40D: Custom WB questions

1.) I've got a grey card thats the size of a credit card. Does it have to fill the frame? I've seen some people just have models hold a larger one next to their head but i dont know if they fill the frame or not.

2.) Is there a way to set the Custom WB and find out what temperature it's set to? I've seen the Sony DSLR's tell u but I cant seem to find out on the 40D, all the WB info just says custom

The manual says that the object you are using for custom WB only has to fill the spot metering circle.

There is no way that I know of to find out the equivalent temperature of a custom WB. I'm not sure that it is even possible in all situations. For example, if your WB correction includes a large green component.

I just take a picture and when i get it into Lightroom, use that little eyedropper on the gray card to set the WB. Of course, it's after the fact but you can see the temperature & green/megenta cast from there and then sync all your pics to that setting.

When fixing things after the fact, RAW format is your friend.

[QUOTE=Steve-R;7809367]The manual says that the object you are using for custom WB only has to fill the spot metering circle.

Excuse the newbie question but after reading the manual it does not mention what f/stop or shutter speed you should use or whether a flash should also be used

Thanks

It depends on the settings that your going to use when taking The actual pic. If your using a flash, then you must do the custom wb adjustments with flash too.

[QUOTE=johnz;7887318]I​t depends on the settings that your going to use when taking The actual pic. If your using a flash, then you must do the custom wb adjustments with flash too.[/quote

In that case when you use the gray card to set up the custom white balance should you set the white balance to auto to take the shot?

Thanks

[QUOTE=colin15;7887440​]

johnz wrote in post #7887318
It depends on the settings that your going to use when taking The actual pic. If your using a flash, then you must do the custom wb adjustments with flash too.[/quote

In that case when you use the gray card to set up the custom white balance should you set the white balance to auto to take the shot?

Thanks

???

The camera cannot read your mind. When you use a grey card to set a custom WB you have to set the WB to custom to use that value. If you set WB to auto then you are telling the camera to make it's own guess at the correct WB.

On the other hand, which white balance you used when you actually took the shot that defines the custom white balance doesn't matter. You just go in and select one image, then sets the camera to custom white balance to actually use that definition of what's white.