multigrade filters

Do two grade 1.0 filters = 1 grade 2.0 filter?

Thanks.

P. wrote:
Do two grade 1.0 filters = 1 grade 2.0 filter?


Not nessisarily, VC papers work by having 2 sensitive layers, one to
yellow, one to magenta, one is low contrast the other high contrast, so
by varying the filtration between the two, you get variable contrast.

W

P. wrote:
Do two grade 1.0 filters = 1 grade 2.0 filter?


Not nessisarily, VC papers work by having 2 sensitive layers, one to
yellow, one to magenta, one is low contrast the other high contrast, so
by varying the filtration between the two, you get variable contrast.

W

"The Wogster" wrote in message
...
P. wrote:
Do two grade 1.0 filters = 1 grade 2.0 filter?


Not nessisarily, VC papers work by having 2 sensitive layers, one to
yellow, one to magenta, one is low contrast the other high contrast, so
by varying the filtration between the two, you get variable contrast.

W

What happens when you don't use a filter on a VC paper?

"The Wogster" wrote in message
...
P. wrote:
Do two grade 1.0 filters = 1 grade 2.0 filter?


Not nessisarily, VC papers work by having 2 sensitive layers, one to
yellow, one to magenta, one is low contrast the other high contrast, so
by varying the filtration between the two, you get variable contrast.

W

What happens when you don't use a filter on a VC paper?

The Wogster wrote:

P. wrote:

Do two grade 1.0 filters = 1 grade 2.0 filter?


Not nessisarily, VC papers work by having 2 sensitive layers, one to
yellow, one to magenta, one is low contrast the other high contrast, so
by varying the filtration between the two, you get variable contrast.

W

In fact, I'd expect two grade 1 filters to be closer to a Grade 0.5 or
even 0.0 filter. They're filtering out the blue to reduce contrast (the
blue sensitive layer is high contrast, while green sensitive is lower
contrast), and you're adding two attenuations of blue light -- if (as an
example, since I don't know the actual densities) a #1 filter blocks 50%
of blue, the second layer would block 50% of what remains, meaning only
25% is transmitted. That means lower contrast, softer than #1 grade.

More complicated still, the curve isn't necessarily linear between
"grade" and filtration -- there's some grade that requires filtering
effectively 100% of blue (probably equivalent of #00), and adding more
layers of the same filters won't soften the contrast any more than that;
you've reached the point where you're effectively printing only with
green light, and can't remove any more blue. Adding a #1 and #0.5 isn't
at all the same as adding two #1s and a #1.5...

--
I may be a scwewy wabbit, but I'm not going to Alcatwaz!
-- E. J. Fudd, 1954

Donald Qualls, aka The Silent Observer
Lathe Building Pages http://silent1.home.netcom.com/HomebuiltLathe.htm
Speedway 7x12 Lathe Pages http://silent1.home.netcom.com/my7x12.htm

Opinions expressed are my own -- take them for what they're worth
and don't expect them to be perfect.

The Wogster wrote:

P. wrote:

Do two grade 1.0 filters = 1 grade 2.0 filter?


Not nessisarily, VC papers work by having 2 sensitive layers, one to
yellow, one to magenta, one is low contrast the other high contrast, so
by varying the filtration between the two, you get variable contrast.

W

In fact, I'd expect two grade 1 filters to be closer to a Grade 0.5 or
even 0.0 filter. They're filtering out the blue to reduce contrast (the
blue sensitive layer is high contrast, while green sensitive is lower
contrast), and you're adding two attenuations of blue light -- if (as an
example, since I don't know the actual densities) a #1 filter blocks 50%
of blue, the second layer would block 50% of what remains, meaning only
25% is transmitted. That means lower contrast, softer than #1 grade.

More complicated still, the curve isn't necessarily linear between
"grade" and filtration -- there's some grade that requires filtering
effectively 100% of blue (probably equivalent of #00), and adding more
layers of the same filters won't soften the contrast any more than that;
you've reached the point where you're effectively printing only with
green light, and can't remove any more blue. Adding a #1 and #0.5 isn't
at all the same as adding two #1s and a #1.5...

--
I may be a scwewy wabbit, but I'm not going to Alcatwaz!
-- E. J. Fudd, 1954

Donald Qualls, aka The Silent Observer
Lathe Building Pages http://silent1.home.netcom.com/HomebuiltLathe.htm
Speedway 7x12 Lathe Pages http://silent1.home.netcom.com/my7x12.htm

Opinions expressed are my own -- take them for what they're worth
and don't expect them to be perfect.

So can I use a 4 filter and a one filter to get a three filter, or a 2
filter and two 0.5's to get a three filter?

I have a missing three filter.

Thanks.

So can I use a 4 filter and a one filter to get a three filter, or a 2
filter and two 0.5's to get a three filter?

I have a missing three filter.

Thanks.

"Alan Smithee" wrote in message news:mOlcd.759358$gE.694343@pd7tw3no...
"The Wogster" wrote in message
...
P. wrote:
Do two grade 1.0 filters = 1 grade 2.0 filter?


Not nessisarily, VC papers work by having 2 sensitive layers, one to
yellow, one to magenta, one is low contrast the other high contrast, so
by varying the filtration between the two, you get variable contrast.

W

What happens when you don't use a filter on a VC paper?

It depends of the spectral curve of your light source.
Papers are commonly matched to a tungsten light source. VC papers would normally give a grade 2 in
such conditions.
If you have a light source giving more blue (VC papers are sensitive to blue and green, yellow stops
blue hence the soft grade, magenta stops green, hence the harder grade) than that, the grade will be
harder.

Regards,
--
Claudio Bonavolta
http://www.bonavolta.ch