Understanding Deepth of field

[akazoly]

I read a book and write this:

To understand how dSLR cameras give you more control over depth-of-field, you need to understand the three factors that control this range:

The distance between the camera and the subject

The closer your subject is to you, the greater the tendency for the objects in front or behind the subject to be blurry.

My question is: What this mean, if subject is closer the blurry is shallower ?

 

[passerby]

I used to have a telescope - the astronomical telescope that was - which hardly used in facing upward work. 95% of it I used it to snoop my surrounding neighbours through their windows. Some of them are nice but most of them are uglies.

Anyway. The focusing ring for it is for up to 2 km distance. Anything over than 2 kms than it is in INFINITY where focusing is unnecessary. In other word anything between the 2 km range must be in the right focus - or it is blurry objects.

Once you understang thhe way the telescope works with it's long reach and need precise focusing, you know now that anything withing the focusing range must be in focus. Anything before and after it is NOT in focus - ie blurry.

Happy snooping.

 

[DSLR noob]

go outside and hold your hand in front of the camera, focus it, take a picture on your maximum aperture setting, then look at the out of focus background. Now, stand about 15 feet from a tree, focus on it, and take a picture, compare the backgrounds. you'll see that hwen a lens is focusing its light closer to the front element, then it'll have more trouble dealing with the light behind it.