Hi C.H., Ken and all,
From: "C.H.Ling" <ch_photo@xxxxxxxxxxxxx>
>I think you have mixed up the capture capability (range) and display
>capability, 4000ED has d-range of 0 to 4.2, it is enough to capture the
>brightness and the darkest range of RVP50.
I'm referring to capture range. But the figures alone are meaningless -- OK,
the 4000ED can "see" up to 4.2D but how clean is the captured image at such
densities? I have never owned a dedicated film scanner, so my experience has
been always noisy shadows -- now I have a CAnoScan 9950F, but the previous
Agfa StudioStar was _much_ worse.
>I don't see why you need to brighten the shadows, brighten the shadows
means
>you are reducing the display d-range.
Sometimes I have to increase the contrast of an underexposed slide. Or
simply want to reduce _global_ D-range (in order to fit inside limited
display capabilities) without sacrificing _local_ contrast -- just like I
would do in the darkroom thru dondging and burning-in.
>Here is a direct scan of RVP50 slide with high contrast scene, from the
>histrogram you can see 4000ED has captured almost every details of the
>brightest and darkest range.
<snip>
><www.accura.com.hk/temp/RVP-direct.jpg>
Seems well captured. However, histograms are meaningless to me -- they
wouldn't tell noise from actual shadow detail...
>Here is the adjusted version, which look more close to the original slide
>view through lightbox:
>
><www.accura.com.hk/temp/RVP-fit-vision.jpg>
It looks much stronger, for sure. But I still prefer the first version,
which has much more shadow detail.
>Also, I don't see limtation on any negative even T-Max 100 since the
d-range
>of negative is much more narrow than slide.
T-Max 100 doesn't have a big density range, IME... a strongly developed
Pan-F or the defunct Technical Pan can be as dark as a slide!
>At the mean time how many
>bit/channel doesn't indicate the capture d-range capability of the scanner,
>too less bit only create potential bending problem for post editing.
Theoretically, each 0.3D equals 1 bit (linear PCM scale), so 4.2 would need
no less tha 14 bits/channel... but again, the A/D conversion may not be
linear and/or noise could invalidate the data from the least significant
bits. Just like digital multimeters, adding another digit does increase the
price steeply, not just for the extra digit itself (almost free) but for the
x10 required precision.
From: Ken Norton <ken@xxxxxxxxxxx>
>I expose slides 1/3 stop higher than I used to for scanning purposes. Neg
>films I still shoot near the rated speed.
It would help lightening the shadows, the most difficult thing for the
scanner to see... but I wouldn't risk the (already delicate) highlights for
scanning purposes. If my intent was a digital end, I probably would shoot
digital from the start -- slides are (or should be) for projectin
pleasure...
Cheers,
--
Carlos J. Santisteban Salinas
IES Turaniana (Roquetas de Mar, Almeria)
<http://cjss.sytes.net/>
--
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