Quote Originally Posted by arthurking83 View Post
I can't see how those 'lens covers' can work properly to be honest .. I think the assumption is that you and/or the camera are within the lighting arrangement that is going to cause the issue.




Unless you want the grey card to help you determine exposure, the percentage rating is irrelevant.
The 18% rating is the shade of grey that will give you a neutral RGB rendering(128, 128, 128)

Most grey cards will be 18%, as this is the most common. Handy device for determining exposure if using film(and a light meter is some kind).

If determining an accurate WB is you objective then a grey card is a grey card, as long as it is grey(and not tainted or stained with other markings and so forth)
Note you can also use a piece of (very)white paper, as long as the white paper is clean.

CFL lighting is difficult to balance properly, but mixed lighting is also a challenge to get colour balance right.

Mix CFLs and standard fluoros and daytime ambient, and you have a hard time finding a good balance.


Are these Grey Cards neccesary .. nope!
Handy .... yes for sure ... but not necessary.

My large fold up grey card thing cost about $20. Handy when it's needed, but it's not needed that often.
It folds in on itself down from 56cm to about 20 or 15cm and is easily transported in most camera bags .. so I thought it was worthwhile having.
And I've used it on many occasions too.
I think the lens covers are supposed to be taken off the camera and used in the frame just like a grey card. I think they are just put on the camera for convenience of carrying around so you don't have one extra item to carry.

I agree with what you have said here. Another thing to add is that not all grey cards are 18% grey anyway, even when they claim to be. I have 3 different grey cards (2 fold up and 1 credit card) and they are all different shades of grey. I don't actually mind the different shades as the one I find provides perfect exposure for product reviews photography I do for a Mac website and the other is better for sports so sometimes its worth experimenting with the different cards to see whether one provides better skin tones. You can see the two of the shades, supposed both 18% grey. If you download and save the picture here, you can test the white balance impact by clicking on each.



I tend to use the grey card whether I need to or not under certain conditions (artificial light) as I have learnt through trial and error which ones the camera is likely to get horribly wrong. Sometimes I'll put all 3 in frame to test the output to see if I prefer a particular look.