White Card vs Grey Card for White Balancing

I'm using the URSA Mini Pro, and I wanted to get suggestions on white balancing with a white card vs an 18% grey card. I've been shooting in ProRes 422 mostly.

Adam

In general when white balancing a camera, both work from a technical point of view, but sometimes depending on the lights, White will ovdrexpose sensor past 100 IRE, so a grey cards works best here, to keep the sensor level below 100 IRE for a more accurate white balance.

Thanks Denny!

Adam

I'm using the URSA Mini Pro, and I wanted to get suggestions on white balancing with a white card vs an 18% grey card. I've been shooting in ProRes 422 mostly.

Adam

Go with a card specifically designed for white balancing. Gray cards are designed to reflect 18% and may not be color neutral. You can get 60% ire white balance cards, but normal "white" white cards will work fine on the URSA. The ire to stops relationship is very linear in the over in 4.6k log mode. 0 stops 38ire, +1 stops 48 ire, +2 stops 58 ire, +3 stops 69 ire, +4 80, +5 stops 91 ire. I read Art Adams article on white balancing for lower ire values, he suggests 60 IRE. I ran a test on the URSA mini 4.6 k, setting the exposures on a white balance card from -1(29 ire) up to +5(91 ire) stops and found no significant differences in color temp or tint.

Thanks for the added info Dan, and yes I agree, a purpose made White Balance card is always the best route to go.
Cheers

I'm using the URSA Mini Pro, and I wanted to get suggestions on white balancing with a white card vs an 18% grey card. I've been shooting in ProRes 422 mostly.

Adam

Go with a card specifically designed for white balancing. Gray cards are designed to reflect 18% and may not be color neutral. You can get 60% ire white balance cards, but normal "white" white cards will work fine on the URSA. The ire to stops relationship is very linear in the over in 4.6k log mode. 0 stops 38ire, +1 stops 48 ire, +2 stops 58 ire, +3 stops 69 ire, +4 80, +5 stops 91 ire. I read Art Adams article on white balancing for lower ire values, he suggests 60 IRE. I ran a test on the URSA mini 4.6 k, setting the exposures on a white balance card from -1(29 ire) up to +5(91 ire) stops and found no significant differences in color temp or tint.

Thanks for the added info here, Dan. Much appreciated. I'll shop for a new white card.

Adam

Hi, all...what is a 60% white target? This is from the description of the X-RITE Color Checker Video: (https://www.bhphotovideo.com/c/product/1191325-REG/x_rite_msccvpr_colorchecker_video.html)

"The white target is a 60% target".

If this in fact is not a full white (IRE 100), then the card can be used for color balance only, and not exposure, correct?

It's a new world now that we have cameras that record hdr and log. Traditionally for a rec 709 curve 90% reflectance is your 100ire white. Exposing middle grey in log at 38ire is going to put white about 3.5 stops up at around 75ire. I'd be cautious about trying to white balance any log shooting camera at 100 ire, many cameras don't even write data into this region because of the way the handle the log curve.