Enlarger timer accuracy required for relative paper speed tests

You may find something that will do either just fine time control, or fine
grade control from the RH Designs range of products. One of the timers has
1/24th stop accuracy and others can control both lamps in an Ilford
Multigrade head and do split grade printing, precise to 1/10 grade.

http://www.rhdesigns.co.uk

Chris

On 7/6/04 1:43 pm, in article
, "Phil Glaser"
wrote:

You can actually see a difference of a 1/12th of a stop on hard grades.
So, if your standard exposure is pretty long, a 0.1s precision is not useful
but if you're constantly below 10s. it may be helpful.

When I did similar tests, I've been impressed by the error I got when
exposing the paper twice similarly, that was caused by voltage fluctuations.
That may take you into wrong conclusions ...

Based on what you and others are saying, my inclination is to wait
until I have a more accurate enalrger timer for doing this particular
test.

I do prefer working with a transparent step wedge (Stouffer, Kodak, ...)
combined with a reflection step wedge (or a reflection densitometer if
you're luvky to have one) for this kind of tests as it gives you the speed
change but also the real contrast of the filter.
This is especially useful for color heads used for B/W Multigrade printing.

Yes, I read about that in Anchel also and am thinking that this is a
better option for now. It seems like knowing that one filter is n
number of 1/3 stops faster or slower (based on counting the number of
completely dark steps until there's a density change) than another is
about as accurate as I would get with my enlarger timer and about as
useful.

One question about this approach. I'll need to slice up my 21 step
stouffer step wedge into three segments and project that. Since I'm
only set up for 35mm, I would need to make my own cardboard carrier
for this purpose. It will be 1.1 cm wider than the standard 35mm
carrier. I don't know if that means I'll need to adjust the condensor.
If I do adjust the condensor, will it affect the outcome of the test?
I mean, it seems to me that in relative terms, the exposures should
work out correctly. But I'm thinking, perhaps the intensity of the
light, which would be changed by the condensor adjusgement, changes
the callier effect? Is this another variable I need to control?

--Phil

"Nick Zentena" wrote in message
...
Phil Glaser wrote:


One question about this approach. I'll need to slice up my 21 step
stouffer step wedge into three segments and project that. Since I'm
only set up for 35mm, I would need to make my own cardboard carrier
for this purpose. It will be 1.1 cm wider than the standard 35mm


Why not contact print it?

Because contact prints have different contrast than negatives enlarged
through the optics. But I are confused now. Maybe that applies only to
condenser heads. It might be sufficiently close for dichro and cold light
heads. ???

One question about this approach. I'll need to slice up my 21 step
stouffer step wedge into three segments and project that. Since I'm
only set up for 35mm, I would need to make my own cardboard carrier
for this purpose. It will be 1.1 cm wider than the standard 35mm


Why not contact print it?

Callier effect causes contrast to be different when enlarging than
when contact printing. That's what Anchell seems to suggest.

(Phil Glaser) wrote

I would like to embark upon the relative paper speed test...

You would like to? With VC paper have you any choice? and for
each and every paper you choose to use.

Heh. Well, no, I'm not looking forward to the testing process, but it
does seem to be necessary.

I used VC paper in 1958 and again a few years ago. I've gone all
graded. I could'nt get out of my mind the LIGHT darkrooms of years
gone by; graded paper darkrooms.
If you need all that calibration in the dark routine, stick
with VC.
For those not aware, there is a great variety of graded fiber base
and resin coated papers available. Dan

As often happens, these discussions take me into uncharted waters. Are
you saying that graded papers have a completely constant speed from
one grade to another, so that, for example, a change from a grade 1 to
a grade 5 made at the same exposure has no effect on highlight
densities? And that all this relative speed testing is _only_
necessary for VC papers? I mean, geeze, that could be worth the cost
of a few extra boxes of paper . . . --Phil


You are missing the point. Many years ago I was impressed by a
very well lighted, easy to see about, graded paper commercial darkroom.
All I'm saying is that you can work with graded papers in a much
improved environment due to the high level of lighting permitted
when useing graded papers. I dare say most who do or would do
darkroom work have never seen a graded paper darkroom.
Shame. I dare say the low level VC safe lighting which abounds,
turns some who would be in the not so dark to another interest.

As for paper speed tests: At least for starters I think you should
do the minimum exposure for maximum density tests. Useing an RC paper
will allow you to do a few exposure tests in short order and establish
a reference point. I've a box of Arista RC Grade 2 which is a good
paper and good for the purpose. I don't think anyone has mentioned
the min-exp for max-dens tests.

Paper grade, VC or Graded, as well as chemistry can effect exposure.
The min for max tests may be all you'll feel necessary for some time.
I don't know why it has'nt been mentioned. Dan

On 6/8/2004 3:36 PM Dan Quinn spake thus:

(Phil Glaser) wrote

I would like to embark upon the relative paper speed test...

You would like to? With VC paper have you any choice? and for each and
every paper you choose to use.

Heh. Well, no, I'm not looking forward to the testing process, but it
does seem to be necessary.

I used VC paper in 1958 and again a few years ago. I've gone all
graded. I could'nt get out of my mind the LIGHT darkrooms of years gone
by; graded paper darkrooms. If you need all that calibration in the
dark routine, stick with VC. For those not aware, there is a great
variety of graded fiber base and resin coated papers available.

As often happens, these discussions take me into uncharted waters. Are
you saying that graded papers have a completely constant speed from one
grade to another, so that, for example, a change from a grade 1 to a
grade 5 made at the same exposure has no effect on highlight densities?
And that all this relative speed testing is _only_ necessary for VC
papers? I mean, geeze, that could be worth the cost of a few extra boxes
of paper . . .

You are missing the point. Many years ago I was impressed by a very well
lighted, easy to see about, graded paper commercial darkroom. All I'm
saying is that you can work with graded papers in a much improved
environment due to the high level of lighting permitted when useing graded
papers.

Well, it's plain that you like using slower papers that permit higher levels
of safelight illumination; I think we get the point after hearing it, oh,
about a dozen times or so.

You like that, but other people might not like the much longer exposure times
required to make a print. That's the tradeoff.


--
Civilization is just a temporary failure of entropy.

- Christine Nelson

"Phil Glaser" wrote in message
om...
1) do one test strip for the highlight exposure -- i.e., where
exposure is the parameter being tested

2) do another strip for the shaddows where the grade is the parameter
being tested.

If the paper speed were constant across all grades, step # 2 would be
a simple matter of using the exposure determined in step 1 on
different grades (in my case, swapping in different filters). Since
it is not, ...

My experience is that Ilford Multigrade filters are ND balanced to hold the
highlight point, while Kodak Polymax filters hold the shadow point. This is
from contact printing step wedges and measuring the results on a
densitometer. Printing real negatives through the optics bears this out.

Will "minimum exposure for maximum density tests" help me figure out
the exposure adjustements for each filter, or are you suggesting a
different exposure methodology altogether?

Run a test strip of the film edge. The shortest exposure that obscures the
35mm sprocket holes (or edge of other film) is printing filmbase + fog at
Zone 0. The exposure time remains constant for Kodak filters. Different film
types, and even rolls of the same film type, can be different. It also
varies as you move the head up and down, as the square of the ratio of the
heights. Measure the height from the easel to the negative. It wouldn't hurt
to tape a tape measure to the column if it doesn't already have a height
scale. I prefer to leave the film base just very faint, not quite full
black, on proof sheets.

David Nebenzahl wrote

You are missing the point. Many years ago I was impressed by a very well
lighted, easy to see about, graded paper commercial darkroom. All I'm
saying is that you can work with graded papers in a much improved
environment due to the high level of lighting permitted when
useing graded papers.

Well, it's plain that you like using slower papers that permit higher levels
of safelight illumination; I think we get the point after hearing it, oh,
about a dozen times or so.

You like that, but other people might not like the much longer exposure times
required to make a print. That's the tradeoff.

Graded papers are just as fast as VC papers, some perhaps faster.
The color of the safelights used for graded paper is attuned to the
eyes most sensitive portion of the spectrum; the green and yellow.
Graded paper is NOT slowed down VC paper. I don't know where
you got that impression. Generaly, Graded papers are blue sensitive
while VC papers are blue and green sensitive. Dan

David Nebenzahl wrote

You are missing the point. Many years ago I was impressed by a very well
lighted, easy to see about, graded paper commercial darkroom. All I'm
saying is that you can work with graded papers in a much improved
environment due to the high level of lighting permitted when
useing graded papers.

Well, it's plain that you like using slower papers that permit higher levels
of safelight illumination; I think we get the point after hearing it, oh,
about a dozen times or so.

You like that, but other people might not like the much longer exposure times
required to make a print. That's the tradeoff.

Graded papers are just as fast as VC papers, some perhaps faster.
The color of the safelights used for graded paper is attuned to the
eyes most sensitive portion of the spectrum; the green and yellow.
Graded paper is NOT slowed down VC paper. I don't know where
you got that impression. Generaly, Graded papers are blue sensitive
while VC papers are blue and green sensitive. Dan

The most important uncontrolled variables will be variation in your line
voltage and aging of your enlarger lamp. Or, if it's a cold-light enlarger,
variation in degree of warmup.

Also, there is batch-to-batch variation in the paper.

I would think a timer accuracy of 10% is plenty good enough; the timer won't
be the weak link in the chain.

"Claudio Bonavolta" wrote in message
...

You can actually see a difference of a 1/12th of a stop on hard grades.

Yes; that's 2^(1/12) or a factor of 1.06, or 6% change.