Voltage requlation requirements

Hi,

I want to eliminate voltage fluctuations as a source of inconsistency
in my printing. I'm using a plain vanilla Beseler 23C II with a
75W/120V tungsten bulb.

I've put my hands on a "Line stabilizer/Conditionier" that claims to
make the output conform to ANSI C 81.1 limits. ANSI C 81.1 is +/- 5%
on a 120 volt base under normal conditons and -8.3% to +5.8% for
"short durations or unusal conditions"
(http://powerstandards.com/tutorials%...Regulation.htm).

My questions:

Is +/- 5 % variation adequate for keeping print exposure consistent?

If not, what kind of a regulator do I need to get for my purpose?

If so, how can I test this thing? I don't have any metering equipment.
What I did do was to observe the effect of turning on and off a 1200 W
hair dryer on a compact fluorescent bulb in my office. I then plugged
the lamp into the stabilizer and observed the effect of the 1200 W
hair dryer being turned on and off. I'm afraid to say that I observed
pretty much the same fluctuation in intensity of the light both with
and without the stabilizer. But I perhaps that variation was 5 %. Or
perhaps the thing just doesn't work. Any other testing suggestions?

Thanks

--Phil

"Phil Glaser" wrote in message
om...
Hi,

I want to eliminate voltage fluctuations as a source of inconsistency
in my printing. I'm using a plain vanilla Beseler 23C II with a
75W/120V tungsten bulb.

I've put my hands on a "Line stabilizer/Conditionier" that claims to
make the output conform to ANSI C 81.1 limits. ANSI C 81.1 is +/- 5%
on a 120 volt base under normal conditons and -8.3% to +5.8% for
"short durations or unusal conditions"
(http://powerstandards.com/tutorials%...Regulation.htm).

My questions:

Is +/- 5 % variation adequate for keeping print exposure consistent?

I would think it might not be. Tungsten bulbs are much more sensitive to
voltage variations than fluorescents (which in turn are sensitive to warmup,
the length of time they have been turned on).

Your voltage is probably stable to within 5% already. Do you have a
voltmeter?

The usual kind of voltage regulator used in darkrooms relies on a special
transformer with magnetic saturation involved. I don't know a lot of
details; what kind of line stabilizer are you looking at?

Michael A. Covington wrote:
"Phil Glaser" wrote in message
om...

Hi,

I want to eliminate voltage fluctuations as a source of inconsistency
in my printing. I'm using a plain vanilla Beseler 23C II with a
75W/120V tungsten bulb.

I've put my hands on a "Line stabilizer/Conditionier" that claims to
make the output conform to ANSI C 81.1 limits. ANSI C 81.1 is +/- 5%
on a 120 volt base under normal conditons and -8.3% to +5.8% for
"short durations or unusal conditions"
(http://powerstandards.com/tutorials%...Regulation.htm).

My questions:

Is +/- 5 % variation adequate for keeping print exposure consistent?


I would think it might not be. Tungsten bulbs are much more sensitive to
voltage variations than fluorescents (which in turn are sensitive to warmup,
the length of time they have been turned on).

When Fred Picker's friend designed their stabilizer for their cold light
heads (I forgot his name), he tested incandescent and cold light heads for
voltage sensitivity. As I recall, fluorescent lamps were much more
sensitive to line voltage than incandescent ones were. But the brightness
really depends on the tube current, not the voltage. But it all depends,
as they say.

I have a voltmeter on my 45MCRX that I can adjust for line voltage. As
long as my window A.C. is off or on steady (compressor), I adjust the bulb
at the start of the session. And I use the incandescent head mainly for
color work (since I can put filters in), and there my color analyzer keeps
track of the bulb changes. Pretty much.

Your voltage is probably stable to within 5% already. Do you have a
voltmeter?

Depends where he lives. My UPS logs my line voltage and it is pretty much
all over the map, especially in summer.

The usual kind of voltage regulator used in darkrooms relies on a special
transformer with magnetic saturation involved. I don't know a lot of
details; what kind of line stabilizer are you looking at?




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/V\ Registered Machine 241939.
/( )\ Shrewsbury, New Jersey http://counter.li.org
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Jean-David Beyer wrote in message ...
Michael A. Covington wrote:

Your voltage is probably stable to within 5% already. Do you have a
voltmeter?

Depends where he lives. My UPS logs my line voltage and it is pretty much
all over the map, especially in summer.

I think I may not need to do any measuring. Just this evening I had
the following experience: I did some printing between 5:00 and 6:30
and got my exposure where I wanted it. I then came back at 7:30 and
made more prints with the same exposure, and they were significantly
lighter than the the ones I made earlier.

Now there was one other factor besides current fluctuations which may
account for the difference: earlier I made one print in my Jobo drum,
but later I made four at the same time. I used the same amount of
developer both times: 100 ml., but used fresh developer for each run.
Is it possible that this amount of developer got stretched too thin to
make four prints? If this explanation is not plausible, I have to
conclude that I've got some significant current variations going on
here.

--Phil

"Phil Glaser" wrote

I think I may not need to do any measuring. Just this evening I had
the following experience: I did some printing between 5:00 and 6:30
and got my exposure where I wanted it. I then came back at 7:30 and
made more prints with the same exposure, and they were significantly
lighter than the the ones I made earlier.

Now there was one other factor besides current fluctuations which may
account for the difference: earlier I made one print in my Jobo drum,
but later I made four at the same time. I used the same amount of
developer both times: 100 ml., but used fresh developer for each run.

Is it possible that this amount of developer got stretched too thin to
make four prints?

Depends on the size of the prints. I take it the developer is Dektol
1:2?

Other variables are the temperature and the time of development.

--
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/

(Phil Glaser) wrote in message . com...
I think I may not need to do any measuring. Just this evening I had
the following experience: I did some printing between 5:00 and 6:30
and got my exposure where I wanted it. I then came back at 7:30 and
made more prints with the same exposure, and they were significantly
lighter than the the ones I made earlier.

--Phil

I got convinced I need a voltage regulator when I was doing tests with
the color head of my enlarger for multigrade printing: two identical
exposures (and developments) gave different densities.

After that I measured the mains voltage throughout the day and saw
important fluctuations depending on people demand.
These are slow changes during the day you hardly see visually.
Beside that, you have faster fluctuations like when a big motor
starts, these changes are easy to see as the light flickers.
Both have an impact on our prints.

It's just the Ohm's law, if you aks a greater current through a
resistor (the electrical circuit between the power plant and your
enlarger) you'll have a greater voltage drop.
This depends a lot on where you live, some may not see significant
fluctuations but for others it can give really inconsistent results.
I recall of a friend who had to change is house bulbs twice as often
as I, just because he lived very close to the plant and the voltage
was constantly higher there.

This is very sensitive with negative processes as the original (the
negative) is a low contrast support so the paper (+developer) has to
be a high contrast material to restore the original contrast.
A 1/10th of a stop difference is visible.
The higher the grade the more sensitive it is.

Positive printing is *much* less sensitive as the original (usually a
slide) has a high contrast so the paper must be soft to compensate.
Ilfochrome has a reputation of being a high-contrast material, in
fact, it is not. The combination of the slide+Ilfochrome might be to
contrasty but the paper by itself is a low contrast material.
A half-stop difference is not that big.

For the same reason, negative color processes are also more prone to
color swifts whith voltage fluctuations than positive color material.

The light source type by itself may also not be very consistent:
- standard incandescent bulbs have an acceptable quick rise/fall times
but are inconsistent during their life: light output and color
temperature lowering with time. That's why they are not very
appreciated in color heads.
- halogen bulbs have a pretty slow rise/fall time but are much more
consistent (both light output and color temperature) during their life
- fluorescent lights (cold light heads) have a light varying with
their tube temperature. Their emissive spectrum is not very regular
and makes them harder to use for color work.
- LEDs are a light source that could be interesting although I don't
know of a commercial traditional enlarger using them. They are very
stable both in short and long term aspects, no rise/fall time, very
long lifetime, etc ...
Output power has increased a lot these last years but is still on the
low side but arrays of LEDs can be made easily.
White LEDs have not a very regular spectrum which would make them hard
to use for color work. Blue/Green combinations would be excellent for
Multigrade and RGB LEDs should work as an additive system for color
work. They need a real supply and can't work with just a transformer.
- ...

Slow rise/fall time may be sensitive for very short exposures (say
less than 2 seconds). I haven't made real measurements but, visually,
it looks to me the fall time compensate somewhat for the rise time,
certainly not perfectly.
To prevent this a solution is to use a shutter, so your timer actions
the shutter and not the bulb itself which is powered on some seconds
before and off some seconds after.

For cold heads, a shutter will also be helpful but you should keep the
head on much longer (which may create other problems like light leaks
between exposures).
Another option is to use a closed-loop system that regulates the light
output according to a cell measuring it.

Conclusion, a voltage regulator is not the absolute panacea but it
does help a lot if you live in an area subject to voltage
fluctuations.
It makes my work consistent to the point I commonly use the contact
print exposure values as a valid basis for the straight print several
days or weeks after.


Claudio Bonavolta
http://www.bonavolta.ch

"Nicholas O. Lindan" wrote in message link.net...
"Phil Glaser" wrote

Now there was one other factor besides current fluctuations which may
account for the difference: earlier I made one print in my Jobo drum,
but later I made four at the same time. I used the same amount of
developer both times: 100 ml., but used fresh developer for each run.

Is it possible that this amount of developer got stretched too thin to
make four prints?

Depends on the size of the prints. I take it the developer is Dektol
1:2?

No, it was Ilford Multigrade Paper developer 1:9. I kept the time and
temperature consistent (though it's possible that the in earlier
session the devloper was a little warmer than later one).

Phil Glaser wrote:
"Nicholas O. Lindan" wrote in message link.net...
"Phil Glaser" wrote

Now there was one other factor besides current fluctuations which may
account for the difference: earlier I made one print in my Jobo drum,
but later I made four at the same time. I used the same amount of
developer both times: 100 ml., but used fresh developer for each run.

Is it possible that this amount of developer got stretched too thin to
make four prints?

Depends on the size of the prints. I take it the developer is Dektol
1:2?

No, it was Ilford Multigrade Paper developer 1:9. I kept the time and
temperature consistent (though it's possible that the in earlier
session the devloper was a little warmer than later one).

Go the Ilford website and download the document on print developers. They
claim 100 8x10s RC in a litre or 50 fibre. The problem is that's in a tray.
You might be killing the developer quicker with all the air being pumped
into the developer using a drum. One other thing. Which drum? If you're
doing 8x10s the only one that can hold 4 prints is the 2850. That needs more
then 100ml of developer.

Nick

Nick Zentena wrote in message news:5q2bq1- Is it possible that this amount of developer got stretched too thin to
make four prints?

Depends on the size of the prints. I take it the developer is Dektol
1:2?

No, it was Ilford Multigrade Paper developer 1:9. I kept the time and
temperature consistent (though it's possible that the in earlier
session the devloper was a little warmer than later one).

Go the Ilford website and download the document on print developers. They
claim 100 8x10s RC in a litre or 50 fibre. The problem is that's in a tray.
You might be killing the developer quicker with all the air being pumped
into the developer using a drum. One other thing. Which drum? If you're
doing 8x10s the only one that can hold 4 prints is the 2850. That needs more
then 100ml of developer.

I've got the 2830, which does two 8x10's or 4 5x7's. So I was doing
5x7's. So the question is whether 100ml of Ilford Multigrade developer
at 1:9 would be stretched too thin developing 4 5x7's than it would be
developing 1 5x7.

You know, now as I think about it, I'm wondering about temperature,
too. I was shooting for 68 degrees and got started with that, but
maybe ambient room temperature was hot enough that by the time I
produced the work print there had been a few degrees upward drift in
the first session. How many degrees warmer than 68 would the developer
need to be to see such a noticable difference in print density? In the
second session it was definitely at 68 because I rechecked it _just_
before I printed. Maybe the second session was the one that reflected
the true density @ 68 degrees.

There are just so many variables here.

"Phil Glaser" wrote

[Ilford says] 100 8x10s RC in a litre or 50 fibre.
[I was doing] 4 5x7's
[in] 100ml of Ilford Multigrade developer
[is this enough developer]

100 x 8 x 10 sq in/1000ml = 800 sq in/100ml

4 5x7's are 120 sq in which would exhaust 15ml

I'd say the developer quantity is OK.

[would] Hot enough [Vs] 68 ... [create] such a noticable
difference in print density ... ?

Cough.

How hot is 'Hot enough'?
What difference is 'noticeable', as such?

Numbers! Numbers! We need numbers!