Archived posting to the Leica Users Group, 2005/10/14
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Too much science for me, but great to know its lurking behind. Thanks for the intro Henning. Cheers On 14/10/2005, at 8:15 AM, Henning Wulff wrote: > At 5:19 PM -0400 10/13/05, John Black wrote: >> > > >>> >>> Dunno how you do it...I can't make 400CN even with red filter. >>> Beautiful. >>> >>> > >> >> I can't either. I gave up several years ago on (at that time T400CN) >> the >> C41 B&W films because I couldn't get any effect much at all with my >> colored >> filters. Looked much the same with as without. Went back to Tri-X >> and >> everything returned to normal with filters. >> >> Don't know what I did wrong. >> >> JB >> > > The spectral sensitivity of the chromogenic films is much closer to > what our eyes see, and what colour film sees than what most B&W film > sees. Most B&W films have somewhat extended blue sensitivity and often > red as well, and are a bit deficient in the yellow-green region. > Therefore, Tri-X needs a light Y-G filter to bring it back to > 'normal', whereas chromogenic film produces a fairly definite 'effect' > with a Y-G filter. > > A deep red, like a 25 or even more so 29 are strong enough to pretty > much overpower most intrinsic spectral inequalities so you should get > a similar result. Most filter effects are affected by relative > exposure, though, especially with standard B&W film and contrast > enhancing filters. Overexpose and filter effects are reduced. > > -- > * Henning J. Wulff > /|\ Wulff Photography & Design > /###\ mailto:henningw@archiphoto.com > |[ ]| http://www.archiphoto.com > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information > > Alastair