Start here.
With the same light, distance, modifier and ISO, double the flash power. For example, change 1/32 to 1/16. Then meter again. That should move a flash reading from f/4 to about f/5.6.
Your three next steps
- Take a flash-only reading at the face.
- Double power: for example, 1/32 to 1/16.
- Meter again. Use the small power steps to reach your goal.
In this lesson
The number is a meter reading
Your camera aperture and your meter reading are not the same control. The aperture is the opening in your lens. The meter tells you how much light arrived at its position.
If you want to shoot at f/5.6, keep the camera there. Adjust the flash until its reading is near f/5.6. For this simple test, use one flash and keep room light low.
One stop means twice as much light
The common whole-stop meter steps are f/2, f/2.8, f/4, f/5.6, f/8 and f/11. Each move to the next larger number needs about twice the light at the meter.
So f/4 to f/5.6 needs one stop more. From f/4 to f/8 needs two stops more, or four times the light. At a fixed distance, try 1/32 to 1/8 for that second example.
| Meter reading now | Goal | Power change to try |
|---|---|---|
| f/4 | f/5.6 | 1/32 → 1/16 |
| f/4 | f/8 | 1/32 → 1/8 |
| f/8 | f/5.6 | 1/16 → 1/32 |
Keep the test fair
Keep the flash, zoom, softbox, grid, aim, distance and ISO fixed. Let the flash recharge fully. Use manual power so TTL does not change it for you.
Hold the incident meter at the face. For this camera-exposure check, aim its raised dome toward the camera. Turn other flashes off for the single-light test. Then check all lights together before the real photo.
What if power is already at full?
You can move the light closer, but that also changes the spread and look. For a small source, moving from 3 feet to about 2.1 feet is a one-stop starting estimate. A big softbox close to a face can behave differently. Meter it.
You could also raise ISO or open the lens, if that fits your photo. Both choices affect more than flash. Check the background and depth of field again.
Do not guess power from the flash name
Two setups with the same flash can give very different readings. A grid, softbox or greater distance can change the result. Start with one measured reading from your own setup. It makes the next step much easier.
Remember this
One stop up: double power. One stop down: halve power. Keep the setup fixed and meter again.
Use your reading. Get the next setting.
Enter the power and meter reading you have now, then choose the f-stop you want.
Find my flash power →Sources & further reading
These are original lessons with our own examples. The links below explain the related principles.
Published by DNA Premium Portraits with AI assistance. This lesson is educational; a suggested setting is not a tested result for your exact setup.