photo files size suddenly reduced?

Hi all

I have been taking photos with the i5700. I notice that (looking at the files in Explorer) they have suddenly dropped in size from and anverage of 1.5Mb to around 680Kb.. the resolution is still 2048x1536 for all of them. I thought it might be a quality setting but I only see this for video quality on the menu.

Something has changed.. but i don't know what.

Thoughts, please ?

 

Solved!

it has to do with brightness of the ambient light.. curious but true..

Just went out into bright sunshine and took a couple of shot.. approx 1.5Mb.. came indoors and shot a scene with plenty of detail.. approx 680Kb. : no change of any settings. if there are any

Thanks for looking anyway