[pure-silver] Re: ZONE VI VC HEAD, was No More Below the Lens Polymax Filter Kits?

  • From: "mail1" <mail1@xxxxxxxxxxxxxxxxx>
  • To: <pure-silver@xxxxxxxxxxxxx>
  • Date: Mon, 9 Feb 2009 01:31:44 -0800

Jean-David Beyer wrote in part.
>I do not remember how to convert density range to Exposure Scale (which is
>what I suppose you mean by ES). I thought they were identical, but your
>results are so different from mine that i doubt they are experimental
>error, so I hope we are talking about different things.

To clarify my understanding of this matter.

It starts by measuring the subject luminance range, then the determination
of the negative exposure, and then developing the negative to produce an
image. The negative density range can be measured either by an on easel
photometer, or a densitometer, or by eye, to determine the print exposure
scale and a paper grade that matches the negative.   
Density Range of the paper is the IDmax minus IDmin of the paper. The IDmin
is usually defined as 0.04 over B+F (paper white) and IDmax is usually
defined as 90% of the maximum obtainable density of the paper.  The IDmin is
usual 0.09 and is represented as a horizontal line starting from the density
scale on the left side of the graph. This line intersects the toe of paper
curve where a perpendicular line is drop to the log exposure scale on the
bottom of the graph.  This establishes the toe side of the paper (ES)
exposure scale. The IDmax varies with the maximum density of the paper and
is another horizontal line that crosses the paper curve where a
perpendicular is dropped to determine the shoulder side of the exposure
scale. This difference between the two points paper is the paper exposure
scale. IT is also equal to the ISO Range. (ES1.0 = ISO Range 100). The ES is
also a relative log exposure which is a measure of Logarithmic value. It is
usually represented on a scale of 0.10 units of density with 0.30 units
equal to approximately 2 steps of a 21 step table. A grade 2 paper, ES 1.00
divided by .15 units equals 6.6 steps of the step table. If you used an
incident light meter modified to measure a projected image by the enlarger
you would measure approximately 3.3 EV values between the high lights and
the shadows of the projected image.

Jonathan Ayers  [mail1@xxxxxxxxxxxxxxxxx]> 








-----Original Message-----
From: pure-silver-bounce@xxxxxxxxxxxxx
[mailto:pure-silver-bounce@xxxxxxxxxxxxx] On Behalf Of Jean-David Beyer
Sent: Sunday, February 08, 2009 3:12 PM
To: pure-silver@xxxxxxxxxxxxx
Subject: [pure-silver] Re: ZONE VI VC HEAD, was No More Below the Lens
Polymax Filter Kits?

mail1 wrote:
> I have not had an opportunity to use the Zone VI 4x5 model.
> 
> With my Zone VI type 1 head maximum green and maximum blue settings
produces
> an ES.78 effective grade 4 shot toe curve.  With the Maximum blue lamp on
> and green off the head produces ES 0.60, eff. grade 5 short toe. So it
> appears the tubes might be different in the 4x5 head.

OK. With mine, I get 12 steps from pure white to maximum black on my step
tablet (0.15 density per step) for what I call grade 00. 1.8 density range.
This is with the green at maximum, and the blue turned off.

With both blue and green at maximum, I get what I call grade 2, with 9 steps
density range. 1.35 density range.

At the other extreme, I get 7 honest steps (or 6 wishful thinking steps) for
what I call grade 5. 1.05 density range. I get 7 honest steps for what I
call grade 4. This is with the blue at maximum and the green turned off. I
have not tried putting a #47B filter in there to get more contrast. I might
if I were desperate, but a piece about 6' in diameter costs a lot these
days.

In my experience, the toe of Ilford MGIV does not change much with the
filters; but the shoulder changes a lot. This is testing my step wedge. It
may be that subjectively there are subtle differences in the toe that a 0.15
wedge step size hides. These tests were all run on a new box of MGIV paper
purchased from B&H, all run in about 2 days with fresh chemicals each day.

I do not remember how to convert density range to Exposure Scale (which is
what I suppose you mean by ES). I thought they were identical, but your
results are so different from mine that i doubt they are experimental error,
so I hope we are talking about different things.
> 
> A thought about the apparent dimness of cold light heads.

I was not saying cold lights were dim, just my Zone VI. I have a one-tube
Aristo D-II HI head that is plenty fast enough.
> 
> My type 1 cold light have a lamp power supply / controller box which
> measures 12x11x6 inches inside this box are two large transformers with
> Variac controllers. This unit appears brighter than my Aristo VCL4500.
This
> is because the difference in tubes between the two light sources. The Zone
> VI has phosphor coated tube with a wider spectrum of light than the
VCL4500
> which uses phosphor coated colored glass tubes so the spectrum is
narrower.
> Since the eyes response to blue tube is very low the VCL4500 appears
darker.

My Zone VI head has a green and a blue tube. Each has some phosphor inside
each tube.

My control box for my Zone VI unit is very small. It contains three
potentiometers, one of which I find useless. If you turn it to max, that is
the brightest the unit will go, so I always leave it at max.
Then there are two, one for green and one for blue.

There is a switch that has two positions. One is Print, one is Focus. In the
Focus position, it turns on both tubes at maximum brightness. I never tried
printing with it in the Focus position.

Those knobs are definitely 1/2 watt cheap potentiometers; I am surprised
they are not the 2-watt Ohmite (probably Allen Bradley) ones which have much
less noise and much longer lasting.
> 
> I checked one of my print logs and noticed an 11-14 enlargement of a 6x6
> dense negative, requiring a paper ES 1.2 was printed on Ilford MC Paper
with
> my Zone VI set at Max Green - Min-1 Blue which equaled eff. Grade 1. The
> time of exposure was 12 sec. at f5.6 using a 90m/m Schneider APO lens. The
> same negative printed on my Durst condenser enlarger 300 watt bulb at 110
> VAC using an Ilford 0 filter; eff. grade 0. The time of exposure was 20
sec.
> f 5.6 105m/m Rodagon Apo lens. If we allow for the difference in lamp
> heights because off lenses and the papers response to the different light
> sources the exposures are similar. The image on the easel from the
condenser
> is quite bright compared to the Zone VI. The VCL4500 is dimmer still, and
an
> addition 1 stop grade 5 burn to the sky would have been difficult for me
> because my eyes seem to have a poor response to the VCL 4500 blue lamp.
> 
> For large print on my Durst I use a 500 watt lamp run at 120 volts which
> leaves the cold lights in the twilight zone.
> 
> I have noticed the different response photo paper has to each of the light
> sources imparts a different rendition of the same negative. Cool.
> 
> Jonathan Ayers  [mail1@xxxxxxxxxxxxxxxxx] 
>  
> 
> -----Original Message-----
> From: pure-silver-bounce@xxxxxxxxxxxxx
> [mailto:pure-silver-bounce@xxxxxxxxxxxxx] On Behalf Of Jean-David Beyer
> Sent: Sunday, February 08, 2009 4:42 AM
> To: pure-silver@xxxxxxxxxxxxx
> Subject: [pure-silver] Re: ZONE VI VC HEAD, was No More Below the Lens
> Polymax Filter Kits?
> 
> With my Zone VI VC head (a 4x5 model), I can adjust the green and blue
tubes
> separately.
> 
>> Some VCL4500 units have a rheostat to adjust the green light level to
> reach
>> the higher contrasts. The Zone VI also includes variable green and blue
>> light. The problem is how to decrease the green light as the blue light
is
>> increased so that the light intensity stays the same so that the exposure
>> does not have to be adjusted with each contrast adjustment.
> 
> Since the Zone VI VC head is so dim, what I do is run either the green or 
> the blue tube at maximum intensity so as to get as much light out of the 
> unit as possible.
> 
> So for grades 00, 0, 1, and 2, I have the green at maximum.
> For grades 2, 3, 4, and (wishful thinking) 5, I have the blue light at 
> maximum. I calibrated things with a step tablet and a photometer so that 
> Zone V always matches the grey card, using a constant 22 second exposure 
> time. This results in apertures of f/8 for the extreme contrasts up to
f/11 
> for grade 2. Fortunately, my enlarging lenses can have their click-stops 
> turned off. So part of my chart looks like this:
> 
> GRADE SOFT    HARD    F/
> 00    MAX     OFF     8
> 0     MAX     B-      10
> 1     MAX     F       10
> 2     MAX     MAX     11
> 3     E       MAX     10
> 4     MIN     MAX     9
> 5     OFF     MAX     8
> 
> This is for Ilford MGIV VC paper in my version of D-72 developer 1+2 using
a
> Kodak T-14 step wedge in my enlarger's negative holder for an 11x14
> enlargement.

-- 
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