modeling lights with different power flash units

[Wayne Melia]

<p>How does one get modeling lights to emulate the flash output from using multiple flash units with different power outputs?<br>

For example, I have an AB (Alien Bee) 800 flash unit (bought used from a pawn shop!), and am considering adding another (possibly AB einstein?) unit so I have more than one light to work with. The AB800 is equiped with a 150w halogen bulb as a modeling light, which can be set to 'track' the power setting of the flash (as flash power is set lower, the modeling light dims). If I added another light to my kit, I would probably choose a more powerful light (bigger is better, a more poweful light can always be dialed down, ignoring for a moment colour tempurature changes).<br>

Now if I try to use them together (eg key and fill), how to get the modeling lights to visualy reflect the actual flash output from the two lights when arranging them? Does one choose modeling lights in the same ratio (watts) to the power output of the lights in watt-seconds? But watt-seconds are a measure of power in, not light out.<br>

I realize that one can:<br>

i) use a flash meter to measure light falling on different areas of the subject to get a numerical f-stop measure of the light falling on each area, or<br>

ii) chimp by experimenting with each permutation of change in light arrangement;<br>

but both negate the value of modeling lights.<br>

I hope I have explained the conundrum lucidly enough to elicit informed responses, and thanks in advance to those who offer replies.</p>

[Matt Laur]

<p>If you do go with the Einstein, and use Buff's CyberCommander remote unit along with the appropriate devices connected to the AB800 and the Einstein, it can manage the modeling light brightness for you, and make them track relative to each other - you just have to tell the unit what wattage bulbs you're using. It will already understand the the Einstein unit, but you could (for example) use a 75 watt lamp in the AB800, and tell the CC unit that detail, and it would be off and running. </p>

[jcuknz]

<p>Life was easier back in the days when all one could do was adjust the flash to subject distance :-)</p>

[Bill C]

<blockquote>

<p>Life was easier back in the days when all one could do was adjust the flash to subject distance :-)</p>

</blockquote>

<p>If you started back when I did, with a flashgun and a shutter solenoid for the sync, you'd have a choice of several reflectors. For smaller bulbs, an adjustable parabolic reflector was common. So you had to look up the guide number correction for the type/setting of your reflector. Guide numbers also depended on the shutter speed (unless it was long enough for a complete flashbulb burn). And for the faster speeds, you had to be sure your solenoid was properly adjusted (by doing test shots). Electronic flash greatly simplified the exposure calcs - THEN it was just the subject distance.</p>

[AJG]

<p>While it seems logical to want the modeling light bulbs to track flash output precisely, it isn't as useful as it might seem. The response of a digital camera (or film) is different from that of the human eye, so reading the differences in the quantity of light with your eye probably won't be that successful. A flash meter is the most precise way to determine this, although chimping would be a close second. The quality (hard, diffuse, etc.) is much more apparent if you know what you are looking for.</p>

[Wayne Melia]

<p>Thanks for the responses</p>

[ellis_vener_photography]

I don't bother and run all of my modeling lights at full power and use the most powerful ML a particular light can handle.

Are you willing to take into account differences in modifiers and distances? Don't forget that dimming a quartz-halogen or

tungsten light warms the color as well.

 

Use your modeling lights to model the shape of your light, not the ratios.

[ellis_vener_photography]

I agree with Andrew. Leave your modeling lights at full.

[ely_lenik]

<p>the modeling light isn't meant emulate the amount of light coming out of the flash unit. a xenon flashtube will emit much more light than a halogen bulb (i found that a 750w halogen light had a similar light output to a 100w strobe, but that was a loose test). <br>

the idea is just to give you an idea where your light is coming from and how it hits your subject. use the track method to get an idea for light ratios because if you have 2:1 ratio with 100w lights or 2:1 on 1000w lights, the ratio of dark to light will stay the same. f-stops work by doubling/halving the light for every stop. but really a light meter is going to be a much more accurate read. hope this helps.</p>

[ely_lenik]

<p>Just a note, the alien bee 800 is actually a 320w/s light. it's a little misleading but a marketing trick some manufacturers use (they say an "effective" 800w/s) so at 1/2 power you have a 160w/s light and so forth. you definitely need to start by knowing the w/s of both of your lights. let's say you got a b1600 which is a 640w/s in which case you would know that if you were using the same modifier at the same distance the 1600 at half power would be the same amount of effective light as the 800 at full power.</p>

<p>in a case where the flashtubes are different power but the modeling lamps are the same it can be a little misleading because they both have 150w lights in them. what you can do is free track them and set the lighting as you like it and then look at what the ratio is between them. if you have your key to fill as a 2:1 meaning modeling lamp A is at full and B is at half, then you know to keep the ratio the same between the 2 lights (might mean keeping both at full power because at full power they have a 2:1 ratio). knowing the actual watt/seconds of what is going on isn't usually as useful as knowing how many stops of light difference is between the two lights. many strobes are now controlled in terms of f/stops as opposed to watt seconds for this reason.</p>

<p>all in all a light meter is going to be a much faster and more accurate read to tell you how much light you have hitting where.</p>

<p>hope this helps.</p>