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Old 04-14-2014   #11
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Very interesting Wayne! My experience has been that the higher the power setting the cooler to color. Interesting enough, old flash tubes tend to carbonize with age. This becomes apparent when the general color balance shows a red bias which is difficult or impossible to fully correct with by on-camera filtration or in post production procedures.

A viable graying or blackening begins to appear where the electrodes enter the flash tube- sometimes even slight blistering or deformation of the glass. This problem occurs a bit prematurely in small linear flash tubes that are confined to small spaces in the lamp head- very typical of speedlights. Perhaps this affect is accelerated by heat without adequate ventilation that is found in plug-in flash tubes in larger unenclosed lamp heads.

I once inquired of a rep form a flash tube manufacturer and his explanation that those carbonized electrodes begin to act like a filament in an incandescent lamp and produce a more red/yellow cast in addition ht the cooler light produced by the ionized gas in the tube- kinda like built in color crossover that can result in mixed lighting scenarios.

I have no scientific data to this effect but when my old tubes begin to blacken- I replace them and there is an immediate return to easily obtainable color balance.

Ed


Monolights do become warmer color at low power, but speedlights are the opposite. Speedlights always operate at the same voltage, but the low power truncation cuts off their trailing red tail. We always have to handle white balance.

But the replacement speedlight flash tubes did restore the color a bit, as did an Alienbees light with a replaced flash tube.

I could not see the flashtubes in the speedlights to know their condition, but they did have nine years of pretty regular duty. Not extreme use, but more than light duty. Heavier professional use probably should follow Nikons two year advice.
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Old 04-15-2014   #12
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Monolights do become warmer color at low power, but speedlights are the opposite. Speedlights always operate at the same voltage, but the low power truncation cuts off their trailing red tail. We always have to handle white balance.

But the replacement speedlight flash tubes did restore the color a bit, as did an Alienbees light with a replaced flash tube.

I could not see the flashtubes in the speedlights to know their condition, but they did have nine years of pretty regular duty. Not extreme use, but more than light duty. Heavier professional use probably should follow Nikons two year advice.

Interesting again!

I have never been a "speedlight user" per se. especially in the latest totally automated configurations. My portable lights for wedding and press work have always been shoulder pack units with separate lamp heads equipped with plug in user changeable flash tubes which I would routinely replace as soon as I observed color balance difficulties, physical changes in the tubes or outright damage to the tube or its envelope.

I use all my studio and location lights in manual mode but I wonder if theses shifts in color result from typical thyristor controlled speedlights where the light output can be a significant blast of light or just a wink of light.

The other instance I can recall from back in the 1970s is that the makers of the Rolleiflex cameras produced a mono-light system whereby the output adjustment was nor controlled by the switching of capacitors or capacitor banks in and out of the circuit. They claimed that the output was continuously adjustable by variations of the voltage. The unit featured a large control knob on the back panel which I assume was some kind of potentiometer or rheostat. I had 4 of theses units and they did work extremely well and enabled very precise adjustment of lighting ratios and there were no detectable shifts in color over a full ranged of outputs. Unfortunately enough, there were other design flaws in their construction and circuitry that led to difficulty in repairs and finally a poor record of longevity. The quickly fell out of favor and their manufacture was abruptly ceased.

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Old 04-15-2014   #13
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Interesting again!

I have never been a "speedlight user" per se. especially in the latest totally automated configurations. My portable lights for wedding and press work have always been shoulder pack units with separate lamp heads equipped with plug in user changeable flash tubes which I would routinely replace as soon as I observed color balance difficulties, physical changes in the tubes or outright damage to the tube or its envelope.

I use all my studio and location lights in manual mode but I wonder if theses shifts in color result from typical thyristor controlled speedlights where the light output can be a significant blast of light or just a wink of light.

The other instance I can recall from back in the 1970s is that the makers of the Rolleiflex cameras produced a mono-light system whereby the output adjustment was nor controlled by the switching of capacitors or capacitor banks in and out of the circuit. They claimed that the output was continuously adjustable by variations of the voltage. The unit featured a large control knob on the back panel which I assume was some kind of potentiometer or rheostat. I had 4 of theses units and they did work extremely well and enabled very precise adjustment of lighting ratios and there were no detectable shifts in color over a full ranged of outputs. Unfortunately enough, there were other design flaws in their construction and circuitry that led to difficulty in repairs and finally a poor record of longevity. The quickly fell out of favor and their manufacture was abruptly ceased.

Ed

My understanding about flash color is this.

We come to realize that what we call warm or cool color actually runs opposite of actual temperature degrees. When metals are heated, red hot is first, and relatively cool and low temp degrees, but the red color looks hot. Blue hot is high temp degrees, but we seem to think the color looks cool (like ice or water maybe ? )

Any variation of power in a flash tube will change its ionization spectrum.
They do of course change color. Ionization is determined by the amps of current flowing through the flash tube.
There are a few ways to vary the power level.

Monolights typically simply reduce voltage to lower the power (there are exceptions, but very few). This lower voltage causes less flash tube current, and less power, but which actually flows longer (lower current), and this changes the color towards (an actually cooler) warm color (red) at lower power.

Speedlights always use regulated full voltage, same initial high peak, same initial current, but they simply cut off the current flow to zero (thyristor type, or IGBT chips today) to truncate the power, to become low power output. Truncation makes it be very fast low power, called speedlights. This truncation removes more of the cooler temperature red trailing tail, shifting their average toward cooler color (blue).

Studio power pack units typically have jumpers to shift more capacitors in or out, with the same voltage, and no cutoff, so less color shift, fewer capacitors are just less ultimate discharge duration (smaller flashes are faster). But other disadvantages, low versatility, and power loss in long cables, etc. White Lightning combines capacitors with voltage in monolights, seems genuine advantage (a big flash unit turned down can be made very fast instead of slow and red).

I don't know about the Rolliflex, but the Einstein flash from Paul C Buff combines voltage and speedlight methods, one method offsetting the opposite color shift of the other, to be constant color if carefully controlled, both adjusted as necessary. This was not unknown, but he did it inexpensively (like a factor of ten). Seems this ought to change the future norm of most studio units.

Nikon (and I think Canon) speedlights have what Nikon calls Flash Color Information Communication, where the the speedlight flash knows its power level, and so can know expected color temperature there (from a firmware chart prepared by designers), and can report this temperature to the hot shoe, and the camera, if in Auto WB, can use it to set the WB. I find this very iffy, and prefer to control WB myself (and I use Raw anyway). And of course, it can only report what the firmware chart thinks WB ought to be.

I'm sure constant color (actually achieved) would be great in studio flash, and it might insure all lights were the same color. Our WB still has to match that color.

But still, we make one setup at a time, we don't change it much during one portrait session. So IMO, just using a white card once for the session seems completely adequate WB control. Not that much problem. However, this effort is much harder in walkaround hot shoe use though, where power level can vary.
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Old 04-15-2014   #14
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Thank you sir- Great information to study and understand!

In my collection of old stuff I have an early model unit made by Wabash. It has oil filled capacitors of very low microfarad ratings- The units uses wet cell batteries, has a vibrator like the ones found in older car radios and operates at extremely high voltage. It boasts a flash duration of one hundred thousandth of a second. The lamp head looks like a sealed beam headlight encased in metal

Great for stopping bullets perhaps for ballistics experimentation or things like that. Miraculously, it still works and I dare not hook it up to a DSLR any time soon. Lord knows what the trigger voltage is like and my multi-meter does not have a HV probe like my old VTVM! I have never been into the lamp head but some of those old units have a small vacuum tube called a "thyrothon" (please excuse the unknown spelling and pronunciation) which enabled safer triggering. All I know is that the power supply sounds like a loudly buzzing transformer mounted on a utility pole!

Back in the day, film shot with this unit required extended development due to reciprocity law failure and accurate color and exposure with mufti-layered color films was next to impossible .
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Old 04-15-2014   #15
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I was into photography back then too, but my level then was the 500 watt photo flood bulbs and 12 inch metal reflectors. Film was fun and exciting at the time, but frankly, the whole process seems unthinkable today.

Film was really hard for anything special. Digital is so much easier, when we can simply see what we are doing.
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Old 04-15-2014   #16
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Default Re: Electronic Flash Maintenance for all Photographers.

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I was into photography back then too, but my level then was the 500 watt photo flood bulbs and 12 inch metal reflectors. Film was fun and exciting at the time, but frankly, the whole process seems unthinkable today.

Film was really hard for anything special. Digital is so much easier, when we can simply see what we are doing.
Thanks to both you and Ed for a very interesting and educational, to me an electronic neophyte, conversation. Working with flash in the 70's - 80's was definitely challenging. I still shoot some 4x5 stuff in b&w, but most is available light abstract kinda stuff. Thanks again.
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Old 07-21-2014   #17
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.... Working with flash in the 70's - 80's was definitely challenging. ...
I'm still using Speedotron Black Line power packs that I bought new in the mid 1980's. The only challenge when working with them is picking them up. They're 4800ws and 48 lbs. apiece.
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Old 12-12-2016   #18
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Thanks Ed for the information!


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