I have just purchased the Lens Cal and will probably be doing this inside my dimly lit home due to the perimeter of my house not being very flat. What I would like to know is if it would be ok for me to use flash while using the device indoors? I have read that it's better to use the lowest ISO possible and I can't do that indoors. The only other option that I can think of is using a low ISO and slow shutter to let more ambient in. Any thoughts would be appreciated.