I used my grey card today to check and set up my exposure for a photoshoot using my Hi-Lite and soft box. It is really easy to do, and it is a great way to ensure that the light is balance correctly.
For the grey card to be exposed properly I am aiming for a peak in my histogram at around the hlaf way point, as that way I can ensure the grey is exposed correctly…. the other peaks are due to the other artifacts I included in the scene.
The image on the left is the back of my subject – the light falling on the grey card is ambient light and light from the Hi-lite, I know I want a white background, but I don’t want to over expose my subject with the flash on low power, I manually set me camera at F11, 1/160 sec, ISO100. I them took a second shot of the grey card (right) this time in front of my subject – you can see the grey peak again in the centre, and I got this by setting the power of my overhead soft box… I think I settle on 1/4 power.
My first shot – a clear glass shape on a clear acrylic table, there is no over exposure, the subject is lit well and it is a lovely clean shot.
I changed the subject to solid wood, left the set up the same and much less light can flow through the object but neverless it is still perfectly exposed and you can see all the detail in the wood.
Keeping the settings the same, I used some of the brand new glasses in the Cath Kidston Specsavers range to create some great product shots., whether I zoom into the subject of change lens the light stays the same, but if I change settings on the camera and decrease the depth of field, I need to change the lighting by the same number of stops to compensate – basic exposure rules!
You can use a light meter to set your exposure, you can use your camera… the grey card is just another method… have you tried it?
If you haven’t this is a useful post that explains grey card metering.