Re: filmscanners: Size of scan files
Richard wrote: > More information in the higher ISO film. That's an interesting way of looking at it. I would have said the opposite; that there is less information lost in *more* noise. > LZW is a near lossless compression. With the > lower ISO film, you had less information. And, > not necessarily grain information in the 800 > film, you could well have greater gamut/saturation, > greater light latitude in the 800 film. The Fuji > 800 films are now pretty darned good on grain size. > That's why you used the higher speed film, right? > To get that information. No, I used it because it's a fast film and I didn't have a choice when buying a fuji disposible underwater camera. :) "Pretty darned good" is a relative thing. The grain is OK when printed on photographic paper in a lab, but it looks pretty darned awful when I scan it. >This is not a case of "bad" compression. Bad compression is where the >algorithm assumes that - say - five pixels are the same, when they >really aren't. Then, on expansion, these five pixels show up as the >same. That is how you get smaller file sizes. You loose information. As I mentioned in my original post I know about compression algorithms etc. Where I disagree with you is on the definition of "information". Yes, the LZW TIFF of a Fuji 800 scan is bigger because there's more variation between pixels and therefore little compression is possible without loss. However I disagree that grain (or grain aliasing) necessarily constitutes useful "information". The print film is likely to have more data in terms of latitude, but a lot less in other respects. It's kind of like comparing a computer image of 320x200 pixels in 16 bit colour with another of 1024x768 in 8 bit colour. The first image can have a lot more tonal information, but the second has more clarity. Rob Rob Geraghty [EMAIL PROTECTED] http://wordweb.com
RE: filmscanners: Size of scan files
Lynn wrote: > That sounds perfectly possible to me. Grain is a form of "texture," > and a textured backround will eat up a *lot* of memory (unless it's > mathmatical--which grain isn't, AFAIK). Exactly. Because the grain pattern is random, it doesn't compress well. I was just pointing out an advantage of a fine grained film like Provia which I hadn't realised before; that the higher resolution actually results in smaller file sizes. This is perhaps counter-intuitive. Rob Rob Geraghty [EMAIL PROTECTED] http://wordweb.com
RE: filmscanners: Size of scan files
Rob wrote: > It looks like the excessive grain of the fast film compresses very poorly, while the almost non-existent grain of Provia 100F compresses very well. That sounds perfectly possible to me. Grain is a form of "texture," and a textured backround will eat up a *lot* of memory (unless it's mathmatical--which grain isn't, AFAIK). --LRA --- FREE! The World's Best Email Address @email.com Reserve your name now at http://www.email.com
Re: filmscanners: Size of scan files
More information in the higher ISO film. LZW is a near lossless compression. With the lower ISO film, you had less information. And, not necessarily grain information in the 800 film, you could well have greater gamut/saturation, greater light latitude in the 800 film. The Fuji 800 films are now pretty darned good on grain size. That's why you used the higher speed film, right? To get that information. Compression squeezes out redundant information. If you have valid "different" bit data in adjacent pixel locations, a compression scheme can't device a method of recreating that unique difference on expansion. Unless you tell it to ignore a certain level of difference, such as in JPEG. LZW won't let you do that. This is not a case of "bad" compression. Bad compression is where the algorithm assumes that - say - five pixels are the same, when they really aren't. Then, on expansion, these five pixels show up as the same. That is how you get smaller file sizes. You loose information. >I was just going through the files on the computer to see what I could >easily archive to CDR and noticed a huge difference in file sizes. I have >some full frame scans from Fuji 800 print film that occupy 30MB as 8bit LZW >TIFF files, yet I am going through Provia 100F scans at the moment which >start out at 36MB 16bit from Vuescan and end up at about 15MB in 8bit. >Logically you might expect this from halving the number of bits, but bear in >mind that my LS30 only produces 10 bits per channel. :) It looks like the >excessive grain of the fast film compresses very poorly, while the almost >non-existent grain of Provia 100F compresses very well. This also makes >sense, but I just hadn't noticed before now how huge the difference could >be. > >Rob > >PS Yes I know about things like run length compression and why it doesn't >work very well when there is a lot of detail or noise. :)
filmscanners: Size of scan files
I was just going through the files on the computer to see what I could easily archive to CDR and noticed a huge difference in file sizes. I have some full frame scans from Fuji 800 print film that occupy 30MB as 8bit LZW TIFF files, yet I am going through Provia 100F scans at the moment which start out at 36MB 16bit from Vuescan and end up at about 15MB in 8bit. Logically you might expect this from halving the number of bits, but bear in mind that my LS30 only produces 10 bits per channel. :) It looks like the excessive grain of the fast film compresses very poorly, while the almost non-existent grain of Provia 100F compresses very well. This also makes sense, but I just hadn't noticed before now how huge the difference could be. Rob PS Yes I know about things like run length compression and why it doesn't work very well when there is a lot of detail or noise. :)
