Contrast filter spacing

I have been curious about using an old Beseler PM2 color analyzer to read
the color differences in contrast printing filters. Today I did some testing
under my Aristo V54 cold lamp using both a Multigrade filter set (about 2
years old) and a new set of Polymax contrast filters. I found that the
Multigrade set did some odd things above the #3-1/2 filter. It would appear
that the magenta/yellow balance in the #4 would REDUCE contrast when moving
up from a #3-1/2, and appears to be tinted to produce contrasts below the
#2-1/2 filter! Here's a link to a web page with a graph.

http://www-schneider.viscom.ohiou.ed...comparison.jpg

I plan to use a step wedge to measure actual paper contrast with these
filters, but before I undertake that lengthy exercise, I wondered if someone
has had a similar experience. Do I have a set of filters that is labeled
incorrectly?

Polymax filters behaved like I would expect of a set of contrast filters,
but the Ilford filters didn't. I'm looking for possible explanations before
I get the next chance to dive into the darkroom again to sort through this
further.

BTW, the unfiltered Aristo V54 lamp reads +10 magenta if you wish to compare
it to the filtered light readings.

Bill Schneider

"William Schneider" wrote

Beseler PM2 color analyzer ... [Ilford multi-] contrast filters ...
Aristo V54

http://www-schneider.viscom.ohiou.ed...comparison.jpg

[What gives with #4 - #5?]

There is an overall 1-stop density increase when going from a #3 1/2
to a #4 filter, but I can't see how this alone would give the effect shown.

I am taking it the filters look plausible and they visually
progress monotonically from yellow to magenta - or do they seem to
'back up' and turn yellowish again?

If it is possible, I would like to see both the yellow and magenta
readings plotted rather than just the difference.

The only explanation I can offer is that the PM2 is at the
limit of it's measuring range and the readings are becoming non-linear
for the Ilford filter set.

I don't have an Ilford set so I am sorry but I can not offer an
independent set of readings.

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
Remove spaces etc. to reply: n o lindan at net com dot com
psst.. want to buy an f-stop timer? nolindan.com/da/fstop/

I am taking it the filters look plausible and they visually
progress monotonically from yellow to magenta - or do they seem to
'back up' and turn yellowish again?

They do not progress smoothly in color, and there is indeed a reversing of
color when viewing them. I had first attributed that to the ND in the
filters to keep exposure constant, but it looks like the eyeball test was on
the mark.

I just made some test prints using a step wedge (they are still wet), and
the #3-1/2 filter produces substantially higher contrast than the #4 does.
Viewing them wet (and that will change a bit with dry-down), I count 9 steps
using the #4 filter, and 6 steps using the #3-1/2 filter. The step wedge
increment is 0.1.

It looks like I need to get a new filter set, or at least re-label the
existing filters in the kit.

Bill Schneider

"William Schneider" wrote in message .. .


Fading?


I have been curious about using an old Beseler PM2 color analyzer to read
the color differences in contrast printing filters. Today I did some testing
under my Aristo V54 cold lamp using both a Multigrade filter set (about 2
years old) and a new set of Polymax contrast filters. I found that the
Multigrade set did some odd things above the #3-1/2 filter. It would appear
that the magenta/yellow balance in the #4 would REDUCE contrast when moving
up from a #3-1/2, and appears to be tinted to produce contrasts below the
#2-1/2 filter! Here's a link to a web page with a graph.

http://www-schneider.viscom.ohiou.ed...comparison.jpg

I plan to use a step wedge to measure actual paper contrast with these
filters, but before I undertake that lengthy exercise, I wondered if someone
has had a similar experience. Do I have a set of filters that is labeled
incorrectly?

Polymax filters behaved like I would expect of a set of contrast filters,
but the Ilford filters didn't. I'm looking for possible explanations before
I get the next chance to dive into the darkroom again to sort through this
further.

BTW, the unfiltered Aristo V54 lamp reads +10 magenta if you wish to compare
it to the filtered light readings.

Bill Schneider

Picking up an old (6/13/04) thread:

"William Schneider" wrote

http://www-schneider.viscom.ohiou.ed...comparison.jpg

[The series seems to repeat at grade #4, and backs up to grade 2. Step
tablet tests confirm the photometry readings.]

I just got a box of Ilford MG 6" filters from B&H, and they
seem to be identical to the above.

Was this problem ever solved?

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
Remove spaces etc. to reply: n o lindan at net com dot com
psst.. want to buy an f-stop timer? nolindan.com/da/fstop/

I just got a box of Ilford MG 6" filters from B&H, and they
seem to be identical to the above.

Did you ever find out the reason or have the problem resolved?


Not really. It still seems like a case of mixing up the filters during
labeling. Paper contrast responds to the filters in a zig-zag way that
supports the color analyzer findings mentioned in my earlier post.

I've been conducting experiments with both Multigrade and Polymax papers
using Multigrade and PM filter sets. I don't have all the possible
combinations plotted, but here's a link to what I've found so far:

http://www-schneider.viscom.ohiou.ed...ast-grades.pdf

You can see that the Multigrade filter set indeed produces higher contrast
with the #2-1/2 filter than with the #4. I'm fairly confident in the data
for those two filters because the step wedges were exposed within a few
minutes of each other and developed together.

You will also see an odd sequence with Polymax filters and Polymax paper -
the # 1/2 filter placed higher in contrast than the #1. I suspect some
experimental error in there somewhere and it may be caused by exposing and
printing the step wedges for these two filters during two different
sessions days apart. That result was unexpected, and I'm trying to resolve
the experimental error.

I have also found that the Polymax paper produces a much nicer curve shape
than Multigrade when using low contrast filters Multigrade produces a
"hump"
in the middle of the curve (I see it using the # 1/2 filter and lower)
that is completely absent in the Polymax. Polymax has also shown a higher
Dmax - up to a 2.4 after selenium toning. I'm impressed with the technology
behind the Kodak product even though I'm a big Multigrade user.

BTW, all papers are fiber. I don't use RC. My enlarger uses a Zone VI
coldlight
with a replacement Arista V54 lamp installed.

I hope this helps, but if your MG filters are like mine, you should do some
testing with a step wedge before you begin printing in earnest.

Bill Schneider
Ohio University School of Visual Communication

I found and corrected the errors mentioned in my previous post. I placed a
revised pdf on my web site.

The pdf shows various contrasts attainable with Polymax and Multigrade fiber
papers when using various contrast filters under an Aristo V54 cold-light
equipped enlarger.