Alas Arthur, the quotes in your post are attributed to me; but they are not my words. Since I did not write them although I did raise some questions concerning the question of 4K RES used to define film recorder resolutions as referring to LPI and not ppi which would mean that the resolution in ppi would be 1.5 - 2 times less than 4K, I am not sure if your post is addressed to me since we apparently are saying the same thing be it LPI or line pairs or if the post is directed to others.
The key practical point is that many if not most film recorders do not actually operate at 4K despite the written specs so their resolution in ppi is going to be far less than the 2000 ppi - 2666.66 ppi that it would be if the 4K lpi was an actual operating resolution. I understand how you derived your 2849 ppi figure; but my math says that to get a 4000 lpi line screen you would have to multiply by a factor of 1.4 (most printers suggest multiplying the ppi by a factor of 1.5 - 2.0 to derive the halftone line screen (lpi). -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Arthur Entlich Sent: Saturday, May 11, 2002 6:07 AM To: [EMAIL PROTECTED] Subject: [filmscanners] Re: 3 year wait Laurie Solomon wrote: > >>"4K" simply means 4000 (and 96) pixels across the 36mm film chip. >>Actually, 2889.9ppi. >> > The problem above is the direction of the film being measured. A film recorder refers to the longer dimension as 4K, so the 4096 pixels across, represents the approximate 1 and 7/16th inch wide frame, (4096 pixels divided by 1.4375" equals 2849 ppi or so) On the other hand, most film scanners scan the narrower width of the film frame, so a 4000 ppi scanner needs to have a apparent sensor density of about 3750 elements across the film frame in the short direction. >>I'd say that 11-12MP of true pixel info IS pretty >>much what (Ektachrome, >>at least) film can resolve. >> > [What is a MP and is that a standard abbreviation?] > > MP is Mega-pixel, as usually used in digital camera sensors. One MP is 1024K pixels (in an array). So a one megapixel array would be about 1200 x 800 pixels. However, the reason the reference is "true pixel" is because other than the new Foveon chip, digital cameras use a CCD or MOS array which can only record one color (RGor B) per pixel location, and therefore an array is used (called a Bayer Pattern) which uses interpolation to take a matrix of 25% R and B and 50% G filtered pixels to make up the color information, and therefore the accuracy is lessened, and interference patterns (moiré) develops with some color combinations. >>T-Max 100 has a resolution rating of around 200 line pair/mm, that's over >>10k samples per inch, and would be a file of APPROXIMATELY FOR EXAMPLE SAKE >>(since you are being anal about arithmetic ;-) ~10k x ~15k or ~150M pixels >> > > I'll leave someone else to explain this part, but the main point is that you cannot measure to a single line because there needs to be a contrast developed, meaning a series of lines, such as black line, white line or blank space, black line, etc, to measure. That is why the term is line pairs, since a minimum of two lines (or the space between them) is required to read the result. Art ---------------------------------------------------------------------------- ------------ Unsubscribe by mail to [EMAIL PROTECTED], with 'unsubscribe filmscanners' or 'unsubscribe filmscanners_digest' (as appropriate) in the message title or body ---------------------------------------------------------------------------------------- Unsubscribe by mail to [EMAIL PROTECTED], with 'unsubscribe filmscanners' or 'unsubscribe filmscanners_digest' (as appropriate) in the message title or body