And for those of you wondering what RAW is and why you would use it, watch for the upcoming series of posts all about the RAW format.
NEVER? Never is a very long time. It is true that we are deleting too many of our photos these days, but should you never delete anything? Probably not, although that is a lovely photo of your shoe. Take more photos, delete mistakes, and keep the rest. A bigger mistake would be keeping your camera inside of your bag.
Always ask yourself does the image communicate? What does it communicate? Is it beautiful to look at? And if it is beautiful and something that you want to look at and admire, does it matter what camera and what f/stop the photographer used? Because even if you had this information, it doesn't mean that you would be able to replicate that photo.