first short on my new camera

[Ernest Worthing]

A tape measure might be useful for calculating depth of field, but it's not much use for actually focusing with EF lenses, as the distance markers aren't all that accurate… it's even less useful on the kit lens, as there are no distance markers at all.

All these techniques are to aid a person in getting more usable shots. And if you are going for a really shallow dof, you're going to have trouble pulling focus to an acceptable level of sharpness when you need to anyway. But the more you stop down, the easier it will be.