Digital BW, The Print

Hi!

I'm about to buy a densitometer, probably an X-rite, for measuring my 
B&W prints, and before I buy such an expensive -even when second hand-
  device, I want to know for sure: is a COLOR densitometer suitable 
for B&W?
Or is it better to buy a densitometer that does only B&W?

Thanks!

I g o r
Amsterdam

> From: igorw2001 [mailto:iwesdorp@...]
>
> I'm about to buy a densitometer, probably an X-rite, for measuring my
> B&W prints, and before I buy such an expensive -even when second hand-
>   device, I want to know for sure: is a COLOR densitometer suitable
> for B&W?
> Or is it better to buy a densitometer that does only B&W?

What's a color densitometer? As far as I know, density has nothing to do
with color. If you buy a colorimeter, it ought to be able to do density as
well, by arithmetic on the three color values. Can't say for sure what
software comes with the X-rite, but my spectro will do density, color, and
spectral measurements.

--

Ciao,               Paul D. DeRocco
Paul                mailto:pderocco@...

Hi Paul,

> > I'm about to buy a densitometer, probably an X-rite, for measuring my
> > B&W prints, and before I buy such an expensive -even when second hand-
> >   device, I want to know for sure: is a COLOR densitometer suitable
> > for B&W?
> > Or is it better to buy a densitometer that does only B&W?
>
> What's a color densitometer? As far as I know, density has nothing to do
> with color.

Color is determined by "sensing" density (just like in a scanner or digital
camera does), through RGB or other color filters, so in that regard,
determining what color something is, is based on "reading" the density.

To answer the original question, for B&W, using an RGB analyzer, each
channel will give the same value...that is what grayscale is.  There may be
a mode that doesn't use any filters (or a Neutral Density filter) to read
unfiltered directly.  What specific model are you interested in, BTW?

Regards,

Austin

> Hi!

Hi Igor.
 
> I'm about to buy a densitometer, probably an X-rite, for measuring my 
> B&W prints, and before I buy such an expensive -even when second hand-
>   device, I want to know for sure: is a COLOR densitometer suitable 
> for B&W?
> Or is it better to buy a densitometer that does only B&W?

Speaking as an X-Rite color densitometer owner, I'd say no. Save your money and get a black and white densitometer, or spend more money and get a spectrophotometer. I consider the classic CMY color densitometer to be an evolutionary dead end.

First, my particular X-rite (I'll dig the meter and model number up tomorrow) cannot combine its cyan, magenta, and yellow readings to give you a black and white reading, so I usually just read the magenta channel and call that "density". That gives you readings that are a little off, but not bad. To get an accurate reading, there's a little excel spreadsheet I can punch all three readings (C, M, Y) into, but that's a pain. Three readings for every single reading out. I've never gotten the computer interface working right, so it's a manual process.

Second, the color densitometer is rather limited. The color filters are narrowband, they do not have a spectral response resembling that of the human eye. This means that the densitometer suffers from observer metamerism. When used with process colors (colors made from a mix of cyan, magenta, and yellow dyes) it's not bad. It's only really accurate when used on conventionally printed color photographs. When used with colors produced any other way, colors that appear neutral gray to the human eye will not meter as neutral on the densitometer. The "problem" colors include anything produced by silver gelatin prints (especially if toned), any alternative process (cyanotype, platinum, etc), any "small gamut" ink set, guadtone or hextone process, or any of the new printers like the Epson R800 (cyan, magenta, yellow, red, blue), Canon 9900 (cyan, magenta, yellow, red, green). And it's always a bit off on Epson pigmented inks, even the older cyan, magenta, yellow sets in the 2200, 4000, 7600, 9600. The densitometer might tell you the gray is too magenta, while your eye tells you it's too cyan.

Something like the photospectrometer that Austin mentioned can measure 31 bands of color, instead of three, and put them together in any number of useful ways: true B&W density, process CMY density, or human vision correct LAB color coordinates.

> Something like the photospectrometer that Austin mentioned can measure 31 bands of color, instead of three, and put them together in any number of useful ways: true B&W density, process CMY density, or human vision correct LAB color coordinates.

Oops. It's Paul that has the spectrophotometer.

"Paul D. DeRocco" <pderocco@i...> wrote:
> 
> What's a color densitometer?

It's a three band narrow band densitometer. It shines a white light, and has three photodiodes with narrow band red, green, and bleu filters. When you measure how much red light is reflected, you now know the "density" of the cyan (red absorbing) ink or dye in a print. Similarly, the amount of green reflected tells you the density of magenta (green absorbing) dye, and the amount of blue reflected tells you the density of yellow (blue absorbing) dye. So it measures (and reports) the densities of the three subtractive primaries: cyan, magenta, and yellow.

They're very useful for checking colors when the colors are produced by cyan, magenta, and yellow dyes or inks, such as a color photograph, a CMKY printing press, or a CMYK printer. The narrowband filters cause substantial color errors whenever the printing process doesn't use CMY dyes. 

> As far as I know, density has nothing to do
> with color. If you buy a colorimeter, it ought to be able to do density as
> well, by arithmetic on the three color values. Can't say for sure what
> software comes with the X-rite, but my spectro will do density, color, and
> spectral measurements.

I don't think X-Rite makes color densitometers anymore. I think the spectrophotometer has pretty much replaced them. As you pointed out, the spectro can do the work of the black and white densitometer (one channel, and a filter that matches the photometric response of the eye, the color densitometer (three narrowband filters designed to "dig into" three dye process color) and the colorimeter (three filters that are designed to match the three color "tristimulus" response of the human eye).

And I have to say, it's nice to run into someone else who signs his messages "Ciao".

Ciao!

Joe

<austin@d...> wrote:

> > What's a color densitometer? As far as I know, density has nothing to do
> > with color.
> 
> Color is determined by "sensing" density (just like in a scanner or digital
> camera does), through RGB or other color filters, so in that regard,
> determining what color something is, is based on "reading" the density.

Hi, Austin.

You're just on the edge of understanding. Or maybe I'm on the edge of understanding what you're understanding. In any way, let's give it a little push, and someone will go over some sort of edge, somewhere.

A scanner is just like a color densitometer. It has three narrowband filters, so it can measure the reflectance of narrow red, green, and blue bands, and "see" the density of cyan, magenta, and yellow inks. This lets a scanner get the maximum color separation when scanning cyan, magenta, yellow prints, such as color photographs, or publications printed on a CMYK printing press.

A camera is just like a different piece of equipment, a colorimeter. The colorimeter has broader filters. It's red response extends all teh way from deep red to green (the peak is in the red), the green filter extends pretty much across the entire spectrum (but the peak is in the green) and the red and green responses overlap, so a pure spectra orange (for example) produces a reading in both the red and green channels. Blue, similary, covers a large portion of the spectrum, and overlaps the green (and even the red, a bit). The colorimeter responses mimic the spectral responses of the three different color receptors in the human eye, so a colorimeter can tell you what "human visible" color you're measuring.
 
> To answer the original question, for B&W, using an RGB analyzer, each
> channel will give the same value...that is what grayscale is.

Unfortunatly, that's not quite how it works. The color densitometer is designed for maximum color separation if the colors used are produced from cyan, magenta, and yellow dyes. In any other situation (including B&W photographic prints) it will typically not read equal CMY when shown a perfectly neutral gray.

Koloshor,

> > > What's a color densitometer? As far as I know, density has
> nothing to do
> > > with color.
> >
> > Color is determined by "sensing" density (just like in a
> scanner or digital
> > camera does), through RGB or other color filters, so in that regard,
> > determining what color something is, is based on "reading" the density.
>
> Hi, Austin.
>
> You're just on the edge of understanding. Or maybe I'm on the
> edge of understanding what you're understanding.

Let's see...

> In any way,
> let's give it a little push, and someone will go over some sort
> of edge, somewhere.
>
> A scanner is just like a color densitometer.

...in the regard you state in this next part:

> It has three
> narrowband filters, so it can measure the reflectance of narrow
> red, green, and blue bands, and "see" the density of cyan,
> magenta, and yellow inks.

Agreed, and there is also transmissive, which is what film scanners do, and
what a densitometer for film will do.

> This lets a scanner get the maximum
> color separation when scanning cyan, magenta, yellow prints, such
> as color photographs, or publications printed on a CMYK printing press.

I'm not sure that this is pertinent.

> A camera is just like a different piece of equipment, a
> colorimeter. The colorimeter has broader filters. It's red
> response extends all teh way from deep red to green (the peak is
> in the red), the green filter extends pretty much across the
> entire spectrum (but the peak is in the green) and the red and
> green responses overlap, so a pure spectra orange (for example)
> produces a reading in both the red and green channels. Blue,
> similary, covers a large portion of the spectrum, and overlaps
> the green (and even the red, a bit).

OK...

> The colorimeter responses
> mimic the spectral responses of the three different color
> receptors in the human eye, so a colorimeter can tell you what
> "human visible" color you're measuring.

I'm not sure how true this is, as I have never used a "colorimeter", but
certainly, by design, one can change the bands of the color filters to
achieve what ever results you want...

> > To answer the original question, for B&W, using an RGB analyzer, each
> > channel will give the same value...that is what grayscale is.
>
> Unfortunatly, that's not quite how it works.

I believe it does work that way, and there is certainly enough evidence (and
my own experience) to support my contention.  Have you ever scanned a
grayscale wedge and looked at the resultant RGB values?  How about as an
experiment, you open PhotoShop, and create a step wedge of all equal RGB
values from 0-255 and tell me what you see...

> The color
> densitometer is designed for maximum color separation if the
> colors used are produced from cyan, magenta, and yellow dyes. In
> any other situation (including B&W photographic prints) it will
> typically not read equal CMY when shown a perfectly neutral gray.

I said RGB, not CMY.  RGB behaves exactly as I said it does, gives equal
values for RGB when analyzing a grayscale target.  Granted, they may be some
%1 (or less for true grayscale), but any difference is in the electronics,
not in the concept, or the color being analyzed is not truly grayscale (like
the tinted base of a film).

Also, my calibration cards for my densitometer support my contention.  The
four calibration points of the transmissive card, and the three of the
reflective card all have RGB values within +-0.02 density value (on a scale
of 0-3.6 or so, which would make it less than %1).

I'm not quite sure what it is you were trying to get at here, but please see
if you can elaborate...though, I'm not an expert in colorimeters or
densitometers (if that is what your interest is), but I do know scanner and
digital imaging system design quite well, and can talk knowledgeably about
those in a detailed sense.

Austin

Hi Joe,

> A camera is just like a different piece of equipment, a
> colorimeter. The colorimeter has broader filters.

Why is a color film scanner not a "colorimeter" as well (though I have never
heard of one being called a "colorimeter", but I have never heard of a
camera being called a "colorimeter" either)?

The definition of a colorimeter (apparently in modern terms) is that it uses
"tri-stimulus values" (three imaging primaries), and a color scanner fits
that bill equally as well as a camera (I assume you mean digital camera?
Either way, film or digital, it seems to fit).

Regards,

Austin

> From: koloshor [mailto:wiz@...]
>
> It's a three band narrow band densitometer. It shines a white
> light, and has three photodiodes with narrow band red, green, and
> bleu filters. When you measure how much red light is reflected,
> you now know the "density" of the cyan (red absorbing) ink or dye
> in a print. Similarly, the amount of green reflected tells you
> the density of magenta (green absorbing) dye, and the amount of
> blue reflected tells you the density of yellow (blue absorbing)
> dye. So it measures (and reports) the densities of the three
> subtractive primaries: cyan, magenta, and yellow.
>
> They're very useful for checking colors when the colors are
> produced by cyan, magenta, and yellow dyes or inks, such as a
> color photograph, a CMKY printing press, or a CMYK printer. The
> narrowband filters cause substantial color errors whenever the
> printing process doesn't use CMY dyes.

Isn't that normally called a "colorimeter" because it reads color? I suppose
we're haggling over terminology here, but I've always been told that a
densitometer measures a one-dimensional quantity, a colorimeter measures a
three-dimensional quantity, and a spectrophotometer measures the entire
visible spectrum in (typically) 10nm slices.

--

Ciao,               Paul D. DeRocco
Paul                mailto:pderocco@...

I had focused on these two models (both discontinued, I want to buy 
one second hand):

X-rite 400: B/W ReflectionDensitometer. 
PDF manual at http://www.xrite.com/documents/manuals/en/400-
500_400_Densitometer_Operation_Manual_en.pdf 

X-rite 408: Color Reflection Densitometer. 
PDF manual at http://www.xrite.com/documents/manuals/en/408-
500_408_Densitometer_Operation_Manual_en.pdf 

Are these good options for measuring B/W quadtone inkjet prints?

According to the 408 manual, it shows measurement data in the display 
for v, c, m and y. But what is "v"? In the manual it is 
called "visual". Is that the same as the "k" in cmyk?
And if so, is that the "density" value I should use when
measuring greyscale wedges?

Or should I go for the 400 B/W Reflection Densitometer?

Thanks again.

I g o r

Hi Paul,

> Isn't that normally called a "colorimeter" because it reads
> color? I suppose
> we're haggling over terminology here, but I've always been told that a
> densitometer measures a one-dimensional quantity, a colorimeter measures a
> three-dimensional quantity, and a spectrophotometer measures the entire
> visible spectrum in (typically) 10nm slices.

I agree with your differentiation between colorimeter and spectrophotometer
(except that I'm not sure that a spectrophotometer always reads the entire
visible spectrum, my understanding is the distinction is that it has more
than three "bands"...kind of like the difference between bass & treble
controls and a graphic equalizer).

But, I believe any of them can be densitometers as well, if they read
density.  At least the X-Rite 810 I have reads RGB as density, and they
actually call it a densitometer (not even a colorimeter).  I would also
classify a scanner and a digital camera as densitometers (simply
uncalibrated), and ones that use RGB filters as colorimeters as well...which
brings up an interesting question (related to scanning), at least to me it's
interesting.  Is there any advantage of using a larger number of bands (like
a spectrophotometer) in color film scanning.  I am not sure, as I am no
color expert.

Regards,

Austin

> From: Austin Franklin [mailto:austin@...]
>
> I agree with your differentiation between colorimeter and
> spectrophotometer
> (except that I'm not sure that a spectrophotometer always reads the entire
> visible spectrum, my understanding is the distinction is that it has more
> than three "bands"...kind of like the difference between bass & treble
> controls and a graphic equalizer).
>
> But, I believe any of them can be densitometers as well, if they read
> density.  At least the X-Rite 810 I have reads RGB as density, and they
> actually call it a densitometer (not even a colorimeter).  I would also
> classify a scanner and a digital camera as densitometers (simply
> uncalibrated), and ones that use RGB filters as colorimeters as
> well...which
> brings up an interesting question (related to scanning), at least
> to me it's
> interesting.  Is there any advantage of using a larger number of
> bands (like
> a spectrophotometer) in color film scanning.  I am not sure, as I am no
> color expert.

Someone else (sorry, I've deleted the message) mentioned that a CMY
densitometer differs from a colorimeter in that it has three narrow-band
sensors, instead of three sensors with overlapping spectra to mimic the
eye's response. The latter would be useful for measuring the appearance of
any light source, while the former would only be useful when measuring inks
or dyes with well-known absorption spectra. If you tried to use a CMY
densitometer for profiling your monitor, for instance, it would probably do
a lousy job, because it would be subject to gross metamerism.

If this is the distinction, then I would expect that a CMY densitometer
ought to do a perfectly good job on B&W prints, but I'd rather have a more
versatile instrument.

As to your last question, I doubt having a large number of bands would be
useful in color film scanning. It would be very cool to have a camera with
lots of bands, though.

--

Ciao,               Paul D. DeRocco
Paul                mailto:pderocco@...

Hi Paul,

> As to your last question, I doubt having a large number of bands would be
> useful in color film scanning. It would be very cool to have a camera with
> lots of bands, though.

You're right about scanning film, as the film isn't really "color" per se,
it is typically 3 different layers each of one color.  What "color" is the
4th layer of the Fuji Press "4th layer" films?  Do you have any knowledge of
that?  I have not tried scanning that film yet, but it is great for "mixed
lighting", in other words, incandescents and fluorescents etc. without the
yellow cast, and the prints come out great.

Regards,

Austin

> From: igorw2001 [mailto:iwesdorp@...]
>
> According to the 408 manual, it shows measurement data in the display
> for v, c, m and y. But what is "v"? In the manual it is
> called "visual". Is that the same as the "k" in cmyk?
> And if so, is that the "density" value I should use when
> measuring greyscale wedges?

I believe it's just the average (perhaps weighted) of C, M and Y. An e-mail
to X-Rite might clear this all up.

--

Ciao,               Paul D. DeRocco
Paul                mailto:pderocco@...

> From: Austin Franklin [mailto:austin@...]
>
> What "color" is the
> 4th layer of the Fuji Press "4th layer" films?  Do you have any
> knowledge of
> that?  I have not tried scanning that film yet, but it is great for "mixed
> lighting", in other words, incandescents and fluorescents etc. without the
> yellow cast, and the prints come out great.

Dunno. Hadn't even heard of it. I wonder if it's a black layer...

--

Ciao,               Paul D. DeRocco
Paul                mailto:pderocco@...

In analytical chemistry the difference between a colorimeter and a 
spectrophotometer is basically in the method of producing the 
"monochromatic" light source used for measurement.  A colorimeter 
typically uses filters although some are now using arrays of LED's and 
produce a narrow band of wavelengths rather than strictly monochromatic 
wave lengths.  A spectrophotometer is capable of producing a spectrum 
of distinct  monochromatic wavelengths and typically uses a diffusion 
grating and a series of pre-filters . Some older spectrophotometers 
used prisms rather than gratings. The X-Rite 810 etc would fit the 
category of colorimeter. Calling them densitometers simply means they 
can do the conversion from percent transmission, %T,  or percent 
reflectance,  %R to optical density, O.D., D,  (mathematically, D = 2 - 
log10  % T)  internally so that they can  output  a linear rather than 
a logarithmic result.

John Bernard Henry's "Controls in Black and White Photography, 2nd 
edition" has a good discussion of densitometry on pages 46-54. It was 
written before the digital age but is still very relevant and if you 
are really into the guts of B&W photography particularly with film a 
must have in my view.

Roger

On Sep 26, 2004, at 11:30 AM, Paul D. DeRocco wrote:



[Non-text portions of this message have been removed]

> From: Austin Franklin [mailto:austin@...]
>
> If you haven't used the Fuji Press (400 & 800) film, I strongly suggest
> trying it.  It allows me to shoot high speed (which to me means not in
> sunlight) color with no yellow cast, which is something that has
> always been
> an issue for me with high speed color films, hence previously always
> shooting B&W at > 400ASA.

Unless I take up MF or LF photography, I'm unlikely ever to use film again.
;-)

--

Ciao,               Paul D. DeRocco
Paul                mailto:pderocco@...

Hi Paul,

> > What "color" is the
> > 4th layer of the Fuji Press "4th layer" films?  Do you have any
> > knowledge of
> > that?  I have not tried scanning that film yet, but it is great
> for "mixed
> > lighting", in other words, incandescents and fluorescents etc.
> without the
> > yellow cast, and the prints come out great.
>
> Dunno. Hadn't even heard of it. I wonder if it's a black layer...

If you haven't used the Fuji Press (400 & 800) film, I strongly suggest
trying it.  It allows me to shoot high speed (which to me means not in
sunlight) color with no yellow cast, which is something that has always been
an issue for me with high speed color films, hence previously always
shooting B&W at > 400ASA.

Regards,

Austin

Hi Paul,

> > If you haven't used the Fuji Press (400 & 800) film, I strongly suggest
> > trying it.  It allows me to shoot high speed (which to me means not in
> > sunlight) color with no yellow cast, which is something that has
> > always been
> > an issue for me with high speed color films, hence previously always
> > shooting B&W at > 400ASA.
>
> Unless I take up MF or LF photography, I'm unlikely ever to use
> film again.
> ;-)

Ah, I was unaware that you had gone entirely digital for 35mm.  Yes, I shoot
a lot of MF (mostly B&W).  I still shoot film (color mostly) for 35mm
though...as I really like the convenience of simply dropping it off and
getting it back double prints with no fuss, no muss.  Granted, it is
becoming increasingly easier to do this with digital in *some* places, but
not so around here yet.

I also hate digital cameras ;-) (not really, as I have a couple of MF backs
I use in the studio quite a bit) as every time I go to use my small format
ones, they have a battery problem...why on earth do they make them take AAs,
yet they don't work on standard alkaline AAs...they *NEED* NiCADs...at least
mine do...so I have to keep a set charged, or wait until they're
charged...what a pain.  I almost got the DigiLux 2, but the LCD viewfinder
is really poor...so until there is a full frame digital that is not the size
of a house (or has an exceptional fixed FAST lense on it), and has a decent
viewfinder, I'll stick to what I currently use for 35mm.

What are you using?  The only one I'd consider right now is the 1Ds (and
actually the Contax D1, though it's only 6MP, but that is really sufficient
for what I shoot miniature format for), but it's (they are) just too bulky
for me.  I'd really like to get one that is just monochrome...but understand
the market is very limited for this.  I do have a monochrome one for the
studio.

Regards,

Austin

> From: Austin Franklin [mailto:austin@...]
>
> I also hate digital cameras ;-) (not really, as I have a couple
> of MF backs
> I use in the studio quite a bit) as every time I go to use my small format
> ones, they have a battery problem...why on earth do they make
> them take AAs,
> yet they don't work on standard alkaline AAs...they *NEED*
> NiCADs...at least
> mine do...so I have to keep a set charged, or wait until they're
> charged...what a pain.  I almost got the DigiLux 2, but the LCD viewfinder
> is really poor...so until there is a full frame digital that is
> not the size
> of a house (or has an exceptional fixed FAST lense on it), and
> has a decent
> viewfinder, I'll stick to what I currently use for 35mm.
>
> What are you using?  The only one I'd consider right now is the 1Ds (and
> actually the Contax D1, though it's only 6MP, but that is really
> sufficient
> for what I shoot miniature format for), but it's (they are) just too bulky
> for me.  I'd really like to get one that is just monochrome...but
> understand
> the market is very limited for this.  I do have a monochrome one for the
> studio.

I've got a Canon D60 and a 10D, along with three Canon lenses. They use
lithium ion batteries, which last for hundreds of shots (at least without
flash), so they're quite convenient. DSLR technology isn't perfect, but I
think the picture quality is excellent. I lugged the pair up a steep trail
in Yosemite a couple days ago, and the weight was an annoyance, but no
worse. The 1Ds is way out of my range, as is the just-announced 1Ds Mark II
(16.7 megapixel).

I'm also such a computer nut that I prefer looking at pictures on my monitor
than on paper, so the convenience of getting double prints means nothing to
me. I only print what I intend to hang on the wall, or give away to friends,
which is only a tiny fraction of what I shoot.

I'd love a monochrome DSLR, too. It would be cool if someone could come up
with some witches' brew to wash the Bayer filter off a standard sensor. I'd
be happy to dedicate one DSLR body to B&W and IR.

--

Ciao,               Paul D. DeRocco
Paul                mailto:pderocco@...

Hi Paul,

> I lugged the pair up a steep trail
> in Yosemite a couple days ago, and the weight was an annoyance, but no
> worse.

I really shouldn't complain about size/weight though, as I lug a Hasselblad
205 all around with the 110/2...but the current issue is I have three small
children, and lugging a camera that can't be handled in one hand doesn't cut
it...so I primarily use a Contax G2 right now.

> I'm also such a computer nut that I prefer looking at pictures on
> my monitor
> than on paper...

Well, me too, that's why I scan, and I find the Piezo output from my 3000
from negatives scanned in grayscale (as the Leaf45 does using a single ND
filter) give me better prints than I was ever able to do in the darkroom,
and I was no slouch in the darkroom.

> so the convenience of getting double prints means
> nothing to
> me.

Yeah, try telling that to my Greek mother-in-law ;-)

> I only print what I intend to hang on the wall, or give away
> to friends,
> which is only a tiny fraction of what I shoot.

You apparently don't have kids, and a Greek mother-in-law!  When my kids get
a bit older, I'll be able to go back to carrying around MF, I hope!

> I'd love a monochrome DSLR, too. It would be cool if someone could come up
> with some witches' brew to wash the Bayer filter off a standard
> sensor. I'd
> be happy to dedicate one DSLR body to B&W and IR.

Someone actually does...but only selected models.

Regards,

Austin

> From: Austin Franklin [mailto:austin@...]
>
> Yeah, try telling that to my Greek mother-in-law ;-)

Actually, I have a Greek mother. ;-)

> Someone actually does...but only selected models.

If you're referring to the "IR guy", he doesn't remove the Bayer filter,
only the anti-alias/IR-block filter. In fact, I bought my used D60 recently
for the purpose of sending him and having him do an IR conversion on it. I
decided to use it as-is for a while, just to get used to it. Now I'm not so
sure I want to give up the luxury of having two color DSLR bodies, so that I
don't have to do so much lens swapping.

--

Ciao,               Paul D. DeRocco
Paul                mailto:pderocco@...

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Paul D. DeRocco" <pderocco@i...> wrote:
> > From: Austin Franklin [mailto:austin@d...]
> >
> > What "color" is the
> > 4th layer of the Fuji Press "4th layer" films?  Do you have any
> > knowledge of
> > that?  I have not tried scanning that film yet, but it is great for "mixed
> > lighting", in other words, incandescents and fluorescents etc. without the
> > yellow cast, and the prints come out great.
> 
> Dunno. Hadn't even heard of it. I wonder if it's a black layer...

If memory serves, it's sensitive to a color between green and blue, and develops a dombination of magenta and ywllow dye, favoring the magenta. So the negative still ends up containing three dyes, cyan, magenta, and yellow.

Roger L Sopher <rlsopher@c...> wrote:
> In analytical chemistry the difference between a colorimeter and a 
> spectrophotometer is basically in the method of producing the 
> "monochromatic" light source used for measurement.  A colorimeter 
> typically uses filters although some are now using arrays of LED's and 
> produce a narrow band of wavelengths rather than strictly monochromatic 
> wave lengths.  A spectrophotometer is capable of producing a spectrum 
> of distinct  monochromatic wavelengths and typically uses a diffusion 
> grating and a series of pre-filters .

Fascinating. I guess an absorbtion spectrometer bears more resemblance to a negative densitometer than a print densitometer or analyzer. 

> Some older spectrophotometers 
> used prisms rather than gratings. The X-Rite 810 etc would fit the 
> category of colorimeter.

All the filtering is done on the received light, typically a diffraction grating in front of a small linear CCD. This allows the spectrophotometer to do double duty, measuring the spectra of emissive targets such as CRT and LCD monitors, or the spectrum of the light in one's print viewing environment. For print densitometry, the spectrophotometer contains a small white light source (which typically has a spectrum that includes ultraviolet, because papers have flourescent brightners added). 

> Calling them densitometers simply means they 
> can do the conversion from percent transmission, %T,  or percent 
> reflectance,  %R to optical density, O.D., D,  (mathematically, D = 2 - 
> log10  % T)  internally so that they can  output  a linear rather than 
> a logarithmic result.

Yup. Except that the convention is that color densitometers have three narrowband filters, colorimeters have three wide band colormetric filters, and spectrophotometers have an awful lot of narrowband filters or a diffraction grating and a fairly high resolution CCD to read it. It's not a great convention, but it's all we've got...

"Paul D. DeRocco" <pderocco@i...> wrote:
 
> I'd love a monochrome DSLR, too. It would be cool if someone could come up
> with some witches' brew to wash the Bayer filter off a standard sensor. I'd
> be happy to dedicate one DSLR body to B&W and IR.

I'm currently destroying sensors in cruel and inhuman attempts to achieve exactly that. 

The "witches brew" is a hot solvent that flushes out the microlenses and the RGB color filters. Then there's the task of resealing the chip...

I'm also tinkering with using a high power UV light source (built for curing UV sensitive adhesives) to fade the filters, hopefully without turning the microlenses opaque.

Ciao!

Joe

"Paul D. DeRocco" <pderocco@i...> wrote:
> As to your last question, I doubt having a large number of bands would be
> useful in color film scanning.

It wouldn't. Because of the nature of the dyes used in film, you can get  pretty much everything the film has to offer with three narrowband filters. Throw in a fourth band, infrared, for dust and scratch detection (the dyes in color film are basically totally transparent to IR, dust and scratches aren't) and you're all set.

> It would be very cool to have a camera with lots of bands, though.

High spectrum cameras are a lot of fun. I got to work with two different systems. One had the filter wheel from hell in front of a monochrome CCD. 10nm filters, 31 of them. Took about a minute and a half to run through the whole wheel. That one had a 1000x1000 CCD. A rare and beautiful antique. (probably about 1995). I could easily put together something with todays technology that could run that 31 color wheel in 3 seconds flat at 6mp instead of 90 seconds at 1mp.

Another was a slit scanning camera. The whole camera rotated, the lens projected an image that was masked off into a vertical slit, which focused on a horizontal diffraction grating, which then gave you vertical location along the y axis and wavelength along the x axis. That one had a DALSA 6mp imager, which was running about 20 images/second. The camera stepper motor drive ran 20 steps/second, and it could image a 2000x2000 scene in 100 seconds, with 151 band (2nm) or even 301 band (1nm) color resolution. That's probably near state of the art. It's enough to do some forms of chemical analysis at a distance, in addition to color perception. ;)

> From: koloshor [mailto:wiz@...]
>
> I'm currently destroying sensors in cruel and inhuman attempts to
> achieve exactly that.
>
> The "witches brew" is a hot solvent that flushes out the
> microlenses and the RGB color filters. Then there's the task of
> resealing the chip...
>
> I'm also tinkering with using a high power UV light source (built
> for curing UV sensitive adhesives) to fade the filters, hopefully
> without turning the microlenses opaque.

Interesting. Doesn't the chip have glass passivation under the plastic
stuff?

--

Ciao,               Paul D. DeRocco
Paul                mailto:pderocco@...

koloshor wrote:


>>Some older spectrophotometers 
>>used prisms rather than gratings. The X-Rite 810 etc would fit the 
>>category of colorimeter.
> 
> 
> All the filtering is done on the received light, typically a diffraction grating in front of a small linear CCD. This allows the spectrophotometer to do double duty, measuring the spectra of emissive targets such as CRT and LCD monitors, or the spectrum of the light in one's print viewing environment. For print densitometry, the spectrophotometer contains a small white light source (which typically has a spectrum that includes ultraviolet, because papers have flourescent brightners added). 

But some models can be bought with UV filters on the light source 
and in some cases in front of the sensor. So three models in total.

Ernst

What has not been mentioned in this thread is the chance that 
your spectrometers do not measure high Dmax as precise as B&W 
densitometers do.  At least I don't trust my SpectroCam much at 
that level.

Ernst

"Paul D. DeRocco" <pderocco@i...> wrote:
> > From: koloshor [mailto:wiz@n...]
> >
> > I'm currently destroying sensors in cruel and inhuman attempts to
> > achieve exactly that.
> >
> > The "witches brew" is a hot solvent that flushes out the
> > microlenses and the RGB color filters. Then there's the task of
> > resealing the chip...
> >
> > I'm also tinkering with using a high power UV light source (built
> > for curing UV sensitive adhesives) to fade the filters, hopefully
> > without turning the microlenses opaque.
> 
> Interesting. Doesn't the chip have glass passivation under the plastic
> stuff?

I'd hope so. ;)

Seriously, I'm not too worried about the chip itself. The big problem
is getting the window off, then disolving all the organics and leaving
the inorganics (chip, bonding wires, etc) clean. Then getting
everything clean enough to put the window back on.

Or the old "drill a hole in the window, fill and flush" approach...

Koloshor, do you know the meter and model number of your particular X-
rite? Was it the 408?

Thanks,

I g o r

"igorw2001" <iwesdorp@c...> wrote:
> Koloshor, do you know the meter and model number of your particular X-
> rite? Was it the 408?

Just checked. Mine's a 414. Sorry about the delay.

Ciao!

Joe

Koloshor, thanks for taking the trouble.

In the meanwhile, I asked X-rite about the mysterious "V" or "Visual" 
value that is shown as a read out on the 408 color densitometer (as 
said, you can toggle between Y, M, C and "V"). They wrote me: "Visual 
is the neutral reporting of Status T,E,G densitometry. It is not a 
pure average of the 3 colors but a weighting of the results based on 
ANSI/ISO specifications".
Difficult, but I guess it means I can use "V" for measuring 
greyscales.

I g o r