Need Help with iso and exposures

[hectcal]

So i have this assignment question: "You are using 100 speed film and your meter gives you an exposure of F16 @ 1/60. What are three different equivalent exposures if you change the ISO to 400 speed?"

I don't need the answer as i want to figure this out myself, i just want to know if ISO 100 is four times slower or faster than ISO 400. Also, i would like to know if i need to let more light in or less light in according to ISO change.

 

[SCraig]

No, ISO 100 is not 4 times faster (or slower) than ISO 400.

Yes, you will need to let more light or less light in when you change ISO.

 

[hectcal]

so do i need to let in 4 times as much light in when i change from iso 100 to 400

 

[hectcal]

i came up with f/11 @ 1/125s, f/22 @ 1/30s, and f/8 @ 1/250s are these all equivalent to the original question?

 

[KmH]

Yes.

 

[hectcal]

thank you

 

[SCraig]

so do i need to let in 4 times as much light in when i change from iso 100 to 400

I don't need the answer as i want to figure this out myself

As you said .....

 

[hectcal]

so do i need to let in 4 times as much light in when i change from iso 100 to 400

I don't need the answer as i want to figure this out myself

As you said .....

i meant i didn't want answer to original question in quotes, not every question that i asked but thanks for the help

 

[Helen B]

The ISO number, when it is written like ISO 100 or ISO 400 is directly proportional to the speed, so ISO 400 is four times faster (four times more sensitive) than ISO 100.

 

[SCraig]

The ISO number, when it is written like ISO 100 or ISO 400 is directly proportional to the speed, so ISO 400 is four times faster (four times more sensitive) than ISO 100.

You are absolutely right. Not sure where my head has been all day but it certainly hasn't been thinking straight. Hectcal I apologize for the bad information and Helen thanks for correcting me.

 

[Light Guru]

So i have this assignment question: "You are using 100 speed film and your meter gives you an exposure of F16 @ 1/60. What are three different equivalent exposures if you change the ISO to 400 speed?"

I don't need the answer as i want to figure this out myself.

Use this simulator to help yourself figure it out.
http://www.canonoutsideofauto.ca/play/

 

[pisto1981]

So i have this assignment question: "You are using 100 speed film and your meter gives you an exposure of F16 @ 1/60. What are three different equivalent exposures if you change the ISO to 400 speed?"

I don't need the answer as i want to figure this out myself.

Use this simulator to help yourself figure it out.
Play | Canon Explains Exposure

Thanks for this link, very helpful

 

[Jad]

ISO or ASA is based on a factor of two, as are all of the other elements of the exposure triangle (shutter speed, aperture and sensitivity), so that when a number doubles, so does the sensitivity. If you change your ISO from 100 to 200 you have doubled (2x) (100% increase) the sensitivity of the camera sensor to light (less pixels required}. So the best way to express a change from ISO 100 to 400 would be a (4x) or 400% increase in light sensitivity required to make an image on either film(less silver grains) or a sensor (fewer pixels needed) Only the aperture and the shutter speed controls that amount of light coming into the camera.

 

[Helen B]

If you change your ISO from 100 to 200 you have doubled (2x) (100% increase) the light coming into the camera.

Did you mean that? If anything, a change from ISO 100 to 200 would permit a halving of the light energy 'coming into the camera'.

 

[480sparky41 40]

ISO or ASA is based on a factor of two, as are all of the other elements of the exposure triangle (shutter speed, aperture and sensitivity), so that when a number doubles, so does the sensitivity. If you change your ISO from 100 to 200 you have doubled (2x) (100% increase) the light coming into the camera. So the best way to express a change from ISO 100 to 400 would be a (4x) or 400% increase in ........

Technical correction: making any changes to the ISO does not change how much light enters the camera.

What changing the ISO does do is allow you to change either the shutter speed and/or the aperture to compensate for the increased processing the camera will perform on the sensor data.