ISO 400 and f8 inside the Sagrada Familia???
When I went I had to shoot at 2.8 and ISO3200 on my old 1D Mark IIN.
The image came out too noisy to be of any use
The ceiling had plenty of light. But other areas were darker, i had to use f4 and a higher ISO. Besides that lens has IS so it helps using a lower speed.
And on that day it was very bright and sunny. On cloudy days it probably is too dark to shoot without a tripod.