Luminous Landscape Forum
Raw & Post Processing, Printing => Digital Image Processing => Topic started by: samosa on January 04, 2007, 04:23:48 pm
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Michael Reichmann, in his "Understanding DSLR Workflow" article on this site, states:
"Digital has a remarkable ability to extract detail from the shadows. When shooting digital, always ere (if you have to) on the side of underexposure."
whereas Bruce Fraser - another highly respected digital processing expert states (in Real World Camera Raw):
"correct exposure in the digital realm means keeping the highlights as close to blowing out, without actually doing so, as possible.....it's better to err on the side of slight overexposure".
So who is right?
I have to say the explanation given by Bruce Fraser seems quite convincing - its too long to go into here but basically there are more levels of data at the brighter end of the scale, so if you subsequently have to "stretch" the data in levels or curves then you'll get more data to play with.
Any thoughts?
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Michael Reichmann, in his "Understanding DSLR Workflow" article on this site, states:
"Digital has a remarkable ability to extract detail from the shadows. When shooting digital, always ere (if you have to) on the side of underexposure."
whereas Bruce Fraser - another highly respected digital processing expert states (in Real World Camera Raw):
"correct exposure in the digital realm means keeping the highlights as close to blowing out, without actually doing so, as possible.....it's better to err on the side of slight overexposure".
So who is right?
I have to say the explanation given by Bruce Fraser seems quite convincing - its too long to go into here but basically there are more levels of data at the brighter end of the scale, so if you subsequently have to "stretch" the data in levels or curves then you'll get more data to play with.
Any thoughts?
[a href=\"index.php?act=findpost&pid=93725\"][{POST_SNAPBACK}][/a]
Sometime back there was an extended thread in the Adobe Camera Raw forum where I expressed Michael's view and Bruce disagreed. It is true that half the information in a linear digital file is in the brightest f/stop and under-exposure does not make use of these tones. Bruce's point was that it is safer to darken a digital image because the highlights are information rich is well taken. However, one could argue that the eye can not make use of all 4096 tones of a digital raw file.
Many digital cameras allow some headroom in the highlights, and these can be recovered with Adobe Camera Raw and other raw converters, up to half a stop or so according to Bruce and depending on the camera. If all three color channels are not clipped, some degree of recovery is possible, although a color shift may occur. However, totally clipped highlights are lost. Under-exposure loses the above tones and also is associated with more noise.
One can make a case for either viewpoint.
Bill
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Michael Reichmann, in his "Understanding DSLR Workflow" article on this site, states:
"Digital has a remarkable ability to extract detail from the shadows. When shooting digital, always ere (if you have to) on the side of underexposure."
whereas Bruce Fraser - another highly respected digital processing expert states (in Real World Camera Raw):
"correct exposure in the digital realm means keeping the highlights as close to blowing out, without actually doing so, as possible.....it's better to err on the side of slight overexposure".
So who is right?
I have to say the explanation given by Bruce Fraser seems quite convincing - its too long to go into here but basically there are more levels of data at the brighter end of the scale, so if you subsequently have to "stretch" the data in levels or curves then you'll get more data to play with.
Any thoughts?
[{POST_SNAPBACK}][/a] (http://index.php?act=findpost&pid=93725\")
Check out Michael's other tutorial on "Expose (to the) Right): [a href=\"http://www.luminous-landscape.com/tutorials/expose-right.shtml]http://www.luminous-landscape.com/tutorial...ose-right.shtml[/url] .
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One can make a case for either viewpoint.
[a href=\"index.php?act=findpost&pid=93743\"][{POST_SNAPBACK}][/a]
Seems you can have your cake and eat it too. Ain't digital just grand.
Does Bruce's position mean "expose to the right?'
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One can make a case for either viewpoint.
[a href=\"index.php?act=findpost&pid=93743\"][{POST_SNAPBACK}][/a]
What really matter is what tone you want to record accurately. If you want them all, then you have to record just short of clipping. If the shadows are your main interest, then it might be advantageous to blow the white clouds, or white shirts, etc.
If you have to gamble, and you want the highlights, then under-exposing, as Michael suggests, will be the safest.
The right answer, most of the time, is that the answer depends on the situation.
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I wrote:
If you have to gamble, and you want the highlights, then under-exposing, as Michael suggests, will be the safest.
[a href=\"index.php?act=findpost&pid=93750\"][{POST_SNAPBACK}][/a]
Some day, we may have cameras in which under-exposing by a stop or two is not a big noise problem. Right now, there is far too much read noise for even low ISOs to have clean shadows. If my Canons had an ISO 100 that was 16 bits, and the least significant 12 of them were as clean as its ISO 1600, I'd be very pleased.
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What really matter is what tone you want to record accurately. If you want them all, then you have to record just short of clipping. If the shadows are your main interest, then it might be advantageous to blow the white clouds, or white shirts, etc.
If you have to gamble, and you want the highlights, then under-exposing, as Michael suggests, will be the safest.
The right answer, most of the time, is that the answer depends on the situation.
[a href=\"index.php?act=findpost&pid=93750\"][{POST_SNAPBACK}][/a]
Sounds like slide film. Expose right (correctly).
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It is just like shooting slide film except that more shadow detail is available to you. The main rule is to know your sensor like you know film. Once you are familiar with the way the sensor responds you don't have to worry about it as you will know what the exposure is going to look like before you take the picture.
Any exposure where highlight detail is lost beyond recovery is undesirable. When you look at bright areas you are used to seeing detail there and a lack thereof (blown highlights) is disturbing. It is more natural to see little or no detail in very dark portions of the image because you are faced with this everytime you go out in the dark; there are areas where you can't see any detail at all
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It is just like shooting slide film except that more shadow detail is available to you. The main rule is to know your sensor like you know film. [a href=\"index.php?act=findpost&pid=93768\"][{POST_SNAPBACK}][/a]
It still sounds like slide film (another positive) but with different dynamic range. I also understand digital is linear and film is not.
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Sounds like slide film. Expose right (correctly).
[a href=\"index.php?act=findpost&pid=93753\"][{POST_SNAPBACK}][/a]
"Expose correctly" is a meaningless concept. The optimal exposure depends on what tonal ranges are most important to you, the camera in question, and your workflow.
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The optimal exposure depends on what tonal ranges are most important to you, the camera in question, and your workflow.
[a href=\"index.php?act=findpost&pid=93780\"][{POST_SNAPBACK}][/a]
That's right. "Expose correctly"
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Hi,
I think that we need to expose for highlight, the shadows are more often than not not a big deal. Best way is probably to use tripod and take three or more exposures and combine with HDR technique.
For optimum shadows we would need to use low ISO.
Best regards
Erik
That's right. "Expose correctly"
[a href=\"index.php?act=findpost&pid=93825\"][{POST_SNAPBACK}][/a]
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That's right. "Expose correctly"
[a href=\"index.php?act=findpost&pid=93825\"][{POST_SNAPBACK}][/a]
I don't think so. "Expose correctly" connotes that any give scene has a single exposure level for a given ISO, for all cameras and workflows; that's how 99% of the people will hear it.
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I don't think so. "Expose correctly" connotes that any give scene has a single exposure level for a given ISO, for all cameras and workflows; that's how 99% of the people will hear it.
[a href=\"index.php?act=findpost&pid=93851\"][{POST_SNAPBACK}][/a]
Well John, I guess you and the rest of the "99%" can't be wrong.
Because I don't use every ISO, all cameras or workflows, I have a correct exposure for me.
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I don't think so. "Expose correctly" connotes that any give scene has a single exposure level for a given ISO, for all cameras and workflows; that's how 99% of the people will hear it.
[a href=\"index.php?act=findpost&pid=93851\"][{POST_SNAPBACK}][/a]
I'm with Howie on this one. For anyone but a rank beginner, it should be obvious that "expose correctly" means that you must consider what tonal ranges are most important to you, the camera in question, and your workflow.
It may happen that for most (or, for some photographers even all) of your photographs require capturing all available highlight detail. But most of us understand that we must make tradeoffs some of the time. To me, when I "expose correctly", it means I have weighed all of the trade-offs and chosen the exposure that best fits my personal vision.
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A while back (months?) someone posted an image composed of vertical strips of varying exposures, each corrected to match the ideal. I can't find it now, but I remember something like 1-2 stops off ideal exposure showed considerable noise.
It was a great example - a landscape at sunset/sunrise - maybe illustrating blended exposures...
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I believe you mean the one Timothy Farrar posted in a related thread here:
[a href=\"http://luminous-landscape.com/forum/index.php?showtopic=13084&hl=]http://luminous-landscape.com/forum/index....topic=13084&hl=[/url]
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Seems you can have your cake and eat it too. Ain't digital just grand.
Does Bruce's position mean "expose to the right?'
[a href=\"index.php?act=findpost&pid=93749\"][{POST_SNAPBACK}][/a]
Yes, I think that is what he recommended. He once stated that proper exposure was not blowing the highlights you wished to preserve, and this involves ETTR.
Bill
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I would imagine that's why Bruce said "expose to the right" and not "overexpose to the right" ...
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I would imagine that's why Bruce said "expose to the right" and not "overexpose to the right" ...
[a href=\"index.php?act=findpost&pid=93943\"][{POST_SNAPBACK}][/a]
Unfortunately, camera manufacturers don't seem to care if we know where the right really ends. They supply absolutely such information, and their software often ignores extreme RAW highlights. Only the lowest ISO on a camera stands a chance of having non-linear extreme highlights; and even so, the camera could be profiled for a proper translation, but they are not. We live in a dark, sloppy age of RAW exposure.
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Thanks to all for your comments. In particular thanks to Eric M for pointing out Michael's other article on the subject ("Expose (to the) Right): http://www.luminous-landscape.com/tutorial...ose-right.shtml (http://www.luminous-landscape.com/tutorial...ose-right.shtml) )
in which he clearly comes around to the same argument used by Bruce Fraser.
To be fair to Michael I think the article which suggested biasing towards underexposure was written before he had spoken to Thomas Knoll about bias of levels towards the highlights.
So there we have it. The experts agree, as does the science: you should, if anything, bias towards overexposure in RAW without clippling the highlights (although some highlight recovery my be possible in the RAW converter).
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Check out Michael's other tutorial on "Expose (to the) Right): http://www.luminous-landscape.com/tutorial...ose-right.shtml (http://www.luminous-landscape.com/tutorials/expose-right.shtml) .
[a href=\"index.php?act=findpost&pid=93748\"][{POST_SNAPBACK}][/a]
Eric oldbean,
in MR's expose to the right essay.
Could you please explain, what "The First f stop, which contains the brightest tones" is.
IE, with what is its reference point.
Surely we do not have to shoot wide open all the time.
jeffoldbean.
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Could you please explain, what "The First f stop, which contains the brightest tones" is.
IE, with what is its reference point.
What Michael is referring to is the first stop's worth of tonal values immediately below the clipping point, and has nothing to do with aperture. Go back and read Michael's article again, and this article (http://www.visual-vacations.com/Photography/exposure_metering_strategies.htm) as well.
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I'd ask "Expose with or without insurance" ?
If you're a street shooter you should underexpose by one stop, or else risk a lost shot if your meter got fooled.
Edmund
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If you're a street shooter you should underexpose by one stop, or else risk a lost shot if your meter got fooled.[a href=\"index.php?act=findpost&pid=165525\"][{POST_SNAPBACK}][/a]
Not quite sure what you mean by that Edmund.
If I am street shooting I simply set the expusure manually and then there are no worries about the meter being fooled.
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Not quite sure what you mean by that Edmund.
If I am street shooting I simply set the expusure manually and then there are no worries about the meter being fooled.
[a href=\"index.php?act=findpost&pid=165531\"][{POST_SNAPBACK}][/a]
So, you set it for something in the sun; then, all of a sudden, you have a small window of opportunity to shoot something in the shade. Your manual setting may result in gross under-exposure, far more than 1 stop. The gamble Edmund speaks of may under-expose a bit at times, but never as much as a fixed manual can.
It's all a matter of what you have time to pay attention to in the type of shooting you're doing. Opportunities don't always sit around and wait for you to meter and turn dials.
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Hi
This is the principle as to how I set exposure and BOTH comments are correct.
IMHO Digital capture is about data collection and I see exposure as really a question about how to capture as much data as possible to best fulfil my final image requirements. I ask a number of exposure based questions when thinking about getting the data to establish what the critical issues are, what the compromises may be, do they provide creative alternatives etc.
In many of my subjects I must have data available from the white clouds in the sky for my final image as I hate blown skies. In crude terms for this kind of shot I set my camera up such that the clouds are not quite clipping, and then adjust exposure by another +1/3 or 2/3 (if feeling brave)
Often the subject is technically under exposed by upto a stop but I have all the highlights and can generate a pretty decent image. To process I have to recover the highlights by moving the ev correction and then add a fairly scary curve to the shadows, or produce multi exposure derivative files and either blend the layers or use something like photomatix to create a starting point TIFF.
If there are NO white clouds then in theory I can set the camera up the same, find the clipping point and and a possibly another 1/3 to 2/3. (Diff cameras and raw capture combinations will have diff values - WB should be set as accurately as possible, although by adjusting exposure in processing I find it will often require revisiting) This time the subject is normally overexposed by up to a stop and I drag the whole image back. In this case shadow detail is better. However we are normally working with less overall light so it may be that my desired combination of ISO, shutter speed, aperture etc are reached before a right exposure is achieved and I may consider any further moving the histogram to the right will not improve the data because of the need to make compromises to ISO, or aperture setting.
I haven't done tests here, but some people have determined that in limiting light conditions overall data is better by accepting an underexposed image and then pushing in processing rather than increasing ISO at image capture.
I carried out an experiment last year and the histogram clip point plus 2/3 over exposed at capture and corrected had slightly more detail in the shadows. Wish I'd kept the files now! It wasn't so much that it would be worth it for everyone, but it was enough to convince me to keep doing it.
I would imagine that there is as to limit to how far one should take a fairly narrow tonal range, but I have had some very good results from data that initially produced a very nearly bright screen!!!
Regards
Steven Draper
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There are a couple of effective approaches here. The simplest is to bracket exposure. However, there can be a disadvantage if timing is critical and capture of the precise moment is desired. It might be safer to change the default order of the exposures so the 'underexposed' shot is taken first.
Another approach which I found quite precise, but a little time-consuming and not ideal for the quick shot, is to focus the camera's spot meter on the brightest part of the scene, white clouds in a landscape or a white napkin in a restaurant, camera in manual mode. Take a note of the shutter speed through the viewfinder, after adjusting the exposure with dial so the needle in the viewfinder is in the centre, whilst still looking through the viewfinder.
Then increase exposure by 4 stops. You should get a full ETTR. The figure of 4 (or is it 3. I haven't tried this for ages) might vary amongst different models of cameras. You'll have to experiment.
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I haven't done tests here, but some people have determined that in limiting light conditions overall data is better by accepting an underexposed image and then pushing in processing rather than increasing ISO at image capture.
There are basically three classes of camera in this regard; cameras that perform markedly better at higher ISOs than with under-exposure (all Canon DSLRs except the original 1D, plus the Nikon D3 and possibly a few other cameras), cameras that perform slightly better at higher ISO (only because there is less noise from the ADC; this includes most DSLRs and some P&S cameras), and cameras that botch high-ISO up and are worse at high ISO than with under--exposure (usually P&S cameras with tight budgets). This is with RAW, of course, and is mainly relevant in regards to shadow areas. Highlight areas are affected more by absolute exposure than ISO settings per se.
I carried out an experiment last year and the histogram clip point plus 2/3 over exposed at capture and corrected had slightly more detail in the shadows. Wish I'd kept the files now! It wasn't so much that it would be worth it for everyone, but it was enough to convince me to keep doing it.
I would imagine that there is as to limit to how far one should take a fairly narrow tonal range, but I have had some very good results from data that initially produced a very nearly bright screen!!!
[a href=\"index.php?act=findpost&pid=165594\"][{POST_SNAPBACK}][/a]
You can take any exposure as high as you want, and bring it back down. That is like shooting at a lower ISO, only the RAW data is actually better. IOW, if you have a scene that is black writing on a gray wall, and shoot at ISO 100 with +3 EC in RAW, and pull the gray back to grey in the converter, you are actually shooting at ISO 12, with better quality than if the camera actually had an ISO 12.
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Michael Reichmann, in his "Understanding DSLR Workflow" article on this site, states: "Digital has a remarkable ability to extract detail from the shadows. When shooting digital, always err (if you have to) on the side of underexposure."
whereas Bruce Fraser---another highly respected digital processing expert---states (in Real World Camera Raw): "correct exposure in the digital realm means keeping the highlights as close to blowing out, without actually doing so, as possible ... it's better to err on the side of slight overexposure".
So who is right?[a href=\"index.php?act=findpost&pid=93725\"][{POST_SNAPBACK}][/a]
Both are right.
The ostensible contradiction only comes from different angles of view ... and from exactly what is the term 'overexposure' supposed to mean. Bruce was looking at the topic from a technical point of view, and 'overexposure' in his context means overexposure of the JPEG image that comes from the capture parallel to the raw file (or from the raw file via standard settings in the raw converter). When the JPEG is (slightly) overexposed then the raw file often still will have some headroom to work with. Michael is looking at the topic from a practical, hands-on point of view. In real life, underexposed images can be saved through proper processing much easier and more often than overexposed ones.
The critical point is, 'as close to blowing out without actually doing so.' If you go just a quarter of an f-stop above the blow-out limit then the image is damaged beyond salvation. If you stay two or even three full f-stops below the limit then the image usually will still be fine.
In any case, Expose To The Right (or expose for the highlights, as we used to say in analog days) is the correct approach. The problem is, how far to the right is far enough? Often, photographers are pushing the exposure too far to the right without noticing, simply because the tiny histogram display on the camera's screen is not accurate enough. The closer you try to approach the the theoretical ideal the more likely you will eventually blow your exposure---and thus, your work.
-- Olaf
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Eric oldbean,
in MR's expose to the right essay.
Could you please explain, what "The First f stop, which contains the brightest tones" is.
IE, with what is its reference point.
Surely we do not have to shoot wide open all the time.
[a href=\"index.php?act=findpost&pid=165514\"][{POST_SNAPBACK}][/a]
The higher in the range of RAW levels you record your subject, the higher the signal-to-noise ratio is at every tonal level in the image. Obviously, you are the artist and/or technician, and should decide what aperture and shutter speed you want, but subordinate to that, within the range of freedom you can allow, you can also improve S:N by increasing the exposure (avoiding clipping desired highlights, of course). With some cameras, you get a significant decrease in shadow noise by going to a higher ISO while maintaining the same absolute exposure, and exposing more to the right.
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Does Bruce's position mean "expose to the right?'
[{POST_SNAPBACK}][/a] (http://index.php?act=findpost&pid=93749\")
Yes. And there IS such a thing as correct exposure, which is what ETTR is intending to accomplish.
[a href=\"http://www.digitalphotopro.com/tech/exposing-for-raw.html]http://www.digitalphotopro.com/tech/exposing-for-raw.html[/url]
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Exposure bracketing would seem to satisfy all concerned.
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Exposure bracketing would seem to satisfy all concerned.
[a href=\"index.php?act=findpost&pid=165643\"][{POST_SNAPBACK}][/a]
Yes, unless you're shooting anything that moves....
Bracketing portraits ain't going fly.
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The higher in the range of RAW levels you record your subject, the higher the signal-to-noise ratio is at every tonal level in the image. Obviously, you are the artist and/or technician, and should decide what aperture and shutter speed you want, but subordinate to that, within the range of freedom you can allow, you can also improve S:N by increasing the exposure (avoiding clipping desired highlights, of course). With some cameras, you get a significant decrease in shadow noise by going to a higher ISO while maintaining the same absolute exposure, and exposing more to the right.
[a href=\"index.php?act=findpost&pid=165608\"][{POST_SNAPBACK}][/a]
John,
how does one characterize these aspects eg S:N vs ISO ?
Edmund
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Both are right.
The ostensible contradiction only comes from different angles of view ... and from exactly what is the term 'overexposure' supposed to mean. Bruce was looking at the topic from a technical point of view, and 'overexposure' in his context means overexposure of the JPEG image that comes from the capture parallel to the raw file (or from the raw file via standard settings in the raw converter). When the JPEG is (slightly) overexposed then the raw file often still will have some headroom to work with. Michael is looking at the topic from a practical, hands-on point of view. In real life, underexposed images can be saved through proper processing much easier and more often than overexposed ones.
The critical point is, 'as close to blowing out without actually doing so.' If you go just a quarter of an f-stop above the blow-out limit then the image is damaged beyond salvation. If you stay two or even three full f-stops below the limit then the image usually will still be fine.
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Shooting fully to the right requires base ISO so that the electron wells of the sensor are filled, collecting the maximum number of photons and giving the best signal to noise ratios at all levels. If you are shooting at an ISO higher than base, you are essentially underexposing and boosting the amplification of the signal. For example, if the base ISO of your camera is 100 and you expose at ISO 1600 you are basically underexposing by 4 f/stops and compensating for this by increasing the amplification of the signal. This is usually done by setting the camera to a higher ISO, but alternatively, one can do this in the raw converter. Because read noise is higher at low camera ISOs it is better to use the ISO route, at least up to [a href=\"http://www.clarkvision.com/imagedetail/digital.sensor.performance.summary/]Unity Gain[/url]. There is little point in increasing ISO above unity gain, since you lose headroom protection from overexposure but collect little if any more information.
Digital cameras have no shoulder on the characteristic curve, and clip abruptly at sensor saturation of overflow of the ADC. You can recover 0.4 to 1 stop of blown highlights with highlight recovery, but beyond that there is a complete loss of highlight detail. Furthermore, highlight recovery is less than perfect and may involve color shifts.
On the other hand, a camera with large pixels and low read noise (e.g. Nikon D3 or Canon 1DMIII) can produce quite acceptable pictures at 4 stops underexposure as defined above. Overexpose by 4 stops and you will lose 3 or more stops of highlight detail and the results will most likely not be acceptable. However, you will get good shadow detail.
As Andrew stated, we should be striving for proper exposure. In an imperfect world, slight overexposure can be tolerated, but gross overexposure will cause major data loss. If you have a good camera, gross underexposure will give more noise and less dynamic range, but you will at least have an image. Since signal:noise is proportional to the square root of the number of electrons, doubling of exposure will improve the S:N by a factor of 1.4, not 2, and this improvement may not be worth the risk of data loss if ETTR is carried to far.
Some argue that a main rationale of ETTR is to make use of the 2048 levels in the brightest f/stop of a 12 but linear file, which contains a total of 4096 levels. However, the eye can distinguish 70 levels per f/stop at maximum, so one can afford to lose a few of these levels without incurring posterization. Posterization in the shadows could occur, but usually noise is the limiting factor there.
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What is rarely mentioned in ETTR discussions like this is the ability to determine dynamic range at the time of capture. If it's beyond the sensor's capabilities it makes ETTR or any exposure technique pointless.
And frankly I'm not even sure what DR really means after experimenting with bracketed RAW shots taken on my Pentax K100D. A midday outdoor scene with the sun directly overhead creates quite a bit of bounced light for backlit objects in the foreground compared to taking the same shot with the sun just over the rooftops meaning there's less light. I can get more detail in the shadows with very little noise without blowing out highlites with the midday shot than I could with the one with less light or maybe contrasty should be a better way to describe the scene.
I can't understand how a scene with less light can create a dynamic range that overpowers the sensors. Something is screwey with the way sensors record light that doesn't fit within our notion of dynamic range.
I've examined dpreview's backlit Stouffer grayramps but it never seems to translate for me how you expect to retrieve more detail with less light as in a sunset than with more light at midday and from this determine the DR capabilities of any given sensor.
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Shooting fully to the right requires base ISO so that the electron wells of the sensor are filled, collecting the maximum number of photons and giving the best signal to noise ratios at all levels
This is correct only
1. if it is possible to expose to the right using the base ISO; but what about insufficient light, moving subjects hand-held shooting, the necessity to work with small aperture?
2. if the base ISO offers the best DR, which is not always the case.
This is usually done by setting the camera to a higher ISO, but alternatively, one can do this in the raw converter. Because read noise is higher at low camera ISOs it is better to use the ISO route
Higher ISO is always better than lower ISO with the same exposure, adjusted in the raw processing, at least up to some ISO limit (and even later, it is never worse than increasing the brightness in raw processing).
Unity Gain (http://www.clarkvision.com/imagedetail/digital.sensor.performance.summary/)
This is woodoo science from a certain level, for the inaccuracy in the data used in the calculation is approaching 100%.
Some argue that a main rationale of ETTR is to make use of the 2048 levels in the brightest f/stop of a 12 but linear file, which contains a total of 4096 levels. However, the eye can distinguish 70 levels per f/stop at maximum, so one can afford to lose a few of these levels without incurring posterization
Those, who keep only the 2048 levels in their eyes are partially blind.
However, there is another side of the issue: utilizing some of those 2048 levels means at the same time increasing the number of levels at the low end.
What worth is an additional "low noise" stop, which contains only eight levels?
Using only the first 2048 levels means, that the seventh stop will consists of only FOUR levels; going to the right increases this to eight levels. So, what about the 70 levels?
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I've examined dpreview's backlit Stouffer grayramps but it never seems to translate for me how you expect to retrieve more detail with less light as in a sunset than with more light at midday and from this determine the DR capabilities of any given sensor.
DPReview's DR measurement concentrates on the "smoothness" of the strips, totally ignoring the details retained on that level (which, of course, can not be measured with the Stouffer wedge).
There is a long discussion of this subject in this thread (http://luminous-landscape.com/forum/index.php?showtopic=21664)
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Those, who keep only the 2048 levels in their eyes are partially blind.
However, there is another side of the issue: utilizing some of those 2048 levels means at the same time increasing the number of levels at the low end.
Exactly! Its about getting as many of the few levels in the last stop (shadows) possible.
And what the eye can theoretically see seems rather moot when we're talking about encoding data for a computer to process.
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And what the eye can theoretically see seems rather moot when we're talking about encoding data for a computer to process.
This is an additional aspect: an image with 70 levels in the higher stops would not withstand any post processing. Details would be rendered unrecognizable due to interpolation, rounding.
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On the other hand, a camera with large pixels and low read noise (e.g. Nikon D3 or Canon 1DMIII) can produce quite acceptable pictures at 4 stops underexposure as defined above. Overexpose by 4 stops and you will lose 3 or more stops of highlight detail and the results will most likely not be acceptable. However, you will get good shadow detail.
As Andrew stated, we should be striving for proper exposure. In an imperfect world, slight overexposure can be tolerated, but gross overexposure will cause major data loss. If you have a good camera, gross underexposure will give more noise and less dynamic range, but you will at least have an image. ...
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Excellent summary.
Those, who keep only the 2048 levels in their eyes are partially blind.
...
Using only the first 2048 levels means, that the seventh stop will consists of only FOUR levels; going to the right increases this to eight levels. So, what about the 70 levels?
[a href=\"index.php?act=findpost&pid=165692\"][{POST_SNAPBACK}][/a]
Recommended homework: see Human Vision and Tonal Levels:
[a href=\"http://www.normankoren.com/digital_tonality.html]http://www.normankoren.com/digital_tonality.html[/url]
If of further interest: about the limitations of the Weber-Fechner Law:
http://www.jgp.org/cgi/reprint/7/2/235.pdf (http://www.jgp.org/cgi/reprint/7/2/235.pdf)
DPL
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This is correct only
1. if it is possible to expose to the right using the base ISO; but what about insufficient light, moving subjects hand-held shooting, the necessity to work with small aperture?
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In these situations, you can't shoot fully to the right and your criticism is irrelevant.
2. if the base ISO offers the best DR, which is not always the case.
[a href=\"index.php?act=findpost&pid=165692\"][{POST_SNAPBACK}][/a]
Read my statement again. I said signal:noise, not dynamic range. The two usually go together, but in some cameras such as the Canon 1D MII, you get the best dynamic range at ISO 100 but the best S:N at ISO 50. See [a href=\"http://www.clarkvision.com/imagedetail/evaluation-1d2/index.html]Roger Clark[/url]. If you can find any examples to support your statement, please supply them.
Higher ISO is always better than lower ISO with the same exposure, adjusted in the raw processing, at least up to some ISO limit (and even later, it is never worse than increasing the brightness in raw processing).
This is woodoo science from a certain level, for the inaccuracy in the data used in the calculation is approaching 100%.
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What's woodoo? Some figment of your imagination? How many peer reviewed scientific articles have you published? Roger has over 200. I already gave you a reference here, so I won't comment further rather than note your assertions are without logic or supporting data.
Those, who keep only the 2048 levels in their eyes are partially blind.
[a href=\"index.php?act=findpost&pid=165692\"][{POST_SNAPBACK}][/a]
2048 levels are grossly in excess of what is needed by human vision or any reasonable tonal adjustments. For a discussion of recording efficiency see [a href=\"http://www.anyhere.com/gward/hdrenc/hdr_encodings.html] this article[/url] by Greg Ward.
However, there is another side of the issue: utilizing some of those 2048 levels means at the same time increasing the number of levels at the low end.
What worth is an additional "low noise" stop, which contains only eight levels?
Using only the first 2048 levels means, that the seventh stop will consists of only FOUR levels; going to the right increases this to eight levels. So, what about the 70 levels?
[{POST_SNAPBACK}][/a] (http://index.php?act=findpost&pid=165692\")
Again, please reread my original statement, "Posterization in the shadows could occur, but usually noise is the limiting factor there." I had already anticipated your and similar criticisms. If you can't make out the levels because of noise, then the number of indistinct levels is not an overriding consideration.
In addition, 8 levels in the darkest f/stop is usually sufficient as explained by [a href=\"http://www.normankoren.com/digital_tonality.html]Norman Koren[/url] because the eye can distinguish fewer levels in shadows.
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So, you set it for something in the sun; then, all of a sudden, you have a small window of opportunity to shoot something in the shade. Your manual setting may result in gross under-exposure, far more than 1 stop. The gamble Edmund speaks of may under-expose a bit at times, but never as much as a fixed manual can.
Not true as you may have a subject that is backlit and then you are grossly underexposed. Whereas you can set a manual exposure at a compromise position if you think you may be shooting in light + shade. But I'd rather set the correct exposure for wherever I'm shooting. Besides on manual I can very easily adjust exposure up or down very easily in a fraction of a second. More easily than with auto exposure.
It's all a matter of what you have time to pay attention to in the type of shooting you're doing. Opportunities don't always sit around and wait for you to meter and turn dials.[a href=\"index.php?act=findpost&pid=165536\"][{POST_SNAPBACK}][/a]
And that is why I use manual.
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Exactly! Its about getting as many of the few levels in the last stop (shadows) possible.
And what the eye can theoretically see seems rather moot when we're talking about encoding data for a computer to process.
[a href=\"index.php?act=findpost&pid=165696\"][{POST_SNAPBACK}][/a]
As Milton Friedman once observed, "There is no such thing as a free lunch." Photography requires many compromises and achieving the best compromise for the intended visualization is part of the art of photography. If the dynamic range of the subject is approximately equal to that of the camera an exact exposure may capture the entire scene. You can bias the exposure slightly to protect the highlights or the shadows but you can't protect both. In most cases the highlights are more important. Of course, 14 bit ADCs could give more shadow levels, but thus far there has been little observable improvement because the obscuring effects of noise.
If the dynamic range of the subject exceeds that of the camera, you must make some choices.
If your pictures are to be viewed by a robot rather than a human, then your concluding remark may make some sense. However, if your audience consists of humans, then what can be seen is important. If you can use computer processing to bring out hidden detail so that it can be seen by the eye, fine, but otherwise your approach is naive and most likely counterproductive.
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Excellent summary.
Recommended homework: see Human Vision and Tonal Levels:
http://www.normankoren.com/digital_tonality.html (http://www.normankoren.com/digital_tonality.html)
If of further interest: about the limitations of the Weber-Fechner Law:
http://www.jgp.org/cgi/reprint/7/2/235.pdf (http://www.jgp.org/cgi/reprint/7/2/235.pdf)
DPL
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DPL,
Excellent information. Had I seen your post prior to making my own, the effort would have not been necessary. The JPL reprint (from the 1920s) is most informative, but will take some time to digest.
Here is a somewhat more accessible description of the limitations of the [a href=\"http://www.neuro.uu.se/fysiologi/gu/nbb/lectures/WebFech.html]Weber Fechner Law[/url]. The Stevens law (described on the next page) is interesting because the slope of the curve for light is the flattest.
Indeed, Norman did note that the Weber-Fechner law was a first order approximation and that the eye is less sensitive to the darker levels, where 8 rather than 70 may be sufficient.
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Not true as you may have a subject that is backlit and then you are grossly underexposed. Whereas you can set a manual exposure at a compromise position if you think you may be shooting in light + shade. But I'd rather set the correct exposure for wherever I'm shooting. Besides on manual I can very easily adjust exposure up or down very easily in a fraction of a second. More easily than with auto exposure.
And that is why I use manual.
[a href=\"index.php?act=findpost&pid=165752\"][{POST_SNAPBACK}][/a]
I'm not arguing that there aren't times when manual works best - it is both simple and optimum when the lighting is consistent, and your subject and background have high contrast that can vary intensity in the FOV with a sweep of recomposition. I'm arguing that there are times when it doesn't work best; case in point - when you don't have time to deal with optimal exposure and must gamble, and both your subject and background will both have an opportunity to suddenly change by a few stops. Reading Edmund in context, my immediate impression was one of a situation where anything can pop up instantly, and you don't have time to mess around with all parameters of shooting, so something must be simplified and sacrificed, and a -1 EC in an AE mode is the chosen sacrifice. When you replied that you shoot manual, in that context, it seemed that you referred to one fixed manual setting, which included enough headroom for whites in the brightest light.
If your scenario is one where you take time for exposure issues, then I don't think it applies in that context, and if you are going to insist that you won't ever miss any opportunities while metering, I think you're probably overrating yourself. However good you are at manually adjusting exposure to meet a relatively immediate need, there is always a more immediate need that you won't be ready for, and I assume that was the context here. If you have to completely automate exposure, it may be safer to do so with -1 EC, which on cameras like the D3 and Canon mk3 cameras, is not a particularly big sacrifice at ISO 200s and 100, respectively. I believe the D3 allows manual AV and Tv with auto-ISO, which is even better than AE, as you can keep the manual setting in a range of lighting.
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In these situations, you can't shoot fully to the right and your criticism is irrelevant.
Read my statement again. I said signal:noise, not dynamic range. The two usually go together, but in some cameras such as the Canon 1D MII, you get the best dynamic range at ISO 100 but the best S:N at ISO 50.
[a href=\"index.php?act=findpost&pid=165738\"][{POST_SNAPBACK}][/a]
It really makes one wonder why a company would ruin an opportunity to have both at one ISO, just to meet a standard of having "ISO 100" in some important hierarchy in the cameras' ISO range. Why not just start at ISO 70? Who would refuse to buy a camera because it had ISOs 70, 140, 280, 560, 1120 instead of what we have now? You could even label it something standard like 64, 125, 250, etc or 80, 160, 320, etc (and get the "standard ones with the 1/3 stop fabricated ones anyway, and explain the real ISO sensitivity in the manual). Almost every Canon DSLR is mildly crippled like this at the bottom of the ISO range. The XTi is the only one that seems to have RAW saturation at its lowest ISO below sensor saturation (its real sensitivity is ISO 85 when it says ISO 100, but meters at 120, and under-exposes the RAW data - they had to screw something up!).
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Yes. And there IS such a thing as correct exposure, which is what ETTR is intending to accomplish.
http://www.digitalphotopro.com/tech/exposing-for-raw.html (http://www.digitalphotopro.com/tech/exposing-for-raw.html)
[a href=\"index.php?act=findpost&pid=165621\"][{POST_SNAPBACK}][/a]
I have funny feelings about the phrase "correct exposure" in the context of ETTR. The connotations of the word "correct" imply to me a context of something like shooting slide film, where you want the slide projected onto the screen to have "normal" intensity for the scene; a scene that is high key should be bery bright on the screen; a scene that is a black beetle on a black cloth should be fairly dark on the screen. The same would apply to in-camera JPEGs displayed with a digital projector, or even regular film developed and printed with fixed parameters (no auto-levels).
People who do not understand the value of ETTR talk a lot about "correct exposure", and are usually referring to the act of literally metering a gray card, or some equivalent exposure technique. And, to tell the truth, I really don't see anything wrong with equating the phrase to this. This "no processing" paradigm needs to exist, even if we don't use it most of the time, out of personal choice, if only as a frame of reference. IOW, a gray FOV, exposed correctly, will leave RAW highlights unused. An exposure that leaves the brightest excursions just below RAW saturation is an "optimal exposure" (assuming, of course, that Av and Tv values are not compromised). "Optimal exposure" is a phrase I am more comfortable with in the context of ETTR.
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how does one characterize these aspects eg S:N vs ISO ?
[a href=\"index.php?act=findpost&pid=165648\"][{POST_SNAPBACK}][/a]
I see too many ways to interpret your question. Could you whittle it down a notch?
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AESTHETIC CONSEQUENCES OF EXPOSING TO THE RIGHT.
I have here a portrait, taken outside, exposed to the right.
Nothing blows, there isn't a single pixel blown.
But through this overexposure that I did exposing to the right, I somewhat changed the appearance of the skin. It looks drier.
Summary: exposing to the right may result in technically perfect images, but this overexposure changes the image characteristics. I found that skin not exposed to the right looked better than exposed to the right.
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AESTHETIC CONSEQUENCES OF EXPOSING TO THE RIGHT.
I have here a portrait, taken outside, exposed to the right.
Nothing blows, there isn't a single pixel blown.
But through this overexposure that I did exposing to the right, I somewhat changed the appearance of the skin. It looks drier.
Summary: exposing to the right may result in technically perfect images, but this overexposure changes the image characteristics. I found that skin not exposed to the right looked better than exposed to the right.
[a href=\"index.php?act=findpost&pid=165837\"][{POST_SNAPBACK}][/a]
You might supply images to back up your impressions. Also, after obtaining your ETTR image, did you bring the tones back down to their proper values with the exposure controls? Since the sensor is linear, the properly processed ETTR and non ETTR images should be quite similar, except the ETTR image may have better tonality and less noise.
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People who do not understand the value of ETTR talk a lot about "correct exposure", and are usually referring to the act of literally metering a gray card, or some equivalent exposure technique.
I can't speak for most people. I can say I use the term "correct exposure" with ETTR because I find people think of ETTR as "over exposure" which it isn't. When they see the suggested exposure based on their meters, based on a JPEG capture, they tend to then think ETTR is over exposure in this context, but its not.
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John,
Assuming ambient illuminantion is adequately exposing the gray card, this card or an incident meter will allow you to determine the unity/area reflected illumination off a diffusing surface. Which will theoretically yield optimal exposure ETTR for such diffusing surfaces.
However, shiny surfaces (metal, glass plastic, wood, paint, water) or textures like skin have specular and radiosity effects associated with them which will render such an exposure inappropriate whenever these entities are imaged.
I don't think it's realistic to assume that we photograph scenes that don't contain skin, metal, glass, plastic, wood, paint or water. Such are present even in studio or architecture work, and worse even in every landscape, street, indoors or nightclub scene. Such scenes also frequently integrate radiant light sources.
So the gray card or incident light approach needs to be tempered with some headroom assumptions, and a decision of how much of the image one is willing to burn or color out. It would be interesting to debate how we could determine the appropriate exposure absent an HDR device.
Edmund
People who do not understand the value of ETTR talk a lot about "correct exposure", and are usually referring to the act of literally metering a gray card, or some equivalent exposure technique. And, to tell the truth, I really don't see anything wrong with equating the phrase to this. This "no processing" paradigm needs to exist, even if we don't use it most of the time, out of personal choice, if only as a frame of reference. IOW, a gray FOV, exposed correctly, will leave RAW highlights unused. An exposure that leaves the brightest excursions just below RAW saturation is an "optimal exposure" (assuming, of course, that Av and Tv values are not compromised). "Optimal exposure" is a phrase I am more comfortable with in the context of ETTR.
[a href=\"index.php?act=findpost&pid=165808\"][{POST_SNAPBACK}][/a]
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It would be interesting to debate how we could determine the appropriate exposure absent an HDR device.
[a href=\"index.php?act=findpost&pid=165879\"][{POST_SNAPBACK}][/a]
Pretty easy...and some people have been doing this for years with film. It's called a spot meter...
Meter the lightest tone you wish to maintain texture. Measure the darkest tone you want to maintain texture. What is the range between them. If less than 7-8 stops, then you can ETTR. If over 9-10 stops then you need to evaluate the scene to determine if the shadows are more important than the highlights. If so, then let the highlights blow and expose for the shadows. If the highlights are more important, then expose for them.
If all detail ranges are important, either do an HDR bracket, add fill light or find a better scene to shoot.
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However, there is another side of the issue: utilizing some of those 2048 levels means at the same time increasing the number of levels at the low end.
What worth is an additional "low noise" stop, which contains only eight levels?
Using only the first 2048 levels means, that the seventh stop will consists of only FOUR levels; going to the right increases this to eight levels. So, what about the 70 levels?
[{POST_SNAPBACK}][/a] (http://index.php?act=findpost&pid=165692\")
There is an easy solution to solving the problem of excessive levels in the highlights and the paucity of tones in the shadows and that is to change the encoding of the data. That the brightest f/stop contains 2048 of the 4096 levels of a 12 bit capture is not due to the nature of light or peculiarities of digital capture, but to the use of linear integer encoding, which works well for current cameras, but would not be satisfactory when we get true HDR output from our cameras.
For example, in discussing the scRBG standard, [a href=\"http://www.anyhere.com/gward/hdrenc/hdr_encodings.html]Greg Ward[/url] has noted, "a linear ramp is employed to simplify graphics hardware and image-processing operations. However, a linear encoding spends most of its precision at the high end, where the eye can detect little difference in adjacent code values. Meanwhile, the low end is impoverished in such a way that the effective dynamic range of this format is only about 3.5 orders of magnitude, not really adequate from human perception standpoint...". You seem to regard plethora of highlight tones to be an advantage, but the experts seem to think otherwise.
By going to floating point encoding (there are special formats than represent the required precision with relatively few bits), the encoding precision is nearly constant over the entire range. Log encoding would make the precision totally uniform, but then you would no longer have raw data. These considerations are discussed by Ward and I would encourage thoughtful readers to look at his paper.
Since noise, not posterization, is most limiting in the shadows, no major manufacturer seems to have done this for still cameras. Another solution to improve shadow tones would be to add a few bits to the ADC, but thus far the results have not been impressive, again for the reasons cited above.
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Pretty easy...and some people have been doing this for years with film. It's called a spot meter...
Meter the lightest tone you wish to maintain texture. Measure the darkest tone you want to maintain texture. What is the range between them. If less than 7-8 stops, then you can ETTR. If over 9-10 stops then you need to evaluate the scene to determine if the shadows are more important than the highlights. If so, then let the highlights blow and expose for the shadows. If the highlights are more important, then expose for them.
If all detail ranges are important, either do an HDR bracket, add fill light or find a better scene to shoot.
[a href=\"index.php?act=findpost&pid=165904\"][{POST_SNAPBACK}][/a]
Jeff,
An eminently concise post. I don't see much room for argument, but others might.
Details of implementation are of interest. I know you and Bruce have discussed this before. Bruce mentioned that he had borrowed a Minolta Spot meter from you and his preferred method was to take a reading from a highlight for which he wished to maintain some texture, and then placed the exposure so many f/stops over indicated according to previous tests. I think he used a factor of 3 EV or so. I have experimented with this method, but find the camera histogram sufficiently reliable for my purposes, especially after running some tests to correlate the appearance of the histogram to the contents of the raw file?
I presume a similar procedure would apply to cases where you wish to preserve shadow tones, but you would use a different offset.
What do you use most in your day to day work?
Bill
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You might supply images to back up your impressions. Also, after obtaining your ETTR image, did you bring the tones back down to their proper values with the exposure controls? Since the sensor is linear, the properly processed ETTR and non ETTR images should be quite similar, except the ETTR image may have better tonality and less noise.
[a href=\"index.php?act=findpost&pid=165857\"][{POST_SNAPBACK}][/a]
Yes, I use the exposure controls.
I posted my comments more in a sense of me exploring the issues.
I remember, in black-an-white film, when you exposed too much (and the negative got too "dense", you lost some skin details.
Of course, that's film, not digital. But it's just a connection that sprang up.
I can see that there is still a lot of room for exploration in this issue. To express yourself in your own photographic language.
All you say makes perfect sense. I have to explore this, if there is a "right" amount of exposure, even in RAW.
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... Ansel Adam's Zone System...
Could there be an equivalent in RAW shooting?
Could it be possible that ETTR preserves more detail in mid-tones, but also changes their character?
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Could it be possible that ETTR preserves more detail in mid-tones, but also changes their character?
"Character" is not in the metadata of raw images :-)
You need to define in technical terms, what kind of changes you mean, or provide comparative examples to point out what you mean.
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"Character" is not in the metadata of raw images :-)
You need to define in technical terms, what kind of changes you mean, or provide comparative examples to point out what you mean.
[a href=\"index.php?act=findpost&pid=166000\"][{POST_SNAPBACK}][/a]
I think a non-linear interpretation across the zones introduced because of the zone-shift through ETTR might be a quantitative interpretation of "character change" ...
For me spot metering and zone system visualization to which ETTR philosophy (?!)augmented by two or three brackets has been applied has worked nicely, using the built-in spot meter linked to the AF point in my 1Ds 2/3.
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There is an easy solution to solving the problem of excessive levels in the highlights and the paucity of tones in the shadows and that is to change the encoding of the data
That's right, however this thread is about exposing to the right, and that is incompatible with the proposal of hightlight-compressed encoding.
Certainly, the encoding could save some of the levels, but not to the degree, as this can be done on an image directly before finalizing it.
Already the fact, that one of the channels (usually the red) may have to be multiplied by two or more in order to achieve white balance, should be enough to think twice before reducing the data.
after obtaining your ETTR image, did you bring the tones back down to their proper values with the exposure controls? Since the sensor is linear, the properly processed ETTR and non ETTR images should be quite similar, except the ETTR image may have better tonality and less noise
I remember to have seen post of you proving just the opposite.
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"Character" is not in the metadata of raw images :-)
You need to define in technical terms, what kind of changes you mean, or provide comparative examples to point out what you mean.
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I guess we are in the stage of developing that. After all, RAW hasn't been around for that many years.
Sharp, descriptive terms you can use when you have complete overview about what you want to say.
At the moment, I have the impression, we are still pretty much at the hunch stage. A sign of this are the amount of opposing theories circulating.
So, at this time, metaphors may be better, as they do not try to give sharp descriptions where we don't have that much knowledge to describe sharply.
Wherever aesthetics and technical terms meet...
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I think a non-linear interpretation across the zones introduced because of the zone-shift through ETTR might be a quantitative interpretation of "character change" ...
Exposing to the right is not meant to keep everything exposed higher than necessary.
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At the moment, I have the impression, we are still pretty much at the hunch stage
Fair enough regarding a sharp description, but you should be able to demonstrate what you mean. I guess when you mentioned this, you were thinking of specific cases you had observed. You should try to create such cases in controlled tests, i.e. shooting a serie with 1/3 stops apart, post-processing them, and pointing out the differences you find detrimental.
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Exposing to the right is not meant to keep everything exposed higher than necessary.
[a href=\"index.php?act=findpost&pid=166010\"][{POST_SNAPBACK}][/a]
The word "necessary" is key here.
How much exposure is necessary?
Isn't ETTR often voluntary over-exposure (to get important tones into the more brightness-levels area), and then reducing the exposure in the RAW software?
This raising of exposure in the camera and reducing the exposure in the software could deliver different results than exposing "correctly" right away...
Maybe ETTR is a great technical idea, which doesn't work out aesthetically?
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Fair enough regarding a sharp description, but you should be able to demonstrate what you mean. I guess when you mentioned this, you were thinking of specific cases you had observed. You should try to create such cases in controlled tests, i.e. shooting a serie with 1/3 stops apart, post-processing them, and pointing out the differences you find detrimental.
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I haven't tested it out so far.
Until now, I have just trusted ETTR, and done it, but doubts had started to form like clouds, and it may rain counter-arguments.
So, no, I haven't decided what to believe yet. And "to know" is even farther away. Which I, creatively, find exciting.
That's the most interesting part of discussion: when there's no firm belief, but exploration.
The tests, comparisons, explorations...
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Exposing to the right is not meant to keep everything exposed higher than necessary.
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Panopeeper, not sure about what your comment means relative to my statement, but I'm kind of dense tonight .
What I was trying to say is that if ETTR were to change the relative values across the brightness zones when development brings it back left to its intended position then that might be interpreted as a "change in character", meaning the tonalities have changed relative to each other thus giving the image a somewhat different look.
However this should hopefully not happen if the sensor and electronics are sufficiently linear and the development algorithms accurate enough, other than whatever might have been pushed out beyond the right margin is now hence blown.
The hoped for effect would be that the brightness values now in their proper place have finer steps differentiating them providing nicer gradients. At least the picture seems clear in my mind, though my verbal translation may have you befuddled and scratching your head ...
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The word "necessary" is key here.
How much exposure is necessary?
"Necessary" is the lesser issue. A real problem is, that you don't know, when you overexpose into clipping, and you won't know that even in the raw processing.
Consequently it can happen, that you think you exposed to the right, while the exposure is in fact over the right. This can lead to loss of contrast and to incorrect color.
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However this should hopefully not happen if the sensor and electronics are sufficiently linear and the development algorithms accurate enough, other than whatever might have been pushed out beyond the right margin is now hence blown.
I clicked on "add reply" before having seen this post of yours. You touched the sensitive point of ETTR.
I got into the habit of shooting exposure bracketing, or simply adjusting the exposure and shooting again, if I feel that the exposure is not the best. I admit to have made already many dozens of shots for a pano series of eight frames. Very unscientific, but the price of memory cards is constantly going down. (The "correct" exposure is particularly a problem with wide panos, which encompass a multitude of sceneries.)
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My experience with ETTR (which I'm defining as exposing so that non-specular highlights are just short of clipping) is that when using ACR, it works 100% of the time with zero negative effects. The people who claim otherwise seem to be using RAW converters such as Capture One and some of the MFDB manufacturer converters that all seem to apply a strong contrast curve by default which one cannot always change. In addition to applying the default strong contrast curve, I suspect that these converters do not handle exposure adjustments as well as ACR.
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My experience with ETTR (which I'm defining as exposing so that non-specular highlights are just short of clipping) is that when using ACR, it works 100% of the time with zero negative effects. The people who claim otherwise seem to be using RAW converters such as Capture One and some of the MFDB manufacturer converters that all seem to apply a strong contrast curve by default which one cannot always change. In addition to applying the default strong contrast curve, I suspect that these converters do not handle exposure adjustments as well as ACR.
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Jonathan,
If you want the hi-levels of your image interpolated from rebuilt color channels, that's your right - but don't call this policy ETTR, call it ETFR (charitably read expose to the Far right).
ETTR = Expose to The True Right.
ETFR = Expose to the Far Right.
Please understand my position: I want software to give you your options (highlight recovery) and me my information (good indication of the real linearity domain of the hardware). If people start to consider that highlight recovery means "real" data, then we're going to head for another marketing war with manufacturers claiming added headroom DR that simply isn't there. I would have assumed that someone as smart as you would hesitate before sucking in the exhaust from the Adobe marketing engine.
Edmund
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If you want the hi-levels of your image interpolated from rebuilt color channels, that's your right - but don't call this policy ETTR, call it ETFR (charitably read expose to the Far right).
Jonathan wrote
which I'm defining as exposing so that non-specular highlights are just short of clipping
this does not include true recovery, i.e. guessing some pixels based on the others.
It is a different issue, what a particular raw processor calls "recovery". For example the "recovery" slider of ACR does not indicate true recovery but a different treatment of the very highlights.
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Jonathan,
If you want the hi-levels of your image interpolated from rebuilt color channels, that's your right - but don't call this policy ETTR, call it ETFR (charitably read expose to the Far right).
I'm not talking about recovering blown highlights via software tricks. Where did you get that notion? I don't care if there are are a few scattered 1-2-pixel specular highlights that clip in an image; that is not going to kill perceived highlight detail even if you aren't using any highlight recovery. If you expose so that there are no clipped pixels at all, your main subject will usually be several stops underexposed and noise will be horrible.
If I'm shooting a bride in a white dress, I'll expose so that the brightest part of the dress is about 1/3 of a stop from clipping in the RAW, and apply a -1/3 to -1/2 stop exposure adjustment in ACR to get the overall luminance right. Same thing with clouds in a landscape shot, assuming they are the brightest objects in-frame.
I think channel reconstruction is a cool software trick that can sometimes save a shot from being unusable, but it's not a crutch I expect to support me all the time.
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I remember, in black-an-white film, when you exposed too much (and the negative got too "dense", you lost some skin details.
[a href=\"index.php?act=findpost&pid=165993\"][{POST_SNAPBACK}][/a]
With digital and RAW, the best "zone" is the one just short of clipping the RAW data. It gets better, and better, as you increase exposure, and then, BOOM!; you clip. Contrast this to print film, where you have maximum quality somewhere in a middle range, and contrast suffers and grain increases as you go towards the extremes and correct in the darkroom.
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It's 3 stops not 4 stops. However, my 20D doesn't have a spot meter mode so I can't confirm that.
Set the camera to manual mode, take a spot meter reading of the brightest part of the image, then increase exposure by 3 stops and all your worries are over. Perfect ETTR every time.
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Maybe we should define different types of correct exposure if we adhere to the ETTR way of exposing. As a 'correctly' exposed JPEG will result in an 'underexposed' RAW file and conversely a 'correctly' exposed RAW file will result in an overexposed JPEG.
Obviously if you shoot both there is a bit of a problem!
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Who knows - sometimes correct looks boring and incorrect looks interesting.
Like the bad guy said, "Shoot them both ..."
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I'm arguing that there are times when it doesn't work best [Manual]; case in point - when you don't have time to deal with optimal exposure and must gamble, and both your subject and background will both have an opportunity to suddenly change by a few stops. Reading Edmund in context, my immediate impression was one of a situation where anything can pop up instantly, and you don't have time to mess around with all parameters of shooting, so something must be simplified and sacrificed, and a -1 EC in an AE mode is the chosen sacrifice.
And if the subject is back lit, then the exposure will be even more off than if say using neutral AE.
When you replied that you shoot manual, in that context, it seemed that you referred to one fixed manual setting, which included enough headroom for whites in the brightest light.
It'll be set to 'correctly' expose what I think I'll want in the situation/scene and usually unless the subject is very contre jour/in shadow one way and well lit the opposite way, that works very well.
if you are going to insist that you won't ever miss any opportunities while metering, I think you're probably overrating yourself. However good you are at manually adjusting exposure to meet a relatively immediate need, there is always a more immediate need that you won't be ready for, and I assume that was the context here.
I wasn't talking about metering to get exposure, I am talking about using a sensible/compromise manual exposure and then if I have to point the camera at something quickly, that is obviously different, I'll just spin shutter or aperture dial in the right direction by a guessed amount, safer than auto against a bark or bright background. It may not be perfect, but if you are shooting that fast, perfect exposure is really not the most important thing.
If you have to completely automate exposure, it may be safer to do so with -1 EC, which on cameras like the D3 and Canon mk3 cameras, is not a particularly big sacrifice at ISO 200s and 100, respectively.
-1EC is as I mention above, is useless if you are suddenly shooting contre jour, not unusual occurence either and less than optimum for recovery with RAW as well as it doesn't survive under exposure that well. Most people do not have a D3 or Mrk III camera either. Anyway I'd rather have a small camera thatn one of those monsters for street shooting. A GRD II with a D3 chip in it would be ideal.
I believe the D3 allows manual AV and Tv with auto-ISO, which is even better than AE, as you can keep the manual setting in a range of lighting.[a href=\"index.php?act=findpost&pid=165799\"][{POST_SNAPBACK}][/a]
It actually makes no difference as the RAW/JPEG exposure is still altered even though the shutter and aperture are fixed.
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Who knows - sometimes correct looks boring and incorrect looks interesting.
Like the bad guy said, "Shoot them both ..."
[a href=\"index.php?act=findpost&pid=166818\"][{POST_SNAPBACK}][/a]
With you 100% on that.
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Who knows - sometimes correct looks boring and incorrect looks interesting.
Like the bad guy said, "Shoot them both ..."
[a href=\"index.php?act=findpost&pid=166818\"][{POST_SNAPBACK}][/a]
However, you can do anything you want to, "incorrectly", in post-processing, with a larger variety of options.
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However, you can do anything you want to, "incorrectly", in post-processing, with a larger variety of options.
[a href=\"index.php?act=findpost&pid=166834\"][{POST_SNAPBACK}][/a]
Sure John, but sometimes doubly incorrect is double the fun !
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A big advantage of the spot metering method of achieving pretty accurate ETTR is the facility to select in the scene what what is the brightest 'relevant' part, composition wise.
For example, you have a heavily backlit subject against foliage and blue sky through the gaps in the foliage. If you really want the blue sky, you would choose that as the brightest part of the image, then increase exposure by 3 stops. The main subject would then appear too dark and would have to be lifted in post processing with consequent noise.
However, a more sensible approach might be to sacrifice the blue sky, take a spot meter reading of, say, the white collar of the dress the subject is wearing and make the 3 stop increase from there.
Such an approach was hampered in previous models of Canon DSLRs because they had only a +/- 2 stop scale in the viewfinder. I think this has now been increased to +/- 3 stops in recent models, which is ideal for this spot metering method. No need for maths to get in the way of the artistic process. One simply turns the exposure dial till the needle is on +3, eye still glued to the viewfinder.
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A really nice feature for this is the metering-on-the-AF-point custom function. And in the MkIIIs pushing the multi-controller lets you bounce the AF between center and the registerd one for a quick alternative measuring spot, great on the tripod so you can meter without having to move the camera around.