AZO Lightsource

bmac · May 24, 2004

Don,

I'm doing normal development (Sandy's times) with +1 stop of exposure. Using an incident meter. The negatives dont look over developed or over exposed to my untrained eye.

Donald Miller · May 24, 2004

bmac said:
Don,

I'm doing normal development (Sandy's times) with +1 stop of exposure. Using an incident meter. The negatives dont look over developed or over exposed to my untrained eye.

Brian,

As I said, I don't have experience with the lamp that you are using. I use 300 and 150 watt reflector flood lamps. I believe the plant grow lamp does emit some UVA whereas the reflector flood lamps emit blue and virtually no UVA so it would seem that the plant grow lamp would require less wattage since Azo is most sensitive to UVA light. However this is conjecture on my part.

It would seem to me, though, that the one stop additional exposure that you are giving above Sandy's tests would double your print exposure times.

bmac · May 25, 2004

I aplan on doing another printing session this weekend and will try out a couple other lights I have (a 200w photo flood, and a 120w R40) and will report back.

sanking · May 26, 2004

bmac said:
You've got me!

There is the distinct possibility that I over exposed the AZO, but with my visual densitometer (my eyes ) I am seeing that with my materials and my processes the negative exposed for Sandy's time with +1 exposure (efs 200) is giving me the negative with the best tonal range from pure white to maximum black.

Not sure where to go next...

In determing exposure with your meter and metering system and making exposures with your own lens/shutter combination you have taken the tests to the area of E.I., or what I call the personal exposure index. At this point what you see is what you get and if your system tells you that the best EI for Tmax 400 with your metering system and lens/shutter combination is 200 then that is what is best for you.

In my own case I base exposures on an incident light reading in the shadows and rate TMAX 400 at EI 1200 and get good shadow detail. Shadow density would be about the same if I were to base my exposures on an average of two incident readings, one in the shadows and another in the highlights, and halve the EI to 600.

In most cases personal EI figures have limited meaning to others, primarily because of the wide variety of metering methods in use, but also because of variations in shutter speeds and lens apertures.

Sandy

sanking · May 27, 2004

bmac said:
Don,

I'm doing normal development (Sandy's times) with +1 stop of exposure. Using an incident meter. The negatives dont look over developed or over exposed to my untrained eye.

Basing exposures on incident readings without adjustment will in some conditions result in underexposure, just as it would when using a gray card, unless compensation is made. The problem, as described by Davis, is as follows:

"... although the meter's dome is designed to transmit 18% of the incident light, the normal pointer of the meter's calculating dial is fixed at the midpont of the normal 7-stop range. In other words, the meter cell assumes that the world is bathed in a 5-top range of uniform, shadowless light, but the calculating dial assumes that the cell's readings relates to the real world whre shade and shadows are every present and where 7 stops is the norm."

What to do when determing landscape exposures for B&W negatives by incident reading? Quick and dirty answers below.

1. Base your exposure on an incident reading in the shadows, but double the EFS (effective film speed).

2. Base you exposures on a highlight incident reading, but halve your EFS.

3. Base your exposure on an average of shadow and highlight incident reading, using normal EFS.

Sandy King

bmac · May 27, 2004

Sandy, that is very good information. I guess I need to stop worrying about what my brain is telling me is right or wrong, and concentrate on what prints best.

Thanks for all your help with this.

Murray@uptowngallery · Jun 17, 2004

AZO and other graded paper blue light source

Pet store fluorescent lamps for marine tanks come in a variety of phosphors. Some mix long wavelength blue with other visible light, and others made for coral peak at 420 nm blue.

I am going to try them some time in a cold light box for a monochromatic lens I want to use for an enlarger (since there's not much point in using it for a camera!). Of course I will have to make an effort to equalize the light across a light box, but for contact printing I would hope that's more forgiving.

For example, Coral Sun Actinic 420 or Arcadia Marine Blue Actinic for linear 18-48" lamps, and SunPaq 420 nm Actinic for 65 and 96 W compact fluorescent. The latter will require special ballasts. The former should use whatever T8 ballast matches the standard phosphor in that size/wattage.

I woul avoid the high output (HO) ones because they usually have a specialty ballast.

I have not tried these yet, so don't break the bank yet.

Murray

Murray

Michael A. Smith · Jun 19, 2004

According to my local, small-town electrical supply store R-40 standard base bulbs (yes, you do not want the mogul base), are a normal item. I was told they should not be hard to get and they should not be expensive. I recall paying less than $20 last time I bought one. Will try to check with the store next week and see what the current price is.

Michael A. Smith

mwtroxell · Jun 20, 2004

Last time I checked, either Home Depot or Lowes's carried R-40 bulbs.

bmac · Jun 20, 2004

The highest wattage I have found locally is 120w, but I think that should do fine for now.

Donald Miller · Jun 20, 2004

I was unable to locate a retail outlet for the R40 300 watt lamp in my city. I finally located one at a electrical wholesale outlet. The cost was substantial in my estimation (above $25 as I recall).

I still contend that a mixture of fluorescent BLB and conventional fluorescent would probably be more efficient then the R40 bulb. The cost to fabricate a light source of this type would be more expensive then the R40 lamp, however.

I also believe, based upon testing by Sandy King on his Pyrocat dev, that a mixture of fluorescent BLB and conventional fluorescent (for the visual componant) would also provide higher effective contrast from a Pyrocat dev. negative then the R40 lamp. This gain would probably be on the order of .30 density units at the peak densities most are using on their Azo negatives.

The reason that I think that this would be true is that the Pyrocat stain is more actinic to UV then it is to light in the blue spectrum. The BLB fluorescent emits primarily in near band UV(A) whereas the R40 lamp provides it's primary exposure componant in the blue band insofar as use with Azo is concerned.

Azo is much more sensitive to UVA then it is to blue light.

Richard Wasserman · Jun 20, 2004

Azo & Flourescent light

Donald Miller said:
I still contend that a mixture of fluorescent BLB and conventional fluorescent would probably be more efficient then the R40 bulb. The cost to fabricate a light source of this type would be more expensive then the R40 lamp, however.

I also believe, based upon testing by Sandy King on his Pyrocat dev, that a mixture of fluorescent BLB and conventional fluorescent (for the visual componant) would also provide higher effective contrast from a Pyrocat dev. negative then the R40 lamp. This gain would probably be on the order of .30 density units at the peak densities most are using on their Azo negatives.

Hello Donald,
I found this post very interesting. Have you tried BLB flourescent light with Azo? Do you have any idea how much wattage would be required to make a feasible light source? I own a custom lighting business and could easily fabricate a prototype unit to play with. I certainly wouldn't mind having a light source that throws less heat than a 300 watt incandescent bulb! I am going to be at a workshop with Michael Smith and Paula Chamlee next weekend and when I return home could work on this.
Thanks,
Richard Wasserman

Donald Miller · Jun 20, 2004

Hi Richard,

I have worked with a single F15T8BLB and found that it exposes Azo much more rapidly then a 300 watt R40 lamp. I exposed a 4X5 neg and found that the coverage at 16 inches from the lamp to neg provided enough beam spread to easily illuminate an 8X10 negative (although I haven't exposed that large a neg with the single lamp). The problem that exists is that the BLB does not emit much visible light and that hinders burning and dodging. Possibly using a BL designation bulb (eliminating the Woods filter) may improve the visible light emission. I haven't tried that yet.

My exposure times with the BLB were on the order of 15 seconds at 16 inches removed. Whereas the R40 times were above 1 minute for the same negative. (light wattage reduction of 20 orders of magnitude and shortened exposure time of 4 orders of magnitude).

Insofar as the number of lamps, that would depend on the size of the negative that one would be exposing. I have thought of using 4 each F15T8BLB in conjunction with 2 each T8 cool whites (or similar) to expose my 12X20 negs. I would imagine that one would want some diffusion under the lamps to assure even coverage (depending on the lamp arrangement). I figured that this would require 3 electronic ballasts at about $25 and change each (my cost) The lamps would be about $55 (total) my cost. Then there would be the enclosure cost.

If you decide to play with this, please inform me of your results.

Thanks and regards,
Donald Miller

mark · Jun 20, 2004

I went out and got the highest watt r-40 bulb I could find. 250 watt. I could not find a frosted one and when I hung it up-about 3 ft above the sink-the illumination was not consistent. even after leaving it on for a while, so I returned it and got abother. The new one had the same problem, so I returned this and guess what the new one had the same problem. Is this normal, and will it print evenly?

juan · Jun 20, 2004

When using R-40 bulbs, be sure to get flood blubs - not spot bulbs. The floods give a more even spread, at least in my shop.
juan

mark · Jun 20, 2004

All my hardware store has is the heat lamp one with the silvered base and the clear glass on top.

Michael A. Smith · Jun 22, 2004

I called our local small-town electrical supply store: Doylestown Electric: (215-348-9074, ask for parts), and asked, " How much is an R-40 300 Watt bulb, regular base?"

Their answer: "About $8 and we have plenty of them in stock."

I find it hard to believe, though it is obviously true, that this would be a difficult item to get.

Michael A. Smith

wdemere · Jun 22, 2004

I went to Home Depot looking for R40 300W and they were out. I went across the street to Menards and asked the guy in the lighting section and he said they had nothing like that and he had never heard of it. Luckily, when he moved aside, I saw that he was standing directly in front of the R40 300W watt bulbs, so I bought one. I think it was $9. I think they labelled it as a "utility light" or something like that ("work light" maybe).

I hang it in a silver reflector about 4 feet above the paper and my times are usually in the 10-20 second range.

They seem to be available around here.

Best,

William

bmac · Jul 2, 2004

UPDATE: New glass, new bulb, new times.

I got a single pane window glass for my frame, and a 120W R40 flood bulb. With the light 24" above my frame, I was able to get printing times in the neighborhood of 8-12 seconds depending on my negs. Very happy now!

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