Under-the-lens multicontrast filters for Durst L184?

[Pasto]

I'd like to use Ilford 6x6 inch under-the-lens multicontrast filters on my Durst L184. The lens adapter that Ilford makes does not fit the large lenses used on 8x10 enlargers. My Durst head does not have an above-the-lens filter drawer. Any suggestions would be welcome...

Thanks,
Luigi

[Drew Wiley]

These kinds of filters are not typically optical grade, so expect some loss in sharpness.
Why on earth do you need 6X6? Why not just thread an appropriate glass filter onto the
enlarging lens just like you do with a camera? All you need is a deep blue and deep green
filter and you can do anything with VC paper.

[Wojtekred]

The multigrade filters are magenta-to-yellow,so how do blue and green filters work?
I use Opemus 6 from Meopta for MF negs and Ilford multigrade filters under the lens and it works well(still working on LF enlarger)

[ic-racer]

Those 6x6in Ilford filters will work fine under the lens when enlarging. You will need to make a filter holder with a hole in it big enough for your enlarging lens exit beam. For some ideas see this thread posts #65 to #72 (http://www.largeformatphotography.in...l=1#post390774)

[ic-racer]

The multigrade filters are magenta-to-yellow,so how do blue and green filters work?
I use Opemus 6 from Meopta for MF negs and Ilford multigrade filters under the lens and it works well(still working on LF enlarger)

The contrast you get in your print is a balance between the green-senstive and blue-sensitive emulsions in the paper.

If you have an additive head (Ilford 500), then dialing in more blue light has the same effect as removing more green by dialing in more magenta filtration on a subtractive head.

[Drew Wiley]

All magenta multigrade filters do is block a certain amt of green within white light, while
yellowish filters block blue, depending on the density of the filter. Exactly the same idea
as in a conventional subtractive colorhead. Identical results can be obtained by simply
time-proportionately using a green filter to expose the low-contrast layer of a VC paper,
and a blue filter to expose the high-contrast layer. They are used one or the other for
extremes of contrast, or sequentially for some of each, or merely to tweak one layer or
the other after a basic white light exposure. This is called split printing. And it is easier to
aquire good permanant glass filters red and blue than magnenta. Yellow filters are rather
weak.

[Sevo]

The multigrade filters are magenta-to-yellow,so how do blue and green filters work?

The paper has green sensitized and unsensitized (natively blue sensitive) emulsions. The yellow/magenta filters are the subtractive set - yellow filters are minus blue, magenta filters are minus green. You can have the same result from an additive set of blue and green - all LED VC heads use sets of blue and green LEDs. Using filters, you'd expose the soft layer through green, the hard one through blue in two separate steps, using the timing of each to control contrast.

A bit of a problem is that the common green taking filters let blue pass, while VC needs a green bandpass that blocks out all blue. These aren't that hard to get as square glass sheets for laser applications (and in that shape neat if you have a filter drawer), but to attach it to your lens you'd have to find someone who mounts it in a filter frame. When using plain off-the-shelf taking filters you'll probably be more successful with a pair of deep blue and yellow filters.

[Drew Wiley]

A 58 green tricolor lets virtually no blue thru, at least not enough to affect any emulsion.
Hold one up and look at anything blue - it will be rendered completely black. I use 29 blue
and 58 green. You can either thread them on the lens or use one of those flip-away holders or turntables that Durst provided. Pretty easy with a bit of practice. Don't confuse 29 blue with 29B blue, which is so dark that it's hard to see what you're dodging and burning. 29 is plenty strong for this kind of work.

[Pasto]

Thanks for the replies. I do use split-grade printing so changing from one filter to another needs to be quick. I split with 0 and 5, and use a 00 for burning in highlights. Are 58 green and 29 blue equivalent to 0 and 5 respectively?

[ic-racer]

When I went through this I looked into some nice 6" square blue and green optical glass filters that could be easily and quickly changed under the lens and they were very, very expensive, as are the gelatin filters (Wratten @ $100 each) in that size. Cokin filters are too small as are the square glass filters sold by Edmond.

I wound up using the filters from the Ilford 6x6 set under the lens.