Aperture

So I think I understand Aperture after reading some books etc, but everytime I read the notes I took I seem to get confused, so I guess I am just looking for some clarification...

Large # f/16= small opening (lets less light in though, right?) Full picture in focus

Small# f/4 = Large opening (I'm also assuming lets more light in) Blurry background (If I was focusing on a person or something)

If this IS the case I guess I am just a little confused...I would think the more light that is let in the whole picture would be in focus..I'm not really sure why I would think this, but it makes sense to me.

I did look at some other aperture posts, but I guess I need clarification on how I am wording it

 

The 'amount of light' is irrelevant when it comes to depth of field. The amount of light determines only if an image over or underexposed. If you want it brighter at the same aperture, just let more light in by leaving the shutter open for a longer time.

Depth of field is only determined by the aperture, as you said. If you take a very very tiny aperture, you do not even need any lenses to focus and depth of field will be more or less infinite. This is the whole idea of a pinhole camera. (OK, there is diffraction, which in the end limits pinhole photography, but this is another story.)

 

You are correct regarding apertures. Regarding your confusion, you're over-analyzing. Think a bit. You can get just as much light through a small opening as through a large opening by adjusting the shutter speed appropriately. The bottom line is that volume of light has nothing to do with depth of field.

 

AH ok...thanks so much both of you.... This has been the one thing driving me crazy. Of course light has nothing to to with DOF...This has really had me stumped for a long time. Duh

 

You already have three excellent answers from three people who KNOW what they're talking about.

Accept this information ... and move on

 

SO I havent fully gotten into SS yet, but as far as I know A fast SS freezes the subject (1/500) and a slow SS shows movement or blurs the photo (1/30)
What does this have to do with light?

 

If a shutter is open for 1/30 second it will allow more light to hit the film/snesor than it would if open for only 1/500 second (assuming the identical aperture). Kinda like watering your lawn for an hour compared with watering it for fifteen minutes (assuming the identical hose).

 

well, if you stay naked in the extreme desert sun for two seconds (short exposure time / short shutter speed), not much will happen. if you do the same for 2 hours (long exposure / long shutter speed), you will get a nasty sunburn. So with longer shutter speeds apparently more light has reached your skin / sensor / film, whatever.

 

Oh ok, so I guess I hadn't gotten to that part yet....The shutter lets the light in (sorry if I'm sounding totally ignorant). Makes total sense now. Thanks!! Sometimes I just need a little clarification.

(bare with me..to compare helps me understand better)
So...In my notes I have "in bright situations small aperture is usually a NO" But this isn't correct because aperture really isn't about the light but the DOF....so maybe I should have "in bright situations a slow shutter speed is usually a no?" Unless having a small aperture will affect my SS??? Okay, I'm thinking that doesn't really make sense and now I am confusing myself again. I guess this is why I shouldn't read books and take my own notes assuming I know what the write is talking about

 

Okay, I think I need to go back and red BigMikes reply about 20 times because I think this answers my question....have any drawings? I am really a visual learner LOL