Quote Originally Posted by Jim Neiger View Post
The effectiveness of HSS flash will also vary with the aperture. Larger less effect, smaller more effect.
Jim, I know what you mean here but I want to offer a clarification to others reading the thread.

For those reading the thread.

Lens Aperature: The larger the f/stop number like f/16, the smaller the aperture's diameter. So f/16 let's in less light then say f/5.6. The smaller the f/stop number like f/4, the larger the aperture's diameter. So f/4 let's in more light then say f/11.

Flash Exposure: Is a constant. Once flash exposure is set (i.e., exposure compensation, etc.) and you take the picture, the flash outputs a constant amount of light. Don't nit-pick over the high-speed flash sync thing here as that is not my point.

So with a constant flash output, f/4 will let more flash illumination strike the camera sensor then say f/11 or f/16. Larger number = smaller diameter = less light reaching sensor = less flash exposure to the image.

So what Jim says is true, a numerically smaller f/stop (larger diameter) will increase the flash's affect on the image and a numerically larger f/stop (smaller diameter) will decrease the flash's affect.