thanks for your reply. I have more general questions, if I may pick your brain for more info...
Is there much image degradation if I were to use a gel (rather than glass filter) over my lens? I happened to settled upon a Roscoe Pink (4830) for my D80. After evaluating a sample set of Roscoe swatches alongside UniWB. I found that the Pink resulted in the least amount of Red and Blue WB adjustment for the D80 with flash as the light source. I never really use the filter, but I was so intrigued by all the posts that I read on dpreview that I had to try it out for myself as an academic exercise.
At the moment, I'm using NX 2.1 for raw conversion; I finally decided to give it a shot after using NX 1.3 for a while. The workflow of NX 2 still isn't very good, but I like the auto color aberration capability, and I just noticed that the WB problem (aka FixNEF) is now resolved.
As a side note, I don't have a Mac... otherwise I would use RPP. I was able to load OSX on my PC, but I had a weird issue with OSX changing my system clock such that it was 12 hours off. Anyway, RPP seemed very nice (evaluated 3 months ago), but I was getting some weird demosaicing artifacts (zig zags, if I recall, with AHD). I noticed that there is new multiprocessor capability with the latest version of RPP, so I may have to give it a shot again.
Very useful. Exceptional noise handling does not mean the exposure can be wrong and the result will be the same as with the correct exposure. I also prefer to know when one channel is truly blown out. I rarely use D3 at base ISO (most of the exceptions are wide angle shots); but when I do I use a gel to balance the sensitivity of the channels if shooting conditions permit. It never hurts to get the per channel exposure correct at the time of shooting instead of postprocessing for correct colour and exposure ;)
How useful is UniWB with the D3? Considering that the D3 is supposed to have exceptional noise handling, do you use UniWB in conjunction with a colored filter (over flash or over lens)? Or do you just use UniWB for histogram evaluation only?
The point in using magenta filter is to achieve better exposure of red and blue channels by allowing less light to hit the sensors under the green filters of sensor CFA. This is physical, pre-capture filtration; and as such it can't be reproduced by tuning the camera or through post-processing.
what if a manual WB is chosen and a -magenta is entered (i don't think most of calibrated in CC)? will this give a similar result?
for example, Sony will allow such a compensation. i have already, through my raw processing, set this as my standard, as i shot at one temperature with -magenta, and then adjust the proper temperature during raw processing.
Interesting you mentioned 'better rawnalyse'. Our feeling is that raw analysis tools are at least as important as raw converters. They help both photographers and developers. You can expect various tools there, not just a raw histogram.
Have you checked Rawnalyze with D40 files converted to DNG?
Were these produced from spectral data, from measured or published LAB values, or from RGB data in a known colorspace and whitepoint? What is the illuminant used?
Thanks for the explanation. If people are somehow reading "The simple lesson to be learned from this is to bias your exposures so that the histogram is snugged up to the right" to mean "bias your exposure so the histogram is snugged u to the left" then they are (sorry to be blunt) clueless, espacially given the two histograms labelled
"Normal Exposure
Centered Histogram"
and
"Histogram to the Right
For Maximim S/N Ratio"
which visually and clearly indicate exposing to the right.
On the other hand, his glib "not to the point that the highlights are blown" is inaccurate. Firstly, some hilights are always blown in a real world scene; its a question of how badly. Secondly, ETTR trades of more blown hilights for less shadow noise. His article should make that more clear.
You may want to look at many underexposed images and ask those who took them why images are so underexposed. Too often you will be referenced to that unfortunate phrase.
The problem is with how people understand what is suggested. Part of it is that using just the LCD on the back of the camera it is very difficult to recognise those highlights that should be left clipped. Part of it is that camera settings affect the point where the highlights start to blink. If the Reichmann's article would go deeper into the practice and warn inexperienced photographers of the possible misreadings and problems many would avoid a lot of disappointing results.
I do not think I need to quote Reichmann article again to show how definite he is when it comes to protecting highlights. That phrasing made a context of itself.
You can find a more accurate formula, like "Expose to place as much data within this linear-encoded RAW image without losing highlight values you wish to reproduce", suggested by Andrew Rodney. He continues, "ETTR presents a few problems, one being that the LCD camera preview, including the histogram and clipping indicators, isn t based on the linear RAW data. Instead, this preview is based on the rendered gamma-corrected JPEG your camera is set to produce, even if you don t save that JPEG and only shoot a RAW file! If your goal is to produce the best possible exposure for RAW, using the ETTR technique, the feedback on the LCD could steer you in the wrong direction."
Still, the major practical problem to many is to recognise the highlights that they want to reproduce from the highlights that can't be reproduced without unacceptable underexposure - not because those are specular, but just because the total range of brightnesses found in the scene is too high. Worse, some even do not know the problem exists at all.
Zone method is the easiest way to recognise the range of brightness and to identify the region that will allow the proper metering for the scene.
Referring to bits of smoke and mirrors, I can't see why you are trying to say the factual mistake Reichmann made is irrelevant. That mistake is a very grave and consequential one, still influencing too many to be considered minor.
Simply quoting that one sentence from the Reichmann article is out of context with the rest of the article and the concept of ETTR.
Read the entire Reichmann article in context and the concept involes pushing things to the right, not to the left; and this should be done for scenes and camera settings where it makes sense to do so.
Why not post the original image used to produce the data for this article and then everyone will be in a better position to make a judgement on the value of the information it conveys. At this stage, I have serious doubts because the article above seems to be aimed at proving the incorrectness of a single, poorly written statement within the context of a different concept.
To me it is easy to blindly protect highlights causing underxposure, even when those highlights are for example specular and should be blown out if a scene is capture properly. Simply shifting things left to protect specular highlights is not an application of the concept of ETTR. So why not post the image so that we can make an assessment of the value of the information.
Overall, nice site and some useful information here, but some of it seems like a little bit of smoke and mirrors.
It was not our label; it is the most common understanding of the subject we are running across over and over again. We were referring to the article http://www.luminous-landscape.com/tutorials/expose-right.shtml , where they say: "The simple lesson to be learned from this is to bias your exposures so that the histogram is snugged up to the right, but not to the point that the highlights are blown. This can usually be seen by the flashing alert on most camera review screens. Just back off so that the flashing stops." The article was written 5 years ago and for all that time since many do understand it exactly as "no flashing of highlights is allowed". Our standpoint is that the article desperately needs a revision.
Thank you for your comments, they will sure help readers to realise that incorrect application of ETTR rule defeats the purpose an is in fact practising the direct opposite, ETTL.
The practice of underexposing to prevent any possible hilight from being clipped is not exposing to the right. Its exposing to the left. It will produce a dark raw image which is then lightened in post (increasing the noise). It does, as you say, give more hilight headroom.
Exposing to the right is deliberate overexposure, to move the midtones into lighter regios where the linear sensor count makes better use of the available bit depth. This results in a light raw image which must be darkened in post (decreasing the noise). It does, as you say, give even less hilight headroom.
I agree with the main point of the article; the available dynamic range of the sensor is insufficient. A given exposure will have lost information from the scene, and this will always be the case until we have non-linear sensors with greater bit depth.
I also agree that using RGB histograms derived from a white balanced image (or worse, a single luminance histogram; or even worse, a single green histogram) does not allow for accurate judgment of how well the 0 - 4095 range has been used for each channel and whether severe under exposure has happened on one of them, or whether one or more channels have clipped. But that also won't change until we have cameras with open source firmware or, at least, the ability to accept on-camera plugins.
So really, all that I am disagreeing with is that you labelled the 'underexposure' method ETTR - which is confusing, and the real ETTR method has different defects than the ones you describe.
Lastly, interesting site and keep up the good work!
Exposing to the right in its extreme, in its blind application, that is while trying to keep all and every highlight from clipping, is exposing to the left when it comes to midtones and shadows.
The purpose of the article is to point out that with current metering there is at most 3 stops from the metering point to highlights; and to help realize that if the range of brightness found in the scene is higher then 3 stops from midpoint to highlights trying to keep highlights necessitates underexposure of midtones and shadows. The price for that and the latitude (that is, by how much one can underexpose still getting acceptable image quality) depends on the camera, ISO, light, colour of subjects in the scene, raw converter in use and some other factors.
I would say with current top cameras, especially in 14-bit mode, underexposure of 1.5 stops at base ISO is relatively safe for outdoor scenes. This allows to have close to 4.5 stops headroom in highlights.
It is also necessary to take into account that it is very difficult to judge the amount of underexposure using histograms on the back of the camera. In our opinion metering and trusting the meter is easier and more predictable for now.
This article argues correctly (here and in other articles on this site) that the single channel, white-balanced histogram is insufficient to detect hilight clipping or channel underexposure.
However, the table in this article is (as Peter points out) not comparing to ETTR but rather ETTL! Which will of course give the noise problems you mention. Underexposure is exposing to the left.
> Riechmann has expressed that poorly in his article
Not only poorly; but extremely misleading. His article causes a lot of headaches for pre-press people and for photographers. One part that is missing is about the range of the brightnesses in the original scene for ETTR to be useful. Nothing wrong with using ETTR given one knows how far shadows can be pushed and how to use exposure compensation with ETTR. We think Zone System gives a very good guideline when it comes to compensating ETTR. Never try to get details in Zone X. The limit to the upper Zone that can be captured is posed by the number of stops shadows can be pushed to become midtones.
thanks for your reply. I have more general questions, if I may pick your brain for more info...
Is there much image degradation if I were to use a gel (rather than glass filter) over my lens? I happened to settled upon a Roscoe Pink (4830) for my D80. After evaluating a sample set of Roscoe swatches alongside UniWB. I found that the Pink resulted in the least amount of Red and Blue WB adjustment for the D80 with flash as the light source. I never really use the filter, but I was so intrigued by all the posts that I read on dpreview that I had to try it out for myself as an academic exercise.
At the moment, I'm using NX 2.1 for raw conversion; I finally decided to give it a shot after using NX 1.3 for a while. The workflow of NX 2 still isn't very good, but I like the auto color aberration capability, and I just noticed that the WB problem (aka FixNEF) is now resolved.
As a side note, I don't have a Mac... otherwise I would use RPP. I was able to load OSX on my PC, but I had a weird issue with OSX changing my system clock such that it was 12 hours off. Anyway, RPP seemed very nice (evaluated 3 months ago), but I was getting some weird demosaicing artifacts (zig zags, if I recall, with AHD). I noticed that there is new multiprocessor capability with the latest version of RPP, so I may have to give it a shot again.
regards / roy
Very useful. Exceptional noise handling does not mean the exposure can be wrong and the result will be the same as with the correct exposure. I also prefer to know when one channel is truly blown out. I rarely use D3 at base ISO (most of the exceptions are wide angle shots); but when I do I use a gel to balance the sensitivity of the channels if shooting conditions permit. It never hurts to get the per channel exposure correct at the time of shooting instead of postprocessing for correct colour and exposure ;)
How useful is UniWB with the D3? Considering that the D3 is supposed to have exceptional noise handling, do you use UniWB in conjunction with a colored filter (over flash or over lens)? Or do you just use UniWB for histogram evaluation only?
regards / roy
both mk2
Which teleconverters were used? Canon EF? Mk I or II?
The point in using magenta filter is to achieve better exposure of red and blue channels by allowing less light to hit the sensors under the green filters of sensor CFA. This is physical, pre-capture filtration; and as such it can't be reproduced by tuning the camera or through post-processing.
what if a manual WB is chosen and a -magenta is entered (i don't think most of calibrated in CC)? will this give a similar result?
for example, Sony will allow such a compensation. i have already, through my raw processing, set this as my standard, as i shot at one temperature with -magenta, and then adjust the proper temperature during raw processing.
To convert, you can use free ColorLab utility
http://www.xrite.com/product_overview.aspx?ID=1071&Action=support&Softwa...
You should be able to convert spectral measurement data using the program above.
thanks for these files
i am using an e1io(uv)and have a delta E of about 3 to the GM spectrolino data
is the program you used to convert the GB measured text lab values to an image available? you would be welcome to my i1 results
thanks
david morrell
by email and comment
Take a look at EMVA 1288
http://www.emva.org/standard1288/standard_for_measurement_and_presentati...
Thanks once again!
I agree that analysis tools help both photographers and developers.
I will try converting to Adobe DNG meanwhile.
It was D50, 3 of CC24 averaged (last batch), 2 SG and 2 DC. Device used was Gretag Spectrolino.
Okay, good. That will produce the best results. What illuminant was used - D65? D50?
Dear Chris,
Interesting you mentioned 'better rawnalyse'. Our feeling is that raw analysis tools are at least as important as raw converters. They help both photographers and developers. You can expect various tools there, not just a raw histogram.
Have you checked Rawnalyze with D40 files converted to DNG?
These were produced from spectral data.
Were these produced from spectral data, from measured or published LAB values, or from RGB data in a known colorspace and whitepoint? What is the illuminant used?
Thanks for the explanation. If people are somehow reading "The simple lesson to be learned from this is to bias your exposures so that the histogram is snugged up to the right" to mean "bias your exposure so the histogram is snugged u to the left" then they are (sorry to be blunt) clueless, espacially given the two histograms labelled
"Normal Exposure
Centered Histogram"
and
"Histogram to the Right
For Maximim S/N Ratio"
which visually and clearly indicate exposing to the right.
On the other hand, his glib "not to the point that the highlights are blown" is inaccurate. Firstly, some hilights are always blown in a real world scene; its a question of how badly. Secondly, ETTR trades of more blown hilights for less shadow noise. His article should make that more clear.
Dear Peter,
You may want to look at many underexposed images and ask those who took them why images are so underexposed. Too often you will be referenced to that unfortunate phrase.
The problem is with how people understand what is suggested. Part of it is that using just the LCD on the back of the camera it is very difficult to recognise those highlights that should be left clipped. Part of it is that camera settings affect the point where the highlights start to blink. If the Reichmann's article would go deeper into the practice and warn inexperienced photographers of the possible misreadings and problems many would avoid a lot of disappointing results.
I do not think I need to quote Reichmann article again to show how definite he is when it comes to protecting highlights. That phrasing made a context of itself.
You can find a more accurate formula, like "Expose to place as much data within this linear-encoded RAW image without losing highlight values you wish to reproduce", suggested by Andrew Rodney. He continues, "ETTR presents a few problems, one being that the LCD camera preview, including the histogram and clipping indicators, isn t based on the linear RAW data. Instead, this preview is based on the rendered gamma-corrected JPEG your camera is set to produce, even if you don t save that JPEG and only shoot a RAW file! If your goal is to produce the best possible exposure for RAW, using the ETTR technique, the feedback on the LCD could steer you in the wrong direction."
Still, the major practical problem to many is to recognise the highlights that they want to reproduce from the highlights that can't be reproduced without unacceptable underexposure - not because those are specular, but just because the total range of brightnesses found in the scene is too high. Worse, some even do not know the problem exists at all.
Zone method is the easiest way to recognise the range of brightness and to identify the region that will allow the proper metering for the scene.
Referring to bits of smoke and mirrors, I can't see why you are trying to say the factual mistake Reichmann made is irrelevant. That mistake is a very grave and consequential one, still influencing too many to be considered minor.
Simply quoting that one sentence from the Reichmann article is out of context with the rest of the article and the concept of ETTR.
Read the entire Reichmann article in context and the concept involes pushing things to the right, not to the left; and this should be done for scenes and camera settings where it makes sense to do so.
Why not post the original image used to produce the data for this article and then everyone will be in a better position to make a judgement on the value of the information it conveys. At this stage, I have serious doubts because the article above seems to be aimed at proving the incorrectness of a single, poorly written statement within the context of a different concept.
To me it is easy to blindly protect highlights causing underxposure, even when those highlights are for example specular and should be blown out if a scene is capture properly. Simply shifting things left to protect specular highlights is not an application of the concept of ETTR. So why not post the image so that we can make an assessment of the value of the information.
Overall, nice site and some useful information here, but some of it seems like a little bit of smoke and mirrors.
It was not our label; it is the most common understanding of the subject we are running across over and over again. We were referring to the article http://www.luminous-landscape.com/tutorials/expose-right.shtml , where they say: "The simple lesson to be learned from this is to bias your exposures so that the histogram is snugged up to the right, but not to the point that the highlights are blown. This can usually be seen by the flashing alert on most camera review screens. Just back off so that the flashing stops." The article was written 5 years ago and for all that time since many do understand it exactly as "no flashing of highlights is allowed". Our standpoint is that the article desperately needs a revision.
Thank you for your comments, they will sure help readers to realise that incorrect application of ETTR rule defeats the purpose an is in fact practising the direct opposite, ETTL.
The practice of underexposing to prevent any possible hilight from being clipped is not exposing to the right. Its exposing to the left. It will produce a dark raw image which is then lightened in post (increasing the noise). It does, as you say, give more hilight headroom.
Exposing to the right is deliberate overexposure, to move the midtones into lighter regios where the linear sensor count makes better use of the available bit depth. This results in a light raw image which must be darkened in post (decreasing the noise). It does, as you say, give even less hilight headroom.
I agree with the main point of the article; the available dynamic range of the sensor is insufficient. A given exposure will have lost information from the scene, and this will always be the case until we have non-linear sensors with greater bit depth.
I also agree that using RGB histograms derived from a white balanced image (or worse, a single luminance histogram; or even worse, a single green histogram) does not allow for accurate judgment of how well the 0 - 4095 range has been used for each channel and whether severe under exposure has happened on one of them, or whether one or more channels have clipped. But that also won't change until we have cameras with open source firmware or, at least, the ability to accept on-camera plugins.
So really, all that I am disagreeing with is that you labelled the 'underexposure' method ETTR - which is confusing, and the real ETTR method has different defects than the ones you describe.
Lastly, interesting site and keep up the good work!
Exposing to the right in its extreme, in its blind application, that is while trying to keep all and every highlight from clipping, is exposing to the left when it comes to midtones and shadows.
The purpose of the article is to point out that with current metering there is at most 3 stops from the metering point to highlights; and to help realize that if the range of brightness found in the scene is higher then 3 stops from midpoint to highlights trying to keep highlights necessitates underexposure of midtones and shadows. The price for that and the latitude (that is, by how much one can underexpose still getting acceptable image quality) depends on the camera, ISO, light, colour of subjects in the scene, raw converter in use and some other factors.
I would say with current top cameras, especially in 14-bit mode, underexposure of 1.5 stops at base ISO is relatively safe for outdoor scenes. This allows to have close to 4.5 stops headroom in highlights.
It is also necessary to take into account that it is very difficult to judge the amount of underexposure using histograms on the back of the camera. In our opinion metering and trusting the meter is easier and more predictable for now.
This article argues correctly (here and in other articles on this site) that the single channel, white-balanced histogram is insufficient to detect hilight clipping or channel underexposure.
However, the table in this article is (as Peter points out) not comparing to ETTR but rather ETTL! Which will of course give the noise problems you mention. Underexposure is exposing to the left.
> Riechmann has expressed that poorly in his article
Not only poorly; but extremely misleading. His article causes a lot of headaches for pre-press people and for photographers. One part that is missing is about the range of the brightnesses in the original scene for ETTR to be useful. Nothing wrong with using ETTR given one knows how far shadows can be pushed and how to use exposure compensation with ETTR. We think Zone System gives a very good guideline when it comes to compensating ETTR. Never try to get details in Zone X. The limit to the upper Zone that can be captured is posed by the number of stops shadows can be pushed to become midtones.
See one of the next articles, http://www.libraw.org/articles/peace-in-lights.html
Pages