Calibrating Your Camera

Verifying ISO

After you accurately tested the flash output, set your camera to manual mode. Use a shutter speed of 1/125 and the aperture to F8. Your cameras ISO should be at 100. Using your standard lens take an image of the grey card. Make sure the grey card is full frame (no other objects in the image). Now, in your camera, look at the histogram of that image.
The histogram shows that the exposure is to low. The peak should be in the middle. So, we now set our flash meter to ISO 80 and retake the image.

This histogram shows the peak in the center and is properly exposed. This tells me to use ISO 80 in the studio with this lens.

So, what does this mean?

It means, I should set my flash meter to ISO 80 and my camera to ISO 100 when I am shooting in this situation (studio, lens…) You should do this test for other shooting scenarios like outside in shade or bright sun.

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