Incandescent Enlarging Consistency?

[neil poulsen]

Recently, I purchased an Omega Chromega XL 4x5 enlarger outfit for a very reasonable price. (I couldn't resist!) I got all the stuff, including lensboards, turet, a Condit pin registration punch (free), etc.

As to my question, I've always thought of enlarging with incondenscent lighting as being consistent, at least more consistent than cold light. But, how consistent would this light source be for variable contrast printing? For example, color temperature probably also changes over time. Does the intensity vary significantly over time? How often should one need to change bulbs to get the most consistent lighting?

I have a compensating timer with an extra sensor, so this would help to stabilize intensity.

[Nick_3536]

What are you trying to do? Make copies?

You could always get a colour analyzer and dial in the filters and times. But bulbs age. Lightboxes age.

[Gary L. Quay]

I've been B&W printing with Chromega almost exclusively for the last year. A couple issues, apart from aging bulbs, I've noticed or read about: a) the color filters fade over time. Omega still sells them. b) the infrared filter may need to be replaced if you bought it used. I don't know how often they need to be replaced. Maybe someone else here does.

I don't assume that a print that I try to make this year will be done at the same exposure time as one I made last year. I keep a final proof of each print in a filing cabinet, and run a test strip first to make sure that it's going to match. I make time and contrast filtration adjustments from there and note them on my exposure logs. So far, they haven't changed all that much, if at all.

[Vaughn]

Personally, I'd say that there will not be any significant changes to worry about. Changes in line voltage will probably have a greater effect than light bulb aging. The way I work, I make a print, then change it to get what I want to see -- rather than determining what I what from the settings I might have used in a previous printng session. Your milage may differ.

Vaughn

[Peter K]

The aging of tungsten filament lamps isn't an issue in b&w printing, compared with the loss of sensitivity of enlarging papers by storage etc. Of course the tungsten evaporates to the glass but this will be compensated by brightness increase by the thinner filament. As Vaughn has written, changes in line voltage has a greater effect. But only when the voltage drops more than 10%.

Peter K

[Ralph Barker]

If you have flaky power (fluctuating voltage), a voltage stabilizer might be helpful. One of RH Designs enlarging meters may be a better investment, though.

[RPNugent]

My Saunders 4550 printed reliably and with reproducable settings as long as I was using the first bulb. When it burned out all settings had to be modified, though not as much for BW as for color. I'm assuming the new bulb will work the same until it burns out and I do it all over again.

[Nathan Potter]

I use a D2V enlarger with a custom made 12 volt halogen lamphouse. The lamphouse is fitted with an aperture to vary the f/no of the light source. Since my house voltage varies from about 105 to 122 volts I drive the lamp with a voltage controlled DC power supply (I think from Radio Shack). I measure and adjust the intensity of the light on the easel prior to each print using a Pentax spot meter and the DC supply for adjustment. I do B&W and Ilfochrome printing. The Ilfochrome is done using color filters and I expose a color filter matrix before my periodic sessions using a matrix of 0 to 50 C, M and Y. The matrix is exposed and drum developed under absolutely identical conditions and the filter pack combination that produces a neutral grey is used thereafter for that session. If I keep the intensity of the bulb consistent from print to print, color rendition is highly consistent. The aging of the paper and chemistry and variation of house voltage is more significant than bulb aging, IMO. This is a bit crude but has worked well for some 30 years for the number of prints that I do.

Nate Potter

[neil poulsen]

My Saunders 4550 printed reliably and with reproducable settings as long as I was using the first bulb. When it burned out all settings had to be modified, though not as much for BW as for color. I'm assuming the new bulb will work the same until it burns out and I do it all over again.

Very interesting. That sure makes sense.

I want to be able to keep notes after making a print, and when I return to the same print later, I want to be able to input the same settings and get the same contrast and exposure.

It sounds as if I've since had a bulb burn out, those notes may not be useful. I put a lot of effort and paper into a print. While there will always be some variation, I at least want to expect the same contrast, assuming my compensating timer maintains the same exposure.

[Kirk Keyes]

Neil - I think you'll have more issues with respect to repeatability from differernt lots of paper than you will ever have from the enlarging bulb aging.

If you want to test the aging of the bulb, use a color analyzer or color temp meter and take measurments of the bulb temp/color as it ages.

[Eric Woodbury]

Neil, a bulb is more consistent than cold light. Cold light's most dominant variable is tube temperature. Incandescent bulb's biggest variable is probably the age of the filament and voltage. If you are voltage stabilized, then I doubt there is much affect on intensity. If not, then a small voltage fluctuation can affect threshold points in B&W. Color temperature would not be significant for B&W. If you are using a closed loop stabilizer for B&W printing, then voltage and age should not affect exposure. A compensating timer does not control intensity, only exposure.

[Andy Eads]

I would like to second the idea of getting a good voltage regulator in line with the lamp(s). I found a surplus voltage regulating transformer for a few dollars. I plugged an 1800 watt hair dryer into the same circuit and cycled it a few times while monitoring a volt meter on the regulated side of the transformer. I detected less than 1 volt shift. With any load less than the hair dryer, the shift was undetectable by my meter. The biggest benefit is the consistency from print to print. Good printing!

[gary mulder]

If you are really concerned about consistency you could buy yourself a closed-loop enlarger. This will give you even after years and years the same exposure.