B&W negative emulsions nearly always have better grain and higher acutance than any color emulsion at the same ASA rating. B&W Processing is extremely variable and plastic, however, so it's hard to make hard and fast generalizations.
The biggest influence on grain structure in color emulsions is exposure, given stable, calibrated machine processing. Negative films are sensitive to UNDERexposure and tend to produce grainy results when underexposed. Transparency films are sensitive to OVERexposure and tend to go clear when overexposed. This creates the illusion that negative films are grainier than transparency films, since most people tend to underexpose film, which leads to richer, more saturated, less grainy results in transparencies. Given proper exposure ...
Positive color emulsions up to ASA 100 had lower grain and higher acutance than Negative color emulsions in the same speed range until the early 1980s. Higher speed color films, both neg and pos, pretty much all sucked when it came to grain until that point, and forget about acutance...
Then the first generation of T-grain emulsion films were introduced in color negative. These immediately proved lower grain at the same ASA ratings and made huge improvements in color saturation and acutance ... ASA 200 and 400 were now usable. It took a while for T-grain technology to move to transparency film due to the more complex emulsion structure of transparencies, but this has brought transparency films closer to but not on par with negative films. The thicker, 6-7 emulsion layer construction of color transparency film works against it on acutance; grain is about the same given the same ASA and proper exposure with today's films.
(In the couple of decades since T-grain technology was introduced, color films have come a long way. But their development has been very slow in the past decade: emulsion technology seem to have reached a plateau where substantial improvement is either not needed or no longer sufficiently profitable to fund the R&D required. The film manufacturers continue to tweak their formulations and drive small gains, but big leaps like T-grain and C41 process B&W film are likely at an end, for the moment at least.)
Godfrey
On Apr 8, 2005, at 10:35 AM, Tom C wrote:
Back when I paid attention to this, the answer was generally yes, IIRC. Positive films tended to have finer grain than negative films. Comparing Kodak and Fuji was like apples and oranges because Kodak measured their grain and differently than everyone else. That made me suspect, and I in general shoot Velvia 50 or Provia 100F. Back when I last checked, they were the finest grain films available.
Caveat... I'm remembering back over 5 years ago. Sorry, I can't provide any info for B&W.
Tom C.
From: Jack Davis <[EMAIL PROTECTED]> Reply-To: [email protected] To: [email protected] Subject: Pos vs neg grain Date: Fri, 8 Apr 2005 09:24:20 -0700 (PDT)
I had a lab owner emphatically contend that.."positive film of the same ISO has finer grain than negative film". Didn't address b&w. We happened to be reviewing a b&w print at the time and their existed a situation wherein the subject couldn't be pursued (customers waiting). I've since emailed him for a follow-up on his recommendation that "b&w film be scanned as positive film". If his answer (if received) is at all decipherable, I'll forward it. Does anyone know or suspect what he may be talking about? I've, also, read the RMS charts but, their results don't appear to be comparable.
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