I am confused. I am reading a book on portrait photography and on the topic that talks about lighting they talk about "key light that puts out an exposure of f/8 and background/hair light that produces an exposure of f/5.6 or f/4."

I know f/8, f/5.6, and f/4 when we talk about using these as apertures in the camera. What I do not know is how this relates to setting up the lights. I have two SB-600s and an SB-800. I will be using one SB-600 for key light, the other SB-600 will be the background/hair light and my SB-800 will stay on the camera to provide fill-flash. The SB-800 will also be used to control the two SB-600s and I will place the SB-600s into different groups so I can use different light levels. In the SB-800, I can set the flash compensation to numerical values like 0.0 which means just right, positive numbers which will give out stronger light, and negative numbers which will give lesser light.

My question is, how does this f/8, f/5.6, f/4 translate to my flash settings?

Please help me ease my confusion.

Thanks.

Marco

PS:

I don't have a light meter.

I am confused. I am reading a book on portrait photography and on the topic that talks about lighting they talk about "key light that puts out an exposure of f/8 and background/hair light that produces an exposure of f/5.6 or f/4."

I know f/8, f/5.6, and f/4 when we talk about using these as apertures in the camera. What I do not know is how this relates to setting up the lights. I have two SB-600s and an SB-800. I will be using one SB-600 for key light, the other SB-600 will be the background/hair light and my SB-800 will stay on the camera to provide fill-flash. The SB-800 will also be used to control the two SB-600s and I will place the SB-600s into different groups so I can use different light levels. In the SB-800, I can set the flash compensation to numerical values like 0.0 which means just right, positive numbers which will give out stronger light, and negative numbers which will give lesser light.

My question is, how does this f/8, f/5.6, f/4 translate to my flash settings?

Please help me ease my confusion.

Thanks.

Marco

PS:

I don't have a light meter.

Allow me to try to answer your question:

Firstly, how do we know that a flash (key light for instance) is at f/8? We meter it (handheld incident meter). If you've seen monolights (studio lights), you'll notice that there's this knob behind that controls that power of your flash--i.e 1/1, 1/2, 1/4power and so on. Now, depending on the distance to your subject, you'll get different meter readings at different settings.

for instance, with your lights setup 2feet from the subject, at 1/2power, your meter reading will be so and so. While at 4feet from your subject, at the same 1/2power, your meter reading will be so and so. There are articles written on this. May mga inverse square laws pa yan if you want to get technical.

Now, depending on what you want to achieve, you can set the aperture given by your meter on your camera, or you can underexpose or overexpose or whatever. So kung f/8 lumabas sa meter, lagay mo sa f/8 yung camera mo. Kung f/5.6, then set your aperture to f/5.6, and etc.

Now, this isn't very different from Sb800. May manual mode yan. You can hold the 'sel' button for a few seconds, tapos pick 'su-4' mode then press mode until may M na lumabas sa upper left ng screen. then your sb800 works like a monolight na: 1/1 1/2 1/4 power adjustments na.

Since you don't have a meter, and you appear to be using Creative Lighting System (where you control each output via the master, Sb800). I don't think you need to trouble yourself with the aperture settings. Of course, I'm not experienced w/ CLS so maybe someone more knowledgeable can help.

Hi Marco.

The f-stops discussed in lighting books refer to the light output of your lilght source as interpreted by a lightmeter. This is then used to determine what f-stop you'll be using or your working aperture. Since you're using the SB800 to trigger the 600 speedlights, I assume you're familiar with CLS. In this case, set your camera to aperture priority and choose an f-stop. If you choose 5.6 as your working aperture, set your key to 0.0 compensation. This instructs the speedlight to give you proper exposure at 5.6. The 800 mounted on your camera may be set to "trigger mode only" or you may set it to -1. For your hairlight - which is normally half a stop or a full stop stronger than your key, set that to +.5 or +1 in the master... hope this helps.

Please post your shots at the "More on CLS" thread. I'd love to see more CLS shots in the forums.

Marco,

Did you get it to work? Post your shots naman.

It might prove easier if you simply set your flash to Manual.

You could then use the GN of your flash to compute for the aperture that you need.

f/stop=GN/distance of flash to subject

The power ratio feature of your flash would help you in controlling the fill light or in creating an accent light.

Marco,

Did you get it to work? Post your shots naman.

Not yet... I'll be doing a shoot tomorrow. I'll see if I can make it work. Thanks for the interest.

It might prove easier if you simply set your flash to Manual.

You could then use the GN of your flash to compute for the aperture that you need.

f/stop=GN/distance of flash to subject

The power ratio feature of your flash would help you in controlling the fill light or in creating an accent light.

Now, this confused me more. I see in the manual that the SB-800 has a GN of 53/174 (ISO 200, m/ft.). When I computed using your formula, I ended up with an f/stop of f/29. I'm getting more and more confused.

f/29 = 174ft / 6ft

Is this right?

Try this link (http://www.planetneil.com/faq/flash-techniques.html) out too, Marco. Or this (http://www.daveblackphotography.com/workshop/0408.htm) one. They both make very good reads. :)

Now, this confused me more. I see in the manual that the SB-800 has a GN of 53/174 (ISO 200, m/ft.). When I computed using your formula, I ended up with an f/stop of f/29. I'm getting more and more confused.

f/29 = 174ft / 6ft

Is this right?
If you're using CLS, you don't need to go manual. You just decide what working aperture you want, and the master speedlight controls everything else from there. Adding or subtracting light output from other units is also controled by the master. Just designate which group does what.
Note: These are ofcourse based on the fundamentals of manual computations. The CLS feature merely simplifies it. BUT it's not excuse to rely on full auto. Foundations muna bago ginhawa.

If you're using CLS, you don't need to go manual. You just decide what working aperture you want, and the master speedlight controls everything else from there. Adding or subtracting light output from other units is also controled by the master. Just designate which group does what.
Note: These are ofcourse based on the fundamentals of manual computations. The CLS feature merely simplifies it. BUT it's not excuse to rely on full auto. Foundations muna bago ginhawa.

Here ya go Marco... If you want real life CLS practice and expertise... This is the guy that can dish it out... Go Pocholo! :)

Your computation is right. Given that the GN of your flash is GN 174 and the subject is six feet away, you would have to use an aperture of f/29 to properly expose the subject.

The GN of 53 was computed using meters and the GN of 174 was computed using feet.

Let's use this in a practical application. Let us say that you are using ISO 100 and the flash is 10 feet away from the subject.

You would divide the GN 174 by 10 feet to get an aperture of f/17.4. That's pretty much an Aperture of f/18.

If you moved the light further away to a distance of 15 feet, your computation would be GN 174/15 feet=f/11.6

f/11.6 is somewhere in between f/13 and f/14.

But take note that your flash probably has a zoom head. The GN actually changes depending on what focal length coverage the flash is set to.


Now, this confused me more. I see in the manual that the SB-800 has a GN of 53/174 (ISO 200, m/ft.). When I computed using your formula, I ended up with an f/stop of f/29. I'm getting more and more confused.

f/29 = 174ft / 6ft

Is this right?