f/stop confusion when light metering strobes

[tell]

A key light is usually brighter than a fill light so that if you set your key light to f 5.6 you could set your fill light to f 4 making the key light twice as bright as the fill light.
What confuses me is this: I thought the smaller the fstop number the brighter it is, so F 4 would be brighter than F 5.6, so when it comes to light metering strobes, why does setting your key light to f5.6 make it brighter than a fill light set at F 4
I do apologize for my ignorance but l am as keen as l am stupid.

[Asylum Steve]

A key light is usually brighter than a fill light so that if you set your key light to f 5.6 you could set your fill light to f 4 making the key light twice as bright as the fill light.
What confuses me is this: I thought the smaller the fstop number the brighter it is, so F 4 would be brighter than F 5.6, so when it comes to light metering strobes, why does setting your key light to f5.6 make it brighter than a fill light set at F 4
I do apologize for my ignorance but l am as keen as l am stupid.

Nah, lighting ratios can cause even the shapest minds to begin to smoke...

Here's the thing: the smaller the f/stop number, the larger the aperture and the more light it allows to pass through the lens. And vice versa...

So, to maintain a consistent exposure, as a light source gets brighter and brighter, you need to make your aperture smaller and smaller. Which means a larger f/stop number.

Ok, so say your key light meters at f/5.6. That means your camera exposure setting will be f/5.6.

So, you then set your fill. Adjust the output so it meters seperately at f/4. This means if you were exposing at f/4, the fill would be at full brightness.

But you're not shooting at f/4, we've already established you're shooting at f/5.6, a smaller aperture.

With the camera set at f/5.6, the fill light that meters f/4 will be one stop underexposed, registering one-half the illumination of the key...

[tell]

I still dont get it Steve. I should be the one with Asylum at the start of my name.
Why would a key light set at F5.6, let in more light than a fill light set at F 4?
F 5.6 is the smaller aperture and should let in less light... Ive been reading lighting ratio's and i know you're right, l'd just love to know where I'm going wrong...Maybe when my lighting equipment arrives, l'll meter up, and the lights will come on... metaphorically.

[WsW-WYATT-EARP]

seems to me your thinking opposite of what you should be for lighting ....

"I thought the smaller the fstop number the brighter it is, so F 4 would be brighter than F 5.6," This is true when your talking camera f-stops. your F4 is letting in more light than F5.6 -

now your talking lighting - set your key light to 5.6 it has to be brighter so to get a proper exposure since your lens aperture is smaller than it would be at f4 so it is letting in more light than it will be when it is set at f5.6

[Asylum Steve]

Why would a key light set at F5.6, let in more light than a fill light set at F 4?
F 5.6 is the smaller aperture and should let in less light...

Ok, this may simply be a question of semantics...

First of all, the light fixtures emit light. The camera lets light in. Try not to think of lights being "set" at an f-stop, because that's confusing terminology.

You adjust a light's power setting (or lamp wattage or distance, etc.), and "set" the camera's lens at an f-stop.

So, let's look at our two lights again, but seperately (btw, this is how you light a scene: you piece together the seperate elements, then look at the overall effect).

Again, the key light meters at f/5.6. Now, metering the fill by itself, your incident meter reads f/4.

This means to get the same average exposure as the key, you would have to open your lens up one stop to f/4.

Your right about f/5.6 letting less light, so if you leave the fill at that power level, and shoot at f/5.6, the illumination of the fill in the exposure will be cut by 1/2. The illumination of the key will be just right. Hence a 1:2 ratio...

I think the only way this will finally click is when you actually get to play with your lighting, and begin to see the relationship between the light readings and their output....

[tell]

Thanks Ben, l see l have to look at both the camera and the lights as functioning differently. i still dont really understand it. But lm sure you're right Steve, when l start experimenting with the lights l will understand the missing connection. Maybe a diagram would help. I find it curious that i am struggling with this. Hey fellows thank you for not putting in some sarcastic comment that you often see on photographic sites such as, "if you cant work out something so simple as this, you shouldnt be getting the lights... Although l dont understand the concept yet , i do have an understanding of how it should work, thanks to sites like this..

[WsW-WYATT-EARP]

just need to remember that the camera collects the light - the lights give the light - need to power the lights so the camera can be set to what you want it to be...

or you get a look you want and adjust the camera to the lights

[Grandpaw]

Think of it this way. You have the fill light set correctly at F4. Now you set the main light to be correct at F5.6. In setting the main and camera to F5.6 you are not making the main brighter you are making the fill light darker. You metered the fill for F4 to be correct and by using F5.6 (smaller opening) on the camera it makes the fill light not as bright as if you had used the original F4 reading, Jeff

[tell]

Oh dear, l remember an old Math teacher telling me, "If you can't avoid being stupid, do at least try to conceal it" But anyway l am starting to see the idea. Steve's comment about not concentrating ones attention on the lights in fstops, both Jeff and steve have me understanding that the fill light metered at f4 is only that bright if left on its own but combined with the key light and camera settings the fill light metered at f4 losses its brightness. I hope that makes sense. I can feel the presence of my Math teacher shaking his head in frustration..