I’ve just ordered your books. I can’t wait to read them. Till then I have a question:
When you use manual flash to set proper exposure for your subject, does it matter how you set your camera to measure the exposure of the ambient light (matrix, center-weighted or spot)? What about TTL?

Thanks.

Brad ..

Aperture most certainly does affect the ambient exposure.
And it affects ambient light as directly as a change in shutter speed would.

Where the ‘SAAF’ concept comes in, is with manual flash where there would be a methodical approach to setting the correct flash exposure. Then changing the aperture means juggling the other variables – ISO, distance, power – and hence it is easier to just change the shutter speed to affect the ambient exposure. (Shutter speed is your only independent variable here which doesn’t in turn affect flash exposure.

Yes … f4 @ 1/250 will give you the same ambient exposure as f2.8 @ 1/500

Here’s a related article which will hopefully clear things up a bit … when aperture does not control flash exposure.

Neil vN

My question is this. I remember reading the SAAF concept. Shutter speed affects ambient light and aperture the flash. I understand why shutter speed doesn’t influence flash (at least below max sync speed) but doesn’t aperture affect ambient light? I’m sure it does some but not directly as much as shutter speed does? In other words as far as ambient light goes if you shot f/4 at 1/250 will you get just as much ambient light shooting f/2.8 at 1/500? And if not why since you are allowing the same amount of light hit the sensor.

Thanks

This site and the book really helped me a lot. I thought the technical part was going to be hard but actually coordinating and posing people was far harder.

Tom, I usually add the focal length where it is important or relevant. But I only sometimes add the focal length when it isn’t of real consequence to the discussion … and then only when I remember. But I’ll make an effort. Thanks.

Neil vN

Alfredo .. at that point you will most likely not be able to use your histogram to check exposure.

To get correct manual flash exposure, you either need to:

1. check your histogram very specifically for a specific tone (white) , and how it is placed on the histogram, to the exclusion of any other brighter areas.

2. use a flashmeter. This is the simplest method.

Neil vN

On several occasions I have tried to balance ambient light with flash, underexposing a stop and added a manual flash, but then the histogram always shows underexposure. Is this normal or I’m doing something wrong?
The conditions and settings are: Sunny Day, 1 / 250, ISO 200, manual flash 1/2 power.

Thanks again,

Alfredo