"Exposing to the right" is over exposed, what now?
in [Photoshop]
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From: Wilba on 10 Oct 2009 00:00 Porte Rouge wrote: > Wilba wrote: >> Porte Rouge wrote: >>> >>> I set my exposure to slide the histogram to the right, without clipping >>> ( when I have time), to capture the most tonal levels . So, now when I >>> am editing the photos they are over exposed(not clipped). A sunrise is >>> a good example. The deep colors are washed out. The obvious fix(to me >>> anyway) in Lightroom or CS4 is to reduce the exposure. Now my question >>> is, by reducing exposure in post, am I just ending up in the same place >>> (histogram to the left) as if I had just ignored the histogram when I >>> was shooting and set the exposure to properly expose the image using >>> my light meter? I guess in short I am asking if Lightroom or CS4 loses >>> tonal values when you reduce exposure in editing. >> >> Yes, reducing the exposure in Lightroom just puts your histogram back to >> the >> left, so that's a waste of time. To avoid having the deep colours washed >> out, you need to make use of the full tonal range available in the image. >> If >> you have done a good job of exposing to the right, your highlights will >> be >> pretty much where they need to be. So then all you need to do is raise >> the >> black point (e.g. using the Levels dialog in Photoshop), so that the dark >> tones in the scene end up as dark tones in the image. If you are using >> the >> Levels dialog in Photoshop, while you drag the black (or white) point >> slider, press the Alt key to see which pixels are clipped (or blown). >> >> (The following relates to my experience with a Canon 450D. YMMV.) > > Aha! :- ) Was that what you actually wanted to know? >> There are two parts to exposing to the right - levels in the image and >> saturation of photosites. Whether you are shooting JPEG or raw, the >> camera's >> histogram display shows you the levels in a JPEG produced from the raw >> data, >> so the shape of the histogram curve depends on your settings for >> sharpness, >> contrast, saturation, colour tone, etc. And white balance, of course. >> If you are shooting JPEG, all you can do is avoid piling up the histogram >> on >> the right, which prevents gross areas of blown highlights in the image. >> >> If you are shooting raw, you can overexpose (beyond the point at which >> the >> histogram curve touches the right boundary), by about two steps and still >> produce an image from the raw without blown highlights. IOW, the headroom >> between blown highlights in the JPEG and saturation of the photosites is >> about two steps (in my experience, with the JPEG settings I use). >> >> So if you are bracketing for the best possible exposure, go at least two >> steps over what the histogram tells you is "correct". The maximum >> possible >> dynamic range occurs at the point where photosites in the highlights >> begin >> to saturate. > > What do you mean by steps? Do you mean stops, or steps on the aperture > or shutter dials? No, nothing to do with the increments by which the camera's controls change the exposure - that's arbitrary. An exposure step is a doubling or halving of the amount of light that reaches the sensor. A stop is a step achieved via the aperture. Most people also say stop when they mean a step achieved via the shutter. > In everyday raw shooting, you can be quite relaxed about having a small > spike on the right of the histogram - that's actually a good thing.
From: Floyd L. Davidson on 10 Oct 2009 01:57 "Wilba" <usenet(a)CUTTHISimago.com.au> wrote: >Porte Rouge wrote: >> Wilba wrote: >>> Porte Rouge wrote: >>>> >>>> I set my exposure to slide the histogram to the right, without clipping >>>> ( when I have time), to capture the most tonal levels . So, now when I >>>> am editing the photos they are over exposed(not clipped). A sunrise is >>>> a good example. The deep colors are washed out. The obvious fix(to me >>>> anyway) in Lightroom or CS4 is to reduce the exposure. Now my question >>>> is, by reducing exposure in post, am I just ending up in the same place >>>> (histogram to the left) as if I had just ignored the histogram when I >>>> was shooting and set the exposure to properly expose the image using >>>> my light meter? I guess in short I am asking if Lightroom or CS4 loses >>>> tonal values when you reduce exposure in editing. >>> >>> Yes, reducing the exposure in Lightroom just puts your histogram back to >>> the >>> left, so that's a waste of time. To avoid having the deep colours washed >>> out, you need to make use of the full tonal range available in the image. >>> If >>> you have done a good job of exposing to the right, your highlights will >>> be >>> pretty much where they need to be. So then all you need to do is raise >>> the >>> black point (e.g. using the Levels dialog in Photoshop), so that the dark >>> tones in the scene end up as dark tones in the image. If you are using >>> the >>> Levels dialog in Photoshop, while you drag the black (or white) point >>> slider, press the Alt key to see which pixels are clipped (or blown). >>> >>> (The following relates to my experience with a Canon 450D. YMMV.) >> >> Aha! > >:- ) Was that what you actually wanted to know? None of it is correct though. What do you get, for example, if you shoot a image that is mostly an 18% gray card, against a black background? If you use ETTR to get the most dynamic range, the gray card will show up as very close to maximum white in the raw data. "If you have done a good job of exposing to the right, your highlights will be pretty much where they need to be. So then all you need to do is raise the black point (e.g. using the Levels dialog in Photoshop), so that the dark ..." Obviously that is not true. The only time it will be true is when there actually *are* highlights that are "pretty much" at pur white. Not all scenes have such highlights, and therefore not all image data will have them "pretty much where they need to be". And that is when you use a raw converter or an editor for "reducing the exposure in Lightroom just puts your histogram back to the left.", and it clearly is *not* a waste of time. .... >>> So if you are bracketing for the best possible exposure, go at least two >>> steps over what the histogram tells you is "correct". The maximum >>> possible >>> dynamic range occurs at the point where photosites in the highlights >>> begin >>> to saturate. >> >> What do you mean by steps? Do you mean stops, or steps on the aperture >> or shutter dials? > >No, nothing to do with the increments by which the camera's controls change >the exposure - that's arbitrary. An exposure step is a doubling or halving >of the amount of light that reaches the sensor. A stop is a step achieved >via the aperture. Most people also say stop when they mean a step achieved >via the shutter. Yes, they usually say that because in fact it is the same thing in the context that you have described, it changes the amount of light reaching the sensor. And how you can say "nothign to do with the increments by which the camera's controls change the exposure" and then describe camera controls changing the exposure... is amusing. >> In everyday raw shooting, you can be quite relaxed about having a small >> spike on the right of the histogram - that's actually a good thing. It is, assuming you want to clip the highlights. Otherwise, it's a fatal error, because there is no way to recover the lost data. On the other hand, if you back off on exposure just enough to make sure no highlights are clipped, the loss of 1/2 to 1 stop of dynamic range probably will mean absolutely nothing (given that you won't print out anything that can show more than 5 or 6 fstops and the camera will almost certainly be recording 8 or more). -- Floyd L. Davidson <http://www.apaflo.com/floyd_davidson> Ukpeagvik (Barrow, Alaska) floyd(a)apaflo.com
From: Floyd L. Davidson on 10 Oct 2009 03:04 "Charles" <charlesschuler(a)comcast.net> wrote: >A link for your enjoyment. > >http://www.rags-int-inc.com/PhotoTechStuff/ETTR/ Yah gotta admit, that one is great entertainment. There multiple whole paragraphs where he gets nothing right! He's also got two links at the bottom of that page, both of which are equally a riot to read. -- Floyd L. Davidson <http://www.apaflo.com/floyd_davidson> Ukpeagvik (Barrow, Alaska) floyd(a)apaflo.com
From: John Sheehy on 10 Oct 2009 10:45 Paul Furman <paul-@-edgehill.net> wrote in news:hajq5b$nt5$1(a)news.eternal-september.org: > OK, this makes sense, the posterizing issue is not really visible in > any sort of normal exposure. It shouldn't be visible in any kind of exposure. My comments about the limit of the value of RAW bit depth or the number of RAW levels is based on torturous tests! > What about Floyd's comment below that the > noise level remains the same but exposing to the right increases the > signal so that overwhelms the noise? The read noise (including any dark current) stays the same, in an absolute sense. In a relative sense, it changes. For shot noise, it changes in both an absolute sense *and* a relative sense. > That seems to tie the two > together in a comprehensible way. The LL link just makes a lot of > sense, it can't be complete BS. > http://www.luminous-landscape.com/tutorials/expose-right.shtml Well, the reasons given for the benefit are not correct. You could take one shot with normal exposure, and one with +1 EC, now using the top RAW stop, and the benefit would still be there if you quantized the top stop to 300 levels, instead of ~8000. According to my calculations and emulations, no current DSLR needs more than 300 levels for the top stop (some older models with few, large pixels may need about 325).
From: Paul Furman on 10 Oct 2009 15:29
Wilba wrote: > Paul Furman wrote: > >> An interesting related issue I don't understand is how the exposure slider >> works in Lightroom or ACR. I don't know how to duplicate that effect in >> photoshop with curves, levels, etc. Those all do like you describe, moving >> the middle parts of the histogram but there isn't an easy way I can see to >> shift the whole exposure. Hmm, the middle slider on levels comes close but >> still doesn't match the effect. > > Image | Adjustments | Exposure... ? Hmph, CS1 doesn't have that. -- Paul Furman www.edgehill.net www.baynatives.com all google groups messages filtered due to spam |