photography class

[chessieiglr8402]

Good morning all. I am taking a physics of light class at the University of Maryland, and right now we are talking about cameras and f-numbers and exposure time. I am working on some practice problems for class and I am not understanding how these two things work together to make a good photograph.

The question is
An exposure meter indicates that, if a correct setting for a photograph is f/5.6 at 1/100 second, then f/11 at 1/25 second is also correct for the same two conditions. Explain this.

I have read the book looked at the notes and i am so lost by this. Can anyone explain this to me in terms i might actually understand??

Thanks in advance.

Amy

 

[boBQuincy]

Ah, the physics of photography, that's one of my interests and fields of study!

Each f stop indicates twice or one-half as much light as the next. f stops are actually a fraction, so as the number gets larger, the opening gets smaller.

f 11 is half as large an opening as f 8, which is half again as large as f 5.6. To get the same exposure at f 11 as at f 8 then takes four times as long, so the shutter has to stay open for 1/25 second instead of 1/100.

 

[chessieiglr8402]

Thank you for the help, I think that I actually understand it. It is a very interesting class and it has helped me with some of my photos that I have taken. They actually look better than before I understoof what I was doing with my camera

Thanks again

Amy