in [SLR Cameras]

Prev: The Value Of An Apology, At Least From A Republican's Perspective!!
Next: "Exposing to the right" is over exposed, what now?
From: Elliott Roper on 25 Oct 2009 13:22 In article <251020091704223902%nospam (a)yrl.co.uk>, Elliott Roper<nospam (a)yrl.co.uk> wrote:> In article <hr4er6-qo4.ln1 (a)ID-52418.user.berlin.de>, Wolfgang> Weisselberg <ozcvgtt02 (a)sneakemail.com> wrote:<snip> > RAW gives me 14 bits/channel to play with later. 128 times better than > the first jpg the camera thought of. Why throw away all that > post-processing fun?. Damn! Would you make that 64 times? -- To de-mung my e-mail address:- fsnospam$elliott$$ PGP Fingerprint: 1A96 3CF7 637F 896B C810 E199 7E5C A9E4 8E59 E248
From: David J Taylor on 25 Oct 2009 13:53 "Elliott Roper" <nospam (a)yrl.co.uk> wrote in message news:251020091722309218%nospam (a)yrl.co.uk...> In article <251020091704223902%nospam (a)yrl.co.uk>, Elliott Roper> <nospam (a)yrl.co.uk> wrote:> >> In article <hr4er6-qo4.ln1 (a)ID-52418.user.berlin.de>, Wolfgang>> Weisselberg <ozcvgtt02 (a)sneakemail.com> wrote:> <snip> >> RAW gives me 14 bits/channel to play with later. 128 times better than >> the first jpg the camera thought of. Why throw away all that >> post-processing fun?. > Damn! Would you make that 64 times? Except that the JPEG contains gamma-corrected data, with a greater white-black dynamic range than 14-bit raw, albeit at a reduced brightness accuracy, so you aren't actually comparing like with like. Cheers, David
From: Elliott Roper on 25 Oct 2009 14:02 In article <yg0Fm.1544$5w5.535 (a)text.news.virginmedia.com>, David JTaylor <david-taylor (a)blueyonder.not-this-bit.nor-this.co.uk.invalid>wrote: > "Elliott Roper" <nospam (a)yrl.co.uk> wrote in message > news:251020091722309218%nospam (a)yrl.co.uk...> > In article <251020091704223902%nospam (a)yrl.co.uk>, Elliott Roper> > <nospam (a)yrl.co.uk> wrote:> > > >> In article <hr4er6-qo4.ln1 (a)ID-52418.user.berlin.de>, Wolfgang> >> Weisselberg <ozcvgtt02 (a)sneakemail.com> wrote:> > <snip> > >> RAW gives me 14 bits/channel to play with later. 128 times better than > >> the first jpg the camera thought of. Why throw away all that > >> post-processing fun?. > > Damn! Would you make that 64 times? > > Except that the JPEG contains gamma-corrected data, with a greater > white-black dynamic range than 14-bit raw, albeit at a reduced brightness > accuracy, so you aren't actually comparing like with like. How can that possibly be so? Where does it get the information from? And where does it put it? Scrunching it up on a log curve is neat, but it still does not invent dynamic range from thin air. I can sure push RAW around in post far more than I can push a jpg. So the gamma correction does not seem to be delivering even that much. -- To de-mung my e-mail address:- fsnospam$elliott$$ PGP Fingerprint: 1A96 3CF7 637F 896B C810 E199 7E5C A9E4 8E59 E248
From: David J Taylor on 25 Oct 2009 16:29 "Elliott Roper" <nospam (a)yrl.co.uk> wrote in message news:251020091802112035%nospam (a)yrl.co.uk...[] > How can that possibly be so? Where does it get the information from? > And where does it put it? Scrunching it up on a log curve is neat, but > it still does not invent dynamic range from thin air. > > I can sure push RAW around in post far more than I can push a jpg. So > the gamma correction does not seem to be delivering even that much. Yes, as I said although the dynamic range is greater (it's about 200,000:1) in a pure gamma-corrected JPEG, the accuracy is much less. At the low end the lowest value 1 is 1/200,000 full scale, and the next value is 1/50,000 full scale. Similarly at the high end the difference between 254 and 255 is 1%, rather than the 0.4% you might expect. The gamma correction delivers you data, which is adequate for a human to view under typical conditions, in a more compact form. Cheers, David
From: Elliott Roper on 25 Oct 2009 16:59
In article <hy2Fm.1571$5w5.557 (a)text.news.virginmedia.com>, David JTaylor <david-taylor (a)blueyonder.not-this-bit.nor-this.co.uk.invalid>wrote: > "Elliott Roper" <nospam (a)yrl.co.uk> wrote in message > news:251020091802112035%nospam (a)yrl.co.uk...> [] > > How can that possibly be so? Where does it get the information from? > > And where does it put it? Scrunching it up on a log curve is neat, but > > it still does not invent dynamic range from thin air. > > > > I can sure push RAW around in post far more than I can push a jpg. So > > the gamma correction does not seem to be delivering even that much. > > Yes, as I said although the dynamic range is greater (it's about > 200,000:1) in a pure gamma-corrected JPEG, the accuracy is much less. At > the low end the lowest value 1 is 1/200,000 full scale, and the next value > is 1/50,000 full scale. Similarly at the high end the difference between > 254 and 255 is 1%, rather than the 0.4% you might expect. > > The gamma correction delivers you data, which is adequate for a human to > view under typical conditions, in a more compact form. I still don't get it. If the camera is detecting 14 bits per channel, that's a dynamic range of 2^14 == 1/16384 per channel. Where are the other 3.61 bits coming from? I'll accept that if you had 'em in the first place, you could trade accuracy for range, as you scrunch down to 8 bits, but the camera's internal jpg processor is only given 14 bits to play with. As a general rule, the camera's un-informed first guess at a jpg is pants, and with the compressed pile of bits it hands back, you are stuck with it. -- To de-mung my e-mail address:- fsnospam$elliott$$ PGP Fingerprint: 1A96 3CF7 637F 896B C810 E199 7E5C A9E4 8E59 E248 |