White Balance: Do I need warm cards?

rrcolwell

I just bought a 7D and also the Blue Crane Videos to go with it (a life saver to this beginner). I have been learning about WB and looking online at different cards, etc you can buy. There is a set on B&H called warm cards. My main photography is going to be portraits of people. My questions are:
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1) If I am doing portraits only do I need warm cards or can I just get by with just a white card?
2) What is the difference between white cards and grey cards?
3) What is a black card for?
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Please understand that I am an amateur photographer, I had a Rebel for years but never took it off the automatic setting. I am just learning about aperture & exposure (it is like discovering an entire new language for me and I am absolutely loving it), etc so you really need to dumb down your answer for me. Thanks

Scott_Quier

I reformatted for better readability and embedded by answers below:

rrcolwell wrote: »

I just bought a 7D and also the Blue Crane Videos to go with it (a life saver to this beginner). I have been learning about WB and looking online at different cards, etc you can buy. There is a set on B&H called warm cards. My main photography is going to be portraits of people. My questions are:

1. If I am doing portraits only do I need warm cards or can I just get by with just a white card?
   If you use a "warm card" as a WB reference in post, (looking at the B&H site here, it appears the "warm card" is, in fact, a warm color) I would think you would end up with cooling effect - usually not what you want for portraits. On the other hand, there is a cooler colored card in the set as well and using this as a PP WB refernce will cause your photos to come out warmer.
   
   
2. What is the difference between white cards and grey cards?
   The luminosity of the card. A white card will be white. A gray card will be gray. Both will be neutral in color. The intent is that the gray card will also allow you to better judge your exposure (they are usually, but not always, about 18% gray).
   
   
3. What is a black card for?
   You got me on that one. A very large black surface can be used to subtract light from a subject, but I don't think that's what you referring to. A link to whatever you are looking at would be nice.

Please understand that I am an amateur photographer, I had a Rebel for years but never took it off the automatic setting. I am just learning about aperture & exposure (it is like discovering an entire new language for me and I am absolutely loving it), etc so you really need to dumb down your answer for me. Thanks

rrcolwell

Scott_Quier wrote: »

I reformatted for better readability and embedded by answers below:

This is from B&H:
http://www.bhphotovideo.com/c/product/529526-REG/Digital_Image_Flow_DGK_1_Digital_Grey_Kard_Standard.html#features

rrcolwell

Scott_Quier wrote: »

I reformatted for better readability and embedded by answers below:

So it sounds as if a grey card would be all I need?

InsuredDisaster

Without looking at the image, I beleive the "black card" is used to set a black point in your image. Forget where i've seen this, but someone used these cards and the dropper tools in photoshop to set the blackpoint, white point, and then the white blance since he had a known reference point as to what should be white, black and grey.

I save a buck or two and just wing it and turn up the blacks until it looks about right.