[ATM] How dark is dark?

[GF]

I think three years ago at Stellafane a fellow showed a 6" or so 
Newtonian that was baffled and gloss black inside. He claimed that with 
the right baffle design less light reached the mirrors or eyepiece than 
with flat because the reflections were directed away precisely and more 
fully.

It was a very bright day and compared to other scopes, his did indeed 
look darker. With other scopes I could see down to the mirror support, 
with his I could just barely make out the first baffle.

 I do also think though that Leitz, Zeiss, Haselblad, Nikon, Canon, and 
so on would have used this in their cameras and lenses years ago if it 
was truly better.

Gary Fuchs


hermit wrote:

>Well, want to bring up another old discussion?  I have been getting back
>into black and white photography recently.  I picked a densitometer to
>help calibrate the process.  Given the same emulsion, a matte  black
>surface will read about 1.7 while a glossy black surface will read 2.0. 
>This is a log scale.  Every .15 is half a stop so this is a big
>difference.   A full stop represents a 'halving' of the light. 
>Basically this says a glossy surface will  appear much darker to the 
>eye.  Well to the densitometer too. ;)  The densitometer is a sensor
>with a little 'ring light' around it so in both cases you are measuring
>reflected light.  Since we don't see the reflection with the matte
>surface do we just 'think' it is better for baffling?
>
>Ken
>_______________________________________________
>ATM mailing list http://www.atmlist.net/
>
>  
>