get a black that absorbs about 4 times as much light (2.4 dmax) over say my 2200 on matte (dMax of 1.8). To me this is an important difference, but to others like Jorge this isn't an issue (sorry if I put words into your mouth Jorge). Why it's important to me is that I can then light the print brighter and have more sparkle and separation in the highlights without making the shadows look muddy. The same reason I love looking at transparencies on a light table.

[tim atherton]

"Tim, what is your definition of dynamic range in this context? We may be speaking about different things, so here is my interpetation on scanning and printing. "

That was the point of my post. Ken raised the issue of scanners and then printing in the context of a discussion on "DMax"

In dealing with scanners you are dealing with Density Range. In dealign with printing (analog or digital) you are dealing with Dynamic Range. My understanding is that the two are not quite (or even) the same thing. But both terms deal with similar issues and both, slightly confusingly, utlize the term DMax, but to slightly different ends.

BTW - as far as I know, it matters not whether the scanned data has to be inverted or not

[Struan Gray]

Tim's friend is talking about the range of densities on film. That is, the range of values you would read with a transmission densitometer. Negative film can faithfully record a wider range of scene brightnesses, and if you insist you can record nine, eleven or I have even heard of fourteen stops of scene brightness on long straight-line B+W films like TMX; but any scene that fits within transparency film's five or so stops, will produce a narrower range of film densities on a negative.





This matters with scanners. Not so much because of density range: any scanner that can handle a velvia slide can handle normal pictorial negatives. The real issue is signal to noise. First, because of film base and fog you always loose a few bits at the low end of the scan range, even if you adjust the scanner's analogue gain to match the lower maximum density of a negative. Second, because of that lower maximum density, and the effect of base+fog, you have to expand the digital values to restore a normal sense of contrast, and that expansion amplifies noise too.





This is a rough scan on an Epson 3200 of a low contrast neg. The blotchy haze is a direct result of my scanner's poor signal to noise, as is the slightly odd loss of saturation in the darker areas like the lower right corner. For this image I rather like the effect, but when I use LF for clarity it's a right pain.

[Robert C. McColloch]

Henry - Well stated; I'm with you.

[Ken Lee]

Sorry if I introduced something off-topic, and thanks for clafifying the terminology.

[Michael Jones]

"If the inkjet print has the same DMax, the same resolution, the same tonality, same permanence, etc, etc, tell me again how silver is better."

Easily: different isn't the same.

Mike

[Frank Petronio]

Struan - doesn't this mean that you need to adjust your film exposure and processing to suit the scanner then? As you would for a Platinum versus a silver print as well...

[Brian Ellis]

I don't know of any excellent silver printer who wants to make prints that show the paper's dMax in some area, so who cares if a test strip reveals that silver has a greater dMax than ink jet? Most of the time a silver print that shows the paper's dMax is going to have little or no shadow detail. For that reason even the ANSI standard for determining a silver paper's density range isn't based on dMax, it's based on 90% of dMax as I recall. I like Dick Arentz's statement to the effect that a print doesn't need to display the blackest possible blacks, all it needs are "convincing blacks." Ink jet prints certainly are able to do that.

[sanking]

"For that reason even the ANSI standard for determining a silver paper's density range isn't based on dMax, it's based on 90% of dMax as I recall. I like Dick Arentz's statement to the effect that a print doesn't need to display the blackest possible blacks, all it needs are "convincing blacks." Ink jet prints certainly are able to do that.

That is of course true. But the reason it is true is because it is virtually impossible to match the characteristic curve of films with the printing process at every point on the curve. This is not true of digital prints, as you remark. And it is also not true of prints that are made with digital negatives, either with silver gelatin papers or with the alternative processes. In these cases it is possible to calibrate input with output through the use of an appropriate corrective curve, and produce a much higher useful maximum reflective density. In my own printing of carbon with digital negatives I am able to use about 98-99% of the maximum possible reflection density of the process on the print, without blocking the shadows and retaining maximum highlight detail. And the figure with kallitype and pure palladium, processes in which I have also printed with digital negatives, is not far behind.

To achieve this, however, you need an optimum curve. For that, consider Mark Nelson's book, Precision Digital Negatives. You might get there by other roads, but Nelson's system works extremely well.

[Struan Gray]

Frank: were I alone on a desert island it would make sense to use a film or processing that made life easier for my 3200, but I don't want to tailor my negs to the weaknesses of what I see as a stop-gap scanner. Better scanners are available, and with time may even become affordable, and I don't want to match my workflow to a temporary weak link. Also, in colour you have to swap films to get the effects of plus and minus development, and I like to keep things simple in the field, with one film and one setting on my meter. I like the look of these sorts of shots when scanned well, or printed conventionally, and mentally adjusting the 3200's proof scans is no harder than the effects of, say, drydown in RA4 printing.

Where I have adjusted to the digitial world is in B+W negatives, where I don't bother with N- development. If anything, a contrasty negative is easier to scan, since scanners are mostly optimised for transparency densities. Of course, you can overdo it, and a scanner won't tame halation or grainy highlights, but in general I now expose for the shadows and let the highlights end up where they will. This assumes the use of TMAX100, where the very long straight line lets you keep adding density to highlights without losing contrast. I do something simiilar in colour, but not when I'm looking for spctroscopic accuracy: Portra 160NC, my favourite film, can turn quite cyan with overexposure.