Homebrew PCBs

Your intensity would increase if you measure up, light falls off 
regardless of band over distance travelled.
The amount of light falling on a surface is the reciprocal, or inverse, 
of the square of the distance.
This is the famous inverse square law.

Obey the law.

On 9/19/2013 7:24 AM, Robin Whittle wrote:
> Hi Slavko,
>
> You wrote:
>
>> Robin can you test what time takes if the led is just 1 cm above
>> (instead 34) board?
> The area covered by the ligh is 1 / (34 x 34) of whatever it is at cm so
> the time scales in the same way.
>
> My exposure tests were at 30cm and I guess that somewhere between 40 to
> 80 seconds would be ideal.  If we assume 60 seconds, then the time to
> get the same exposure at 1cm would be:
>
>    60 / (30 * 30) = 62 milliseconds
>
>> I know the area will be small but I'm just interested how big efect the
>> distance have on time?
>> If source is point then relation is square from distance but the led
>> isn't point source...
> For a photoplotter you would have quite a different optical arrangement
> from simple radiant light hitting the Riston.
>
>    - Robin
>
>
>
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