Path: ccsf.homeunix.org!ccsf.homeunix.org!news1.wakwak.com!nf1.xephion.ne.jp!onion.ish.org!onodera-news!newsfeed.media.kyoto-u.ac.jp!newsfeed.news2me.com!newsfeed2.easynews.com!newsfeed1.easynews.com!easynews.com!easynews!c03.atl99!news.webusenet.com!pc01.webusenet.com!fe01.atl2.webusenet.com.POSTED!not-for-mail From: "Don" Newsgroups: fj.comp.dev.digital-camera References: Subject: Re: ASA and digital cameras Lines: 27 X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 6.00.2800.1158 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 Message-ID: X-Complaints-To: abuse@usenetserver.com X-Abuse-Info: Please be sure to forward a copy of ALL headers X-Abuse-Info: Otherwise we will be unable to process your complaint properly. NNTP-Posting-Date: Fri, 27 Jun 2003 13:52:47 EDT Date: Fri, 27 Jun 2003 11:02:37 -0700 Xref: ccsf.homeunix.org fj.comp.dev.digital-camera:377 Yes and no. The higher speed films have larger grains, which make them more likely to receive the required number of photons to sensitize the grain, but also more visible. In a CCD, the "grain" (charge bucket) stays the same size, but the signal is amplified more before it is digitized. Since the primary noise source is the shot noise of this amplifier, the noise is amplified more. That's a simplified explanation. It's quite difficult to assign an ISO (ASA) rating to a digital camera that makes it comparable to the same rating in a film camera. There is currently no accepted standard, although I've heard that ISO is currently working on one. Don "David Haas" wrote in message news:MPG.19664b725293d3e9989880@news-server.nc.rr.com... > > I understand the relationship between shutter speed and aperture but what > happens in a digital camera when you change ASA readings. Does it actually > increase sensitivity as in film? Exactly what does it do? > > ------ > D. Haas >