Pixtus - Photography Forum, Photographers, Photo Tips

jchooper12 · **Metering -** 02-07-2007, 10:33 AM

Scott Watters wrote this in another thread.
--------------------------------------------------------------------------------
To set your light ratio, meter the light individually with the dome pointed directly at the strobe. For the main exposure, point the dome directly at the camera position and meter with both strobes active. Then use the aperture indicated for your exposure.
--------------------------------------------------------------------------------

Scott, the method of metering above will tell you what apeture to use based on a ratio you set between the fill and main but what is the best setup method to use if you want to ensure you are shooting at a predefined aperture. So lets say I want to shoot at f8, what are some easy steps to follow to get your main and fill set up correctly. Then also, above I assume you are talking about main and fill lights, how do you add a hairlight and background lights into the mix. Do you want to meter each light indivually first then turn on the other lights and see what you get for apeture reading? If you or anyone else has ideas on this please share.

Thanks

jchooper12 · **No Takers? -** 02-08-2007, 05:20 PM

I hope someone here can shed some light on this!!!

Randy Couper · 02-08-2007, 11:31 PM

There are two wasy to meter; metering for balance, and metering for exposure. There are front and non-front lights. Metering front lights are metered with the dome out, metering non-front lights is with the dome in. If you want your camera to expose to f/11 then set you main to f/11 and your non-front lights to be whatever you want them to be to that relationship. Don't forget too that light is "additive" in nature and often adding a fill will often add another 1/4 of a stop to certain areas. Metering is hard to describe and put "in a nutshell" it's best to read and experiment. But setting the main at whatever you want your camera to be is a good start.

srwatters · 02-09-2007, 08:04 AM

If you want your final aperture to be f/8, then meter your main alone for maybe 1/3 stop below that (f/7.1). When you add the fill at it's ratio, check the value pointed at the camera. Adjust as needed, but remember to adjust both the key and fill to keep the desired ratio.

In truth, I cheat and just move the light fore or aft to get what I want or better yet, just adjust the aperture +- 1/3 stop. If shooting a zoom and DOF is critical, you can step forward or back just a touch and re-zoom to keep it constant with a change in aperture.

For portraiture, +- 1/3 or even 1/2 stop shouldn't adversely effect the image. IMHO, of course.

bfphoto · 02-09-2007, 07:42 PM

OK, let's say you want f8 at a 3:1 ratio. The main light will have to be 1 and a half stops more than the fill. If fill is f4 then the main would have to be f5.6 and one half. Each light is metered with the dome pointing toward the light one at a time. Point the dome toward the camera and fire both lights to get the f stop for the camera. (Same as what Scott said) It should be close to f8, but if is not, adjust both light up or down the same amount to get the desired f stop.

For secondary lights, I set at the same power as the fill as a starting point and adjust up or down until I get the desired effect. For a hair light, the power would be less for a blond and more for someone with black hair.

bondarnes · 02-09-2007, 08:06 PM

Quote:

Originally Posted by bfphoto

OK, let's say you want f8 at a 3:1 ratio. The main light will have to be 1 and a half stops more than the fill. If fill is f4 then the main would have to be f5.6 and one half.

According to my old Upton and Upton Photography Book what you just described is actually a 1:4 ratio. It seems that recently there has been some disagreement on ratio lighting. As I learned it from Dean Collins back in nineteen-hundred-and-none-of-your-business your fill light gives you one unit of light and since your main light is one and a half stops brighter it is giving you three units of light. However since your fill light also contributes one unit of light to the highlight area then three plus one would equal four. And the correct way to say it is "a one to four ratio". It only becomes important when two photographers are talking about a certain ratio, but one is using the terminology as it has been taught for years and the other is using something else.

bfphoto · 02-09-2007, 08:33 PM

Thanks Don, I think you are right. I forgot to add in the fill. It's been a long time since I saw Dean too. I seem to be forgetting a lot lately. As far as 1:4 or 4:1, I've heard it presented both ways, and never really figured out which was right. I just know that I usually set my main one and one half stops more that the fill and that's the ratio I seem to like best.

Anyway, thanks for reminding me.

bfphoto · 02-09-2007, 09:17 PM

Hey Don, I found out where I went wrong. What I was illustrating was reflective light readings not incident. If you take a reflective light reading off the highlight side and then the shadow side, then what I was stating is true. A 2:1 ratio means the highlight side is is twice as bright as the shadow side so there is a one stop difference between the two. In a 4:1 ratio, the highlight side is 2 stops brighter than the shadow side. I'm sure eveyone is totally confused by now, but the difference is in how you take the meter reading, reflective off subject or incident, light falling on subject.

When you go to different instructors, who teach different methods, it can get confusing.

Randy Couper · 02-12-2007, 10:01 AM

There seems to be some misinformation on this thread, which isn't suprising considering that metering is both a critical and often misunderstood science. It's been said that photography is 1/2 scient and 1/2 art, and metering is one of the science parts ;)

When you say "one unit" don are you talking about one stop? If so that's definitely not true. The additivie nature of lighting that you're refering to often makes more like a 1/3 of a stop, but it depends, there's a forumula that determines the value and it's not that simple, I won't claim to know it off the top of my head either but I just look it up when I need to :)

As for metering with the dome point in/out, again as I mentioned, it depends on whether you're metering front or non-front lights.

Quote:

Originally Posted by srwatters

In truth, I cheat and just move the light fore or aft to get what I want

Of course, that changes the "quality" of the light as well. The rest of the stuff you mentioned reiterated my original post.

srwatters · 02-12-2007, 11:08 AM

Quote:

Originally Posted by Randy Couper

Of course, that changes the "quality" of the light as well. The rest of the stuff you mentioned reiterated my original post.

I'm talking about moving a softbox in or out six inches to adjust for +- 1/3 to 1/2 stop. I seriously doubt that will have a visible effect on the quality of the light, but I suppose it is possible. In any case, unless you're shooting slides, I wouldn't run my lights that close to a limit. Metering is an exact science, but for portraits like John is talking about, it just isn't that critical. YMMV.

Randy Couper · 02-12-2007, 06:14 PM

Maybe you set up your lights that way, but not everyone wants to. I was merely answering the question... but thanks for explaining. Metering and calculating ratios and the additive nature of lights definitely part of the "science/math" of photography and shows that it isn't a "pure art" as some say.

bondarnes · 02-12-2007, 09:43 PM

Quote:

Originally Posted by Randy Couper

When you say "one unit" don are you talking about one stop? If so that's definitely not true. The additivie nature of lighting that you're refering to often makes more like a 1/3 of a stop, but it depends, there's a forumula that determines the value and it's not that simple, I won't claim to know it off the top of my head either but I just look it up when I need to :)

As for metering with the dome point in/out, again as I mentioned, it depends on whether you're metering front or non-front lights.

Not always being informed to the highest degree of accuracy, I hesitate to elicidate and articulate upon your statement for fear that I might deviate from the true course of rectitude. However, having a college degree in photography and many hours of graduate studies I will nonetheless plunge into the lighting ratio abyss.

The unit of light that I mentioned is not an f-stop of light. It is an unspecified quantity of light. It could be f2.8, or f5.6, or 300 lumens, or 3,000 foot candles. But it is a measureable quantity of overall (fill) light and it has a value of one unit of light. For illustration we will say that it is f5.6.

If we add another light that in this illustration measures f5.6 or is equal to the fill light then we have our subject's highlight side receiving one unit of light from the second light plus one unit of light from the first light equaling two units, while the shadow side receives only one unit of light from the fill light this would give us a 1:2 ratio.

If we increase the output of our second light so that in this illustration it now measures f9.5 or one and one-half stops more light and we know that f8 would be twice as much light as f5.6 so that would equal two units of light and the additional amount of light to bring us up to f9.5 would raise the total amount of light from the second light source to three units of light. Add to that the first light's one unit of light and we have a 1:4 lighting ratio.

Use of a dome of any type is to simulate the roundness of the human face. I only use a flat disc, because I only want to read light from the direction I am pointing the meter. This is especially important outside when light coming straight down will register on your dome, but sometimes it is not striking the face of your subject because their hair hangs over their forehead or for some other reason.

Different people have different methods of metering and I encourage you to use what works for you. But over the years I have found that the method I use gives me the exact lighting ratios that I like and my results are very consistent.

JP Images · 02-22-2007, 10:10 AM

Quote:

Originally Posted by jchooper12

So lets say I want to shoot at f8, what are some easy steps to follow to get your main and fill set up correctly. Then also, above I assume you are talking about main and fill lights, how do you add a hairlight and background lights into the mix. Do you want to meter each light indivually first then turn on the other lights and see what you get for apeture reading? If you or anyone else has ideas on this please share.

Thanks

Too many varaibles... The type of light modifiers, size of them, distance from each light to subject....

But why does it matter if you are shooting digital? With 2/3 stops it's a whole new game!! Set your main, add you fill for the desired ratio (if your even are using it...) and then set your BG, hair, kicker or what ever else you want.

When I meter it is with dome in (and I meter a lot...) and aimed right back at the light source. After setting my ratio I split the distance between light & camera and then take a reading with both main & fill lights firing, this is my camera setting. With this reading I now can set my hair, accent and BG lights.

If I use a fill light it is always lighting the mask of the face. I have no pre-set lighting ratio that I use for anything, I light case-by case rarely using the same thing twice.

Play with light, and write it down...