Paul C. Buff, Inc. Technical Forum

wow, 1000° color shift! haha Well within the +/- 30°

As I have stated many times, color meters tend to accentuate near UV and typicaly over read this sort of error.

Last night I tested Profoto D1 500, Elinchrom RX600, AB 1600 and Einstein in actual photographs using Nikon D300 and Kodak professional color cards and RAW in Adobe Bridge CS4.

The RX1600 and AB1600 were almost identical in color VS power setting. At 1/32 power AB was 375° lower color temperature than at Full and had a red/green axis error of -7, with R/G = 0 at Full. The RX600 was 400°K lower at 1/32 power and had an identical R/G of 0 at Full and -7 at 1/32. Both were 5600K at Full.

Profoto D1 was 6100°K at Full, with R/G of -4. At 1/64 (its minimum) the color shift was down 525°K and the R/G error was -13.

Einstein was 5600°K from Full to 1/256 power within the stated 50°K, and R/G error was within +/-2 from 0 throught the range.

I then powered all the tested units from Vagabond Mini Lithium. Two RX600 units (1200WS) worked fine with a recycle time 6.5 seconds, same for two AB1600s (1280WS). Two Einsteins (1280WS) were fine with a slightly longer 7 second recycle. Profoto D1 500 crashed every time, even at minimum power, and would not function at all from Mini.

All units were successfully fired with CyberSync.

If you could host a separate forum with non PCB employees moderating and following very strict rules. No discusion just zap an offending post. Repeat offenders are banned.

Of interest on IGBTs and color, etc, from my post on Fred Miranda"

BrianO wrote:
Okay, so capacitor switching, IGBTs, and thyristors can all curtail the flash based on time, rather than changing voltage, but each has a different way of handling the details.

Paul replies:
Correct. Almost all monolights use voltage control, with some like WLX combining cap switching and voltage control. Most power packs primarily use cap switching but augment it with voltage control for fine tuning. All speedlights use low power IGBT switching, which provides the greatest control of color and duration. It's necessary for TTL and HSS functions. Top end packs like Grafit, Scoro, etc us high power IGBTs, as does Einstein and Photogrenic Solair.

As mentioned, the sharp light cutoff of IGBTs results in cleaner and effectively shorter action stopping than equivalent t.1 times obtained from cap switching or voltage control.

IGBT flashes require a processor algorithm to vary charge voltage as power is adjusted to achieve constant color. Without the voltage control algorithm the color temperature rises dramatically as power is lowered . . . the opposite of voltage controlled flashes.

Einstein and ultra high end IGBT packs allow changing the voltage vs power algorithm to achieve either constant color or absolute minimum durations (at the cost of color getting bluer as power is lowered.) Einstein "action" algorithm allows color to rise from 5600°K up to about 6300° at low power to achieve 1/13,500 t.1 durations at reasonable color. Durations could be made even shorter with different algorithm but color would rise into the 10,000°K range. Einstein Color Mode holds color constant at 5600°K but still achieves 1/8000 second t,1 times at lower power settings.


See http://blog.bronimaging.com/2010/01/bro ... trol-ectc/ for more explanation.

Thank you for measuring and posting color consistency results for those flashes. As we say in my biz, "data wins."

I've run into many people on Internet discussion groups who are vexed about color consistency of flash units. I've measured and posted results from the WL X1600s I have. If operated in high range from 1/1 to 1/4 and the low range from 1/1 to 1/8, mine show very little color variation. That's pretty good across effectively 1/1 to 1/32, where I usually work. The color shift is modest outside those ranges. I measured as variation of the gray card in LAB color space rather than in color temperature and R/G shift.

Each time someone pops up to say that their flash system has superior color consistency, I ask them to post test results so that we can admire them. Of course, that never happens.

Someone once asked what lighting system I'd want to show up with if Vogue asked me to shoot a cover for them. The correct answer is that I would ask whoever called me up to stop teasing me.

I don't know what is going on over at Fred Miranda but it does seem that some people are determined not to learn something.

I have been a commercial shooter for 35+ years working with all kinds of flash gear going back many years: Ascors, Flashmaster, Speedmaster, Bron, Speedotron, Norman, Balcar, White Lightning and Alien Bees. I received a BS degree in photography from RIT in 1974 and studied photography at the Polytechnic of Central London in my junior year.

You know what?

Despite the formal education and reading instruction manuals that came with my flash gear, just about everything I know about how flash units actually work (e.g duration and color temperature) I learned from your posts on various forums and on your sites.

Thanks.

Thanks for the compliments Alan. I do try to pass on what I learn (I learn everyday). There is so much faulty information on all the forums it hard for me not to comment when I see things mis-stated or misunderstood. That's what get's me in trouble. To many, ignorance is bliss.

I can assure you, measuring and grasping the meaning of flash duration and color temperature and other such topics is extremely complex and very few have any mastery. Notice I say "any mastery". I include myself in the group that has some mastery of these things.

It's like, "Does anyone really have complete mastery of Photoshop?"

Here are graphic results of my testing of Profoto, Elinchrom and Einstein units. AB1600 is almost identical to RX600 except has 50° less color shift from Full to 1/32 power.

http://www.paulcbuff.com/pcb2009/e640detail.html