Hi Herb, On Sun, 5 Jan 2003 00:57:19 -0500, Herb Chong wrote:
> [...] i still think that i see less noise that you see [...] I'm confused. Do you think you see less noise on my scans or yours? For the rest of this reply, I'll assume you mean you see less noise on your scans that the exemplars I posted a couple of days ago from my scanner. > one question that arose in my discussions with my Kodak > contacts was whether the Canon scanner does one pass or > three passes to get RGB values for a scan row. Sorry, I don't know either. If they'd open source the driver I might be able to tell. :-) > i always have multisampling 4X enabled and that reduces > noise effects too. I'm using the Canon software rather than Vuescan, so, AFAIK, I don't have the option to multisample. I'd love to be corrected on that, though. > if it was aliasing effects because 4000dpi is reasonably close > to clump size, you would see aliasing and moire effects on the > scans. i didn't see any. Wait a second. I think we're using different definitions here. The chroma noise in those exemplars looks just like physical (Nyquist) aliasing to me. I'm not an expert, but I'm not a novice either, when you get into signal sampling and aliasing. Moire effects are going to occur, but will be almost completely obscured by the randomness of the physical distribution of the grains/dye clouds that are "moire-ing" with the regular pattern of pixels on the scan sensor, so they _shouldn't_ be visible, unless the silver halides were one big crystal across the whole frame. > try scanning an image that has a large even > light tone and posting that. I'll try to get that done later today (Sunday). I'll post back when I've done it. I've got a perfect exemplar for that. > the contact asked me if the image was properly exposed according > to ISO rating and i said i didn't know but assumed so. Hmm. I'm not sure how to answer that. The film was exposed 1) without any form of exposure compensation 2) with sensing of DX coding from the canister 3) in accordance with Tv program mode (I requested 1/250 shutter and the computer set the aperture, usually f/11 or f/16 or f/22, but I don't know the exact aperture for each of the exemplars). TTYL, DougF KG4LMZ
