Xref: utzoo comp.graphics:13243 alt.graphics.pixutils:250 Path: utzoo!attcan!lsuc!becker!bdb From: bdb@becker.UUCP (Bruce D. Becker) Newsgroups: comp.graphics,alt.graphics.pixutils Subject: Re: Anyone handle TIFF images with response curves? Message-ID: <36170@becker.UUCP> Date: 10 Sep 90 01:17:52 GMT References: <50230003@hpcupt1.HP.COM> Organization: G. T. S., Toronto, Ontario, Canada Lines: 28 In article sigma@pawl.rpi.edu (Kevin J Martin) writes: |dclaar@hpcupt1.HP.COM (Doug Claar) writes: |>I noticed that neither the PBMPLUS utilities nor the FBM utilities |>handle TIFF images with grey/color response curves. Has anyone |>written a TIFF to {something} converter that doesn't just grab the |>raw bits? (The grey response curve indicates the actual value of each |>level of grey. I believe that this is called 'gamma correction'? For |>example, the actual mappings might be 0 10 50 100 for a 4 level grey image). | |Incidentally, can anyone explain that 'gamma factor' a little better than |what I've seen in the TIFF specification? Examples would be good. gamma refers to the fact that there is a non-linear relationship between excitation and brightness for many diplays, such as CRT's and film. Since the relationship is approximately logarithmic, gamma is an expression of the degree of the equation - for example, a gamma of 2.5 says that output brightness varies with input excitation taken to the 2.5 power. -- ,u, Bruce Becker Toronto, Ontario a /i/ Internet: bdb@becker.UUCP, bruce@gpu.utcs.toronto.edu `\o\-e UUCP: ...!uunet!mnetor!becker!bdb _< /_ "I still have my phil-os-o-phy" - Meredith Monk