There is quite a bit of mention that the gain in such color correctness has been done at the expensive of the ISO gain, as the base ISO is now 35. I am wondering if the higher ISO response of this back is the same as the older IQ3100, or if one is to expect about 1 stop of less gain throughout the ISO range. This would mean that for the gain in color, one will loss a higher ISO response, just curious if that is the case or not.
I'm far from being able to spend 40.000$ on a camera, this makes me wonder if it's really not possible to remove UV peaks with a simple filter, I'm shure there is a knowable member that could detail the reasons behind this impossibility stated in the article. I really want to get rid of the magenta skies without post processing.
Thanks for taking the time to do this. The whole thing makes a ton of sense now where before, based on P1's initial marketing, it really made no sense at all.
Thanks for the informative read.
A UV filter in front of the lens can help with some of these issues for some cameras. But in many cases slight color contamination can be caused by near UV light (light that is still inside the visible spectrum) leaking into blue pixels or green pixels which have unintended (if slight) response outside their intended range.
Hi,
Doug's posting is not a scientific article but it does contain some alternate facts.
Doug shows a spectral plot of traditional CFA filters:
[image]
But, traditional filters look like this:
[image]
[...]
So, my impression is that it is a marketing hyperbole. The curves that Doug shows are patently fake. If the article starts with fake facts, why would be believe the rest?
The colour differences Doug demonstrate are well within the capabilities of properly designed camera profiles. The effects shown can possibly achieved just buying a proper test target and use Lumariver's Profile Designer.
the whole story has some smell to it, it stinks.
I've now added, per your post the additional sentence: "This will include illustrations of spectral transmission that are meant as a learning aid; these are crudely drawn and exaggerate differences to make them easier to consume, and should not be taken literally, but for those not steeped in scientific measurements of spectral transmission they will help visualize relevant improvements."
The spectral charts are simplified and exaggerated and only there to help visualize the improvements. They are absolutely "fake" as you say.
Thanks for the change, but the information is still fake. Just saying that the curves are for illustration does not change the fact they are fake.
Reminds me of that guy sitting in that white house in Washington DC.
Traditional CFAs (as the ones you posted show) often:
- Leak red (and sometimes green) in the 400-500nm near-UV range (look at your own charts). It's not a lot and our graph exaggerates it to make it clear.
- Err a bit on the side of too much overlap, prioritizing ISO over better color.
- Leak green and blue in the 600-700 near-IR range. Again, our graphs exaggerate it to increase clarity.
Note that the illustration of the spectrum we used is not of any one specific traditional CFA camera. Not every traditional CFA has every issue it illustrates.
Here from MaxMax measurements for three dSLRs without IR-cut filter in place, compared to the illustration we provided:
(https://maxmax.com/Old_Web/images/Cameras/Technical/Canon_40D_Response_CurveB.jpg)
(https://maxmax.com/Old_Web/images/Cameras/Technical/D700_ResponseCurveAdj4.jpg)
(https://maxmax.com/Old_Web/images/Cameras/Technical/Nikon_D300_SpectralResponse.jpg)
(https://digitaltransitions.com/wp-content/upload/Graphs-Layered-1000px-traditional-CFA-1-800x400.jpg)
Note that I've used the words "near UV" and "near IR" a couple times here and in the article to refer to the outside range of the visible spectrum. In more scientific terms this would normally refer to the area immediately below and above visible light. That's probably a faux pas on my part. But again, scientists are not the target for this article. And this thread illustrates why: scientists tend to get caught a bit in the pedantic weeds.
Personally, I would be interested in seeing a more scientific take on what the spectral responses etc, are. With labels on the Y axis. ;)
not clearly laying out what the advantages of the product are can only generate controversy (see above), which won't help sales.
thanks for the comparison on the high ISO. That being it was taken at 12K, it's an interesting comparison as the non Trich back has more details IMO, but for sure the Trich back has more shadow recovery. Odds are in the 400 to 1600 range, where I would be shooting the new back will have overall an advantage and for sure at base ISO, the Trichromatic will have an advantage in shadow recovery.
Traditional CFAs (as the ones you posted show) often:
- Leak red (and sometimes green) in the 400-500nm near-UV range (look at your own charts). It's not a lot and our graph exaggerates it to make it clear.
- Err a bit on the side of too much overlap, prioritizing ISO over better color.
- Leak green and blue in the 600-700 near-IR range. Again, our graphs exaggerate it to increase clarity.
Note that the illustration of the spectrum we used is not of any one specific traditional CFA camera. Not every traditional CFA has every issue it illustrates.
Here from MaxMax measurements for three dSLRs without IR-cut filter in place, compared to the illustration we provided:
(https://maxmax.com/Old_Web/images/Cameras/Technical/Canon_40D_Response_CurveB.jpg)
(https://maxmax.com/Old_Web/images/Cameras/Technical/D700_ResponseCurveAdj4.jpg)
(https://maxmax.com/Old_Web/images/Cameras/Technical/Nikon_D300_SpectralResponse.jpg)
(https://digitaltransitions.com/wp-content/upload/Graphs-Layered-1000px-traditional-CFA-1-800x400.jpg)
Note that I've used the words "near UV" and "near IR" a couple times here and in the article to refer to the outer most range within the visible spectrum. In more scientific terms this would normally refer to the area immediately below and above visible light. That's probably a faux pas on my part. But again, scientists are not the target for this article. And this thread illustrates why: scientists tend to get caught a bit in the nitty-gritty scientific details, which is great for research, but a bit stuttering for normal photographers wanting information to help make purchasing decisions.
You don't happen to have real world CFA plots from the Thrichromatic and say the IQ3-100MP, showing the difference you get?
The advantage is the color the camera produces. For that raw files, comparative tests, and the availablity of the camera for testing by prospective buyers are all far more useful than charts. We provide all of those.
Traditional CFAs (as the ones you posted show) often:
- Leak red (and sometimes green) in the 400-500nm near-UV range (look at your own charts). It's not a lot and our graph exaggerates it to make it clear.
- Err a bit on the side of too much overlap, prioritizing ISO over better color.
- Leak green and blue in the 600-700 near-IR range. Again, our graphs exaggerate it to increase clarity.
Erik, I addressed this in the intro to the article. You seem to be taking an unusually insulting, mean spirited and derisive tone in this thread, which isn't like you. Is everything okay?
Do you have an IQ3 100mp you are considering upgrading? If so I'd suggest working with your local dealer to arrange whatever testing you would consider useful. We (DT) are glad to arrange that for anyone in the US.
Even if the intellectual property of those plots were available without an NDA my strong recommendation we be against buying a camera based on a chart. Your own hands on testing is always preferable; short of that, relevant raw files are a reasonable substitute if they match up to your type of photography.
Hi Doug,
I am a bit irritated because you give fake information. No camera maker has CFA designs you describe! Would you mention any camera vendor by name, you would have lawyers knocking on your door.
Best regards
Erik
| (https://digitaltransitions.com/wp-content/upload/Graphs-Layered-1000px-side-by-side-800x286.jpg) | (http://echophoto.dnsalias.net/ekr/Articles/SpectralPlot/plot1.png) | (https://digitaltransitions.com/wp-content/upload/Graphs-Layered-1000px-side-by-side-800x286.jpg) |
Erik.
There's a difference between 'fake' and simplified information. Fake implies 'deliberately misleading'. Doug's article was targeted to an audience with a certain level of technical understanding and his simplified graphs were easy to get the gist of.
In my opinion, you have been a bit of an insulting dick towards Doug, who has responded graciously with his enquiry as to your wellbeing.
A well written article by the way Doug.
Garry
Erik might be a bit upset in his tone but I think he is right.
Doug's spectral sensitivity graph for the Trichromatic looks basically exactly like Eric's last graph for a normal Canon 5DII/ Sony NEX/ Nikon D2X, so what's so special about Phase' new back? And btw, the artistic graphs from Phase' website illustrating a complete absence of cross-channel sensitivity were wrong and misleading anyway ...
I believe that the Tri might have a very slight advantage in color reproduction (Doug's samples show this better than Phase' samples on their website) compared to the normal IQ3100 but still seams mainly a marketing hype to me.
I consider to attend a Trip demo this week in Munich, so let's see what I can report from there.
(I hope Phase sends also an engineer/physicist not only marketing people to be able to provide some profound information.)
Less overlapping filters are not new, in fact as far as I know early sensors had much less overlap than newer ones. This yields more saturated colors directly out of the sensor, and the advantage of this is that the camera profile (or manual post-processing) does not need to increase saturation further.
This yields more saturated colors directly out of the sensor
Hmmm. You lost me right about there. The whole concept of a bayer sensor, at least a sensor with non-trivial overlap, having "saturation" is not, IMHO, very useful. They really don't (a) in any way that it's useful for a human to think about or (b) in any way that makes sense in a mathematical form.
Looking at the comparison "slider" images on the DT website, the difference is so small I just don't get it. Personally I don't care that much about "accurate" color since I tweak them anyway in post.
Now here we have the implication your old back is no good so you need to upgrade. Not a chance.
Whether those "tweaks" were significant or not depends on your disposition and what's important to you. And this is where I give Doug a break. DT, CI, Dodd, and all the other dealers I've had the pleasure doing business with say the same thing: Try it before you buy it. If you prefer the results, then buy if you want. If you do not prefer the results, or do not think the results are worth the price, don't buy it. ... as if P1 and its dealer network are advertising sugar-soaked cereal to unsuspecting 6 year-olds on TV. That is not the context of how this stuff is sold.
I believe that the Tri might have a very slight advantage in color reproduction (Doug's samples show this better than Phase' samples on their website) compared to the normal IQ3100 but still seams mainly a marketing hype to me.
I consider to attend a Trip demo this week in Munich, so let's see what I can report from there.
(I hope Phase sends also an engineer/physicist not only marketing people to be able to provide some profound information.)
DougDolde, could you please point me toward the passage in the article that you feel implies this? I'd like to modify any such passages as it was certainly not my intention to imply that.
For example:
"...this article will not answer whether you should purchase a Trichromatic. As a company DT doesn’t feel it’s our job to 'sell' – but rather that it’s our job to provide the tools, information, and testing opportunities that our clients need to evaluate whether, what, and when to buy."
"I think it’s suitable to say the native color response of the IQ3 100MP Trichromatic is 'Better Than the Best Ever.' But by no stretch of the imagination does that mean the previous 'best ever' was less than totally awesome. "
"Will that twinge be enough to justify the cost? As we said at the top, that’s not our call to make – it’s yours. Our job is to help you understand the decision you’re making as fully as possible. The color on the Trichromatic is improved over any camera we’ve ever used; in most cases the difference is subtle; in some cases of problematic subject matter the difference is quite large. The color on the traditional-CFA IQ3 100MP was and continues to be very good."
For what it's worth, the word "subtle" appears 8 times in our article.
All that said, "I don't care that much about color since I tweak them anyway in post" misses the point that in some cases the improved color discrimination will facilitate exactly that kind of post processing.
...my IQ180 is just fine .
Doesn't matter I can't afford a new back my IQ180 is just fine .
Doug Dolde, You make this comment
'Now here we have the implication your old back is no good so you need to upgrade. Not a chance.'
Doug Peterson gives you response, that would have taken 30 minutes out of his day, asking where that was implied; showing you examples where he had clearly stated that the previous backs were already great; asked you where he may have implied that they weren't so that he could change any suggestion that they weren't.
Out of respect, I would have thought that your answer would have been.
'Yep, you're right, there was no such implication. Sorry about that. Thanks for taking the time to set that straight.'
Commenting generally of the genius forum.. good manners are free. Less arrogance, more humility and certainly, less of a chip-on-the-shoulder attitude would improve the acuity of discussion on the forum in general.
A general comment for this forum, good manners are free.
As difficult as it may be when a bunch of geniuses get together, many members being experts in their respective fields, showing less arrogance, more humility and certainly, less of a chip-on-the-shoulder attitude would improve the acuity of discussion.
ROTFL,
Coming from the person who called one of the true ‘gentlemen’ of this forum ‘an insulting dick’ ...
patronising snd humbug, all rolled into one.
Hmmm. You lost me right about there. The whole concept of a bayer sensor, at least a sensor with non-trivial overlap, having "saturation" is not, IMHO, very useful. They really don't (a) in any way that it's useful for a human to think about or (b) in any way that makes sense in a mathematical form.
Agree with that, unless the sensors are Luther-Ives compliant (and then the saturation would be perfect by definition). I took the remark to discuss colors after multiplication by the compromise matrix, however.
This is news to me. In the work that Jack Hogan and I have done so far on the relationship of overlap and SMI, it appears that SMI suffers when there is too much and when there is too little overlap. We have not -- so far -- investigated the direction of the errors.
Are you suggesting that in the computation of the optimum compromise matrix that reducing overlap biases the errors wrt the reference values for the training set in the direction of increased chroma?
It should be possible to test that, but before I do so, I want to verify if that's what you are claiming.
Let me examplify. A saturated red color: with lots of overlap the raw value may become 100% R 40%G and 20% B. With little overlap 100% R 10% G and 0% B.
If you without any camera profile just display that on screen (white balanced to not make it look green) the color from the sensor with less overlap is more saturated.
The problem is, you can't really display an an image without a camera profile. What you describe there is actually a profile with a unity diagonal, and no tables, but it's still a profile.
Related, this presentation contains some nice examples of what happens if the CFA has certain shapes:
http://www.slideserve.com/nigel/theoretical-and-practical-limits-to-wide-color-gamut-imaging-in-objects-reproducers-and-cameras
For those interested in discussing this article in person, both I and the Head of Phase One R+D will be at the DT / Phsea One Booth at Photo Plus (http://forum.luminous-landscape.com/index.php?topic=121176.0) this Friday.
Doug, the audience in this forum is well known and require hard evidence. You might get proactive and publish the *real* CFA curves rather than lose control of the spin when someone else does it . As these curves can be measured, there is no way you can argue they are a trade secret. I am sure there are plenty of nasty things one can find to say about anybody here, but if you *choose* to post about color technology in a forum where many participants are engineers, software authors or even senile PhDs like me you can expect scepticism in the absence of hard data.
Edmund
Hi Edmund,
I agree with what you say. It is probably right as you say, the CFA data can be measured easily. That is if you have access to a back. It does not take fancy gear to do. Jack Hogan has measured the CFA response of his Nikon D90 using a 39$ spectrometer, and came up with this:
-------
You are right, some of the guys posting are engineer, some are developing camera profiling tools and some are deloping raw conversion software. Personally, I can not take credit for anything like that. But even amateurs can have some experience with real world data.
Erik
Hi Erik,
In my book, you are a Vulcan and a gentleman ;)
Can you link the *post* where Jack details his method? I think Iliah once told me to just get a monochromator from ebay, and of course university labs own all the stuff required.
Edmund
Hi,
Doug's posting is not a scientific article but it does contain some alternate facts.
Doug shows a spectral plot of traditional CFA filters:
(https://digitaltransitions.com/wp-content/upload/Graphs-Layered-1000px-traditional-CFA-1-800x400.jpg)
But, traditional filters look like this:
(http://echophoto.dnsalias.net/ekr/Articles/SpectralPlot/Scplot2.png)
Or this:
(http://echophoto.dnsalias.net/ekr/Articles/SpectralPlot/plot1.png)
Or this:
(http://echophoto.dnsalias.net/ekr/Articles/SpectralPlot/plot3.png)
So Doug illustrates traditional CFA designs with fake info. There is a sensor that has some characteristics similar to the traditional CFA illustration in Doug's presentation and that is the human vision, corresponding to curve A, below:
(https://4.img-dpreview.com/files/g/TS560x560~3691256.jpg)
The reason such curves are not used in digital cameras is that it would cause excessive levels of noise.
Regarding UV-filtering and IR filtering, that is really a job for the cover glass, that has an IR-filter. Optical glass doesn't transmit much in UV anyway. If UV/IR is an issue, it is not about a new design, it is about Phase One designing an underperforming cover glass on the older models.
The colour differences Doug demonstrate are well within the capabilities of properly designed camera profiles. The effects shown can possibly achieved just buying a proper test target and use Lumariver's Profile Designer.
So, my impression is that it is a marketing hyperbole. The curves that Doug shows are patently fake. If the article starts with fake facts, why would be believe the rest?
To Dougs's defense, I would assume that he just uses info he got from Phase One, but I don't think he should have use it as to much of the info is fake and it should be obvious to anyone doing colour stuff.
Best regards
Erik
On glancing at Doug's article, I immediately saw that his spectral response of a "typical CFA" was nothing like the spectral response of CFAs of actual dSLRs that I had seen in the literature.
---
Bill
Bill
I see that yet another Vulcan lover of fact and logic just got here ;)
I am not very qualified in the theory of color science as I only took Professor Hunt's short course. This lack of education may be the reason why the text in Doug's article seems a bit hard to grok.
HoweverI like the photographs
. If the article were reduced to the photos it would be both a good article and a good sales tool.
Maybe one line more: "We have spent xx years improving the color in our backs, and this is what we have to show you"
Edmund
Hi Edmund,
I just ordered The Reproduction of Colour by R. W. G. Hunt on your inspiration.
You may find this posting of some interest: https://www.getdpi.com/forum/medium-format-systems-and-digital-backs/62676-phase-one-trichromatic-depth-article-raw-files.html#post742819
Best regards
Erik
Interesting comparison. Though i'd like to point out that ir and uv oddities that may occur with normal daylight spectrum will likely be less of an issue with proper artificial light.
The difference in red rendition is notable. Did you try to increase contrast in the first image to see how close it gets to the bottomleft? Or visa versa, decreasing in bottomleft to match topleft?
What This Article Will and Will Not Contain
If you came to this two-part article hoping for a PhD dissertation on color science you’ll be disappointed. I do not hold a PhD in color science, nor do many of our clients. If you’re hoping this article will contain precise 10nm-sliced spectral transmission curves generated by a monochromator, along with associated data tables, then you’ll be disappointed [...] Personally, I won’t shed tears over either of these omissions; in my experience neither PhD dissertation nor highly detailed Spectral Transmission Data is of all that much value to a photographer deciding which equipment is the best fit to their needs and budget.
Hi Edmund,
I just ordered The Reproduction of Colour by R. W. G. Hunt on your inspiration.
Best regards
Erik
I quote myself from the first part of the article:
In short, if your interests lean more toward the academic study of color science than toward the daily practice of photography then this article is not for you.
The charts are very clearly described in the article as "crudely drawn" with "exaggerated differences to make them easier to consume" which "should not be taken literally" – coming to this thread and decrying their lack of scientific accuracy is missing the point to say the least. To say they are "fake" when I've posted a direct comparison (http://forum.luminous-landscape.com/index.php?topic=121132.msg1006648#msg1006648) showing their key features in specific cameras is insulting. But that's okay; one doesn't write articles on the internet without expecting to be insulted by someone somewhere :).
If anyone would like to write an academically-oriented article on the Trichromatic CFA we are very glad to help! We will gladly provide a back and work bench at our LA or NYC office for your testing at no cost, or arrange a reasonable way for you to evaluate it elsewhere in the US. We will gladly connect you to the Phase One R+D team to ask questions. I'm even glad to connect you to a few of the PHDs in color science that I communicate with on a regular basis should you wish to have your article peer reviewed and published in an academic journal. If you'll allow us, we (DT) will gladly publish your results on our blog, and though I can't speak on their behalf I suspect strongly Luminous Landscape would be glad to publish on their page (and for sure, you are welcome to post to the forum). I'm not being facetious or sarcastic; please feel free to contact me to start that process.
Until then, please consider the intended audience of our article and the difficult task of trying to provide some entry-level education on a topic as complex and dry as color science to a group as diverse as "photographers".
The reason you are getting criticised for your post has nothing to do with Phase quality, it's a PR issue: you don't understand the culture of the color community. [...] The fashion photography crowd expects a launch party, the geeks want color curves.
Our article was not for the "color community" (i.e. academics immersed in matrices, measurement, metamerism, and minutia).
Our article was for photographers – our clients. So far as I can tell it was very well received by that community.
I'm really okay if color PHDs found the article lacking in academic details. I literally said in the introduction to the article that they would "disappointed".
Our article was not for the "color community" (i.e. academics immersed in matrices, measurement, metamerism, and minutia).
Our article was for photographers – our clients. So far as I can tell it was very well received by that community.
It's really understandable if color PHDs found the article lacking in academic details. I literally stated in the introduction to the article that they would "disappointed".
It's a bit like I hosted a Wine Tasting Night and noted on the invite "Before the tasting, a brief introduction of wine will be given. Wine making is a rich and complex topic. If you're a professional sommelier you will find our explanations oversimplified or even technically inaccurate." and then a few soms attended and complained that I didn't provide detailed terra acidity analysis studies. We're glad to host those soms at the winery to do their own soil tests; the Wine Tasting Night just wasn't the proper time and place for it.
I just ordered The Reproduction of Colour by R. W. G. Hunt on your inspiration.
Hi Erik,
Hunt's model of color vision is very clearly explained in his book 'Measuring Color' (https://www.amazon.com/Measuring-Colour-R-Hunt-2001-01-03/dp/B01FJ17XWM/ref=sr_1_3?ie=UTF8&qid=1509398569&sr=8-3&keywords=hunt+measuring+color&dpID=51a1QVkSQ9L&preST=_SY344_BO1,204,203,200_QL70_&dpSrc=srch). I find it much more relevant to photography and prefer it to 'The Reproduction', which I also own.
Jack
Interesting comparison. Though i'd like to point out that ir and uv oddities that may occur with normal daylight spectrum will likely be less of an issue with proper artificial light.
The difference in red rendition is notable. Did you try to increase contrast in the first image to see how close it gets to the bottomleft? Or visa versa, decreasing in bottomleft to match topleft?
Please don't change the name of the subjectIt gives the illusion that something worth reading has been said.
Hi Jack,
Thanks for the info, it seems I need to cancel one order and make another one!
Best regards
Erik
Erik,
I think the Hunt book I own is "measuring color", but I only used it for reference, not to learn. I think it doesn't really matter which book you own provided you understand the logic which postulates a scientific explanation of the factors which evoke the sensation. Because in the end, make no mistake, it is a sensation. And then a well written book will explain the issues of color spaces etc, which are placeholder representations for this sensation which represent certain measurements.
Although this is probably high-school philosophy, I think that listing the *factors* which enable and evoke the sensation is a more constructive exercise than perfecting the representations. But that is probably a professional deformation of a senile PhD. However, good lighting in museums would make me happier than accurate print in magazines :)
Professor Hunt is interesting because he helped create some of the first color emulsions, I believe, and also some of the first color TV systems, so he understands what choices got made at the start of the game.
I personally continue to feel that accurate color reproduction by storing color information in files is a losing proposition because the variation of the sensation in the population is too strong due to genetic variation in the pigments in the eyes. Multispectral representation make more sense IMHO.
Edmund
While I might agree that Doug’s plots over emphasized the red contamination, the spectral plots of many of the cameras posted indicate to me there is plenty of red contamination getting all the way into the blue and green sensels that perhaps cleaning this up and creating more consistent crossover would offer some advantage.
As to whether it can be corrected with custom profiles, perhaps it might be improved but perhaps most photographers really don’t want to get into the technical aspect of creating their own profiles, If the camera and CFA’s can be engineered to provide a better solution, why not? While the current price point doesn’t make sense for most, like anything new, if it’s good and helpful, it will trickle into other products over time most likely with far less impact on price.
In reviewing the article, I actually wonder if his two original graphs are labeled backwards, because he does state one is based on the eye, other on a sensor, but the way they are shown the graph that is typical of one used for the eye is labeled as a sensor and vice versa.
I reprocessed the image in LR CC Classic, but using an emulation of Capture One's film-curve instead of ACR tone-curve in my DCP profile. In addition I increased "Vibrance" from 0 to 10 and also "clarity" from 0 to 10.
Here are the results:
(http://echophoto.dnsalias.net/ekr/Articles/TMP/ThreeProcs.PNG)
Left Capture One, defaults except exposure. Center Lightroom CC with Capture One Film Curve and +10 in vibrance and +10 in clarity. Right Lightroom CC with ACR-tone curve, 0 vibrance and 0 clarity.
What is your take?
Best regards
Erik
It seems to me that the colordifferences between apps in their representation of red are rather significant. If you tinker with spectral response curves of a sensor for supposedly better colorrendition, then at least the application should reproduce something within that same precision. (Note that I carefully try to avoid the word "accurate").
To me, the Adobe red has too much blue in it, almost like a haze, so the pepper doesn't look snappy since the shadows aren't red-black but something blueish. The pepper doesn't look quite realistic as far as memory goes.
The C1 rendition of the pepper seems a bit hot, (and as far as memorycolor goes, a bit too yellow), but the colorchecker on the other hand seems to suffer blueish tint in yellows and light skintone.
As far as matching between apps is concerned: the tone-curve version seems to do a slightly better job in contrast (and contamination), but the middle version might be slightly better at saturation. Neither version manages to match the C1 reds obviously.
Was the pepper indeed the same color as the dish?
The takeaway here though seems to be that at least green lime is not an issue of concern to the point that it needs to be addressed by tinkering with spectral sensitivity.
when i started out doing color management i got some red yellow and green peppers, photographed them, made a print and then put the peppers on the print.
actually for test images just random fresh raw foodstuff, salads etc is quite good, stuff you're used to eating. Raw meat is also a good one because our eyes instantly spot it when the meat color goes off. peppers are nice pictorially but actually not something we instinctively assess. I guess if you're into fish, sushi will be good too :)
I had a steak file, printed by Canon with their profiles and with mine. With my profiles it looked like nice raw meat, with theirs by comparison like something looking for a dumpster.
Edmund
It seems to me that the colordifferences between apps in their representation of red are rather significant. If you tinker with spectral response curves of a sensor for supposedly better colorrendition, then at least the application should reproduce something within that same precision. (Note that I carefully try to avoid the word "accurate").
To me, the Adobe red has too much blue in it, almost like a haze, so the pepper doesn't look snappy since the shadows aren't red-black but something blueish. The pepper doesn't look quite realistic as far as memory goes.
The C1 rendition of the pepper seems a bit hot, (and as far as memorycolor goes, a bit too yellow), but the colorchecker on the other hand seems to suffer blueish tint in yellows and light skintone.
As far as matching between apps is concerned: the tone-curve version seems to do a slightly better job in contrast (and contamination), but the middle version might be slightly better at saturation. Neither version manages to match the C1 reds obviously.
Was the pepper indeed the same color as the dish?
The takeaway here though seems to be that at least green lime is not an issue of concern to the point that it needs to be addressed by tinkering with spectral sensitivity.
Hi Oscar,
I have discovered a couple of issues, one is that the screen dump tool I use does not tag color profile in the dumped image. I would assume that in the RGB coordinates of my screen.
The red pepper has the colour Lab(32, 50, 36), that is average of five samples. All taken within black rectangle. There is a Lab(x,50,36) patch on the left of the black markings.
My major focus rendition of greens (lime greens) but I learned a lot.
Did you have the opportunity to shoot the Thrichromatic?
Best regards
Erik
This would be a hopefully more correct visualisation of the reds:
http://echophoto.dnsalias.net/ekr/Articles/TMP/RedPeppersComparison2.jpg
(http://echophoto.dnsalias.net/ekr/Articles/TMP/RedPeppersComparison2.jpg)
The simple test of a "better" CFA would be for colors with different spectral setup that look identical to human eyes to look identical on the pictures. A good test eg. would be an IR reflective black material and a non-reflective one, eg a polyester black and a natural fiber black.
Over on DPR, in my thread about CFA simulation, I asked if anyone had a database of naturally-occurring metamers. I got no answers. Does anyone know of one? Just the spectra would be a big help.
Jim
Not exactly metamers, but you could have a look at the ASTER library: https://speclib.jpl.nasa.gov/
And then calculate them from the reflectance spectra.
Thanks for the link. I ordered a copy. CD-ROM only. 6-8 week delivery time? What century are we living in?
I'd have to create the metamers by a combination of lighting and direct search.
Jim
I think there are a bunch of artist's paints with weird spectral properties.
... as everyone here has already pointed out I am neither really a photographer nor a scientist ...
Edmund
I do have this:
https://www.rit.edu/cos/colorscience/mellon/Publications/Artist_Spectral_Database_CIC2016.pdf
jim
Actually, you can take some random stuff, take spectro readings and make inkjet patch prints. This could maybe give you same-colored pairs of objects, one with a spectrum from inkjet pigments and one possibly with a strange spectrum. I think there are a bunch of artist's paints with weird spectral properties. One can probably extend this idea to mounting all of this stuff in little squares on a piece of cardboard, which makes lighting and comparing easier.
That's an interesting idea, Edmund. My reservations about it are that the reproduced inkjet versions will have only a few basis functions behind them (maybe expanded a bit by KM mixing, which I have to admit I never really understood well), since there are only 4 or 6 or so inks involved, the "light" versions being diluted (The concept of "light black" does tickle me, though). If the camera were going to be used to make images of inkjet prints, this would be an extremely useful exercise, but I think that's an unlikely use case.
You are causing me to think in directions I would otherwise have not, and I thank you for that.
Jim
I am a bit irritated because you give fake information. No camera maker has CFA designs you describe! Would you mention any camera vendor by name, you would have lawyers knocking on your door.
I don't think competitors are that impressed by NDAs, by the way. The MFD industry must be in deep trouble if they cannot afford a monochromator and a spectrometer. Alexey Danilchenko and Iliah Borg published specs for an open source spectrometer, BTW.
The Phase One seem to be covering everything with NDA these days - including specs for the IR filter glass that they were known to share in the past without any NDA's at all. In respect of transmission or sensitivity curves this is completely pointless since it is fairly easy to recover those.
I also find the whole "trichromatic" announcement complete marketing gobledy gook. In respect to Doug artcile explaining the stricter sensitivity curves - if any of that is true then as they say in Russia "everything new is well forgotten old". That is simply because the Kodak sensors used in P+ backs (at least P20, P25 and P45) had the same CFA characteristics - non of the humps from one channel in the other and less cross talk between the channels. Partially some colour shifts problems can be attributed to profiles but from the little I have tried it seems that a lot of it has to do with IR glass Phase One was using - Schott BG50 glass is absorptive type of IR filter and does not have sharp transition from transmitting to blocking. It is therefore has some tails that let in a prortion of UV and IR range that affect the sensor response. UV portion seems to be significant for BG glass (the filter transmits well below 400nm). Kodak's original ProBack using KAF16801CE sensor (that is 1 generation before KAF16802CE sensor used in P20) used a reflective IR cut filter that cut UV response at 400nm pretty sharp and cut out reds pretty much to 0 at 700nm (whilst not suppressing reds up until 650-670nm - depending on filter variations).
Perhaps all the trichromatic trying to achieve is similar traits (regardless of the how it does it these days).
But until the CFA is retrieved it will be hard to guess having all the unnecessary secrecy.
Hmm, I don't think he can draw the conclusions he is drawing based on that test: one image is more saturated than the other, contrast seems to be different and he says one has a color cast = at least one 'incorrect' profile. As a result I am also not convinced about the color noise and chromatic aberration claims: could be a lens profile issue. And doesn't the IQ3-100 standard back normally take a hot plate?
In the end he may well be right but I don't think the procedure he used can lead to such conclusions.
Jack
The one thing he says in that test is, "White balance is exactly the same for both images...". I assume that means the Temperature and Tint sliders were identical. I suppose that is useful for highlighting how a camera responds to lighting, but I don't know how practical it is. I think it is more useful to white balance both on the color checker and evaluate colors with a balanced file.
I also do not understand his second image about chromatic aberrations. In the first image, that scale looks much more "magenta" in the Trichromatic image. Either he mixed those up or it is a different image. I didn't see that when I tested them, but then again I wasn't looking for it.
Erik, how did you get a Lumariver profile for the backs? Did you create them from that file? If you did, great idea! In other words, why didn't I think of that? Curious because the apple looks exactly the same as it did with mine on the 3100. Reds look darker on the Lumariver / Trichromatic file too. Must be Anders' personal spin on the twists.
:)
Dave
Dave
Hi Jack,
My guess is that part of the difference that can be observed may depend on different cut off regarding IR or UV, that could effect axial chroma and also explain some of the yellow contamination of vegetable greens that some observers object to with Phase backs.
Top left, Lightroom with Lumariver profile. Top Right Capture One
Bottom Left, IQ3100 with Lumariver profile, Bottom Right Capture One.
One row is Trichromatic the other one is standard back? Anders' profiles are obviously better. Have you computed deltaE's?
It is not terribly useful to measure the DeltaE of the target from which you made a profile. It's like telling someone that your father's name is "Edward" followed by quizzing them on their knowledge of your family by asking them the name of your father... of course they will get that right; if you teach to the test the test tells you about the teaching, but not about the underlying knowledge.It is not useful to use the same shot from which profile was made yes. The same target is perfectly useful - shot under different lighting for example to evaluate your profile behavior. It is even more useful if profile was build from spectral sensor measurements even for that very target - to evaluate the profile.
Could be Erik. Doesn't the standard back IQ3100 have a hot plate (IR/UV filter)?
One row is Trichromatic the other one is standard back? Anders' profiles are obviously better. Have you computed deltaE's?
Jack
; if you teach to the test the test tells you about the teaching, but not about the underlying knowledge.
BTW, raw files of those images Erik used are available here, along with others.
TCv3100 Hightail link (https://spaces.hightail.com/space/HtAMyc7o9y)
The last file is a legend in excel.
Dave
BTW, raw files of those images Erik used are available here, along with others.
TCv3100 Hightail link (https://spaces.hightail.com/space/HtAMyc7o9y)
The last file is a legend in excel.
Thank you David. I took the ColorChecker files for the Trichromatic and Standard Back IQ3-100 and, under the assumption that lighting is about D65 (RawTherapee says about 6480k for the Standard Back) I estimated compromise matrices for them based on average BabelColor (http://www.babelcolor.com/colorchecker-2.htm#CCP2_data) spectral reflectance. There are a large number of provisos and non idealities - lighting, different ISO and exposure, position of cc24 (probably resulting in contamination of some of the patches by reflectance from items in the scene), absence of direct spectral measurements, etc. - not least of which the fact that I am not a (color) scientist and often prone to embarrassing mistakes (:-) so I would take these results with a pinch of salt. Nevertheless I think that they start to give a relative idea of some of the differences in the CFAs in the two backs.
Interestingly, with the assumptions above, the Standard Back is able to achieve better dE and dE2000: SMI is an excellent 86.7, average dE2000 is 1.49, 10 patches have dE2000 less than 1 and only 5 greater than 2. In these conditions this is very good:
The same values for the Trichromatic are: a decent SMI of 81.1, average dE2000 of 1.87, 8 patches less than 1 dE2000 and 11 patches above 2 ( Recall that 1 dE2000 is supposed to represent a just noticeable difference). Decent, but at first glance the SB is more accurate than the TC (shown below):
A strong hint as to what has been changed is given by the CameraNeutral values, that show that the R and B channels are more sensitive relative to G in the TC (an alternative interpretation could be that G is less sensitive, I didn't check it). The wbRaw->XYZD65 matrices suggest that the TC is a little better at blues but the SB is a little better at reds. The weighted sum of RGB negative coefficients suggests that the TC should have a slight advantage with noise but given the large number of differences in the setup I wouldn't put much weight on it.
Finally, here is a screen capture with the two images rendered via their relative wbRaw->sRGB matrix and nothing else, just to show that they work - I did not try particularly hard to match their brightnesses (332, left, is TC; 336, right, is SB):
Jack
PS Information here (http://www.strollswithmydog.com/determining-forward-color-matrix/) may be helpful in understanding the procedure I followed to generate what's above.
* SB first, TC second.
PS Information here (http://www.strollswithmydog.com/determining-forward-color-matrix/) may be helpful in understanding the procedure I followed to generate what's above.
I personally would ignore the numbers and look at the files with my eyes. IMO, the fruits in the files shot with the TC back look richer than the fruits in the files shot with the Standard back. The TC file has an enhanced three dimensionali quality compared to the SB file. It appears as if a veil has been lifted. What I don't know is whether the TC back file has been "cooked" in some way to add a touch of clarity or midtone contrast. It would be interesting to see if the SB file can be processed to look more like the TC file. It would also be interesting to see how Hasselblad's H6D-100 and X1D files look in comparison.
. Your comment about the richness / veil is interesting. I didn't notice that, but I didn't compare them with their matrixes the way Jack did.
Dave
Dave, quite frankly, I did not expect much from the TC backs compared to the already impressive files out of the IQ3 100. However, looking at the files presented here by Jack with my iPad Pro, I really am struck by the visual differences. The SB files look flat and two dimensional. The TC files look more lifelike and three dimensional. I have no idea why this difference exists. As I suggested, Phase may have worked on the default settings on import in a way that bumped the midtone contrast. I don’t know anything about color science, so it may also be that the purity of the colors has been enhanced and this in and of itself produces better color differentiation and therefore a more three dimensional look. Something is happening here, what it is ain’t exactly clear....
Dave
(http://www.davechewphotography.com//temp_images/trichrometest/laduecompare.jpg)
(The water looks different because the cloud cover was slightly different for the two photos which caused a different reflection)
Hi,
Doug's posting is not a scientific article but it does contain some alternate facts.
Doug shows a spectral plot of traditional CFA filters:
(https://digitaltransitions.com/wp-content/upload/Graphs-Layered-1000px-traditional-CFA-1-800x400.jpg)
But, traditional filters look like this:
(http://echophoto.dnsalias.net/ekr/Articles/SpectralPlot/Scplot2.png)
Or this:
(http://echophoto.dnsalias.net/ekr/Articles/SpectralPlot/plot1.png)
Or this:
(http://echophoto.dnsalias.net/ekr/Articles/SpectralPlot/plot3.png)
So Doug illustrates traditional CFA designs with fake info. There is a sensor that has some characteristics similar to the traditional CFA illustration in Doug's presentation and that is the human vision, corresponding to curve A, below:
(https://4.img-dpreview.com/files/g/TS560x560~3691256.jpg)
The reason such curves are not used in digital cameras is that it would cause excessive levels of noise.
Regarding UV-filtering and IR filtering, that is really a job for the cover glass, that has an IR-filter. Optical glass doesn't transmit much in UV anyway. If UV/IR is an issue, it is not about a new design, it is about Phase One designing an underperforming cover glass on the older models.
The colour differences Doug demonstrate are well within the capabilities of properly designed camera profiles. The effects shown can possibly achieved just buying a proper test target and use Lumariver's Profile Designer.
So, my impression is that it is a marketing hyperbole. The curves that Doug shows are patently fake. If the article starts with fake facts, why would be believe the rest?
To Dougs's defense, I would assume that he just uses info he got from Phase One, but I don't think he should have use it as to much of the info is fake and it should be obvious to anyone doing colour stuff.
Best regards
Erik
Now I see that we have "data" but it appears to be compromised.
This looks like a shocking result, I did notice that P1 was returning pure market-speech when they introduced the new tool.
I stopped paying attention. I wanted to know "what they actually did". Now I see that we have "data" but it appears to be compromised.
... ending up in a better color space like Adobe RGB to check more meaningful visuals and clipping there.
...without going deep about ir and uv filters, while I calibrate and custom profile very often I have to visually adjust certain “colors” manually while in phocus or acr, if I was using p1 I believe would be the same story, it primarily happens with gems(they have many different properties as well) most often it’s yellow...
Okay, I think I figured it out. Attached are the two icc profiles. They are preliminary results because I haven't created visual confirmation yet, but after thinking about it, it could well be the point:TC = less colorspace = more colordepth
We’ve worked with a few shooters who specifically shoot gems, and have a system installed at the GIA (the Gemology Institute of America).
A trichromatic won’t suddenly solve all your problems or make you feel young again, but I think you would be surprised at the reduction in frequency with which you had to make such manual color corrections. The Focus Stacking tool built into the XF can also be very helpful for such work and the tethering toolset in C1 (eg overlay, color editor, Focus mask, compare variant, diffraction correction) is top notch for tiny colorful subjects. Your local P1 dealer can help you set up a test; if you’re in the US we’d be glad to.
Okay, I think I figured it out. Attached are the two icc profiles. They are preliminary results because I haven't created visual confirmation yet, but after thinking about it, it could well be the point:TC = less colorspace = more colordepth
Should anyone be interested I have put a little more detail online about my thinking and analysis of David's captures with the two backs (geek alert):
http://www.strollswithmydog.com/phase-one-iq3-100mp-trichromatic-linear-color-i/
Jack
Interesting Oscar, kind of makes sense in a ProPhoto vs Adobe RGB working color space sort of way. I am not familiar with the primaries shown, do you know how they are computed?
Yes, similarly to your forward-matrix description, but when you have the XYZ coordinates you convert to Yxy.
(Regarding your description for forward matrix conversion it may be of interest that technically there are only 6 unknowns. One coordinate of each primary is given by subtraction from white. The xy coordinates of the primaries are therefore "sufficient" to describe the space.)
Ah, ok. So what are the three raw coordinates that are converted to Yxy: (1,0,0), (0,1,0) and (0,0,1)?
... but I normally prefer to let all 9 fluctuate in the process of finding the optimum compromise matrix (as you know some people use 12, adding a bias term to each channel). I then check the final resulting white point to make sure it is in the ballpark of the illuminant, and it normally is pretty close
Fantastic job Jack. Heck, even I could follow it!
As I mentioned in a message to Jack, I apologize for shooting them at different ISOs, but I wanted to compare them as I would typically use them. I was less interested in a scientific comparison. Although now I am intrigued by Jack's posts. Someday I should do this again.
Although I took several images from each bracketing by 1/3 stops, no exposures were identical between the two backs. Perhaps if I would have set the backs to 1/2 stop increments instead of my normal 1/3 stop increments...
Regardless, fascinating stuff Jack, and thank you for the analysis.
Dave
So, to eliminate as many variables as possible, it is probably best practice to fix the whitepoint, and – to avoid as many cans of worms as possible – I personally prefer to use illuminant E. The latter simplifies spectral data conversions for the colorpatches. No need to know the spectral data of the original illuminant, or obfuscate the results with daylight spectra.
So you compute the matrix that best converts white balanced raw data to reference xyz/Lab values resulting from the target being lit by illuminant E?
Then perform a chromatic adaptation to D65 for a/sRGB?
Since the matrix varies with (the inverse of) color temperature, how accurate does it come out compared to trying to estimate it for the correct illuminant as I did? Maybe I should try it out.
Yes. I specifically converted the Babel color spectral data to XYZ using NO illuminant spectrum. That results in the cleanest XYZ-E reference for my purposes. I can make those XYZ colors available if you'd need them.
Yes, although I convert to ICC D50 using straight multiplication for adaptation. Then let colorsync figure out conversion to whatever the user selects as outputspace. I may change this later to incorporate colorclipping control. The trick then is to adapt the outputmatrix to illuminant E by simply dividing out its original illuminant.
I prefer to use simple division/multiplication for illuminant conversions because during several steps of the process it is already done that way. i.e. whitebalancing the raw data is done by multiplication, Lab to XYZ is generally defined with multiplication.
Using bradford transforms has a disputable theoretical advantage if you allow 2 degree observer logic to assess a 10 degree observer problem for extreme conversions. That advantage is however not of the precision that would radically change the desired results, especially in smaller conversions.
Some thoughts:
the algorithm trying to find the matrix uses reference XYZ values. If those values are given with D50 or D65 illuminant, then the algorithm should end up finding D50 or D65 illuminant, since you already whitebalanced the data.
If you have the spectral data of the patches, and the spectral data of the original scene illuminant, then you could theoretically adapt the patches using spectral conversion, though I doubt that the entire process recognises that kind of precision, and the objective of colormatching is to generalise the matrixes so they can easily be adapted under normal PCS circumstances.
That is: we're trying to find matrixes that are optimised for use in XYZ and straight illuminant conversions.
Note also that CCT is not an equivalence. That is an unfortunate mistake perhaps introduced by RAW converters. CCT is a one-way conversion, and very sensitive, it may be insightful to try and figure out the size of the differences in XYZ vs the corresponding size of the differences in CCT (and then try to translate that to a perceptually uniform error space). But that would be (euphemistically) left as an exercise for the reader...
That's interesting Oscar. So you compute the matrix that best converts white balanced raw data to reference xyz/Lab values resulting from the target being lit by illuminant E? Then perform a chromatic adaptation to D65 for a/sRGB?
That leaves you open to illuminant metameric failure. Adaptation != Illumination.
Jim
The layman's explanations have been more confusing to me than the scientific ones.Stick with the scientific ones! Marketing speak is a much bigger, moving target.
From the user perspective, I would like to select the sensor response for the type of illuminant. Daylight vs Tungsten for example. What I certainly do NOT want is a RAW converter that decides to interpolate between Daylight and Tungsten primaries based on my abuse of a colortemperature parameter which is what I am offered for colorcast appearance. I'm fairly certain that errors introduced by that logic are far greater than the errors of adaptation by multiplication in PCS.