"Exposing to the right" is over exposed, what now?
in [Photoshop]
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From: Mike Russell on 8 Oct 2009 03:54 On Mon, 05 Oct 2009 15:23:57 -0800, Floyd L. Davidson wrote: [re film's "expose for shadows", digital's "expose for the highlights"] > Actually, since film is a negative, the two are in fact > actually the same. Expose for the brightest range of the > *recording* *mechanism*. > > That just happens to be the dark areas of a scene with > film (where the negative is clear) and the bright areas > of a scene with an electronic sensor (the highest > voltage output). No - both refer to areas of the scene. The full rule of thumb for film is "Expose for the shadows. Develop for the highlights". Exposing for the shadows establishes the area of minimum negative density, and development has a much greater effect on the highlights than the shadows. For digital, exposing for the highlights amounts to playing chicken with the brightest significant information in the image, by choosing an exposure and ISO that puts the brightest significant subject material as close as possible to the max sensor value, without actually losing information. Your other points are technically true, but belie the fact that film's Achilles heel is loss of subject shadow detail, while digital's is loss of subject highlight detail. <snip> -- Mike Russell - http://www.curvemeister.com
From: Floyd L. Davidson on 8 Oct 2009 04:23 Mike Russell <groupsRE(a)MOVEcurvemeister.com> wrote: >On Mon, 05 Oct 2009 15:23:57 -0800, Floyd L. Davidson wrote: > >[re film's "expose for shadows", digital's "expose for the highlights"] >> Actually, since film is a negative, the two are in fact >> actually the same. Expose for the brightest range of the >> *recording* *mechanism*. >> >> That just happens to be the dark areas of a scene with >> film (where the negative is clear) and the bright areas >> of a scene with an electronic sensor (the highest >> voltage output). > >No - both refer to areas of the scene. The full rule of thumb for film is >"Expose for the shadows. Develop for the highlights". Exposing for the >shadows establishes the area of minimum negative density, and development >has a much greater effect on the highlights than the shadows. > >For digital, exposing for the highlights amounts to playing chicken with >the brightest significant information in the image, by choosing an exposure >and ISO that puts the brightest significant subject material as close as >possible to the max sensor value, without actually losing information. > >Your other points are technically true, but belie the fact that film's >Achilles heel is loss of subject shadow detail, while digital's is loss of >subject highlight detail. ><snip> Interesting way to say, "No, you are right." -- Floyd L. Davidson <http://www.apaflo.com/floyd_davidson> Ukpeagvik (Barrow, Alaska) floyd(a)apaflo.com
From: Floyd L. Davidson on 8 Oct 2009 04:42 "DRS" <drs(a)removethis.ihug.com.au> wrote: >"Floyd L. Davidson" <floyd(a)apaflo.com> wrote in message >news:87vdiqqqso.fld(a)apaflo.com >> Contrast settings change the shape of the >> graph between the right most edge and the the left edge >> *but* *do* *not* *change* *the* *location* *of* *the* *right* *edge*. > >Yes, they do. Everybody sees it except you. Increase the contrast setting >and the histogram expands left and right. Decrease contrast and the edges >shift inwards especially on the right edge. The change in the location of >the right edge between -4 and +4 stands out like dog's balls. .... >>> It is possible to improve the accuracy of the histogram relative to >>> the Raw data and the fact that you cannot see it when it is right >>> before your eyes is your problem, not ours. Those images show 5 >>> different histograms where the only variable is the contrast >>> setting. Since the exposure has not changed then only one of the >>> histograms can be the most accurate relative to the Raw image. It >>> happens to be the -4 setting. >> >> All five show *exactly* the same exposure. > >That is not in dispute. If you payed attention you'd have noticed that in >that very paragraph I said, "Since the exposure has not changed..." The >fact that the exposure is the same is necessary to the point being made, >which is that changing one and only one variable, the contrast setting, >changes the accuracy of the histogram upon which decisions about exposure >are *subsequently* made. You can't have it both ways. First you say that the contrast setting moves the histogram's indication of exposure, and now you say it does not. All five of those histograms show *exactly* the same exposure, even though they have 5 different contrast settings. If that is the desired exposure, not one of those histograms would suggest that the camera's exposure should be changed to be more accurate. >> They all have exactly the same right edge, to the degree >> that it can be determined (which is exceedingly > >No, they don't. Blind Freddy can see the right-edges shift by at least 1 >stop from -4 to +4, and probably more. You apparently are looking at that huge peak value to the left of the right edge, as it is the only thing that moves by "at least 1 stop". But that peak has *nothing* to do with setting correct exposure. See the little itty bitty value down in the lower right hand corner? That is the value of significance. That is the "right edge". >>> You are really not in any position to lecture on logic. >> >> Other than I use it, and you don't? Seems like a good >> position... > >The proof is in the pudding is in the eating. Cute. I'll settle for being logical. -- Floyd L. Davidson <http://www.apaflo.com/floyd_davidson> Ukpeagvik (Barrow, Alaska) floyd(a)apaflo.com
From: DRS on 8 Oct 2009 05:04 "Floyd L. Davidson" <floyd(a)apaflo.com> wrote in message news:87eipeqnt0.fld(a)apaflo.com > "DRS" <drs(a)removethis.ihug.com.au> wrote: [...] >> That is not in dispute. If you payed attention you'd have noticed >> that in that very paragraph I said, "Since the exposure has not >> changed..." The fact that the exposure is the same is necessary to >> the point being made, which is that changing one and only one >> variable, the contrast setting, changes the accuracy of the >> histogram upon which decisions about exposure are *subsequently* >> made. > > You can't have it both ways. First you say that the > contrast setting moves the histogram's indication of > exposure, and now you say it does not. I have always said it changes the indication of exposure. It is you who made the false claim that I and others were saying it had anything to do with changing the actual exposure, which we have repeatedly denied. > All five of those histograms show *exactly* the same > exposure, even though they have 5 different contrast > settings. And because of the different contrast settings the 5 histograms show the exposure differently. The exposure hasn't changed but the accuracy of its representation has. Which is all that has been claimed. > If that is the desired exposure, not one of those > histograms would suggest that the camera's exposure > should be changed to be more accurate. None of the 5 histograms indicate overexposure. What they do indicate, to different degrees of accuracy, is the room for exposure compensation. Only 1 can be the most accurate and it is the -4 histogram. [...] >> No, they don't. Blind Freddy can see the right-edges shift by at >> least 1 stop from -4 to +4, and probably more. > > You apparently are looking at that huge peak value to > the left of the right edge, as it is the only thing that > moves by "at least 1 stop". But that peak has *nothing* > to do with setting correct exposure. See the little > itty bitty value down in the lower right hand corner? > > That is the value of significance. That is the "right > edge". In this instance that indicates specular highlights, which as has been noted by several people, may be blown without spoiling the image. That is a choice by the photographer. [...] >> The proof is in the pudding is in the eating. > > Cute. I'll settle for being logical. Good. I hope to see it soon.
From: Floyd L. Davidson on 8 Oct 2009 05:42
"DRS" <drs(a)removethis.ihug.com.au> wrote: >"Floyd L. Davidson" <floyd(a)apaflo.com> wrote in message >news:87eipeqnt0.fld(a)apaflo.com >> "DRS" <drs(a)removethis.ihug.com.au> wrote: > >[...] > >>> That is not in dispute. If you payed attention you'd have noticed >>> that in that very paragraph I said, "Since the exposure has not >>> changed..." The fact that the exposure is the same is necessary to >>> the point being made, which is that changing one and only one >>> variable, the contrast setting, changes the accuracy of the >>> histogram upon which decisions about exposure are *subsequently* >>> made. >> >> You can't have it both ways. First you say that the >> contrast setting moves the histogram's indication of >> exposure, and now you say it does not. > >I have always said it changes the indication of exposure. It is you who >made the false claim that I and others were saying it had anything to do >with changing the actual exposure, which we have repeatedly denied. > >> All five of those histograms show *exactly* the same >> exposure, even though they have 5 different contrast >> settings. *All* *five* *show* *the* *exact* *same* *exposure*. Not one of them shows any 1 f/stop difference as you claim. The only thing that moves 1 f/stop are the tall peaks in the graph that have *nothing* to do with exposure. It is well to the left of the right edge, and it is that right edge that indicates exposure. >And because of the different contrast settings the 5 histograms show the >exposure differently. The exposure hasn't changed but the accuracy of its >representation has. Which is all that has been claimed. They *don't* show the *exposure* differently. >> If that is the desired exposure, not one of those >> histograms would suggest that the camera's exposure >> should be changed to be more accurate. > >None of the 5 histograms indicate overexposure. What they do indicate, to >different degrees of accuracy, is the room for exposure compensation. Only >1 can be the most accurate and it is the -4 histogram. All of them indicate there is no room for any "compensation". Increasing the camera exposure will result in clipping, and each of those histograms shows that. Oddly enough, the +4 histogram shows it the best! >>> No, they don't. Blind Freddy can see the right-edges shift by at >>> least 1 stop from -4 to +4, and probably more. >> >> You apparently are looking at that huge peak value to >> the left of the right edge, as it is the only thing that >> moves by "at least 1 stop". But that peak has *nothing* >> to do with setting correct exposure. See the little >> itty bitty value down in the lower right hand corner? >> >> That is the value of significance. That is the "right >> edge". > >In this instance that indicates specular highlights, which as has been noted >by several people, may be blown without spoiling the image. That is a >choice by the photographer. The tall peaks are *not* a "specular highlights", and one look at the image should demonstrate that there are no light sources or reflections in the image. Those peaks are probably the whiter parts of the background, but might be from one or more of the crayons too. It isn't possible to determine from looking at the histograms just where the actual values are that make up either those peaks or the right edge of the histogram. It does appear that the whitest part of the watch face, around the 12 and 6, are probably where the right edge of the histogram values are from. Note that only in the +4 histogram are the values at the right edge more than maybe 2 pixels high on that graph. They are very hard to see because of the white portion of the gray scale below the graph and the lack of contrast with the gray background. >>> The proof is in the pudding is in the eating. >> >> Cute. I'll settle for being logical. > >Good. I hope to see it soon. With a bit of logic you'd have seen it already. You know, logically if what you said made sense the article would have discussed it in some way, but it does not even hint at it. If changing the contrast displayed a more accurate *exposure* (right edge location), why didn't they point to it? -- Floyd L. Davidson <http://www.apaflo.com/floyd_davidson> Ukpeagvik (Barrow, Alaska) floyd(a)apaflo.com |