very basic shutter speed tutorial....

slip · 04-17-2011, 02:27 PM

I was thinking if I extend this tutorial to explain ISO as like a light through a magnifying glass... the more the pixels are magnified, the more light is on the sensor, but the noise also increases with magnification.
or something in that line.

any thoughts?

thanks everyone for all the input so far... wondering if there is a section where we could post home tutorials? we can also target functions of pentax cameras... or is there already a section?

cheers

newarts · 04-17-2011, 03:54 PM

Originally posted by slip

I was thinking if I extend this tutorial to explain ISO as like a light through a magnifying glass... the more the pixels are magnified, the more light is on the sensor, but the noise also increases with magnification.
or something in that line.

any thoughts?

thanks everyone for all the input so far... wondering if there is a section where we could post home tutorials? we can also target functions of pentax cameras... or is there already a section?

cheers

I think a more accurate analogy goes like this:
You wait till the bucket is full for an ISO of 100. For an ISO of 200 you only fill the bucket 1/2 way (hold the lid off for 1/2 as long) then multiply what's collected by 2; for an ISO of 400 you open the lid for 1/4 as long then multiply what's collected by 4.

Because noise is proportional to the square root of the the number of photons collected, ISO 400 has twice the noise of ISO 100. (400 is 4 times 100 and the square root of 4 is 2.)

sterretje · 04-17-2011, 09:31 PM

I would use smaller buckets (as said)

Each bucket basically has it's own tap (replaces the small beam of light reflected by the subject).

Place a few buckets next to each other and imagine the taps being high(er). Open one tap; most water will end in the intended bucket but some water will end in the buckets next to it (due to splashing). That is noise.

Small buckets that only need e.g. 100 drops of water to be filled and that get 1 drop of water are already 1% full (which is noticable / can be measured); in big buckets that need 10000 drops to be filled, 1 drop will be barely noticable.

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04-17-2011, 02:27 PM	#16
slip Veteran Member Join Date: Oct 2006 Location: 2 hours north of toronto ontario canada Photos: Gallery \| Albums Posts: 3,535 Original Poster	I was thinking if I extend this tutorial to explain ISO as like a light through a magnifying glass... the more the pixels are magnified, the more light is on the sensor, but the noise also increases with magnification. or something in that line. any thoughts? thanks everyone for all the input so far... wondering if there is a section where we could post home tutorials? we can also target functions of pentax cameras... or is there already a section? cheers

04-17-2011, 03:54 PM	#17
newarts Inactive Account Join Date: Dec 2008 Location: Ames, Iowa, USA Photos: Albums Posts: 2,965	Originally posted by slip I was thinking if I extend this tutorial to explain ISO as like a light through a magnifying glass... the more the pixels are magnified, the more light is on the sensor, but the noise also increases with magnification. or something in that line. any thoughts? thanks everyone for all the input so far... wondering if there is a section where we could post home tutorials? we can also target functions of pentax cameras... or is there already a section? cheers I think a more accurate analogy goes like this: You wait till the bucket is full for an ISO of 100. For an ISO of 200 you only fill the bucket 1/2 way (hold the lid off for 1/2 as long) then multiply what's collected by 2; for an ISO of 400 you open the lid for 1/4 as long then multiply what's collected by 4. Because noise is proportional to the square root of the the number of photons collected, ISO 400 has twice the noise of ISO 100. (400 is 4 times 100 and the square root of 4 is 2.)

04-17-2011, 09:31 PM	#18
sterretje Veteran Member Join Date: Dec 2008 Location: Roodepoort, South Africa Photos: Gallery \| Albums Posts: 3,561	I would use smaller buckets (as said) Each bucket basically has it's own tap (replaces the small beam of light reflected by the subject). Place a few buckets next to each other and imagine the taps being high(er). Open one tap; most water will end in the intended bucket but some water will end in the buckets next to it (due to splashing). That is noise. Small buckets that only need e.g. 100 drops of water to be filled and that get 1 drop of water are already 1% full (which is noticable / can be measured); in big buckets that need 10000 drops to be filled, 1 drop will be barely noticable.