CIBACHROME  FILTER FINDER 

Mr. & Mrs. C. M. Pearle. Area Thirteen.

Since Iford have stopped giving the Filtration for various films on packets of Cibachrome paper we have had difficulty in getting the Filter Pack right without wasting several sheets of paper. And the resulting Filters have been vastly different from the Filters recommended on the packet. So we made a Filter Finder, which seems to work every time.

We had to cut strips off our Cibachrome Filters in order to fit them into the Filter drawer of our enlarger, so we used these strips - cut into 1cm x 7cm and attached them in order, side by side to three 7cm square cover glasses - one for each colour. Leaving a strip  l cm x 7cm clear. Next, we made a paper carrier for the test strip out of hardboard - consisting of a frame 7cm wide and inches long with three doors each 7cm square. 

Now. with a new package of Cibachrome paper we can, find the correct Filtration using only one exposure and. Just a small piece pf paper 8”x 7cm. First we remove all the Filters from the drawer except for the U.V. filter, place a piece of clear film in the negative carrier, and raise the enlarger head to give a picture size about 9” x 12”. 

We then focus the lens and stop down to the smallest aperture  - we may need to cut down the light even further in order to not burn out the colours when, exposing through the clear glass squares - so in that case we could put a Neutral density filter in the filter drawer, i.e. 10 magenta 1.0 cyan and ten yellow.  

In the dark, place the piece of Cibachrome paper in the paper holder and close all the doors. Then, using either the safelight or the light from the enlarger, take the magenta and cyan filters and putting them together at 90 degree to each other, turn off the light, open the door NO. one and place the two filters on top of the Cibachrome paper. Now we make the first exposure - using the usual time that we would use for an 8” x 10” print., Remove the filters and close the door. We repeat this operation using the cyan and yellow filters and door No.2 and then again using the magenta and yellow filters and door No.3. 

Now we remove the Cibachrome paper and process it following normal processing method. It is important that the test piece has the usual exposure and processing methods as this will affect the colour balance. 

The results will be three blocks of small squares one of which will be neutral gray and this is your Filter pack. Don’t try to assess the neutral gray until it is dry and to make it easier we use a piece of neutral gray card with a small hole punched in it The neutral gray square is easier to compare when viewed on it’s own through the small hole.

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