Why so many color filters for black and white papers?

[Grandpa Ron]

I have done some 4x5 contact printing with grade 2 and 3 paper.

I know that variable grade paper uses nearly a dozen color filters to vary the paper grade. Do these color density and tints allow in-between grades like 2 1/2 etc. Or, is there another reason for so many filters.

 

[480sparky]

Multi-grade paper is sensitive to two colors, blue and green. So you need different shades of magenta to control the green sensitivity, and an equal number of shades of yellow to control the blue sensitivity.

 

[dxqcanada]

I used to use the Ilford filter pack which had only 12 types from 00 to 5 ... https://www.ilfordphoto.com/amfile/file/download/file/1824/product/1701/

If you are using a color head with filters in it, then you have a lot more combinations.
example ... https://www.ilfordphoto.com/amfile/file/download/file/1824/product/1701/

 

[Derrel]

Half-grade filters are common.

 

[webestang64]

And to confuse you more I use a cold light diffusion enlarger where you just punch a grade on a key pad and the enlarger head mixes blue/green light for the selected grade.

 

[Grandpa Ron]

Yep, I am confused, it has been many years since I tinkered in the dark room.

I have an 80's vintage enlarger for 35 mms and 120 format. It has a slot for a filter between the bulb and negative.

I assume the variable contrast paper manufacturers will specify what filter for a specific grade. I believe the enlarger has an incandescent bulb.

I do not understand the blue/green issue.

 

[Soocom1]

When I started to play with that, I wasn't educated on the filter thing very well.
But I had found effects from diff. colors to have some interesting results.
including blue, purple, orange and a combination.

Most of it was a look and see thing, but I couldnt do alot because of cost of paper and chems.

Most folks don't even bother anymore.

 

[webestang64]

I have an 80's vintage enlarger for 35 mms and 120 format. It has a slot for a filter between the bulb and negative.

When using the filters you are taking out the red colors and leaving the blue/green light to the paper. My "cold light" enlarger skips the filters and uses straight blue/green to expose the paper.

Graded paper you do not need the filters, multigrade paper is just that, you can adjust the grade by those filters.... https://www.freestylephoto.biz/pdf/product_pdfs/ilford/Ilford_MGIVRC.pdf

 

[terri]

I used to use the Ilford filter pack which had only 12 types from 00 to 5 ... https://www.ilfordphoto.com/amfile/file/download/file/1824/product/1701/

If you are using a color head with filters in it, then you have a lot more combinations.
example ... https://www.ilfordphoto.com/amfile/file/download/file/1824/product/1701/

This.

I have always liked the data sheet that Ilford provides. They give excellent information on their papers, and on using filters with them.

Yep, I am confused, it has been many years since I tinkered in the dark room.

I have an 80's vintage enlarger for 35 mms and 120 format. It has a slot for a filter between the bulb and negative.

I assume the variable contrast paper manufacturers will specify what filter for a specific grade.

Yes, that's exactly right. As with any product, some manufacturers provide better info than others.

Click on dxqcanada's bottom link up there to get a look at Ilford's data sheet. Go to page 3 to look at the actual table on filtration, by specific enlarger brand. (There's also a table listing several enlarger brands, and where they fall on that filtration table, which only lists 3 enlarger brands - I have a Super Chromega 5, for example, and I follow the filter specs listed under Kodak.)

My enlarger has a color head, so I can turn a dial to control the magenta or yellow filtration suggested to get a certain grade. So, under the Kodak column, 5M means dial magenta to 5, leaving the yellow and cyan at 0, to get to Grade 2.5, for example. But the enlarger you have only requires you to drop in colored filters, clearly labeled, into the slot you described. It's very easy that way.

The Ilford table also tells you that their variable contrast paper is essentially at Grade 2 without using any filter at all - basically, just turning on your white light. Depending on your negative, you'll add a magenta filter to increase your contrast, or yellow filter to reduce it. That's your artistic decision for each print.

A fun and easy exercise to help you with each new paper brand you try is to make a basic test print from each filter grade you have. Develop and fix them out the same way, wash, dry - then spread them out or hang them up. You'll have a good idea of what each paper will give you by grade. I'd start with Ilford, but that's just me.

Have fun with it!