Understanding manual H/L

I havent really figured it out yet.. i think.
My Sigma flash has a Manual HIGH and a manual LOW (1/16th) mode.. but when should these be used?
I tried fire off manual high on a big parkinglot and the entire image had a white veil.. i couldent see anything, it seems to be a very strong flash.

I think.. that manual HIGH should be used with a high f/ like maybe 20? But when should the manual LOW be used and what does the 1/16th mean.. is that it can not go below 1/16th.. so if i put the shutter on 1 second, wont the flash work in manual low?

I'm rather new to flashphotography so i would appreciate some answeres regardign this.

I've read the manual (poor manual.. REALLY poor) and tried google on this, i find mostly articles about high speed sync.

1/16 refers to flash power.. it has nothing (directly) to do with any setting on your camera.

High is probably 100% ( 1/1 ), low is 1/16th of the high power.

The best way to determine the power output of a specific flash unit is to place it 11 feet from a test subject. Set it to 1/1 or 100% or whatever is the highest setting. Set camera to ISO 200, shutter to sync speed and aperture to about F11. Take a test shot. Ideally with a color checker in the shot. Or at least a crumpled up white paper towel. If there are blinkies on the camera LCD stop down another stop, and make another test shot. If the blinkies are gone, open up 1/3 stop and take another test shot. If the blinkies are just starting. Then the previous test is the base exposure setting for your flash.

Once you have that base line you can estimate the proper settings for other situations.

BrandonSi wrote in post #15460464
1/16 refers to flash power.. it has nothing (directly) to do with any setting on your camera.

High is probably 100% ( 1/1 ), low is 1/16th of the high power.

Aha, thanks.

dmward wrote in post #15460523
The best way to determine the power output of a specific flash unit is to place it 11 feet from a test subject. Set it to 1/1 or 100% or whatever is the highest setting. Set camera to ISO 200, shutter to sync speed and aperture to about F11. Take a test shot. Ideally with a color checker in the shot. Or at least a crumpled up white paper towel. If there are blinkies on the camera LCD stop down another stop, and make another test shot. If the blinkies are gone, open up 1/3 stop and take another test shot. If the blinkies are just starting. Then the previous test is the base exposure setting for your flash.

Once you have that base line you can estimate the proper settings for other situations.

That sounded hard... "shutter to synch speed", what do you mean there?

bent toe wrote in post #15460572
Aha, thanks.

That sounded hard... "shutter to synch speed", what do you mean there?

Looks like there's a bit of a knowledge gap.. I'd start here.

https://photography-on-the.net/forum/showthre​ad.php?t=171657

BrandonSi wrote in post #15460583
Looks like there's a bit of a knowledge gap.. I'd start here.

https://photography-on-the.net/forum/showthre​ad.php?t=171657

Yea, flashes isent my strong side. Thanks for the link.. will look into it.