Monolight Modeling Light Question

dandaluzphotography · May 5, 2011

Hi Guys,

I just purchased a monolight kit that has modeling lights. I'm not sure if they all do, but this one does.

Anyway, my understanding of the use of this modeling light is to see what the brightness of the flash will be once the shutter is opened. This is used to set the proper exposure on the camera. I used it last night for the first time and didn't realize this until after I was done using it (if I'm correct).

My question is about the accuracy of the modeling light in determining the brightness of the flash. Is this something I can rely on to get the right exposure. Before I thought of this use of the modeling light, I found myself adjusting the brightness of the flash between shots to get a good exposure. If it matters, I am using flashpoint 320M lights.

Thanks,
Danny

tirediron · May 5, 2011

I'm not quite sure I follow you; the purpose of modelling lights is to allow you to "see" your light, that is where shadows will fall, and what the scene will look like in that instant that the strobe fires, not to determine exposure. Since strobes are always shot in manual, you really need a flash meter to gauge proper exposure.

Big Mike · May 5, 2011

I just purchased a monolight kit that has modeling lights. I'm not sure if they all do, but this one does.

Anyway, my understanding of the use of this modeling light is to see what the brightness of the flash will be once the shutter is opened. This is used to set the proper exposure on the camera. I used it last night for the first time and didn't realize this until after I was done using it (if I'm correct).

My question is about the accuracy of the modeling light in determining the brightness of the flash. Is this something I can rely on to get the right exposure. Before I thought of this use of the modeling light, I found myself adjusting the brightness of the flash between shots to get a good exposure. If it matters, I am using flashpoint 320M lights.

No....that is wrong.
The modeling light is used to see where you light is (and isn't). It has very little to do with the actual exposure.

Many monolights will allow you to 'track' the power of the modeling light...so that when you turn up the power of the strobe, the power of the modeling light will adjust as well. This is just so that you can visualize the difference between lights.

The exposure you would get from the modeling light...and the exposure that you could get from the flash tube (when it fires) are not going to be the same. The camera can 'meter' off the light from the modeling lights....but that won't be accurate for the flash exposure. Actually, the camera can't meter for the flash exposure....which is why you need to have the camera in Manual mode when using studio lighting.

A key point here, is that when shooting with ambient light (including the modeling lights), you exposure is determined by the aperture, the ISO and the shutter speed. But when shooting with flash/strobe...it's the ISO, the aperture and the power/distance of the light. In other words, the shutter speed does not affect the exposure from the flash/strobe. (as long as you keep it under the max sync speed of the camera).

So how do you determine the exposure settings when using your strobe? The best way is with a flash meter...but you can also use trial and error. Keep in mind that you can adjust the aperture, ISO, flash power or flash position to change the exposure from the flash.

*Note*
You can use your modeling lights to shoot (without triggering the flash)...but if you do, the shutter speed will be a factor in the exposure...and it's likely that you'll require a long(ish) shutter speed....and of course, that isn't ideal when you're holding the camera or when the subjects may move (people).
Some (usually higher end) studio lights do have a rather powerful modeling light...and can be decently used for shooting....but it sort of defeats the point of having strobes in the first place.

ghache · May 5, 2011

You dont set your exposure with your modeling lights,

You should use your modeling light to see where your light is going to fall and what shadows are created and filled.
You canlso use you modeling light to setup reflectors to see where the light goes.

Edit: Mike covered it all lol

dandaluzphotography · May 5, 2011

Hey Guys,

I live really close to where I work, so after posting this I went home for lunch and tried to meter using the modeling light. What I got was an extremely overexposed image (completely white). Lol.

I understand now the use of the modeling light from what you guys replied with.

Now...

Like I said before, I was adjusting the intensity of the flash after each pic to get to the exposure I thought looked right. In some instances I opened or closed the aperture. I kept the shutter at 1/200th (i get the rear curtain black bar above that speed) and the ISO at 100; never touched those.

How exactly would a flash meter get the exposure right? By trial and error, I was able to get a decent enough looking histogram and the picture looks ok, so it's close, but would the flash exposure meter get it even closer?

I love this forum. All the answers are here. On the flip side of that, I will definitely do my research online.

Thanks,
Danny

ghache · May 5, 2011

Your flash meeter will measure light based on the ISO setting and the shutter speed you did set your meeter at. It will give you the right aperture to use to get a weel exposed image.

Big Mike · May 5, 2011

Yes. A flash meter is put where your subject is (will be) and measures the light from the flash. You input the ISO on the meter and it will tell you the aperture to use.

Many flash meters can give you values as precise as 1/10th of a stop. (your camera probably only lets you adjust in 1/3 stop increments).

The real value of a flash meter, especially in portraiture, is that you can measure different lights and thus set the ratio that you want.

dandaluzphotography · May 5, 2011

My camera actually does both 1/2 and 1/3.

I just saw an adorama TV youtube video on light meters. I get it. They're pretty simple to use and pricey. Do you guys know of any "value priced" meters?

Danny

Ed Bray · May 5, 2011

Without being flippant, buying a light meter is like anything else, you tend to get what you pay for.

Try secondhand meters, gossen, sekonic and minolta all make good flash meters.

Buying new, I would go for something like a sekonic 308s as a minimum and if you have the bucks a Sekonic 758D.

ghache · May 5, 2011

I have a sekonic l-358. Its priced right and it works flawlesly.

Big Mike · May 5, 2011

Besides used, there really aren't many (or any) good 'value priced' options for a flash meter. The suggestions above are good ones.

Village Idiot · May 5, 2011

ghache said:
I have a sekonic l-358. Its priced right and it works flawlesly.

With Pocket Wizards.

dandaluzphotography · May 5, 2011

I think for now I'm good with the trial and error approach (at those prices). I think I will eventually want to spring for the sekonic or similar.

Thanks for all the help!

Danny

gsgary · May 5, 2011

Here you go i still have one of these as backup and it still works well
SHEPHERD XE99 Flash Meter | eBay

These are not bad
Portaflash Flash meter STUDIO LIGHTING SYSTEM | eBay

Newer version of xe99
Shepherd FM990 Electronic Flash Meter | eBay

slate mike · May 5, 2011

A used Minolta lll or Wein 500 or 1000 (I have both the lll and 1000) are both economical and good meters. I think I paid $15 for the Wein and $70 for the Minolta on ebay. The Wein is strctly for flash metering while the Minolta does both flash and ambient.