Luminous Landscape Forum
Equipment & Techniques => Medium Format / Film / Digital Backs – and Large Sensor Photography => Topic started by: narikin on October 12, 2016, 08:43:57 pm
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I wondered if there is any point in using the higher bit option of Phase's IIQ-L 16bit, if you are going much above base ISO 50/100?
Has someone smarter than me done tests?!
-I can see very fine benefits of using it at 100asa, and maybe at 200asa it's still marginally worth it, but 400 and up, surely the noise and color degradation renders the finer details potentially in full 16bit, rather moot?
I'm happy with the IIQ-L file normally: smaller, quick shooting, and more shots per CF card.
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but 400 and up, surely the noise
if you do not saturate your sensels (exposure = aperture/t-stop + exposure time) then the higher gain (might be a result of some higher nominal ISO dialed in, unless for example camera is doing ISO-by-tag - in this case there is no analog gain pre ADC and no digital multiplication of DNs post ADC ) in many sensors is actually better for S/N in deep shadows, for some sensors - quite irrelevant /ISO-less sensors or where ISO-by-tag is used/ and for some when you use some "intermediate" nominal ISO values it may be worse... so you want to test how ISO/gain is actually implemented in a particular P1 back/sensor combo before saying "surely"...
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Hi,
Probably so but may be not always.
Increasing ISO is essentially the same as underexposure. Full exposure at base ISO fills up the photodiode fully. If you reduce exposure with one EV it will be half full. Reducing well utilisation to half means you loose an EV in DR.
DR on the IQ3100 is around 15 stops. So, if you underexpose one stop you will have 14 EV of DR that fits exactly in a 14 bits wide data path.
There is an exception, though. Reducing exposure will protect specular highlights, unless raw data is manipulated when increasing ISO.
Best regards
Erik
I wondered if there is any point in using the higher bit option of Phase's IIQ-L 16bit, if you are going much above base ISO 50/100?
Has someone smarter than me done tests?!
-I can see very fine benefits of using it at 100asa, and maybe at 200asa it's still marginally worth it, but 400 and up, surely the noise and color degradation renders the finer details potentially in full 16bit, rather moot?
I'm happy with the IIQ-L file normally: smaller, quick shooting, and more shots per CF card.
-
I wondered if there is any point in using the higher bit option of Phase's IIQ-L 16bit, if you are going much above base ISO 50/100?
Has someone smarter than me done tests?!
-I can see very fine benefits of using it at 100asa, and maybe at 200asa it's still marginally worth it, but 400 and up, surely the noise and color degradation renders the finer details potentially in full 16bit, rather moot?
Hi,
Good question. I have not done specific tests, but I do assume that above ISO 400 there will be insufficient effective DR to warrant 16-bit encoding, 14-bit should suffice. Whether ISO 200 or ISO 400 is the turning point, would take more analysis/testing to determine.
Cheers,
Bart
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I'm happy with the IIQ-L file normally: smaller, quick shooting, and more shots per CF card.
I haven't tested it, just wondering how much smaller and quicker it is.
I would also wonder if it is enough to warrant considering, if it might be worthwhile to also use when the scene dynamic range isn't really pushing the extremes. Would shooting in 16bit offer anything if there are only 8 or 9 stops of dynamic range in the scene?
I do know a scene I shot in Colorado where the colors were pretty much unbelievable, and the camera actually seemed to nail what I remember seeing (even though they were so extreme they were unbelievable on the screen and I had to tone them down). My buddy shooting beside me on the a7r2 didn't get the same results, and can't quite get the tones out of the aspen trees that I did. That may be more to do with C1 (my file) and Lr (his file).
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Ok, I may be wading in here where I normally don't want to, but help me understand why the question of the relevance of 16 bit capture is answered almost exclusively in terms of dynamic range?
You know, I've always been about the image. The image on your screen, the image you print on paper or whatever. But, always about the image. What does it mean in terms of end results, etc.
And for someone who leads toward the non-scientific approach, please try to keep this in laymans terms.
Thanks,
Steve Hendrix
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Hi Steve,
The reason is that DR is the amount of usable information of the image. It is defined as maximum usable signal (normally called full well capacity) divided by signal where Signal/Noise Ratio is 1.
One bit is needed for stop of DR. So if DR is 15 EV there is 15 bits of information, the rest is noise. With 13EV there is 13 bits of information and so on.
It is quite possible to transfer say 15 stops of DR trough say 12 bit of data using a tone curve, but using more bits than what corresponds to DR is just waste of band width. This may be over-simplified, but it is a pretty good rule of thumb.
A good article by Jack Hogan is here: http://www.strollswithmydog.com/how-many-bits-to-fully-encode-my-image/
Emil Martinec has a classic piece on the issue here: https://theory.uchicago.edu/~ejm/pix/20d/tests/noise/noise-p3.html
Getting back to the original posting. Assume that you expose fully to the right. That means that your relevant highlights go up to Full Well Capacity (FWC). You utilise the sensor fully. If DR is 15 EV it means that noise floor is 32768 times below FWC, so you need 15 bits of linear data to represent the usable output from the sensor.
Now, cut exposure by half, we no longer utilise the full FWC, just half of it. But, noise is still the same, at least regarding readout noise. So we now only have 16384 bits worth of data, needing 14 bits. We can multiply the signal with 4, but that would multiply the noise by four, too.
Astronomers may utilise deeper data (below SNR = 1).
A small note, if you pick up spec sheets from Kodak or Dalsa sensors they will mention readout noise in electron charges and saturation level also in electron charges. The saturation level is FWC. They may also give the dynamic range of the sensor, say 71 dB. You can convert dB to stops by dividing with 6 (6.021 to be more exact). Using either calculation you will end up with the figures DxO measures at base ISO in what they call screen mode and that figure normally fits vendor data very closely.
Best regards
Erik
Ok, I may be wading in here where I normally don't want to, but help me understand why the question of the relevance of 16 bit capture is answered almost exclusively in terms of dynamic range?
You know, I've always been about the image. The image on your screen, the image you print on paper or whatever. But, always about the image. What does it mean in terms of end results, etc.
And for someone who leads toward the non-scientific approach, please try to keep this in laymans terms.
Thanks,
Steve Hendrix
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I haven't tested it, just wondering how much smaller and quicker it is.
I would also wonder if it is enough to warrant considering, if it might be worthwhile to also use when the scene dynamic range isn't really pushing the extremes. Would shooting in 16bit offer anything if there are only 8 or 9 stops of dynamic range in the scene?
I do know I of scene in Colorado where the colors were pretty much unbelievable,and the camera actually seemed to nail what I remember seeing (even though they were so extreme they were unbelievable on the screen and I had to tone them down). My buddy shooting beside me on the a7r2 didn't get the same results, and can't quite get the tones out of the aspen trees that I did. That may be more to do with C1 (my file) and Lr (his file).
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Now, cut exposure by half, we no longer utilise the full FWC, just half of it. But, noise is still the same, at least regarding readout noise. So we now only have 16384 bits worth of data, needing 14 bits. We can multiply the signal with 4, but that would multiply the noise by four, too.
What if you still shoot ETTR, so you are close to FWC, but meaning there aren't any tones on the left side of the histogram. So dynamic range is half of the sensors capability.
Does still shooting in 16 bit offer anything, or would 14bit offer the same quality of raw capture?
(I'm with Steve on this, wondering if 16bit still offers the best file quality and best chance at the highest possible rendering in the raw processor even in cases like this)
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Hi Wayne,
No, I would not say data path width would matter with 8-9 stops of DR.
The greatest differentiator may the colour profiles used in the converter. Lightroom has several profiles. I always use home made profiles.
What it may be worth I enclose two screen dumps. I happened to shoot two very similar images with my P45+ and my Sony A7rII.
The first one shows the Sony A7rII image processed with different colour profiles, DCampProf (what I use), Camera Landscape and Adobe standard. I also include the P45+ mage processed in Lghtroom with a DCamProf profile.
The second one I also processed the image with Capture One, I have very little experience with that tool, I have done some local adjustment on the sky and bright side of the image, similar to Lightroom.
After taking that image, I set up the back for horisontal shooting and it came loose from the camera (altough it felt solidly attached) and fell four fee on pretty solid ground. It seems to survived with the sensor still in alignment. An ouch experience!
Best regards
Erik
I haven't tested it, just wondering how much smaller and quicker it is.
I would also wonder if it is enough to warrant considering, if it might be worthwhile to also use when the scene dynamic range isn't really pushing the extremes. Would shooting in 16bit offer anything if there are only 8 or 9 stops of dynamic range in the scene?
I do know I of scene in Colorado where the colors were pretty much unbelievable,and the camera actually seemed to nail what I remember seeing (even though they were so extreme they were unbelievable on the screen and I had to tone them down). My buddy shooting beside me on the a7r2 didn't get the same results, and can't quite get the tones out of the aspen trees that I did. That may be more to do with C1 (my file) and Lr (his file).
-
Ok, I may be wading in here where I normally don't want to, but help me understand why the question of the relevance of 16 bit capture is answered almost exclusively in terms of dynamic range?
You know, I've always been about the image. The image on your screen, the image you print on paper or whatever. But, always about the image. What does it mean in terms of end results, etc.
And for someone who leads toward the non-scientific approach, please try to keep this in laymans terms.
In laymans terms, higher dynamic range means that there are more levels to be encoded. For that you need more bits. Therefore dynamic range and bit depth are directly linked.
What the question means for the image is that, with higher iso, the image will be the same when using 16 or 14 bits. The answer, which I don't know, depends on the internal design of the camera. Specifically about the presence or absence of analog amplification before the ADC.
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The Sony sensor used in the IQ3-100MP has almost certainly no variable analog amplification before ADC.
Some Sony sensors use a trick invented by Aptina that reduces FWC at a certain ISO setting, we cannot say before we have seen photon transfer curves.
Best regards
Erik
In laymans terms, higher dynamic range means that there are more levels to be encoded. For that you need more bits. Therefore dynamic range and bit depth are directly linked.
What the question means for the image is that, with higher iso, the image will be the same when using 16 or 14 bits. The answer, which I don't know, depends on the internal design of the camera. Specifically about the presence or absence of analog amplification before the ADC.
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Hi Wayne,
In that case I would guess that the shadows are dominated by shot noise and neither DR or bit depth is really relevant.
So what happens when you rise ISO. Is the Raw data just multiplicated by 2 for each EV? Or is the raw data just tagged with the ISO value? What does the histogram show? Does the raw converter change noise reduction based on ISO?
The physics are well known, in camera processing is a great unknown…
Best regards
Erik
What if you still shoot ETTR, so you are close to FWC, but meaning there aren't any tones on the left side of the histogram. So dynamic range is half of the sensors capability.
Does still shooting in 16 bit offer anything, or would 14bit offer the same quality of raw capture?
(I'm with Steve on this, wondering if 16bit still offers the best file quality and best chance at the highest possible rendering in the raw processor even in cases like this)
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What if you still shoot ETTR, so you are close to FWC, but meaning there aren't any tones on the left side of the histogram. So dynamic range is half of the sensors capability.
Does still shooting in 16 bit offer anything, or would 14bit offer the same quality of raw capture?
Hi Wayne,
Increasing the ISO is typically done to compensate for underexposure. Underexposure means reducing DR. When the DR is low enough to not carry more than 14-bits of information, then there is little benefit in encoding with higher precision.
'Accuracy' and 'Precision' are two concepts that have a distinctly different mathematical meaning. As we underexpose, the average recorded signal will get less Accurate. There will be more noise fluctuation recorded instead of the actual signal level, and it's caused by Readnoise (affecting the shadows more), but there will also be less absolute shotnoise (affecting the midtones and highlights, and also less signal), but we can still encode that inaccurate noisy signal with very high Precision (e.g. 16-bit).
That's where Signal to Noise ratios are a useful concept, they tell us about the (average) Accuracy, regardless of the Precision (14 or 16-bits) with which we encode that noisy signal. More exposure usually means higher S/N ratio (because shot-noise increases less than the signal level increases). So then underexposure will reduce Accuracy to the point that it gets so inaccurate that there is little benefit encoding it with high precision.
As said, it would take more in-depth testing and analysis to mathematically determine the exact tipping point, but I expect it to be somewhere around ISO 400.
Cheers,
Bart
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Increasing the ISO is typically done to compensate for underexposure. Underexposure means reducing DR. When the DR is low enough to not carry more than 14-bits of information, then there is little benefit in encoding with higher precision.
What if I'm not increasing ISO ... a low dynamic range scene which I would "overexpose" to get ETTR, so I end up with a histogram empty of any data on the left 1/4-1/3. Perhaps even if it isn't exposed to the right (example attached), there still isn't any data on the left and in this case on the right side of the histogram.
Does the 16bit file offer anything at all in flexibility in post processing? Does the process of making a 16bit tiff from a 14bit raw produce an identical result or is there perhaps some small gains to be had from making a 16bit tiff from a 16bit raw? (from a practical standpoint not necessarily from a bit by bit standpoint).
My unscientific "logic" based on this discussion tells me there is no point in shooting 16bit on scenes with lower dynamic range, or probably when pushing the ISO past 400 up since all of the available dynamic range can be encoded precisely/accurately enough with 14bits.
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In laymans terms, higher dynamic range means that there are more levels to be encoded. For that you need more bits. Therefore dynamic range and bit depth are directly linked.
What the question means for the image is that, with higher iso, the image will be the same when using 16 or 14 bits. The answer, which I don't know, depends on the internal design of the camera. Specifically about the presence or absence of analog amplification before the ADC.
Ok, thank you and everyone for pitching in on that question. But I am aware of the relationship between bit depth and dynamic range. My question was specifically why is Dynamic Range exclusively being discussed with regard to bit depth? Because for years, I've heard from clients who shoot 35mm DSLR and medium format and complain about color with 35mm DSLR. About the "global color response". Some have attributed this to CMOS vs CCD. I have not felt this to be the case. Instead, I attribute this to 14 bit vs 16 bit (if not completely, at least to a significant degree).
When you shoot IIQL 16 bit, IIQL, and IIQS, there are color differences. In the few tests I've done, it is very subtle, but there is a difference. Whenever I do this type of test, I feel like I can see it, and it feels to me like the 14 bit captures are splashing the color round while the 16 bit capture is differentiating more effectively and accurately. Today I shot a quick few shots at ISO 1600. There are color differences, it is very subtle, but I can see it. Inevitably, these differences can be hidden or magnified as one shoots many different scenes. Screenshots are below.
Keep in mind, for me, it's a moot point. I don't have any need to try and optimize storage or increase capture rate by shooting 14 bit files. I want the full 16 bits, no matter how subtle a difference there is.
Steve Hendrix/CI
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Sort of my thinking as well, maybe even having to do with the question I asked earlier about more accuracy because the file isn’t being expanded to 16bit from 14bits.
I did notice 14bit still works in Lr, for some that might be useful. I’m not particularly worried about file sizes (which aren’t remarkably smaller in 14bit) or capture speed either, but I do not like how i’m forced to use C1’s cataloging tools in my workflow, and can’t opt to use Lr for my DAM and preliminary image adjustments so I can move to C1 for the images I want to work on. Additionally some images I’m more comfortable with LR’s local adjustment tools.
Not sure that will make me switch, because I’m more afraid of leaving at 14bit and end up shooting a sunset where I need the dynamic range.
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Sort of my thinking as well, maybe even having to do with the question I asked earlier about more accuracy because the file isn’t being expanded to 16bit from 14bits.
I did notice 14bit still works in Lr, for some that might be useful. I’m not particularly worried about file sizes (which aren’t remarkably smaller in 14bit) or capture speed either, but I do not like how i’m forced to use C1’s cataloging tools in my workflow, and can’t opt to use Lr for my DAM and preliminary image adjustments so I can move to C1 for the images I want to work on. Additionally some images I’m more comfortable with LR’s local adjustment tools.
Not sure that will make me switch, because I’m more afraid of leaving at 14bit and end up shooting a sunset where I need the dynamic range.
Hi Wayne
From reading this can LR open a 14 bit IQ 100 file? I have given up on LR Working with the 16 raw.
Thanks
Paul C
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Hi Wayne
From reading this can LR open a 14 bit IQ 100 file? I have given up on LR Working with the 16 raw.
Thanks
Paul C
Lr sees the files on the card and shows the image unlike the 16bit files. I assume it will import them, though I didn't actually follow through. but then I opened them in ACR and was able to manipulate them fine.
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Thanks Wayne
I never thought to try the 14 bit files in LR. This is good to know as it looks like Adobe may never get support for the 16 bit versions.
Paul C
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When you shoot IIQL 16 bit, IIQL, and IIQS, there are color differences. In the few tests I've done, it is very subtle, but there is a difference. Whenever I do this type of test, I feel like I can see it, and it feels to me like the 14 bit captures are splashing the color round while the 16 bit capture is differentiating more effectively and accurately. Today I shot a quick few shots at ISO 1600. There are color differences, it is very subtle, but I can see it.
It is more likely that the effect you observe comes from inaccuracies in handling the differences between 14 and 16 bits in colour profiles.
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Hi Steve,
I can see the differences but it is very hard to find an explanation for their existence.
Landscapephoto's suggestion that it is difference in handling of colour profiles is interesting. But, little is know about Capture One internals. Bart may have some interesting input.
Best regards
Erik
Ok, thank you and everyone for pitching in on that question. But I am aware of the relationship between bit depth and dynamic range. My question was specifically why is Dynamic Range exclusively being discussed with regard to bit depth? Because for years, I've heard from clients who shoot 35mm DSLR and medium format and complain about color with 35mm DSLR. About the "global color response". Some have attributed this to CMOS vs CCD. I have not felt this to be the case. Instead, I attribute this to 14 bit vs 16 bit (if not completely, at least to a significant degree).
When you shoot IIQL 16 bit, IIQL, and IIQS, there are color differences. In the few tests I've done, it is very subtle, but there is a difference. Whenever I do this type of test, I feel like I can see it, and it feels to me like the 14 bit captures are splashing the color round while the 16 bit capture is differentiating more effectively and accurately. Today I shot a quick few shots at ISO 1600. There are color differences, it is very subtle, but I can see it. Inevitably, these differences can be hidden or magnified as one shoots many different scenes. Screenshots are below.
Keep in mind, for me, it's a moot point. I don't have any need to try and optimize storage or increase capture rate by shooting 14 bit files. I want the full 16 bits, no matter how subtle a difference there is.
Steve Hendrix/CI
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What if I'm not increasing ISO ... a low dynamic range scene which I would "overexpose" to get ETTR, so I end up with a histogram empty of any data on the left 1/4-1/3. Perhaps even if it isn't exposed to the right (example attached), there still isn't any data on the left and in this case on the right side of the histogram.
In that case, it helps to shoot at 16-bit precision. When exposure is high, or even ETTR, the Accuracy of the signal capture is relatively high (a high S/N ratio). Then increasing the precision at which the levels are recorded helps to create more robust data for Raw conversion (similar to 8-b/ch versus 16-b/ch postprocessing, but instead here we compare 14-bit to 16-bit encoding).
The bits are not only used to cover the DR, but also to more precisely encode the more Accurate signal levels. A 1-bit ADC can record a huge DR, 0 for deepest black, a 1 for the lightest white, but without any precision for intermediate tones. With 14-bits we can encode luminosity differences as small as 1/2^14 = 1/16384, and with 16-bits we can encode luminance differences as small as 1/2^16 = 1/65536, or 4 times as precise.
Does the 16bit file offer anything at all in flexibility in post processing?
Yes, but it already helps to make a more precise demosaicing and Raw conversion.
Does the process of making a 16bit tiff from a 14bit raw produce an identical result or is there perhaps some small gains to be had from making a 16bit tiff from a 16bit raw?
This is post-capture. It doesn't help the demosaicing and Raw conversion much since no higher precision data is added but the range is only stretched and divided more finely. The 16-bits do help when the demosaiced data is manipulated, e.g. gamma precompensated or contrast adjusted, because intermediate tones have an up to 4x higher precision (which helps during cascaded processing steps, but is overkill for output). Raw converters like Capture One already use higher bit levels to do most of the caculations with higher precision.
My unscientific "logic" based on this discussion tells me there is no point in shooting 16bit on scenes with lower dynamic range, or probably when pushing the ISO past 400 up since all of the available dynamic range can be encoded precisely/accurately enough with 14bits.
DR is not the sole reason to use 16-bit encoding. The old analogy of a ladder applies. The height between the first and last rung is the DR (and it can be a long or a short ladder), the number of bits is the number of rungs from the lowest to the highest rung, and determines how precise intermediate levels can be achieved and how easy it is to go from one level to the next.
It would require more in-depth analysis to establish whether the IQ3 100's Analog to Digital Converters (ADCs) achieve a higher ladder, or only adds more rungs to the ladder, but it's circuits do warrant the use of 16-bit encoding since it effectively expands the recordable DR beyond 14-bits. More importantly, it also increases precision, which is helpful in the demosaicing of the ETTR signal levels and produces more solid files for postprocessing.
Cheers,
Bart
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It is more likely that the effect you observe comes from inaccuracies in handling the differences between 14 and 16 bits in colour profiles.
Yes, that and Demosaicing (they are linked). The ADC settings may also play a role, but that would need further analysis.
Cheers,
Bart
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In that case, it helps to shoot at 16-bit precision. When exposure is high, or even ETTR, the Accuracy of the signal capture is relatively high (a high S/N ratio). Then increasing the precision at which the levels are recorded helps to create more robust data for Raw conversion (similar to 8-b/ch versus 16-b/ch postprocessing, but instead here we compare 14-bit to 16-bit encoding).
Bart,
This is a rare instance in which I do not entirely agree with you. With the low DR high key image, using 16 bits does allow capturing high bit data with ETTR. In this case high DR is not needed, since the DR of the scene is low; however the high bit data with ETTR will collect more photo electrons and improve the SNR. ETTR has more to do with SNR than the number of levels in the high bit data.
However I'm not sure that increased precision is all that helpful since the high bit data are dithered by shot noise. It does not make sense to quantize the data much finer than the noise in the signal, and shot noise is highest in the highlights, as Emil Martinec explains here (http://theory.uchicago.edu/~ejm/pix/20d/tests/noise/noise-p3.html). As he explains, the Nikon lossy NEF compression discards superfluous highlight data with no visual loss of IQ.
Bill
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Hi Steve,
I can see the differences but it is very hard to find an explanation for their existence.
Landscapephoto's suggestion that it is difference in handling of colour profiles is interesting. But, little is know about Capture One internals. Bart may have some interesting input.
Best regards
Erik
This perhaps is an example of my priorities in terms of the subject matter. I am not so much concerned with the why (I am interested, but not as interested) as I am with the what. And regardless of the reason, the color from the 16 bit files - at any ISO setting - appears superior. Whatever the reason, the 16 bit capability yields the best possible result. So unless I need faster capture rates, or I have a storage limitation, I see no reason to not shoot 16 bit, in fact I only see a preference for anyone wanting to take advantage of the best possible quality.
Steve Hendrix/CI
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Lr sees the files on the card and shows the image unlike the 16bit files. I assume it will import them, though I didn't actually follow through. but then I opened them in ACR and was able to manipulate them fine.
Wayne,
I did a few tests this morning. You are right, LR sees the 14 bit files and will import them, however it uses a "matrix" color profile which is way off the real colors. I was also not able to select a different profile, as I wanted to try a different CMOS profile. I may be doing something wrong on the selection of a different profile as I don't do that very often. But the "matrix" is really off on the yellows and greens.
Back to the waiting game.
Paul C
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Hi Bill,
It seems that Steve can demonstrate a clear difference, and that is what really matters.
I also don't buy Bart's explanation.
1) Highlight and midtone data is extremely noisy in absolute numbers. Say that FWC is a 64000 and mid tones are exposed 3EV below FWC they would have 8000 e-. That 8000 e- would lead to noise with sigma of 89. So an absolute grey would vary between 7911 and 8089, to be correct 65% of the pixels would be in this range. The quantisation error of 16 bit representation is 1 that is 0.05% of the 2*sigma, absolutely negligible. The quantisation error of 12 bits would be 0.2% still absolutely negligible.
Going six stops below, we would have 1000 e- and Sigma would be 32, so that near black area would vary between 968 and 1032. Quantization error for 12 bits would be 0.4% while shot noise would vary 3.2%.
So shot noise would mask any quantisation error by large margin.
2) Once the data are read in, in all probability they are automatically converted to 16 or 32 bits. Computers normally use data width that are multiples of 8. So 8 bits, 16 bits and 32 bits are natural for computers.
To find out the reason for colour depending on coding data in 14 or 16 bits we would need to analyse C1 internals. Would be interesting of the difference is unique to C1 or if it would show up in a an OpenSource raw converter like RawTherapee.
But, it is reality that matters. Whatever the explanation, it seems that using 16 bit is the safest choice.
Or we could say, would someone give me an IQ3-100MP I would gladly invest in a bunch of 8TB hard disks.
Best regards
Erik
Bart,
This is a rare instance in which I do not entirely agree with you. With the low DR high key image, using 16 bits does allow capturing high bit data with ETTR. In this case high DR is not needed, since the DR of the scene is low; however the high bit data with ETTR will collect more photo electrons and improve the SNR. ETTR has more to do with SNR than the number of levels in the high bit data.
However I'm not sure that increased precision is all that helpful since the high bit data are dithered by shot noise. It does not make sense to quantize the data much finer than the noise in the signal, and shot noise is highest in the highlights, as Emil Martinec explains here (http://theory.uchicago.edu/~ejm/pix/20d/tests/noise/noise-p3.html). As he explains, the Nikon lossy NEF compression discards superfluous highlight data with no visual loss of IQ.
Bill
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Hi Paul,
If you really need LR you could make your own profiles. Both DNG Profile Editor and Color Checker Passport generate usable profiles. Or, you could invest some time in Anders Torger's DCamProf.
I don't know what Phase One gives up in 14 bit files. Steves samples show a visible difference for which I have no good explanation.
I looked into a couple of IIQ L and IIQ S files from my P45+. "Here be dragons!" is all I can say…
Best regards
Erik
Wayne,
I did a few tests this morning. You are right, LR sees the 14 bit files and will import them, however it uses a "matrix" color profile which is way off the real colors. I was also not able to select a different profile, as I wanted to try a different CMOS profile. I may be doing something wrong on the selection of a different profile as I don't do that very often. But the "matrix" is really off on the yellows and greens.
Back to the waiting game.
Paul C
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Hi,
Steve presents very good empirical evidence that 16 bits vs. 14 bits affects colour rendition. It is quite obvious it matters.
IMHO it doesn't play well with theory, but any good experiment can prove any theory wrong. But, you can never prove a theory with an experiment, theories are very hard to prove…
Still I find it interesting to discuss this.
Below is a screen dump showing dark grey patch on a IQ3100MP shot 16-bit file, taken from DigitalTransitions testing:
(http://echophoto.dnsalias.net/ekr/Articles/DRExample/IQ3100MP.png)
The nice gaussians represent a single tone of grey. In absence of shot noise this would be just a spike, but nature of light gives these variations.
I would love to have an IQ3100MP, but I don't have one. But, I can show what happens going from 14 bit to 12 bit on my Sony A7rII. The image below is the 14 bit version.
(http://echophoto.dnsalias.net/ekr/Articles/DRExample/SonyA7rII_14bits.png)
While this one is 12 bits. Note that shapes are the same but sampling is more sparse. Now keep in mind that all these shapes correspond to a single colour.
(http://echophoto.dnsalias.net/ekr/Articles/DRExample/SonyA7rII_12bits.png)
It would be very interesting to check out a good ColorChecker shot with the IQ3100MP saved in different raw formats.
Best regards
Erik
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DR is not the sole reason to use 16-bit encoding. The old analogy of a ladder applies. The height between the first and last rung is the DR (and it can be a long or a short ladder), the number of bits is the number of rungs from the lowest to the highest rung, and determines how precise intermediate levels can be achieved and how easy it is to go from one level to the next.
I would agree, but it does seem the new format benefits dynamic range pretty dramatically which implies it has made the ladder taller, instead of perhaps placing the rungs more closely together. But certainly both might be possible.
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This perhaps is an example of my priorities in terms of the subject matter. I am not so much concerned with the why (I am interested, but not as interested) as I am with the what. And regardless of the reason, the color from the 16 bit files - at any ISO setting - appears superior. Whatever the reason, the 16 bit capability yields the best possible result. So unless I need faster capture rates, or I have a storage limitation, I see no reason to not shoot 16 bit, in fact I only see a preference for anyone wanting to take advantage of the best possible quality.
Steve Hendrix/CI
I certainly feel similarly, although I would point out from your examples it just showed a difference, not necessarily a better capture and I would never shoot anything at 1600 ISO. I’m just frustrated by the cataloging tools of C1 as well as some of the limitations of the local adjustments and so was curious in circumstances where the dynamic range is manageable if shooting 14 bit would lose anything. But at this point I also don’t think I want to expend the energy and effort to create profiles for the 14bit files so LR can take advantage of them, since most of my conversions start from C1 anyway, only a few are done inside of Lr.
I’ve managed to kludge together a decent workflow at this point. Doesn’t really seem to be an answerable question, which leaves me in the same position, better to stick with 16bit which I know won’t compromise anything.
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Hi Wayne,
The IQ3-100MP has a dynamic range very close to 15 EV. Sometimes it will be beneficial.
Phase One always claimed to have 16 bit of data, so I can not really understand that they need a new raw format when they actually have a sensor being able to deliver 15 bits of data.
But it is a good thing they have 15 bit of DR and a new format actually supporting it.
Does it matter? I guess so, in a few very rare cases… There may be some other improvements on the sensor side that matters a lot more.
Best regards
Erik
I would agree, but it does seem the new format benefits dynamic range pretty dramatically which implies it has made the ladder taller, instead of perhaps placing the rungs more closely together. But certainly both might be possible.
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I certainly feel similarly, although I would point out from your examples it just showed a difference, not necessarily a better capture and I would never shoot anything at 1600 ISO. I’m just frustrated by the cataloging tools of C1 as well as some of the limitations of the local adjustments and so was curious in circumstances where the dynamic range is manageable if shooting 14 bit would lose anything. But at this point I also don’t think I want to expend the energy and effort to create profiles for the 14bit files so LR can take advantage of them, since most of my conversions start from C1 anyway, only a few are done inside of Lr.
I’ve managed to kludge together a decent workflow at this point. Doesn’t really seem to be an answerable question, which leaves me in the same position, better to stick with 16bit which I know won’t compromise anything.
In my experience, and to my eyes (perfect score on the Xrite Color IQ Challenge, does that count?), yes, the captures do show a difference, but what I see is the capture is a better capture at 16 bit, if color is an important element.
Steve Hendrix/CI