Bart van der Wolf wrote:
>
> "Ernst Dinkla" <(E-Mail Removed)> wrote in message
> news:2811$44912eae$3ea3eb6a$(E-Mail Removed)...
>>
>> Everybody here seems to agree that the mask in color negative
>> film is a good thing. I think we would be better off without a
>> mask if it is for scanning.
>
> The benefit would manifest itself in reduced scan times if compared with
> masked CN film. For pictorial, portrait or product photography however,
> color accuracy should be the deciding factor IMHO. Films like Portra NC
> scan quite well, and they are not terribly dense (which also means they
> can become grainy with boosted contrast/gamma). I usually overexpose
> them a little (1/3rd stop) for scanning, it helps shadow definition and
> may reduce graininess a bit.
The color could be sufficiently corrected by custom profiling.
I do not see a reason for masking if the film itself is no
longer used for analogue prints. Increasing the AG (exposure
time actually) for Blue at 3.5x and Green at 2.5x and on top
of that a correction profile doesn't sound as a better
solution than good software + a custom profile. Slides are
scanned too and they also suffer of color inaccuracy but that
is solved with profiling as well. The inconsistency of the
mask influenced by the development process is a known issue,
so at one hand there is an analogue color accuracy created by
the mask but it also creates inaccuracies.
I also use 100/160-320/400 for Portra NC. Portra has been made
more suitable for scanning (including new surface coats for
better ICE results since 2005), it still is a color negative
film for analogue prints in the first place. Even the Agfa
Aviphot can still be used for analogue prints if needed. I
included it as an example of a maskless film but do not see it
as a ideal maskless film for scanning.
>
>> Agfa and Kodak made maskless negative films for aerial photography and
>> copy work that had to be scanned. Making color prints was not the
>> first goal of that material. There must be a good reason why they made
>> it maskless.
>
> Indeed, color accuracy isn't the main goal with Aerial photography, but
> feature discrimination usually is, so they went for resolution and
> contrast (to cut through the haze) and a simpler/cheaper design. The
> faster scan speed apparently played a roll as well, as they make
> specific mention of it (but they also hasten to add that the colors are
> clean and saturated).
>
> In the PDF link you provided, it is striking that they omitted the
> Spectral Dye Density Curves commonly provided to illustrate the amount
> of secondary absorptions (implying the effect a mask could have on color
> accuracy/saturation).
>
> Wat also is clear, is that the goal was for a neutral film base and,
> while they came close, there is still some scanner gain/channel exposure
> adjustment needed (as far as we can take the graphs for accurate), but
> it might scan twice as fast as a masked film. Also clear is that the
> non-parallel RGB density curves will require a white balancing (+
> complex gamma adjustment) after invertion, as usual, because we're not
> printing but scanning.
>
>> Better S/N and grain is mentioned for the Aviphot maskless films.
>>
>> http://www.agfa.com/docs/sp/aerial/a...4-06-15_en.pdf
>
> As usual, by relaxing a few constraints, it is possible to improve some
> other aspects.
>
> In most types of aerial photography, resolution (for high altitude
> recognisance or topography) or speed (both film sensitivity and
> processing speed) are the more important aspects. For low altitude
> oblique photography, films with more contrast allow to cut through the
> haze (heavy UV-filtering alone is not enough), unless there is an
> exceptionally clear atmosphere.
>
> Bart
I'm not convinced that a general purpose color negative film
needs a mask if it is only used for scanning. The Aviphot x100
is just one of several aerial Agfa films, some with higher
contrast, some with a mask, some with higher speeds. They are
made more suitable for Aerial photography but their features
for that task are not in a 1:1 relation with being maskless.
The color accuracy of a masked film is more in relation to
analogue printing but maskless will not be more of a problem
in scanning than slides are. The same secondary absorptions
happen with slide photography and can be dealt with in
profiling and software.
There's some analogy in the separation workflow of printing.
Thirty years ago it was a long and slow process to separate
slides for FC offset printing. Secondary absorptions in the
film emulsion and the printing inks had to be taken care off.
Film masks were needed and special analogue methods + color
masking films were used. Today that's all done with software
for even the simplest desktop inkjet. Custom ICC profiling on
top of that to increase the accuracy. I do not see why that
can't be done with color negatives.
Of course one could use slide film. But reversal film has in a
way a similar dual task, it is still made to suit projection
display. For that it has a higher contrast so it can't have
the tone compression and latitude a color negative film has.
An ideal scanner film could be negative or positive but should
have a dynamic range and Dmax that just suits the best desktop
scanners like the Nikon 9000 and still have the nice
compression/latitude of the color negative film. Color
inaccuracies can be cured in another way. That film will be
worthless for any other purpose than scanning.
Ernst
--
--
Ernst Dinkla
www.pigment-print.com
( unvollendet )
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