You've seen pics posted, digital grey cards. Three cards on a lanyard, one white, one grey, one black. For once and for all, you can use them for white balance. Very helpful as a bonus for adjusting exposure later as a reference (blacks stay black, whites white, etc) Balance in LR off the white or the grey, whichever you prefer and / or whichever gives you the best results. Some shots, grey is better for me, and other shots, the white is better. Pretty cheap, and very helpful. I love em.