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Daylight Lamps

Published : 30th July 2007

Hello everybody,

Daylight lighting and especially HMI lamps sometimes have a shift in colour – sometimes excessive magenta or other “pink-ish” feeling and sometimes other colour related problems. I’ve seen many DP´s handle this differently: gels on the lamps (STRAW, for example), on-camera correction when it’s video, leaving it to post etc.

As this is a known issue, I’d like to know how other DP´s handle this challenge.

Tal Lazar
AC / Cameraman
Tel Aviv, ISRAEL
http://www.talazar.net


class="style2">>>Daylight lighting and especially HMI lamps sometimes have a shift in >>colour – sometimes excessive magenta or other “pink-ish” feeling and >>sometimes other colour related problems

I usually add plusgreen if I find that a certain lamp is magenta. I've noticed that a lot of times when they get that magenta shift they will also turn bluish as they get old, so usually wee add some kind of a plusgreen-cto sandwich.

Jaime Reynoso
Cinematographer
México


class="style2">>>Daylight lighting and especially HMI lamps sometimes have a shift in >>colour ­ sometimes excessive magenta or other ³pink-ish² feeling and >>sometimes other colour related problems"

Watch out for dimmed HMIs, they often go green after a while. Uncorrected HMI are often so obvious(to the trained eye), especially together with kinos and tungsten.

I use plus and minus green, sometimes straw(I wish there where 1/16 filters available) I often find it necessary to correct kinos with 1/4 cto(3200 tubes) I don’t have a colour meter and like to do it by eye, it hasn’t failed me yet.
Although I listen to my gaffers with colour meters the final tweaking is done by eye, as is exposure...

Best regards and a happy new year

Jens Jakob Thorsen D.F.F.
Denmark(EU)


Jens Jakob Thorsen D.F.F. wrote:

class="style2">>>..I often find it necessary to correct kinos with 1/4 cto(3200 tubes) I >>don’t have a colour meter and like to do it by eye, it hasn’t failed me >>yet

When we bought our Kinos I was advised by a friend to buy 2800 tubes, rather than 3200, because they match real world tungsten. None of our tungsten units, floods or Fresnel’s, ever measures a true 3200 K.

The 2800 tubes match very nicely.

Wade K. Ramsey, DP
Dept. of Cinema & Video Production
Bob Jones University
Greenville, SC 29614


Wade K. Ramsey, DP

class="style2">>>When we bought our Kinos I was advised by a friend to buy 2800 >>tubes, rather than 3200, because they match real world tungsten.

That's odd.

Have you ever measured the line voltage in your studios?

If it isn't 120 volts but lower then standard 3200K bulbs like BTR's, DPY's, DTY's, etc. won't be 3200K. Another possibility, is someone buying long life bulbs like the Source Four HPL575X's? To get long life they run cooler therefore their colour temperature isn't 3200K. I use "X" bulbs for stage but not for film.

Hal Smith
Engineer and Somewhat DP
Edmond, OK


class="style2">>>That's odd. Have you ever measured the line voltage in your studios?

It's not an isolated electrical problem. There's a reason 2900k Kinos are so popular, and it's because they really do match tungsten units in regular use in a wide variety of situations. 3200's just plain look bluish in comparison to tungsten units, because tungsten units rarely burn that cool.

The exceptions are the Diva lights and any other fluorescent tubes that have U-turns in them. They don't seem to be able to make those the proper colour temp yet. Diva tubes, in particular, are really off : Diva 2900 tubes are way too magenta, and the Diva 5600 tubes are...

Well, I don't remember what the correction we used on them was, but it was weird.

I'm told that the Diva colour improves if you burn them in for 72 hours. I haven't managed to convince anyone I've rented them from to do that, so I don't rent them anymore.

Art Adams
Director of Photography
Film | Hidef | Video
San Jose, CA, USA
www.artadams.net


class="style2">>>I'm told that the Diva colour improves if you burn them in for 72 hours. >>I haven't managed to convince anyone I've rented them from to do >>that, so I don't rent them anymore.

They appear somewhat magenta and also take at least a full minute to come up to full output and achieve a stable colour temp. When you're doing live production and have to turn them on and off for going to air, it's a challenge. I do like the fact that you can dim them, though.

I ran three different live college football booth greenscreen compositing setups for the last four months, with one of them using Divas and the other two 'standard' Kinos. The lights needed to be off until seconds before going to air, because they interfered with the announcers' view of the field. The booth with the Divas required that I ride the iris (and to a lesser extent paint controls) through about 20-25 IRE's of change in the 60 seconds or so the shot was on the air. Not deadly, but certainly annoying.

Bob Kertesz
BlueScreen LLC
Hollywood, California
http://www.bluescreen.com


Hal Smith wrote:

class="style2">>>That's odd. Have you ever measured the line voltage in your studios? >>If it isn't 120 volts but lower then standard 3200K bulbs like BTR's, >>DPY's, DTY's, etc. won't be 3200K....

Yes, the line voltage varies from about 116 to 121 volts, but my theory is that the lamps rarely if ever get 120v at their terminals because of line drop on the cables and/or studio line voltage already being low. (Some day, when I've nothing better to do, I'm going to rig a VOM to the terminals in a unit and boost voltage until it is exactly 120v just to see what the colour temp will be.)

The Fresnels have glass lenses, some of which are yellowed (but even those that aren't don't get above about 3000K) and probably dust and burned bugs on the reflectors of open face units. But even clean, any time light is reflected off another surface it loses about 100K.

In any case, the 2900 Kinos look perfect with our tungsten.

Wade K. Ramsey, DP
Dept. of Cinema & Video Production
Bob Jones University
Greenville, SC 29614


Wade Ramsey wrote:

class="style2">>>When we bought our Kinos I was advised by a friend to buy 2800 >>tubes, rather than 3200, because they match real world tungsten.

I found this to be the case too when I attended UCLA film school (many were 25 plus years old). I am sure Bob Jones University where Wade works has equally as old Mole Richardson type lamps. Open them up and look at the reflector. Instead of a nice mirrored surface you'll probably find a rusty flaky reflector, thus giving you that extra 1/4 CTO for free, and also pretty drastically reduced light levels. Additionally, as another posted posted, the line level might be way below 120V as it would be front a plant or proper soundstage transformer.

In the real world (newish well maintained fixtures from Cinelease and Paskal), tungsten fixtures do measure closer to 3200. Kinos are a strange animal. I've always found that Kinos look cooler/bluer as an edge than they do as frontal fill. Anyone else find that?

Roberto Schein
Los Angeles
Chief Lighting Technician (IATSE 728)/ Sometimes DP
http://www.robertoschein.com
M: 310-592-6158


I recently learned that wrong orientation of the Diva fixture can give you a 400 degree colour shift, toward green. The manual states that the lamp base should always be the higher end of the tube:

"This orientation keeps the mercury away from the cathodes and provides best colour temperature stability and best colour rendering. DO NOT operate fixtures with lamp base in the down position. Colour can diverge up to 400K and will get very green."

Even when horizontal, the lamp base should be slightly higher than the lamp base.

I like the Divas for their dimmers and for their no separate ballast convenience, but I have not been happy with their colour. Maybe this is why.

Pat Blackard
DP/Gaffer
Austin, TX


class="style2">>>I've always found that Kinos look cooler/bluer as an edge than they do >>as frontal fill. Anyone else find that?

I've found that any light source with a slight colour bias shows that bias more when used as an edge light than as a frontal light. I don't know why... something about spectra shifts when light bounces off a surface or something. I know that the wavelength gets longer every time you bounce or diffuse a source so maybe an edge light shifts a bit and exaggerates an otherwise unnoticeable hue.

The best way to find that an HMI has a colour shift is to use it as a scratch light.

Art Adams
Director of Photography
Film | Hidef | Video
San Jose, CA, USA
www.artadams.net


class="style2">>>I like the Divas for their dimmers and for their no separate ballast >>convenience, but I have not been happy with their colour.

At this price point, the Diva is a VERY expensive one-trick-pony.

The dimmer is next to useless unless you don't mind juggling colour correction every time you use it. Fine for single source work, of course.

A very under whelming product from a company that makes some really cool stuff.

David Perrault, CSC


class="style2">>>I've always found that Kinos look cooler/bluer as an edge than they do >>as frontal fill. Anyone else find that?

I found that any light used as an edge or hair light tended toward a cooler temp, even tungsten lights. I remember my Dad telling me that he always put a 1/4 straw on any back light to balance it to the key.

(This in an era before Kinos, HMIs and LED's)

Sincerely,

Ed (strike the arc on that brute) Colman, President
SuperDailies, Inc.
Cinematographer Supervised Video Dailies
www.superdailies.com


The cooler quality is caused by reflective other than absorbed light from light source to camera.

I can guarantee that Bob Jones reflectors are well maintained.

Bulb manufacturers do not normally make lamps at 3200 degrees although the Dedo comes very close. Mole Richardson lamps work better with DC current although its difficult to find DC on any Hollywood stages.

Roy H. Wagner ASC
Director of Photography


class="style2">>>...manufacturers do not normally make lamps at 3200 degrees...Mole >>Richardson lamps work better with DC current although its difficult to >>find DC on any Hollywood stages.

How does the DC vs AC help this issue?

I'm curious as we recently shot in Paramount's DC Utility room which had DC generators dating back to 1904. A great facility (and amazing looking too)... but word is it will close down in 2 years to be converted into a cafeteria. Paramount lighting is always very happy to have anyone use DC - which is almost nobody (need for old DC dimmers and so on).

Just curious though on other side-effects of the flat line current, as most of us were raised mostly on AC.

I know one advantage of powering coops via DC is that they don't bug the sound dept anymore. Now bring out the beautiful carbon arcs.

Mark Doering-Powell
LA based DP


class="style2">>>Just curious though on other side-effects of the flat line current, as >>most of us were raised mostly on AC. I know one advantage of >>powering coops via DC is that they don't bug the sound dept anymore.

Yes, quiet lamps are a bonus, as is the fact that (expensive) bulbs last much, much longer when not being pulsed on and off 60 times a second. No flicker issues at any frame rate, either. Highly simplified power distribution (no three phase, no neutral).

Some down side issues are the mechanical (and thus HUGE) individual dimmers, incandescent bulbs only (in general), and of course the fact that enough DC is only available using, as you mentioned, ancient generators.

Bob Kertesz
BlueScreen LLC
Hollywood, California


class="style2">>>Yes, quiet lamps are a bonus, as is the fact that (expensive) bulbs last >>much, much longer when not being pulsed on and off 60 times a >>second. No flicker issues at any frame rate, either

Hi Bob,

Please give me a feel for what a 10kW or so completely self-contained DC dimmer and power supply with analog and DMX inputs might be worth to the production community. I've done a fair amount of power supply customisation and design over the years and could produce them either from scratch or by modifying existing commercial supplies. At 10kW they'd be three phase input with dimmable 120 volt DC output. I could get the ripple down to 1% easily.

Hal Smith
Engineer and Somewhat DP
Edmond, OK


class="style2">>>Please give me a feel for what a 10kW or so completely self-contained >>DC dimmer and power supply with analog and DMX inputs might be >>worth to the production community.

Wow. Not a clue. Sorry.

Bob Kertesz
BlueScreen LLC
Hollywood, California



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