Proper Exposure Use with Diferent Colored Objects on White Background

Started Jan 25, 2013 | Discussions thread
Barrie Davis
Barrie Davis Forum Pro • Posts: 21,460
Re: Proper Exposure Use with Different Colored Objects on White Background

cmpman1974 wrote:

I have a 18% grey card. Are you saying to use AE lock with a shot of the grey card and retain that exposure level for every shot afterwards?

Yes. You got it! That's the principle.

But it isn't necessary to use Auto Exposure and then lock it. It is easier to establish a correct exposure with the grey card, and then employ those exact same shutter-speed/aperture settings across all shots using the MANUAL exposure mode. This works because...

You do NOT need to change exposure for different colours or tones of vegatables.

A tripod would be useful, too.

However, you will get better lighting if you do not use the harsh and frontal camera flash.

Instead, construct your set-up close by a window or patio doors, but out of direct sunshine. If necessary, place a white card on the opposite side to the window to bounce light into the shadows. Don't overdo this reflected "fill" lighting, or you will kill the shape, and it will not look any better than flash from the front.

Then, just before starting your shooting, perform Custom White Balance, and then do Exposure Metering with grey card.

Then get shooting.

Until your confidence in this "one exposure for all colours/tones" principle has built up, allow yourself the luxury of shooting bracketed exposures... that is, do an additional one lighter and one darker than the grey metered reading. If your camera provides, it use the Auto-bracket feature to do this. That way you will get three slightly different densities to choose from. If the process is working well, the middle one will be the right one in almost very case.

Final point: Remember to redo CWB and metering every time the light level, or light colour quality, changes.

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