Multi Grade Filters

Pieter12 · Jul 1, 2019

I would like to understand something about multigrade filters: the Ilford MG filter set has filters ranging from 00 to 5, all warm, ranging from a pale straw color to medium magenta. However, I read about people using blue and green filters for split-grade printing. What am I missing here? Even the Ilford data sheet about using a color head for contrast control gives values in yellow and magenta.

Rick A · Jul 1, 2019

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

Pieter12 · Jul 1, 2019

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

That paper states "By varying the proportion of blue to green light, a contrast range between these two extremes can be obtained. The simplest way of controlling the colour of the light reaching the emulsion during exposure is by the use of filters: a magenta filter absorbs green light and transmits blue; a yellow filter absorbs blue light and transmits green. In this way, high and low contrast images can be made."

I understand using blue & green sources such as LEDs. But maybe I am mistaken that people using blue & green filters?

Vaughn · Jul 1, 2019

One can either add or subtract the colors the VC papers are sensitive to in order to change contrast. Green is the opposite of magenta -- and blue the opposite of yellow, more or less.

Pieter12 · Jul 1, 2019

Vaughn said:
One can either add or subtract the colors the VC papers are sensitive to in order to change contrast. Green is the opposite of magenta -- and blue the opposite of yellow, more or less.

OK. I assume there is a specific green/blue filter that corresponds to 00 & 5 grades.

Rick A · Jul 1, 2019

The filters restrict the amount of blue and green light, a blue or green colored filter won't do the same.

Vaughn · Jul 1, 2019

I was thinking more along the lines of addiitive systems rather than subtractive systems (filters). Ignore my ignorance on this...

pentaxuser · Jul 1, 2019

The question which springs to my mind is: given we can use either blue/green or yellow/ magenta why did Ilford chose to use yellow/green for over or under the lens filtration rather than blue/green?

pentaxuser

AgX · Jul 1, 2019

Blue and green filters we got typically are bandwidth filters. They typically are most transmissive for either green or blue, and thus not good for controlling these two colours.

Doremus Scudder · Jul 1, 2019

pentaxuser said:
The question which springs to my mind is: given we can use either blue/green or yellow/ magenta why did Ilford chose to use yellow/green for over or under the lens filtration rather than blue/green?

pentaxuser

VC paper only cares how much green and blue it sees, and in what proportion. There are a number of ways to accomplish that.

Yellow and magenta both contain red, which the paper is blind to, but your eye can see. Using yellow and magenta filters, like the Ilford filter set, makes the image brighter and easier to work with than an image with the red removed partly or mostly by varying strengths of green and blue filters. This is the main reason VC filters are yellow and magenta.

Ilford's VC filters are also "speed matched," so that, once you learn to work with them, you can get much closer to a final correct exposure when changing filters.

I use the filtration on my color head for 95% of my VC printing, but can get more contrast from just about any paper with a #47 blue filter than maximum magenta filtration. The image on the easel, however, is quite dim.

Blue and green filters of varying transmission corresponding to VC paper grades don't exist. If one uses split-printing techniques, exposing to varying degrees with a #47 blue filter and a #58 green filter will get you any contrast gradient the paper has to offer.

A similar approach is taken by enlarger heads with additive systems. They project a combination of blue and green light. Again, any contrast gradient is possible by varying the proportion of one to the other.

Best,

Doremus

pentaxuser · Jul 1, 2019

Thanks Doremus. I was convinced that someone here or perhaps more than one used blue and green instead of yellow and magenta for grades but from what you have explained it must have been split grade printing. It just goes to show that what you think you have read in the past can get distorted

pentaxuser

Bill Burk · Jul 1, 2019

The variable contrast filters all pass red too . This is just for your convenience so you can see what you are printing.

Blue and green do all the work and red does nothing to the paper. It just lets you see better.

MattKing · Jul 1, 2019

What Doremus said.
In addition, the bulbs used traditionally in enlarger light sources typically emit lots of red light. If you use a pure green and blue additive system, you waste a lot of that light, which could otherwise come in quite handy when composing at the easel or focusing.
I use an Ilford Multigrade 400 head which, like the very early Multigrade 500 heads, used magenta and yellow dichroic filters. It is quite a bit easier to use when composing or focusing than my friends' blue and green light Ilford 500 heads, but it doesn't give quite as wide a contrast range as those later heads.

cowanw · Jul 1, 2019

Also in a subtractive system you can combine filters; In an additive system you cannot do this, as you cannot add a colour that has already been taken away. If you combine a blue filter and a green filter below a white light nothing passes (filter inefficiency discounted)

pentaxuser · Jul 1, 2019

MattKing said:
What Doremus said.
I use an Ilford Multigrade 400 head which, like the very early Multigrade 500 heads, used magenta and yellow dichroic filters. It is quite a bit easier to use when composing or focusing than my friends' blue and green light Ilford 500 heads, but it doesn't give quite as wide a contrast range as those later heads.

Thanks Matt. I had a feeling that there was an Ilford head using blue and green and you have confirmed that my memory was maybe not as distorted as i had thought. Whoever uses this blue and green "swears" by it and maybe it is this wide contrast range that "wins his day"

Does this mean that blue and green give greater than 6 grades (00-5) or is it simply that Y and M heads give less than 6 grades so that blue green gives the same as MG filters but both MG filters and blue green give more than a Y and M muitigrade head?

Thanks

pentaxuser

MattKing · Jul 1, 2019

pentaxuser said:
Does this mean that blue and green give greater than 6 grades (00-5) or is it simply that Y and M heads give less than 6 grades so that blue green gives the same as MG filters but both MG filters and blue green give more than a Y and M muitigrade head

It means that my relatively ancient 400 series head doesn't offer quite as wide a contrast range - particularly at the high contrast end - as the later 500 and 600 series heads.
Of course, I can easily add a below the lens #5 filter for the very few times when I need to attenuate even more green light than I can accomplish through the 400 head alone.
The upside of the 400 series head is that it doesn't need the cooling fan that the 500 and 600 series heads need.
And the 400 series control panel and head together are definitely more mid century modern in styling .

RalphLambrecht · Jul 2, 2019

Rick A said:
The filters restrict the amount of blue and green light, a blue or green colored filter won't do the same.

by definition, blue or green colored filters do exactly the same.

Rick A · Jul 2, 2019

RalphLambrecht said:
by definition, blue or green colored filters do exactly the same.

Yes, but how would you calibrate the effect to get variable contrast. Maybe I misinterpreted the OP's thoughts on Ilford filtration, and the issues involved with additive vs subtractive filtration and light transmission.

MattKing · Jul 2, 2019

Rick A said:
Yes, but how would you calibrate the effect to get variable contrast.

The same way that the magenta and yellow filters were originally calibrated.
The subtractive magenta and yellow filtration systems were created first, and they have been used for a very long time, so most of the complications have been well worked out.
If I understand correctly, the required blue and green transmission filters are more difficult to make and more expensive. Dichroic interference filters are a more recent phenomena.

Pieter12 · Jul 2, 2019

I am coming to the conclusion that using green & blue filters is only practical for split-grade printing and the only advantage is the ability to get a higher contrast grade from VG paper. (The difficulty focusing and composing is not a factor, since that is done under white light.) Otherwise there is no reasonable upside to using green & blue vs yellow & magenta. Finding durable green & blue filters for a filter drawer or below the lens seems less likely than the readily available Ilford sets.

RPC · Jul 2, 2019

RalphLambrecht said:
by definition, blue or green colored filters do exactly the same.

If one speaks of filters mentioned earlier such as the #47B or #58, these are not designed to restrict blue or green in any amount but completely pass them. On the other hand, yellow and magenta filtration generally occurs at different degrees with the intent of restricting different degrees of blue and green.

MattKing · Jul 2, 2019

Pieter12 said:
I am coming to the conclusion that using green & blue filters is only practical for split-grade printing and the only advantage is the ability to get a higher contrast grade from VG paper. (The difficulty focusing and composing is not a factor, since that is done under white light.) Otherwise there is no reasonable upside to using green & blue vs yellow & magenta. Finding durable green & blue filters for a filter drawer or below the lens seems less likely than the readily available Ilford sets.

If you are working with an existing light source that does not have a built in blue and green light based filtration system, the magenta and yellow filters make the most practical sense.
If you are designing a system from scratch, a blue and green light based filtration system gives you the most control.
By the way, you can use a blue and green light based filtration system for non-split-grade filtering - the Ilford 500 (later model) and 600 Multigrade systems do just that - but they do that with two lamps and an adjustable green filter on one of the lamps and an adjustable blue filter on the other lamp.

Bill Burk · Jul 3, 2019

You all know that blue plus red is magenta... and green plus red is yellow, right?

Patrick Robert James · Jul 3, 2019

I print both ways. My Saunders 4x5 VCCE enlarger has magenta/yellow and for filtration on my Focomat 1c I use blue/green. Like has been mentioned above, magenta/yellow is brighter. I prefer to print with blue/green though. I split print everything anyway, so when I use magenta/yellow I don't use any intermediate grades. In the end it is all the same really.

Doremus Scudder · Jul 3, 2019

RPC said:
If one speaks of filters mentioned earlier such as the #47B or #58, these are not designed to restrict blue or green in any amount but completely pass them. On the other hand, yellow and magenta filtration generally occurs at different degrees with the intent of restricting different degrees of blue and green.

You guys are talking at cross purposes. Any filter passes some light and absorbs others. A green filter passes green, but absorbs blue (and red, etc.) and vice versa. So yes, a green filter restricts blue and a blue filter restricts green. It's just how you look at it. Geez...
Doremus

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