Using the grey card - one standard picture for pictures with the same lighting?

Hi,

I am about to take some pictures for my new website. The products in the pictures have very different colours. Is it necessary to use a grey card to adjust exposure every time I use different coloured products, or is it enough to take one picture with the grey card if I am using the same lighting for all pictures?

Also is it enough to adjust the lighting settings with the grey card on my camera, or should I do this with GIMP?

Thanks for reading, and hope someone can help this newbie!

Once you find the WB setting for the lighting, you can use it for all the images taken under that lighting and never have to worry about it again.

And you don't need a gray card. Just set a Custom White Balance by using the instructions from the manual.

Your questions open a whole area of discussion... Basically, you can take one test shot with the grey card for your lighting setup... that determines your white balance... You can also take a test shot using a method whereby you make the adjustment in the camera, and then use that setting going forward... assuming your lighting setup doesn't change...

Insuring your colors are correct is another whole area of discussion about calibrating your monitor, and creating color corrections in the software you use. I don't use GIMP, and don't know how important or even whether you can save color corrections in GIMP as a preset and whether you can apply that preset to multiple images as a group...

For exposure (as opposed to white balance), you do not need to do a new grey card reading for different items. In fact, that's the whole point of the 18% grey card. It lets you set the metering correctly for the light in manual, and prevents exposure changes that happen when your subjects are different colors or levels of brightness had you been using camera metering for each shot. So long as your lighting stays the same, just calculate the correct exposure one time with the grey card, lock those settings in Manual mode, then shoot away.