I think that is probably not the way it is. Most film development has
been to make more uniform and smaller crystals even to stacking them
on end which sort of shoots down the various grain size theory. We
already know that digital photo sites are so small that they
essentially count the photons hitting it. I suspect that grain works
in a similar manner, especially when the photosensitive crystals are
even smaller. A crystal probably requires a certain number of
photons to hit it before it is changed chemically and would explain
why ISO gets lower with a smaller crystal structure. I think it is
more the randomness of photons for such small targets rather than the
other way round.
Winsor
Long Beach, California, USA
On Mar 10, 2006, at 11:57 AM, Wayne S wrote:
> At 05:23 PM 3/10/2006 +0000, james wrote:
>> Wayne S wrote:
>>> At 03:01 PM 3/10/2006 +0000, you wrote:
>>>
>>>> The second way to get 256 combinations from 8 grains is if you
>>>> *assume*
>>>> each grain is twice the size of the next one. i.e. grains are
>>>> not all
>>>> the same size
>>>
>>> So you would get: 0,1,3,7,15,31,63,127,255 as values, not all 256
>>> values.
>>> ...
>>
>> not if *some* grains are on and some are not then you can fill in the
>> missing numbers just like 8 bits in a computer byte give 256
>> combinations...
>
> Yes, but you can not say to one grain "turn on if the light is this
> bright, and any
> left over light, go check with these grains", ... it is not that
> selective. More likely
> the grains bigger than X will be on and all grains smaller than X
> will be off. You
> can't have one small grain turn on and one big grain turn on and
> all other grains
> in between stay off. I'm sure it is more complicated than that, but
> you cannot get
> 256 states of value from 8 binary weighted grains without some
> selection process.
> A/D converters have comparators that do this discrimination, and
> add/subtract
> circuits for calculating remainder, or in the case of flash
> converters, 256
> comparators for 8 bit converter.
>
> You may be able to get a type of log response though with a
> distribution of grains.
> Which is a bit more discriminating than just on/off single sized
> grains.
>
> Wayne
>
>
> ==============================================
> List usage info: http://www.zuikoholic.com
> List nannies: olympusadmin@xxxxxxxxxx
> ==============================================
==============================================
List usage info: http://www.zuikoholic.com
List nannies: olympusadmin@xxxxxxxxxx
==============================================
|