Paul C. Buff, Inc. Technical Forum

Hi! I'm a bit confused about the concept of what you see is what you get modeling light usage.

I'm fairly new on all this so excuse me if I say something that makes no sense.

As the flash result depends on the f# used on the lens, what you see with the modeling light should depend also on the biggest aperture of the lens, which is usually used while you look through the viewfinder, since the lens remains fully opened until you take the photo, so then I do not understand how the flash unit can track the modeling light against the flash without knowing both f# , and as soon as I change the f on my camera, unless I adjust the modeling light relation to flash power, it will not be the same again.... also with the flash unit thinking it has a 250w lamp but actually having a 150w one, how can this work?

May be I'm getting the whole concept wrong?

Thanks for any help that can help me understand how this works.

Thanks!!!

Victor Wolansky

Personally, I don't really consider the camera when using the modeling lights. I look at modeling lights as a preview of how the strobe light will fall on the subject but NOT a preview of how much light there will be in the exposure. I view it by eye rather than with the camera.

When it comes to model light tracking, I've always thought of that as a way to view lighting ratios or the power of your flashes relative to one another (again by eye rather than through the camera). This way the camera and f-stop don't matter.

I hope the above makes sense. I feel like I'm not explaining it well :?:

It is a rather convoluted answer to a a relatively simple question.

First, we must distinguish the difference between the human eye and a camera sensor or film. The primary difference is the ability for the human eye to see a wider dynamic range than that of any sensor or film. I forget the approximate range of the human eye, but the best cameras are about 12 stops of dynamic range. This 12 stops then is wider than that of most (or all) monitors and paper. Additionally, the human eye can adjust quickly on the fly in real life where as the final image is rather "fixed", and you cannot adjust for detail in darker areas or lighter areas when looking at a print. If looking through an optical viewfinder, whether you are using a largish or smallish aperture, the eye and brain will compensate (at least somewhat) for the brighter or darker scene in front of them. So if you are translating model lamps from even the best systems or shooting in continuous light, the camera will record things differently than how the eye sees it, regardless of aperture, shutter speed, or ISO settings on the caemra.

Where model lamps do help is in the modeling of shadow patterns. Lets say you have a 200Ws flash (flash "A")coming from the left, and a 100Ws light coming from the right ("B"). If flash A has a 150W model lamp, and B has a 75W model lamp, there will be heavier shadows on the right side of the face of your subject (the opposite side of the stronger light source). When the photo is taken, the shadows will fall in the same direction as the ones from the model lamp.

If you were to reverse the model lamps, but leave the flash units as they are, then the model lamps will show shadows on the left, because the higher wattage bulb is on the right. But when the photo is taken, the shadows still fall to the right because the flash is stronger on the left.

Model lamps can be used for relative intensity and shadow location, but a flash meter should be used to measure the actual light output to determine the camera settings.

Thanks! Both questions make sense, I guess I got a bit confused by WYSIWYG term... but makes total sense, just wanted to be sure I'm not using it incorrectly.

Another doubt I have is, does the lamp goes off fast enough to not be part of the lighting on the photo? or one should be turning it off once one is ready to start taking the photos? I guess that depends on the intensity ratio between the lamp and flash right?

I highly doubt that the modeling lamp contributes much, if anything, to the exposure. The worst case (most contribution) is with the modeling lamp illuminated throughout the exposure. Try setting everything up and taking a picture as normal. Now disconnect the triggers tot the flashes (cords or transmitters) and re-take the picture - same shutter, f/, and ISO and see what the modeling lights contribute.

It depends on which unit you are using. Our analog lights cut the signal to the model lamp as the flash is being fired, while Einstein does so when the trigger signal is recieved. The difference in the two being a fraction of a second. In either case, the nature of a light bulb is such that when the power is cut, the filament has to cool, and there is not an instantaneous shut off, but rather a gradual shut off.

In the vast majority of cases, the intensity of the flash tube is far greater than that of the model lamp, and would not create any noticable difference in intensity or color. In teh worst case scenario, would be an E640 with full power model lamp on continuously and a minimum power flash.

At 1/250 of a second shutter/sync speed, you would capture 1/250 of a second's worth of a 250 watt bulb, a.k.a. 1Ws. Minimum power for Einstein is 2.5Ws. you would have a 1:2.5 ratio of model lamp to flash power. Again, with the lamp used as a recycle indicator, it will extinguish (to at least some degree) during the flash pulse and will not have that strong of a ratio. All other units have a stronger minimum power flash to maximum power model ratio.

If you decide it is a problem, you can lower the model lamp power via the head in some cases or the CC in all cases.

Thanks! It is not problem, I'm just wondering, it is my first time with flashes of this kind, I was using before 3 Canon 580, and I'm totally blown by the Einsteins, to the point I'm considering sell the 580, keep only one for when I go out, and get more Einsteins...

a tip..hang onto your 580's...horses for causes.. ;)

WYSIWYG has nothing to do with the camera or exposure level. A good WYSIWYG system does two things:

1. Produces the same position in the reflector and diffusion characteristics from the modeling lamp and the flash tube,

2. As you adjust power, the modeling lamp lumen output must track the flash power accurately.

Given these requirements, you can then depend on an accurate visual preview (with your eyes) of the scene as viewed with modeling lamps vs the exposure that ends up in the camera.

BUFF monolights are the only lights in the world, to my knowledge, that use fully voltage regulated modeling lamps that track the flashpower with essentially zero tracking error over the entire power range. Most other monolights exhibit up to a full f stop of tracking error over the power range, thus producing up to a one f stop visual deviation from accurate WYSIWYG.

As for the comparison of flashtube and modeling lamp position and diffusion, Einstein is absolute in this regard - the modeling and flash produce virtually identical results. This is extremely important when using aluminum reflectors or silver PLMs™, particularly relatively narrow beam modifiers.

In most monolights, the modeling lamp filament is around one inch forward of the flash tube. The typical result of this position error is that a given "standard" reflect may produce, say, an 80° beamspread and low center-of -pattern output from the modeling lamp, and, say, a 30° beamspread and a bright hotspot in the center of the pattern when flashed.

Thus the relative brightness and the coverage circle may be drastically different (perhaps a 2-3F stop or greater) in modeling vs flash error . . . WYSINWYYG (what you see is not what you get) and the modeling lamp preview and the visual modeling lamp preview becomes a nearly worthless indicator of what the camera will capture.

Thanks a lot, I understand perfectly now what this really means, and I'm totally fine with it, actually love how it works, I found it extremely useful.