Contrast filter use with black and white film

[Todd Barlow]

I hope this is not too stupid a question, but I could really use some help.

I have a subject made up of solid blue and green tones and I want to use contrast filters to provide seperation between tones that would normally be very close in print values.

I meter the solid blue at luminance value of 8
I meter the solid green at luminance value 8.5

I place the solid blue on zone VI
The solid green falls on zone VI 1/2

I use a green filter and provide an additional 1.5 stops (filter factor is 2.8)

Will the solid blue still fall on zone VI?
Does the solid green fall on zone VIII (VI 1/2 + 1.5 zones)? If not can you estimate how many zones lighter the solid green tone will be?

Thanks in advance

Todd

 

[Donald Miller]

Meter the two tones through your filter and it will give you an indication of the amount of separation that you will obtain by using the filter.

I don't use the Zone System any longer and don't concern myself with placements any longer. I only concern myself with the density range of the negative and having that match the exposure scale of the paper.

However, if you apply the proper filter factor your placement should not vary.

 

[noseoil]

Todd, this is a case in which a large format camera and sheet film can help a lot. With the filter in place, try a couple of shots and then vary development times to get what you need. I would use a film with great expansion potential (Efke 25 would be my first choice) because, in essence, you will be doing a plus development to get what you need. Don't forget your heavy tripod.

With roll-film, you can use the old "snip test" to try differing times. Sounds like trial and error will have to be the approach here, unless you have a densitometer available to plot the development curve. In either case, just keep track of the time, temperature and agitation, so you can see which is the right amount of contrast needed for your visualization. Best of luck, tim