About modeling light

Hello,<br><br>

1) From you experience, how powerfull a modeling light should be? I

saw that most of the studio flashes have either 250-350W or ~650W

(at theirs maximum flash output, or modeling turned at 100%). When

do you need 650W of modeling light? And when 250W is simply not

enough?<br><br>

2) Wouldn't be a 650W of incandescent light too hot for the model

or/and photographer? I have a 500W tungsten light and I feel it like

a small Sun at several meters. In the summer I'll sweat because of

it if the climate control is off.<br><br>

3) How the 3200K modeling light is not "contaminating" the white

light of the flash tube (~5600K)? The flash durration is very short,

usually 1/400-1/1500 seconds, which is way too short for an

incandescent light to shut down. The filament has to cool down to

stop emitting light. The problem seems more severe if you set the

flash

power low and the modeling light to 100% (not prop.).<br><br>

Thanks for the responses and sorry for this quite long list of

questions.

1. As bright as possible. The main problem IMO that beginners have is that they don't get the results they expect from flash. The reason for this is that the modelling lights are simply not bright enough to show the contrast. In other words, the actual contrast produced by the flash is much higher than the modelling light indicates because the modelling light is too dim and the shadows don't show up strongly.

 

2. No

 

3. Quite simply, the power of the modelling light is overwhelmed by the power of the flash. For example, if the modelling lamp (alone) needs an exposure of 1/4 sec and the camera is set to 1/125th, the exposure from the modelling lamp (and any colour shift) is 6 stops underexposed.

 

Hope this helps

My experience: 100W are a joke or nothing. Softboxes eat lots of modelling light. You can switch your modeling light of after arranging the flashes before your subject is toasted. Weaker bulbs are cheap. Getting Flashes allowing more powerful modeling light is very expensive.

1.) 250 watts if you are using any sort of light modifier -- umbrella, softbox, grid spot ,

etc., or work with the flash at any distance from the subject. For close in work you can get

by with a 150 watt modeling light as long as it is a quartz-halogen and not a tungsten

type.

 

2.) Most flash heads with modeling lights are fan cooled. This helps the heat problem to

some degree. generally you might need that powerful of modeling light if you are working

with a really big light modifier like the Plume,ltd. Jumbrella or similar ultra-large umbrellas

from Broncolor or Profoto or if you are shooting large format film. And if it is very hot, well

lots of moving air helps.

 

3.) That will depend on the shutter speed. The Sekonic L-558 meter has a percentage

feature which will automatically display how much of a flash + constant light exposure is

just the flash in 10% increments (100%, 90%, 80%, etc.) Tungsten and Quartz Halogen

lights are much less efficient at turning energy (watts) into lumens than an electronic flash

tube turns watt-seconds into lumens, so a 250 watt Quartz-Halogen light at 1/60th of a

second is about the equivalent (I say "about" as different electronic flash units have

different efficiencies of turning watt-seconds into light) of maybe a 5 watt-second flash.

For example: The modeling light alone in a Profoto D4/Acute head fitted with the standard

reflector set to the widest angle beam spread setting (100 degrees), measured at close to

6 feet & meter set to ISO 100, reads f/0.77 (really f/0.7 + 7/100ths) @ 1/60th. The

lowest power setting on a D4 2400 watt-second pack is 19 watt-seconds. repeating all of

the same settings as above I get a reading of f/4.1 (really f/4 + 1/10th) and that 100% of

the light measured at those settings is from the flash. Drop the shutter speed to 1/30th

and the reading changes to f/4.2 and now 90% of the light is coming from the flash and

10% from the modeling light. With the D4 set to 600 watt-seconds, I get f/22 from the

flash , still metering at 1/60th. So you can see that the contamination is likely to be

minimal. The good news is that you can use this contamination to your advantage by

selecting a longer shutter speed to add a bit of warmth to the image without having to

resort to filtering the camera or gelling the light.

Thanks everybody for the valuable inputs.<br>

Ellis, thanks and sorry for the confusion on 550EX thread. It was

entirely my fault.