Why Magenta and Yellow

[dennyr]

Wanted to ask about enlargers that have integral filtration.
I realize some enlargers DO use Green and Blue, which seems more intuitive to me.
Though i have never used one.

However, it seems MOST enlargers use a Magenta and Yellow filter.
Why is that.?
I have never printed color (by myself) Is that the reason.?
Are enlargers that use Green and Blue just contrast colors for printing Black and White.?
Again, i have never used a Blue and Green enlarger, so i am not sure if they have a third color or not.

Thank You

 

[480sparky]

Variable contrast paper is sensitive to blue and green........... which are opposite magenta and yellow on the color wheel.

 

[dxqcanada]

This is an explainer from Ilford

https://www.ilfordphoto.com/wp/wp-content/uploads/2017/03/Contrast-control-for-Ilford-Multigrade.pdf

 

[dennyr]

Variable contrast paper is sensitive to blue and green........... which are opposite magenta and yellow on the color wheel.

Right, but WHY use "Magenta" to pass Blue in stead of Blue and why use "Yellow" to pass Green instead of Green.?

 

[dennyr]

This is an explainer from Ilford

https://www.ilfordphoto.com/wp/wp-content/uploads/2017/03/Contrast-control-for-Ilford-Multigrade.pdf

I might be missing it, but i do not see where they get into using Magenta and Yellow Vs Blue and Green.

 

[480sparky]

Right, but WHY use "Magenta" to pass Blue in stead of Blue and why use "Yellow" to pass Green instead of Green.?

Magenta will not 'pass' blue.... blue passes blue. You use magenta to restrict green.

 

[dennyr]

Magenta will not 'pass' blue.... blue passes blue. You use magenta to restrict green.

Does a Magenta Filter let Blue light hit the paper.?

 

[480sparky]

Does a Magenta Filter let Blue light hit the paper.?

Some. Magenta filters controls the green, yellow filters controls the blue.

If you're shooting b&w film, and want the blue sky to be darker, you use a yellow filter.

 

[NS: Nikon Shooter]

-

Maybe, you want to investigate "chromogenic emulsion"
where not only luminance will have effect but chrominan-
ce as well.

 

[dennyr]

Some. Magenta filters controls the green, yellow filters controls the blue.

OK
Having Internet problems, sorry..........i will keep playing.
I understand what you are saying. Thank You

I have talked to photographers that use an enlarger that have Blue and Green instead of Magenta and Yellow.
Does using a blue filter (or green) have "The Same" end effect on contrast as a Magenta or Yellow Filter does.?
If so, why do enlarger manufactures choose one method over the other.?

 

[dxqcanada]

The Physics of Light and Color - Light Filtration | Olympus LS

The Physics of Light and Color - Light Filtration

www.olympus-lifescience.com

 

[480sparky]

OK
Having Internet problems, sorry..........i will keep playing.
I understand what you are saying. Thank You

I have talked to photographers that use an enlarger that have Blue and Green instead of Magenta and Yellow.
Does using a blue filter (or green) have "The Same" end effect on contrast as a Magenta or Yellow Filter does.?
If so, why do enlarger manufactures choose one method over the other.?

I assume some enlargers are marked 'blue' and 'green' to remove one mental step in the process. If you want to control the green sensitive portion of the paper, making an adjustment marked 'green' is a bit more intuitive than, "I want to adjust green, so I have to use the 'magenta' filter."

The only thing a 'true blue' filter can affect is the exposure time needed for the blue-sensitive portion of the paper.

 

[dennyr]

The Physics of Light and Color - Light Filtration | Olympus LS

The Physics of Light and Color - Light Filtration

www.olympus-lifescience.com

A great link Thank You
Part of my slowness to grasp this is the fact i was a painter.....Painters Union, not artist.
I made hundreds of colors and stains over the years.
So approaching everything with Primary of R Y B has been ingrained in my head.
I appreciate the help. My search for info did not turn up the link you provided.
Thanks Agiam

 

[dxqcanada]

I started in art painting before photography ... so I remembered that we look at this a bit differently.

 

[dennyr]

I assume some enlargers are marked 'blue' and 'green' to remove one mental step in the process. If you want to control the green sensitive portion of the paper, making an adjustment marked 'green' is a bit more intuitive than, "I want to adjust green, so I have to use the 'magenta' filter."

The only thing a 'true blue' filter can affect is the exposure time needed for the blue-sensitive portion of the paper.

A great link Thank You
Part of my slowness to grasp this is the fact i was a painter.....Painters Union, not artist.
I made hundreds of colors and stains over the years.
So approaching everything with Primary of R Y B has been ingrained in my head.
I appreciate the help. My search for info did not turn up the link you provided.
Thanks Agiam

I will Thank You Both right here.
As i say, i was a painter. So not only did i learn the one odd primary color, we did not think in terms of light passing "Through" anything, or how something (like film) saw color.
We just dealt with how color was reflected to the human eye.

Well, ONCE in awhile we had to be careful if were were near ( i worked in a lot of high-rise buildings) some heavily tinted or heat absorbent glass, THAT could really F with your color matching.

I was shocked at the effect of clear glass. I had to match a stain on a guys coffee table at Charles Schwab . Big corner office. HUGE 9x3 coffee table with 1/2 inch glass. No way i could move it. TWO of us could not safely move it enough to overhang the table to make the color sample.
I burned up four 8x10 inch Cherry Wood samples trying to match the color through the glass. I could not do it.
I forget the guys name, he was next to "Chucks" office. (he really did say "Call me chuck")
Anyway, THAT guy walked in and i explained to him the trouble we were having.
He said, Don't worry the the table is going WAY over there, just get it as close as you can, nobody will ever know.
So that is a glimpse into the exciting world of a painter.

Thanks Again