[shuttertalk]

If you're ever "stuck" without a grey card or expodisc to set your white balance in the field, you can use a takeaway coffee cup lid as a makeshift expodisc. Apparently it's not 100% perfect, but good enough, and a bonus is that it might just fit into your lens hood.

http://www.flickr.com/photos/steveblackdog/5182197780/

To use, I set the focus to infinity, place the cap over, then set the custom WB. I dont even need to hold it as it fits nicely inside my lens hood, but that is just a lucky coincidence

Nice!

[nia]

I haven't heard it before, does it work really?

Thanks and love,
nia

[Zig]

Absolute nonsense surely?
Placing the cap over the lens will just reduce the amount of light.
Also, is there some confusion between setting exposure and setting white balance here?
For goodness' sake, when did people lose the basic camera- awareness to either meter off well-lit green grass for 18% grey reflectivity or spot-meter off a face and add 1.5 compensation.?(or is this just proof that people buy cameras without any thought of what they are doing?)
These little "clever workarounds" merely reveal the general camera-carrying populus to be lacking in basic knowledge and displaying the dependence of an infant on an external fix. Beats me how people are allowed to have cameras without knowing anything about light.

(er, do you reckon I could be less equivocal here..? )

[EnglishBob]

There should be a test and a permit required to own an SLR!

[shuttertalk]

meter off well-lit green grass for 18% grey reflectivity

First time I've heard that - thanks for the tip!

By the way, it is supposed to work in the same way as the expodisc does - which many people use successfully. If you think about it, the disc or coffee lid is translucent to light and will let in the ambient light in the scene - and since the coffee lid is a constant shade - your camera should be able to set the white balance off it.

Never tried it though, just saw it on the internet. Then again, what's that saying... don't believe everything you read... ?

[Zig]

You're both very gracious and indulgent in my times of ranting... Lovely to see you about Craig!

You're right of course Jules; it'd act as a diffused light source(still leaves the exposure to do though?)

The grass trick is from the days of film SLRs that were posh enough to have spotmetering: getting the exposure set from a patch of well-lit green grass, then flipping to manual, also thus having an idea of how many stops' worth of ND grad to use for skies.
White balance is now presumably newspeak for colour temperature, in a sense: ah...the bad old days of having to get up early to shoot, as colour temperature dropped like a stone in the summer months as the sun is overhead. At least with digi we don't have to lug warmup filters around...jolly expensive if using Lee filters for medium-format.