This is the first time I've ever candled eggs! I checked the first batch of 40 that were set 6 days ago and except for 2 that were cracked, all of them had big dark areas! Most are dark brown, so I couldn't see veins, but I could see a blob in the middle of the dark area. I used a small LED flashlite and my hand. I tried it out on some fresh eggs to have something to compare to.
I just added some pic's to my candling post: https://www.backyardchickens.com/forum/viewtopic.php?id=34629&p=2 I'm only on day 4 - could not STAND the wait...