Originally posted by Not a Number In manual mode the onboard always fires at full power. You need to either use a hand held flash meter or use the Guide Number to determine the aperture to use. The GN for the K-30 built-in flash at ISO 100 is 12 meters (39.4 feet). Just divide the GN by the flash to subject distance to get the f-stop. So if the distance was 3 meters the f-stop to use would be f4 (12 / 3 = 4).
Using the onboard flash for fill is difficult in manual mode as it always fires at full power. You have to adjust the flash to subject distance or scrim or filter the flash to reduce the amount of light from the flash.
Guide number - Wikipedia, the free encyclopedia We need clarity here rom the OP. In manual flash mode yes, the flash fires at the power it is set at, but in manual exposure mode, but the flash in P-TTL mode, the flash meters correctly, it is just you are in control of the aperture and shutter
Let's find out the case first. Also, I like to use flash in Spot metering mode and concentrate on the subject, otherwise, with varying background distance the meter can take the background and this will overexposed the subject simply because exposure is a function of distance