Ratios with Speedlights

Please help me wrap my brain around speedlights and lighting ratios.

First, I am have been studying lighting and light ratios. Can anyone who is versed in light ratios help me wrap my brain around 1 + 1 = 2:1 lighting ratio? What I have gathered from my reading is that fill (1) + key (1) gives me a lighting ratio of 2:1. Am I totally misunderstanding that? Because it seems to me that if the two are the same that there wouldn't be a difference...as in a 1:1 ratio. Or does it have to do with position to get the ratio?

I have two flashes with the same gn (58). Suppose they are both on manual and zoomed to the same distance. How do I achieve a 2:1 ratio, 3:1 ratio, etc? What power increment on a flash equals to one stop of light?

I know these questions may seem quite elementary to some of you, but I really want to grasp this well.

Thanks for your time.

You will find that there are two incompatible nomenclatures applied to lighting ratios!

The recent trend/School ("Cool Dudes") has been to consider two values incident on the subject - say one from cam right & one from cam left - and if one is twice as bright at the subject as the other, then a 2 to 1 ratio is said to apply.

However . . .

the earlier School ("Old Masters") would claim differently:

Consider your key light - say 45 degrees cam right - but with your fill light on-axis, close to and parallel to, your lens axis. Now, the lights may differ (measured incident at the subject) by 2 : 1 - but adherents here would say that bright to shadow would have a 3 to 1 ratio.

Both are correct in their own terms!

Brenda.
OR is almost correct.
The only way to correctly apply ratios to lighting schemes is to first understand that light from multiple sources striking the same surface is additive.

A) fill light is on axis and reads F8 at subject. Main light is 45* off axis and is striking one side of face and reads F8 at the subject. With both lights on and meter at subject facing camera the reading will be F11, because both F8 lights are striking the highlight side of the face. And F8 plus F8 is F11. Expressing that as a ratio is 2:1

B) One light is 90* off lens axis striking the subject from camera left. The second light is 90* off lens axis striking the subject from camera right. Both lights read F8 at the subject with the meter dome pointed at the light. Meter reading from subject with meter aimed at the camera may era a bit less than F8 to a bit more than F8 depending on where in the light cone the meter is placed. When describing this lighting I tend on to refer to a ratio because the lights are each lighting a unique portion of the subject. The only way to make one side of the face brighter is to increase the light. Usually by increasing power.

Generally, ratio, is the may to express the relationship of shadow to highlight on a subject. So, if you tell me you want to have a 1:3 ratio for men and to shoot at F11, I know I need to set the main to about F9 or 10 and the on axis fill to F 5.6. That will get me close. Then the main or fill can be quickly adjusted to get the exact look and exposure.

How did I get to that? F11 is two stops brighter than F5.6 so the absolute ratio is 3:1. But since you said you wanted to shoot at F11, I really need to have the main a little under that aperture, about a 1/3 stop is a good starting point. Then put the fill in at F5.6, which I know is a bit hot. Then the meter reading for the combined lighting scheme will tell me wether I need to decrease the fill or increase the main to get to exactly F11.

Ok. I need to back up here a minute. I don't have an incident meter. Is buying a meter the only way I am going to be able to calculate ratios? I guess my brain is too simplistic and I haven't explained myself well. How does one choose a manual setting on speedlight to get the different ratios. Even if I did have a meter, where would I start? And once I had a start and wanted to change the levels, How do the increments that I see on the back of my speedlight work in relation to stops of light? Does that make any sense at all? LOL I feel like I am lost in a foreign country.

Hi, I would (did) buy an incident flash/ambient meter.

Probably you'll use it on shoots but even if you don't, it's a great learning tool.

In fact there's some really great info & videos on Sekonic's site - maybe spend some time grapling with what they offer. But when reading or watching anything on the topic of lighting ratios, I'd suggest trying to decide into which of the two camps mentioned above, the author falls. Otherwise you can end up even more confused.

A 'stop' change represents a halving or doubling of exposure - depending on the direction. So on a Speedlite, going from 1/8 to 1/4 is a one stop power output change.

Thank you for the suggestions. I will look into the videos. And thanks for the explanation on the "stops"...now that you explain it, I can say "duh" on me. LOL I should've been able to figure that out.

NewCreation wrote in post #16877822
And thanks for the explanation on the "stops"...now that you explain it, I can say "duh" on me. LOL I should've been able to figure that out.

i still have a very difficult time with ratios so i rely on stops. That's just the way my brain works, and at this point i am too old to try and reacquire the brain cells i killed that used to understand ratios. At least I think they used to understand them.

IMO, speaking in ratios is super important for communicating your vision to other people, if you work alone, just do it however works best.

Lets say in portrait that the fill light is lighting all of the face = 1 unit of light on both halves of the face.

The key light lights only the half of the face closer to the keylight (split light).

2.1
The shadow side gets 1 unit of light (fill light only)
The highlight side gets 2 units of light ( fill + key)

3:1
If the key light is 2 stops over the fill (double power = 2 units of light vs one)
highlight side gets 3 units of light and the shadow side gets 1

hes gone wrote in post #16877854
=he's gone;16877854]i still have a very difficult time with ratios so i rely on stops. That's just the way my brain works, and at this point i am too old to try and reacquire the brain cells i killed that used to understand ratios. At least I think they used to understand them.

IMO, speaking in ratios is super important for communicating your vision to other people, if you work alone, just do it however works best.

Thanks for that. My ol' brain isn't what it used to be either. I have been reading/studying trying to learn all I can as I prepare to plunge into the wedding photography pool. I have always just gone with what I liked and thought looked good. However, I thought it would be good for me to KNOW how to get what I am envisioning without too much fussing around. I won't be a master as ratios and all the math, but I do want to have a firm grasp of concepts so I can use them how I want when I want.

Nonnit wrote in post #16877866
Lets say in portrait that the fill light is lighting all of the face = 1 unit of light on both halves of the face.

The key light lights only the half of the face closer to the keylight (split light).

The shadow side gets 1 unit of light (fill light only)
The highlight side gets 2 units of light ( fill + key)

Now THAT I can grasp! Thanks!

you might want to watch this video to help understand light ratios. Mr Wallace is using studio strobes but the principle is the same for speedlights

http://blog.snapfactor​y.com/?p=392

Already we have examples of each School:
Nonnit is from the Old Master School
&
Snapfactory is Cool Dude School.

They are both 'right' - but they are not the same. Cheers

tsilva wrote in post #16878158
you might want to watch this video to help understand light ratios. Mr Wallace is using studio strobes but the principle is the same for speedlights

http://blog.snapfactor​y.com/?p=392

Thanks for the link

OceanRipple wrote in post #16878183
Already we have examples of each School:
Nonnit is from the Old Master School
&
Snapfactory is Cool Dude School.

They are both 'right' - but they are not the same. Cheers

Thanks for pointing that out so I could "compare" without getting more confused.

I also found this helpful to visualize. https://www.youtube.co​m/watch?v=9AqnZLfY77g

Brenda.Dont get hung up on light ratios.Joel Grimes has some great stuff on you tube.Go to the B&H tutorial sites.he doesn't even use one.He says that a technical instrument cannot make an artistic decision.Kinda makes sense