The use of filters and filter factors are sometimes not well understood. This is a perfect example of the apparent confusion that exists. The use of filters in black and white photography is for the purpose of affecting contrast. In this case the unfiltered exposure value of the green foliage and the red roses were probably very near each other. If a photograph were made without the use of a filter the print values of the green foliage and the red roses would have been near each other. By using a red filter the blossoms were rendered lighter and the foliage is darkened. Conversely if a green filter such as a 58 would have been used the blossoms would have been darkened and the foliage would have been lightened. The use of a filter factor and how it applies to the manner in which colored objects are rendered are of only approximate value in determining the rendering of these objects. In this case had a 23 or a 25 red been used the effects would not have been so severe. The only way, of which I am aware, that one can determine more nearly the effects that filters have on colored objects is to meter through the filter with a meter that has the spectral response of the modified Zone VI.

In this case the effects that this 90 red filter produced are perfectly predictable. It created enough contrast between the roses and the foliage that the development of the film was too extreme for the film to contain the contrast range. The characteristic curve of the film and it's inherent properties were violated.

If you wish to continue to use the 90 red filter on this subject matter, you will need to compensate by giving at least three stops more exposure (to gain detail in the foliage) and reduce development to reduce contrast. This would probably be on the order of at least a minus 4 development. This would probably require a water bath or another means of compensating development. The results would be better using a less severe filter.

The use of an orange filter may have very little effect in lightening the rose blossoms, just as a yellow would. The orange would however darken the foliage.