How Vast & Varied Are Enlarging Bulbs...

....and do they significantly affect printing - contrast/grey tones, etc, depending on which bulb is in use?
I use the Omega Color-Head (Diffuser?) at the community darkroom , and wonder since the bulbs were changed, if it's that or me for my prints seeming too contrasty, lacking more greys which I like. I'm having to "fix" my prints sometimes with as much as a 50-70 yellow.
Also, printing times (seconds) seem to be much quicker (shorter) than before - light seems brighter, whiter as well.

It certainly makes a difference, as a fresh bulb emits more light (is brighter). Using an enlarging exposure meter should level this out

Also colour temperature falls continuously over the lifetime of a conventional incandescent lamp.
incandescent

Myself and some other people on another forum that I use (http://www.film-and-darkroom-user.org.uk) have also been experimenting with the newer, lower wattage LED lights. An similar wattage to 60 to 75 watt have been used, with the 'warm' tone ones working better than the 'neutral' bulbs and yes, the exposure times have been reduced as well.

Terry S

tezzasmall said:

Myself and some other people on another forum that I use (http://www.film-and-darkroom-user.org.uk) have also been experimenting with the newer, lower wattage LED lights. An similar wattage to 60 to 75 watt have been used, with the 'warm' tone ones working better than the 'neutral' bulbs and yes, the exposure times have been reduced as well.

Terry S

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I've been experimenting with this as well. Unfortunately, the lower light output and discontinuous spectrum makes the available LED substitutes (for an EFP bulb) unsuitable for my use of variable contrast papers.
My LPL 7700 enlarger with the variable contrast light source and a 50W equivalent LED led to f/5.6 exposures in excess of two minutes for a 5x7 at the setting for equivalent grade 3. The contrast steps are also much less linear.
I've kept the bulbs, because they will serve in an emergency, and I really liked how cool they run.
LED bulbs are changing constantly, so I'm open to revisiting this in the future.

At the Kodak darkrooms for employees after hours, the enlarger bulbs were calibrated every week with the color adjustment posted with each enlarger.

How were the bulbs calibrated? This practically could only be one by tweaking the voltage.

With the more advanced VCNA translator system of the Omega D5500, lamp color was alway accounted for by the sensors in the mixing box. So, once one was calibrated to one's Video Color analyzer, the calibration would stay constant as the lamp aged.

The first important point is to buy high quality bulbs to begin with, like Japanese-made USHIO or US made GE. There are also EU made bulbs. GE is out of the bulb business, but a lot of inventory still exists. Just be aware that GE offered both domestic product and imported junk. Avoid any bulb made in China. They fail much much sooner; but even before then might exhibit shifts. Power supplies are intended to tightly regulate the voltage as well as prolong the life of the bulb; so when these start acting up, it affect things. And before of old lamp sockets that are corroded; these sometimes need cleaning or replacement. It's also a good idea to get ahold of a good voltage meter and test your input voltage from time to time. Right now, with all kinds of grid problems in certain parts of the country, I'd unplug the whole system due to surge risks, where that applies.

I had a wall of eight Beseler 23CIIs that kept blowing bulb after bulb. It was getting expensive, but there seemed to be no cause -- Plant Operations put a meter on the curciut for a few days and found nothing. I finally traced it down to a bad Time-O-Lite timer that sent a zap of power into the line when it shut off. If someone on the same curcuit had their enlarger lamp on at the same time as the the bad timer shut off, it would blow their lamp.

Good lamps were not easy to find back then (90s to 2015).

DREW WILEY said:

Power supplies are intended to tightly regulate the voltage as well as prolong the life of the bulb.

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Voltage regulators are regularly hinted at here. But they only make sense if there actually is a variation at the mains over a long period or as dips or spikes (if the regulator can even cope with this), or if there are voltage dips due to other consumers within the own house.

In first place one should use lamps or fixed power supplies designated for the actual voltage, which likely often is not the case with old equipment due to changes in mains voltage standards.

A surge of 15V or above is ordinarily going to cause malfunction or damage. That's rough rule of thumb. It all depends. Old power mains are uncommon in this area for the past 30 yrs. Everything has been upgraded residentially, and has to be if a house is sold. But that still leaves two kinds of potential problems. Many studio and rental art spaces are set up in old industrial warehouses with high incoming voltage, and less than ideal step-down transformers.

Then there are certain conditions which affect the grid itself. We had a lot of issues here with severe forest fires last summer interrupting supply and involving rerouting complications. And right now, the middle of the country has its grid all messed up by severe winter storms. There's a lot of talk about modernizing the entire country with a single strong grid. It will be horrendously expensive to do, but seems essential if we're going to keep up with the temper tantrums of climate change as well as the anticipated shift to mostly electric vehicles, and all the new cleaner manners of harvesting and distributing the necessary energy.

Backlash voltage spikes with internal equipment are a more unusual condition, but exist, just like Vaughn noted. I once used an industrial spectrophotometer which would build up a lot of energy in a capacitor, then suddenly release it all in a giant burst of xenon light sufficient to be split into 11 different channels and spectral points of reading. There were three serial surge protectors or "valves" on that line to prevent backlash, plus one inside the machine itself. But it wasn't enough. One day the capacitor blew and outright permanently ruined every computer on that same huge 7200 sq ft floor, about 12 of them.

But we do not know where the OP is located. And there are parts of the world where the mains voltage is right on. So a voltage regulator should be stated as an option if necessary, not as a standard prerequisite.

Voltage is nearly always right on here too. But giant storms, fire events, and serious earthquakes can easily disrupt that from time to time. I lived right on the canyon which had the most extensive hydroelectric power plant system on earth. My dad was a supervisor in the building of dams etc. Those transmission lines and towers were built to amazing standards in remarkably steep terrain. But when you get a thermal cloud 70,000 feet high with multiple fire tornados going on inside it at the same time, throwing burning tall trees around like toothpicks and leaving the soil still 2000 deg F days afterwards, or else something like a giant mudslide once the season gets its first severe rainstorm, well, it's just gonna happen - often payback for what we've done to it.

During our last power outage (a week or so ago), the power came back on for awhile. Lights came on, fridge tried to kick on, the igniters of the gas stove top would not work, my fan ran at one speed -- slow. I got my meter out and I only had 60V coming thru the lines. I already had my computer disconnected...

Our last local power outage had nothing to do with the storms. Some crackpot or gangbanger decided to do shotgun target practice at a pole transformer. The bigger instance was earlier when, hoping to improve upon overhead distribution risks, they were burying new main lines under a trenched out street, and backhoed apart their own recently laid cables. I mistrusted them to begin with, so deliberately shut down my darkroom power and computer circuit in advance.

Miscommunication stuff like that is common in city works projects. When Fed stimulus money was given to cities a decade or so ago, one batch of the funds was used to beautifully repave all the streets and sidewalks in the Civic Center district, but then AFTERWARDS, a different fund was used to tear up some of the very same streets for sake of underground fiber optic lines. Now there are unintended lumpy asphalt "speed bumps" about every ten feet apart.