I am only posting two replies to what has been posted during my overnight. This one is a short response to the nitty gritty of Austin's argument. The other includes replies in a single post to other points by everybody.
There are two points I am addressing in this post: 1. Dynamic range is a range, not a resolution 2. Dynamic range is the range that the scanner can capture AT ONE TIME i.e. dynamically i.e in one scan I address them purely by providing the resource that Austin requests. For logical discussion, see other posts. 1. Dynamic range is a range, not a resolution ************************************************* Julian: > > It is a simple enough concept. Most explicitly, dynamic RANGE is > > ***not*** > > the RESOLUTION, Austin: >Yes it absolutely is. Julian: > > and there is no book or standard that has ever said > > this. Austin: >Well, the ISO spec shows clearly it is exactly what I've said it is, as well >as every other resource I've posted on this subject before. I simply don't >understand where you get the resources for your misguided understanding of >it. YOU HAVE NO RESOURCES THAT SUPPORT YOUR BELIEF. Julian now replies: Hmmm. Here is the draft ISO spec, from http://www.pima.net/standards/iso/tc42/wg18/WG18_POW.htm . It is entitled "Photography — Electronic scanners for photographic images — Dynamic range measurements." Perhaps there is another ISO spec from which you are deriving your beliefs? Perhaps you could post it? -------direct quote from Proposed ISO standard------------------- 7.2 Scanner dynamic range The dynamic range is calculated from the Scanner OECF by: DR = Dmax - Dmin (7.2) DR = Scanner Dynamic Range Dmax = Density where the Signal to noise ratio is 1 Dmin = Minimum density where the output signal of the luminance OECF appears to be unclipped -------end quote from Proposed ISO standard------------------- (and OECF is opto-electronic conversion function) You will notice, it is exactly as I have described it, a RANGE. It is the range between Dmax and Dmin. It is not a resolution, there is no mention of resolution. Can you tell me then how this says that Dynamic Range is a resolution? 2. Dynamic range is the range that the scanner can capture AT ONE TIME ******************************************************************************** Julian: > > DYNAMIC RANGE on the other hand, is the smaller range within the Density > > Range that the scanner can capture AT ONE TIME i.e. dynamically i.e in one > > scan. It is the instantaneous range the scanner can handle. Austin: >Absolutely not correct. Where on earth did you get that? Please please >provide any credible source that says anything to the such. The ISO spec >doesn't define dynamic range that way...nor do any of the resources I have >seen. On the contrary, the ISO standard states a fairly precise process in which the Dynamic Range is measured by scanning a single slide in a single pass. (They do repeat the same single-scan measurement several times to improve accuracy). Here is the relevant text, remembering that the dynamic range is calculated from the OECF: ----quote from proposed standard------------ 6 Measuring the Scanner OECF The scanner OECF shall be calculated from values determined from a test chart 4 that consists of a density range higher than the range the scanner is expected to be able to reproduce. For reflective targets the density range shall be higher than the range of typical reflective media scanned on this scanner. Many scanners will automatically adapt to the dynamic range of the scene as reproduced on the film or reflective media and the luminance distribution of the film. The results may also differ if the scan mode is grey scale or RGB A minimum of 10 trials shall be conducted for each scanner OECF determination. A trial shall consist of one scan of the test chart. For each trial, the digital output level shall be determined from a 64 by 64 1 pixel area located at the same relative position in each patch. Identical, non-aligned patches may be averaged, or the patch with the least scanning artifacts, such as dust or scan lines, may be used. The scanner OECF so determined shall be used to calculate the resolution measurements for this trial. If the scanner OECF is reported, the final digital output level data presented for each step density shall be the mean of the digital output levels for all the trials 6.1 Scanner settings The scans for the determination of the scanner OECF shall be made in RGB or grey scale mode with a resolution set to the maximum sample frequency (given in Dpi or Ppi) divided by an integer to avoid interpolation R = Rmax / i R = scanning resolution Rmax = maximum scanning resolution of the scanner i = integer value (6.1) The scanner shall be set to automatic adaptation to the dynamic range and the digital values representing the dark grey patches shall be increased by applying a suitable gamma correction so that the maximum number of patches can be distinguished ... -------end quote-------------------------------------------------- Austin, I have looked long and hard through archives to find where you have quoted supporting information for your views, without success. There is not a single quote I can find anywhere which contradicts what I am saying. Perhaps you are assuming what I am saying, not actually reading it? Julian ---------------------------------------------------------------------------------------- Unsubscribe by mail to [EMAIL PROTECTED], with 'unsubscribe filmscanners' or 'unsubscribe filmscanners_digest' (as appropriate) in the message title or body