Flash exposure compensation direction

[Blind Bruce]

I can't wrap my head around which way to vary my FEC. Eg if I am shooting a white dress on a white background, do I go - or + to keep the skin tone? Being color blind, I want to know ahead of time rather than looking at the result.

 

[fmw]

All that white will tend to underexpose the subject so you should add some exposure compensation - perhaps 1 1/2 stops. Another option would be to spot meter the face.

 

[Blind Bruce]

So would that be "-"? If it were blacks would that be "+"?

 

[Overread16 4]

When you meter a scene the camera (and flash) aim to produce a middling grey tone as its default exposure. This means that if you point your camera at a very bright subject (like snow, sky or a white dress) the camera will underexpose the photo and you will get a greyer subject due to the underexposure.

Similarly if you aim at a dark subject the camera will try to expose it brighter than it would otherwise be.


This is where exposure compensation comes in. By using exposure compensation in the camera (forget the flash for just a moment) you can tell the camera to take its meter reading and over or under expose using the settings it has control over (if you're in manual mode you just pick the settings yourself that give the desired amount of over or under exposure).
The camera then adjusts its setting based on teh meter reading and the exposure compensation.


Eg:
A white dress; the camera would meter and aim to expose it as grey and thus underexpose; you'd thus tell it to over expose and thus it would be + exposure compensation; the camera will thus meter the scene and set the exposure to over-expose based upon what it read the light to be.

Result should be a properly exposed dress


Flash exposure compensation is exactly the same; only instead of changing a setting in the camera the flash puts out more (+) or less (-) light to balance the exposure based upon the meter reading

 

[wfooshee]

In your example, you want more flash, so it would be +.

The plus or minus is what you're doing with the light from the flash; adding or subtracting from the metered value.

 

[fmw]

So would that be "-"? If it were blacks would that be "+"?

Other way around. Add exposure (+) for your white subject. The (-) would be required for the black cat in a coal bin.