With the /summon command introduced , now it is possible to create endercrystals . However there's a noticable ammount of lag when ender crystals are summoned in the overworld . I guess it is due to the large ammount of lighting updates .

What I expected to happen :
It should behave like those endercrystals in the end so not much lag will be caused.

What actually happens :
It cause considerable ammount of lag.

Details:
Without ender crystals : 35-50 fps
3: 12-25 fps
6:9-16 fps
9: 5-12fps
In the end : 30-50 fps ( more than 15 crystals are present)

Steps to reproduce :
1. Go to creative mode
2. fly around
3. Do /summon EnderCrystal
4. Jump into the end , compare
( I guess it is not much noticeable in high ended devieces )

Extra: It is found that placing crystals in the air will cause even more lag . I guess that's because the ammounts of blocks requried for update is more in the air .

Also those test are made under day time . In night time it is very noticable that those crystals cause flash lights .

The screenshots show the huge difference between have it or not. Another screen shot show that it run smoothly in the end .