Re: Does MF color slides scanning in 24 bit still make sense
Re: Does MF color slides scanning in 24 bit still make sense
- Subject: Re: Does MF color slides scanning in 24 bit still make sense
- From: Ernst Dinkla <email@hidden>
- Date: Mon, 18 Jan 2016 15:44:52 +0100
To create less flare in desktop scanners would require other sensor types
than the usual linear or 3 linear CCDs. Even if the halogen, CCFL or linear
LEDS are replaced by something like a flying spot illumination there will
be neighbour sensor wells receiving light that should not go there. I have
thought about different geometries in the optical path, with for example
the linear CCD at an angle to the scan direction + a flying spot
illumination but then the usual narrow split mirror path would not be
possible and the data stream more complex
Googling for the use of RGB LEDstrips (+ Ulbricht sphere etc) to make an
ideal light source for slide copying I came across this thread where they
use the RGB LEDstrips and more:
http://www.dpreview.com/forums/thread/3546695
They aim at LF films there, so step and repeat copying. I think they should
mask the film more, if the videos show actual practice.
I use wet mounting on the Coolscan 8000 and was probably the first one to
do that. In a camera/film copying system for B&W 35mm film strips I think
it should be possible to make a narrow glass channel filled with fluid that
allows a faster wet mounting/embedding when strips are pulled through frame
by frame and still keep focus then by an AF system. In movie film copying
other wetting systems are used (but with flying spot illumination which
reduces flare).
The Silverfast and Vuescan multi sampling settings for several scanners do
deliver if dynamic range has to be increased.
On optics, the best 1:1 macro resolution lenses are probably the
Printing-Nikkor lenses. Marco Cavina is quite sure that the larger Coolscan
8000 has that lens design integrated as well, explains part of the pricing.
It can not be the film holder + frame switching, worst part in the design
of that scanner.
http://www.marcocavina.com/articoli_fotografici/Nikon_EL-Nikkor_lenses/00_pag.htm
Bottom page, in Italian but Google does its best in the translation.
Met vriendelijke groet, Ernst Dinkla
Dinkla Grafische Techniek
Quad, piëzografie, giclée
www.pigment-print.com
On Sun, Jan 17, 2016 at 11:35 PM, Don Hutcheson <email@hidden> wrote:
> The main issue with camera capture vs drum scanning is not resolution nor
> dynamic range, it’s flare.
>
> Before discussing what I mean, let’s look at the question of resolution:
>
> Using a high quality, short focal length enlarger lens and sufficient
> stitching, any high-MP camera can easily equal or exceed the so-called
> “sampling resolution” (pixels per inch) of any drum scanner, for whatever
> that’s worth. Pick your pixel count and you can achieve it, subject to a
> little care in the stitching.
> But how much resolution do you need? The sharpest low-ISO slide films
> were capable of perhaps 60 line pairs/mm at 40% MTF, which, according to
> Nyquist, needs a sampling rate of about 6,000 dpi, give or take. But good
> luck finding a film original with such extraordinary image detail. It
> would have to have been captured (a.) on Kodachrome 25 or similar, (b.)
> with a very fine macro optic at optimum aperture and (c.) on a perfectly
> stable tripod, etc. Most of the images we think of as “tack-sharp” have
> about half that real resolution if they’re lucky, and we love them.
> Bottom line - whatever sampling resolution you decide you need, you can
> get it by camera stitching. Albeit with patience.
>
> Of course there’s the question of whether camera-captured pixels are as
> "sharp” as drum scanner samples. I won’t get into that, except to say that
> you’d be surprised how cheap some drum scanner lenses were. The notion
> that Crosfield, Hell, Screen and ICG spent the farm on high quality
> apochromatic microscope lenses is a little exaggerated.
>
> Next let’s look at dynamic range.
>
> Most good slide films have a dynamic range of at least 4.0 (max. - min.
> dye density) which corresponds to an f-stop range around 14.
> Interestingly, most drum scanners struggled to get anywhere near 4.0 DR.
> The log amp (logarithmic photomultiplier tube amplifier) in Crosfield
> scanners was artificially limited to about 3.0 but I was able to squeeze
> about 4.3 out of ICG scanners, with a bit of PMT noise.
> Few digital cameras can approach a 14 stop range in one shot, but with
> careful HDR, they can easily exceed it. However this is where flare begins
> to muddy the waters (or shadows).
>
> The flare problem.
>
> The one area in which drum scanners easily trounce flat-bed scanners is
> gross optical flare. The only flare you’ll find in a drum scanner is
> within a few microns of the scanning spot, the actual flare radius
> depending on the scanning plane optics. However all line-at-a-time (a.k.a.
> “CDD” or “flat bed”) scanners suffer from a much more severe problem that I
> call “linear flare", manifested as streaks of unwanted lightness where
> light and dark image areas meet. What makes this flare offensive is that it
> only occurs at right angles to the scanning direction. These directional
> flare lines are caused by the fact that light image areas must be
> illuminated at the same time as dark areas in the same scan line are being
> sampled. Drum scanners don’t do this.
>
> Camera captures also suffer from optical flare in the lens itself, but
> lens flare is often less noticeable (unless you go looking for it) than
> flat-bed scanner flare, because (a.) it’s “radial” and therefore
> symmetrical around the bright detail and (b.) it is often mistaken for
> flare in the original, i.e. caused by the original taking lens.
> Unfortunately, if you rely on HDR to expand your camera-copy dynamic range,
> the copy-camera’s lens flare can actually be magnified. That’s because the
> HDR process typically relies on some form of blurred masking to blend light
> and dark exposures. The blurred mask can itself contribute to ghostly
> shadow anomalies if you’re not careful.
>
> The good news is that scanner-produced flare (whether linear or radial) is
> mostly noticeable when you have to exhume dark shadow detail, i.e. open up
> an under-exposed transparency. Normally-exposed slide scans usually look
> fine.
>
> OK. That’s enough typing for a cold New Jersey Sunday.
>
> ........................................................
> Don Hutcheson, President
> HutchColor, LLC
> Washington, NJ USA
> email@hidden
> M: 908-500-0341
> ........................................................
>
>
>
>
>
>
> On Jan 17, 2016, at 15:00 , email@hidden wrote:
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> > 1. Re: Does MF color slides scanning in 24 bit still make sense
> > (Paul Schilliger)
> > 2. Re: Does MF color slides scanning in 24 bit still make sense
> > (Mike Strickler)
> >
> >
> > ----------------------------------------------------------------------
> >
> > Message: 1
> > Date: Sat, 16 Jan 2016 22:37:53 +0100
> > From: Paul Schilliger <email@hidden>
> > To: Ernst Dinkla <email@hidden>
> > Cc: "email@hidden"
> > <email@hidden>
> > Subject: Re: Does MF color slides scanning in 24 bit still make sense
> > Message-ID: <email@hidden>
> > Content-Type: text/plain; charset="ISO-8859-1"
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> >
> > ------------------------------
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> > Message: 2
> > Date: Sat, 16 Jan 2016 20:36:41 -0800
> > From: Mike Strickler <email@hidden>
> > To: email@hidden
> > Subject: Re: Does MF color slides scanning in 24 bit still make sense
> > Message-ID: <email@hidden>
> > Content-Type: text/plain; charset=us-ascii
> >
> > I think one should be clear about the intended purpose of such DSLR
> captures. Expectations should probably be set at slide shows on computer
> displays and small prints--IOW good quality digital archiving. Sharp prints
> at 10X or greater enlargement may require higher spatial and tonal
> resolution (and lower flare) than these cameras can achieve. Best results
> with a camera will be had with a dedicated copying lens such as the
> Apo-Rodagon D and a slide copier. Enlarging lenses can also do a good job.
> Be mindful that the the focus error alone with mounted slides may seriously
> compromise results. A PMT drum scanner will, on the other hand, fix the
> entire film orignal at a precise distance from the lens, which is normally
> an apochromatic microscope objective, diffraction-limited at below f/1. 36
> MP captured on such a device is a rather different thing from what you will
> get on a Nikon D800. A proper drum scan for a 10X enlargement of a medium
> format film will begin at 4,000 dpi, yielding over 60 MP, and will reveal
> the subtlest gradations and grain structure. A compromise between speed and
> quality might be found in a dedicated slide scanner such as the Nikon
> Coolscan. But even here wet mounting is recommended, and this again takes
> too much time for most people trying to record many images. My preference
> would be to drum scan any image to be critically printed and shoot the rest
> on a slide copier using a copy lens and decent DSLR.
> >
> >
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