RE: STARTING POINT
> > Hi Bob > > Excuse me joining in late from the antipodes. > > You may perhaps have a focus problem using variable contrast enlarging paper > in a large format camera. Ctein reports in Post Exposure that some vc > emulsions are extraordinarily sensitive to the uv end of the spectrum which > the human eye can't see to focus. Of course he was testing with enlarger > lenses, which may perform differently from camera lenses, but he found the > plane of focus for uv was as much as 12mm away from the visible plane of > focus at about 10x enlargement for the Kodak paper he was using. > > If this is a problem then I guess a uv filter would solve it, but at the > expense of a good deal of speed because it seems the paper has little > sensitivity above green. If this was a SERIOUS problem, then most of the images found in the B&W gallery over at www.f295.org wouldn't exist and the general consensus as to paper "speed" as a film wouldn't exist. Ilford MG IV RC works fine. With or without a 0 or 00 printing filter to lower contrast or a #15 camera filter but at the expense of "speed". You can also pre-flash the paper as 0 to help with contrast control. Also used lots of Arista EDU.ULTRA VC RC (because it was cheap to play with) and it worked fine, it is one of the Foma papers, can't remember which exactly. Graded paper works too. Lately been using the Arista.Ultra VC Graded #2 (again, cheap and made by Foma) and that works very well with a preflash. Also used lots of HP5+ in Rodinal and Pyrocat for when I wanted both sky and shadow (obviously ot photo paper so off-topic, but it works great). The papers are quite UV sensitive and so sky tend to blow out if you are exposing for good shadow detail. Likewise, urban scenes with lots of concrete (reflected UV) tend to burn out for the same reason. Or you can expose for sky and get good detail there at the expense of shadow detail elsewhere. Same old story for ortho emulsions since before Brady was sniffing the ether. Short answer, just go forth and experiment. Know that your contrast range will be compressed relative to B&W film. Know that you will have a bit of a soft focus (but you can control that a bit with good pinholes and careful camera contruction) and that there will be some chromatic distortion. It is tough to make an APO pinhole after all... Rob
|