Diluted C41 Tested

[pentaxuser]

If the mask is a weird colour, and the negatives look unreasonably dense, the likelihood is much greater!
When one actually works with the scans, it reveals itself quickly whenever you have a subject that is both in the light and in shadow.

Thanks Matt. I had another look at David's negs but to my admittedly untrained eye the negs do not meet either of the two aspects of a weird mask colour or being unreasonably dense. Is there a section on any of them that has an object that meets being in the light and shadow?

Thanks

pentaxuser

 

[koraks]

weird mask colour

The mask is quite dense and extremely yellow, especially for a fuji film stock. But of course I had the benefit of actually having the negatives in my hands, so I could see this quite easily.

 

[David Lyga]

Perhaps the best thing to do in order to settle this would be for koraks to provide a TIFF tile of the NEGATIVES to all, maintaining the negative image, just as it is now, Then people would work with those negatives and make their own determinations. Maybe what my untrained minds says about digital is incorrect, but I think that you might be able to see some logic here. - David Lyga

 

[koraks]

The tiff files of the negatives are linked to in one of my posts above. They're scanned 'as is', but there's always the hidden magic of the scanner software at work. However, I think those files are as close to 'reality' as is realistically feasible.

 

[MattKing]

Is there a section on any of them that has an object that meets being in the light and shadow?

David's negatives are singularly lacking in such examples .
The best example is probably the church, but even it isn't great (as an example for checking crossover) due to the harsh nature of the lighting.
If you look at the environmental portrait I posted, you can follow the subject's skin tones from highlighted forehead to shadows under the chin. As you do so, you will note no change in hue. If the source had been suffering from crossover, the hue would have changed.
And by the way, I looked at the tiffs of the negatives themselves that koraks linked to. I would agree that they are quite dense, and really yellow.
I'm not trying to castigate David for his approach - just caution those who might wish to apply it, if they are expecting negatives that are free of crossover.

 

[pentaxuser]

The mask is quite dense and extremely yellow, especially for a fuji film stock. But of course I had the benefit of actually having the negatives in my hands, so I could see this quite easily.

The tiff files of the negatives are linked to in one of my posts above. They're scanned 'as is', but there's always the hidden magic of the scanner software at work. However, I think those files are as close to 'reality' as is realistically feasible.

Are the tiff files those on your #77 where you have what looks like negatives turned into prints of the same size? I cannot see any other negative sized prints or pics of the negatives sent by David. If these are the "as is" scans of the negatives turned into positives then of course these cannot be examined as negatives but interesting enough if these are the genuine "as is" scans of the negatives then in the red car scene the tarmac looks the same each side of the car which seems not to confirm the change in colour you mentioned you were getting in the big scan

In David's digital pics of his actual negatives they do not look particularly dense nor extremely yellow but it may be my judgement is wrongWhat we now have is a 3/4 way at most conversation on this which is helpful in some ways but in others less so as there is no-one else giving their views on what they are seeing in your tiff files or David's pics of his prints and negatives

lt leaves me wondering whether we are looking at crossover or simply negatives that are at least OK and could be made into better crossover-free RA4 prints.

Matt, I understood your point that you made about your portrait and what to look for there but as you say there is unfortunately no similar negs or prints in David's set.

In my opinion this has been a great discussion done by all parties in the way most investigative discussions should be done on Photrio and I don't think anyone sees your comments, Matt, as anything close to castigation of David

pentaxuser.

 

[MattKing]

Are the tiff files those on your #77 where you have what looks like negatives turned into prints of the same size?
In my opinion this has been a great discussion done by all parties in the way most investigative discussions should be done on Photrio and I don't think anyone sees your comments, Matt, as anything close to castigation of David

pentaxuser.

These are the links that koraks was referring to as essentially being photos of David's negatives:

Sure, let me see if I can help.
....
(3) the set of 16-bit 'scanned as positive' TIFFs. I downsized these to keep the files relatively small (~20Mb each). If you require full res scans, let me know, I can share them via Wetransfer.

Set 3 (scanned as positive to 16-bit tiff, resampled to 50% linear):
Image #1
Image #2
Image #3
Image #4

And I hope that my reference to "castigating" David:
1) clearly reveals itself as being said with tongue firmly in cheek; and
2) by using a word like "castigating", also clearly reveals itself as an "homage" to his inimitable posting style!

 

[David Lyga]

David's negatives are singularly lacking in such examples .
The best example is probably the church, but even it isn't great (as an example for checking crossover) due to the harsh nature of the lighting.
If you look at the environmental portrait I posted, you can follow the subject's skin tones from highlighted forehead to shadows under the chin. As you do so, you will note no change in hue. If the source had been suffering from crossover, the hue would have changed.
And by the way, I looked at the tiffs of the negatives themselves that koraks linked to. I would agree that they are quite dense, and really yellow.
I'm not trying to castigate David for his approach - just caution those who might wish to apply it, if they are expecting negatives that are free of crossover.

On the contrary, what we are after is truth, not feelings. I appreciate ANY feedback from ANYONE. This is a positive attitude which will help us all. - David Lyga

MATT: As far as "Inimitable", perhaps mine is a prolix style which should, instead, be duly disdained rather than reverently revered!!! Matt, you are a VERY funny man.

 

[pentaxuser]

Are the tiff files those on your #77 where you have what looks like negatives turned into prints of the same size? I cannot see any other negative sized prints or pics of the negatives sent by David. If these are the "as is" scans of the negatives turned into positives then of course these cannot be examined as negatives but interesting enough if these are the genuine "as is" scans of the negatives then in the red car scene the tarmac looks the same each side of the car which seems not to confirm the change in colour you mentioned you were getting in the big scan

Matt, I am unsure if your post is confirming or otherwise that my reference to koraks #77 is correct. What I was trying to say is that the only pics of David's negatives were those made by David. There are no other pics of David's negatives? If that is the case then short of the digital pics of the negs I am unsure how we judge your comments on the signs of crossover such as yellow cast or density

Thanks

pentaxuser

 

[MattKing]

koraks used a scanner to essentially "photograph" the negatives. He then adjusted the resulting file so that we can see what the negatives look like to him.
He posted:
(3) the set of 16-bit 'scanned as positive' TIFFs. I downsized these to keep the files relatively small (~20Mb each). If you require full res scans, let me know, I can share them via Wetransfer.

Set 3 (scanned as positive to 16-bit tiff, resampled to 50% linear):
Image #1
Image #2
Image #3
Image #4

This is a resized version of the file corresponding to Image #4 of in koraks' post:

Of course, by my posting that here, my software and the Photrio downloading tool have together added further complexity by becoming involved in the process. Even so, I think it is obvious how yellow and dense the negative appears.

 

[MattKing]

And by the way, while these negatives appear yellow, there is no special connection between a yellow appearance and crossover. It is the fact that the negatives have an unusual colour (yellow, or red, or green, or blue or ...), or greater than normal density that serves as a quick "red flag" to warn the person seeking to print them that he/she may be in for a challenge.
I certainly have encountered worse crossover in negatives that didn't appear to the naked eye as unusual as these ones. And an unusual colour doesn't automatically mean that you will have to deal with crossover.
And also by the way, I rarely respond to a reference to a specific post number, because if you or I have someone on "ignore" who has posted in the thread, our post numbering will most likely be different.

 

[koraks]

Thanks Matt, yes, those are them! And I agree; mask color alone doesn't say much in itself. In fact, I still find color negatives very difficult to 'read' with the naked eye. Only very gross problems are easy to spot. By far the most effective way of determining the quality of negatives in my opinion (short of densitometry) is printing them.

 

[RPC]

Since the mask is there to correct for dye impurities, if it is off-color, I don't see how it could be doing its job properly. It obviously was not formed properly, and it is likely the dyes weren't either.

We could more easily see the effects of crossover, mask errors, and the process in general if two sets of negatives and prints were made, one with the standard process, and one with the diluted process, and compared them side-by-side, with skin tones and a gray scale included in the subject matter. Any tests made of this or any non-standard process should always include a grayscale, IMO. It easily shows any crossover.

As always, acceptability is in the eye of the beholder.

 

[pentaxuser]

We could more easily see the effects of crossover, mask errors, and the process in general if two sets of negatives and prints were made, one with the standard process, and one with the diluted process, and compared them side-by-side, with skin tones and a gray scale included in the subject matter. Any tests made of this or any non-standard process should always include a grayscale, IMO. It easily shows any crossover.

A good point, RPC, in respect of your suggested test.. My problem which you may have gathered is that what I look at governs what I see and what I see depends on what I look at. So David's digital pics of his negs look OK but unlike koraks I do not have them in my hand to look at with my naked eye. David's digital pics of at least his own prints of the red car scene do not seem to exhibit the colour differences in the shadows on either side of the car either as is the case in koraks' scans of the red car scene but his conversion of the negs to positives via tiff files suggests that the negs are OK.

On the other hand the flower box does look a bit strange no matter which pic I look at and suggests on balance that there is evidence for and against there being crossover. So I'd like to be able to reach a conclusion on the presence of crossover but I just feel that the evidence so fat has not been conclusive.

I may never use David's method for various reasons and one of the principal reason is likely to be that I will never be a big enough user of C41 to make it worthwhile but it would be nice if I were able to reach as close to a definite conclusion on it as is possible

Frankly my agnostic view has not been helped by another thread where crossover once again reared its head where the reason seemed to be largely connected to gross over-exposiure of Ektar but where on asking questions of the OP it appeared that little or no over-exposure took place and the film was developed by standard commercial C41 development. Frustratingly that discussion just seemed to fade away

pentaxuser

 

[MattKing]

Frankly my agnostic view has not been helped by another thread where crossover once again reared its head where the reason seemed to be largely connected to gross over-exposiure of Ektar but where on asking questions of the OP it appeared that little or no over-exposure took place and the film was developed by standard commercial C41 development. Frustratingly that discussion just seemed to fade away

With respect to that other thread, I think there is a good chance that the crossover we saw initially arose at the scanning stage, rather than the film exposure and development stages.

 

[Mr Bill]

We could more easily see the effects of crossover, mask errors, and the process in general if two sets of negatives and prints were made, one with the standard process, and one with the diluted process, and compared them side-by-side, with skin tones and a gray scale included in the subject matter. Any tests made of this or any non-standard process should always include a grayscale, IMO. It easily shows any crossover.

In my view this sort of test is the most obvious way to somewhat conclusively prove things out. I say "somewhat" because the lighting conditions are not specified nor are any reference colors in the scene, etc., other than a gray ramp. Now, if a gray scale shows a visual color shift this is pretty conclusive that there is a color cross. But a good gray scale does not prove the absence of ANY color cross.

I recall as a youngster being involved with such tests and finding significant color crosses in the skin tones, but NOT in a gray scale. At the time it seemed surprising, but when one thinks about the situation it is apparent that the gray scale is using a more or less equal balance between the cyan, magenta, and yellow dye layers of the film. Whereas with a flesh tone this relationship between the film dye layers is significantly unbalanced. So if interactions between dye layers are used as a means of controlling color reproduction then one can see how the two color scales (light to dark) might have different color cross characteristics.

A good point, RPC, in respect of your suggested test.. My problem which you may have gathered is that what I look at governs what I see and what I see depends on what I look at.

And I would say these are good points. So as I consider what I think you are looking at, ok there are original scenes that you presumably did not see personally. So you don't know for sure what they looked like. Someone photographed them, developed the film, and made some darkroom prints. Then they photographed the PRINTS with a digital camera, which we presumably don't know the spectral characteristics of that camera ( but they're almost certainly not a match for the human eye, which is what photo printscare really intended for). Then the prints and negs were sent to a different person who substantially repeated the process. Then the digital images were uploaded, and you viewed them on a monitor (with its own spectral characteristics). That's what you are using to make a judgment, right?

Now personally I would not wanna make too many conclusions from this sort of data. Now, if someone specifically wanted me to, I'd probably ask for a somewhat universal color reference, such as a Macbeth ColorChecker with its known spectral characteristics, to be included in the scene. Then I could at least sort of qualify the digital images (I wouldn't do it visually; I'd look at the RGB values in whatever color space is used, then convert these to CIELAB color, then compare against what the Macbeth chart nominally is. Without this, I wouldn't want to make any hard judgments about the film results.

I've spent a lot of years working with color printing (large scale, overseeing QC and solving lab color problems), and I know how touchy it is getting consistent good color reproduction in portrait work. So if the process varies significantly from spec I take it almost as a "given" that there will be unwanted color crosses. For reference I described some of the testing in this post: https://www.photrio.com/forum/posts/2192714/
Now, I've been specifically trying to keep my nose out of this thread, as I recognize that a group of people are trying to explore this situation, and come to their own understanding of how such things work. But I think that RPC's position should be taken seriously, so I'm just weighing in a bit.

Ps, I should point out that the sort of testing I was involved with was specifically directed at studio portrait work. If we had been involved in photographing brightly colored cars, or perhaps foliage and flowers, etc., the test scenes and methodology would have probably been quite a lot different.

 

[pentaxuser]

Thanks Mr Bill and I agree that RPC's test is a pretty good test of the existence of colour crossover. In my case I haven't come to a conclusion but would like to try to do so and so far I have found this difficult with what appears to be conflicting evidence.

What concerns me to an extent and this is even more concerning in the other thread started by Bormental about Ektar, is that if there is a problem in a scan which fails to conform to what another person believes is what it should look like then the fallback is to cite colour crossover as the cause without suggesting a route by which to navigate to the truth or being prepared to answer perfectly reasonable questions asked by what they seem to regard as "upstart crows" instead of saying to themselves that these are questions that deserve answers that can cover what has been asked.

The problem with colour crossover is that without a rigorous route to examine and test the truth of whether it exists or not in a negative is that those who may admittedly have a lot of experience of C41 development and believe they know the cause which usually is that of the fallback cause of colour crossover, end up answering the disinterested outsider's questions with the kind of answers which border on saying it is a form of science that is a little like alchemy that only a few of us are given the privilege to understand.

pentaxuser

 

[David Lyga]

Thanks Mr Bill and I agree that RPC's test is a pretty good test of the existence of colour crossover. In my case I haven't come to a conclusion but would like to try to do so and so far I have found this difficult with what appears to be conflicting evidence.

What concerns me to an extent and this is even more concerning in the other thread started by Bormental about Ektar, is that if there is a problem in a scan which fails to conform to what another person believes is what it should look like then the fallback is to cite colour crossover as the cause without suggesting a route by which to navigate to the truth or being prepared to answer perfectly reasonable questions asked by what they seem to regard as "upstart crows" instead of saying to themselves that these are questions that deserve answers that can cover what has been asked.

The problem with colour crossover is that without a rigorous route to examine and test the truth of whether it exists or not in a negative is that those who may admittedly have a lot of experience of C41 development and believe they know the cause which usually is that of the fallback cause of colour crossover, end up answering the disinterested outsider's questions with the kind of answers which border on saying it is a form of science that is a little like alchemy that only a few of us are given the privilege to understand.

pentaxuser

In my entire 70 years I have yet to hear a response as targeted, succinct, and all-encompassing as this. - David Lyga

 

[MattKing]

Thanks Mr Bill and I agree that RPC's test is a pretty good test of the existence of colour crossover. In my case I haven't come to a conclusion but would like to try to do so and so far I have found this difficult with what appears to be conflicting evidence.

What concerns me to an extent and this is even more concerning in the other thread started by Bormental about Ektar, is that if there is a problem in a scan which fails to conform to what another person believes is what it should look like then the fallback is to cite colour crossover as the cause without suggesting a route by which to navigate to the truth or being prepared to answer perfectly reasonable questions asked by what they seem to regard as "upstart crows" instead of saying to themselves that these are questions that deserve answers that can cover what has been asked.

The problem with colour crossover is that without a rigorous route to examine and test the truth of whether it exists or not in a negative is that those who may admittedly have a lot of experience of C41 development and believe they know the cause which usually is that of the fallback cause of colour crossover, end up answering the disinterested outsider's questions with the kind of answers which border on saying it is a form of science that is a little like alchemy that only a few of us are given the privilege to understand.

pentaxuser

Crossover is a fault.
It can be caused by several things.
Some of those things didn't exist before digital processes existed, while others have a longer history. Developing film to non-standard targets almost by definition leads to colour response that differs in contrast between the different colour emulsions. If those emulsions have different contrast, every scene with a range of tones will exhibit crossover.
It frequently gives you really ugly prints.
It sometimes is harder to see, because its visibility varies with your subject.
There are no good solutions for it if you print optically, although there are some techniques that can make it appear less obvious or objectionable.
There are digital techniques available that can sometimes minimize or essentially eliminate it, but they require that the operator have really good post-processing skills and significant experience with dealing with colour channels separately - all of which requires scans that retain a lot of colour detail.

 

[Raghu Kuvempunagar]

Is there a principled method for detecting and measuring colour crossover in colour image processing literature? Strangely I couldn't find anything on this subject on google scholar which makes me wonder if this phenomenon has a different scientific term. There are a couple of patents that mention anti-colour-crossover agents in colour emulsions but there's not much discussion on what they do.

 

[pentaxuser]

Is there a principled method for detecting and measuring colour crossover in colour image processing literature? Strangely I couldn't find anything on this subject on google scholar which makes me wonder if this phenomenon has a different scientific term. There are a couple of patents that mention anti-colour-crossover agents in colour emulsions but there's not much discussion on what they do.

It's interesting you should say this, Raghu, as it mirrors my findings as well. On a lot of subjects a diligent search on Google usually turns up some useful information but none that I could find on this subject.

I'll visit Mr Bill's link and Matt gave a good description of what he would expect to see if there was a colour crossover in a portrait using one of his own portraits but on most other situations short of a picture of a Macbeth chart any colour crossover can be near impossible to detect unless you were the taker of the picture and have a very good memory of what was there in terms of colours and what the actual shadows were like in terms of colour changes

Unfortunately for those wishing to learn there are contributors who are usually very experienced and this be part of the problem, who take dogmatic stands on issues to which they believe they have the answers so who do not wish to entertain replies to questions which may cast doubt on their entrenched positions.

Seeking the truth then becomes as about productive in achieving this as does wrangles between politicians where entrenched positions is the "rule of the house" and always overrides the truth

pentaxuser

pentaxuser

 

[pentaxuser]

In my entire 70 years I have yet to hear a response as targeted, succinct, and all-encompassing as this. - David Lyga

Thanks David for those kind words.

pentaxuser

 

[RPC]

Crossover manifests itself with unwanted shifts in color with changes in density. You'll have it when characteristic curves (plotted exposure vs.density measurements of the cyan, magenta, and yellow densities of a gray scale) are non-linear or non-parallel. In prints of a gray scale, if you balance the print on the middle gray patch for example, the other patches, instead of remaining a shade of gray, will have have some degree of color shift and the shift is more noticeable the more the density changes from the middle gray.

Another affect you would see would would be in shots made with different exposures. With a good film and good processing and parallel curves, you should see nearly identical color at normal, +1, +2, and +3 stops exposure but with non-linear or non-parallel curves the color would shift to some degree each exposure, and the look of the print could change as the crossover effects change.

I definitely observed crossover in the tests for this process I did a while back with curve plots made with my densitometer, as I described in an earlier post. So did Greg Davis, as I recall. Curves had both degrees of non-linearity and non-parallelness.

This, coupled with the off-color mask (another important issue IMO), certainly indicates the diluted process has observable and measurable problems compared to the standard process.. Subject matter may play a role in whether these problems are readily noticeable or not, but keep in mind they will always be there nonetheless, because of crossover and improper dye-impurity corrections.

I am not sure why there continues to be questions for anyone. Just run whatever tests you need to determine if these problems are acceptable to you if what people say or show is not conclusive or convincing, or if a greater understanding of the effects of crossover is needed. That is what I have done.

 

[MattKing]

on most other situations short of a picture of a Macbeth chart any colour crossover can be near impossible to detect unless you were the taker of the picture and have a very good memory of what was there in terms of colours and what the actual shadows were like in terms of colour changes

I think I have an idea why you are having a problem with this.
While it is relatively easy for me to observe the signs of crossover in an individual, static image - because I have dealt with a fair number of instances of crossover before - most people won't necessarily identify the problem as being crossover without actually either optically printing or digitally post-processing the image.
Initially, most people will simply notice that colour looks off. It is when they try to fix that problem - say by adding red to make the photo look less cyan - that they notice that while the highlights look neutral (less cyan) and therefore better, the shadows turn red, and look far worse.
With crossover, any change that improves the look of one part of the image will most likely make another part of the image look worse. In some cases, and with some images, that result can be acceptable, if not ideal.

 

[pentaxuser]

Iread Mr Bill's link which was specifically about colour film's latitude for under and over exposure but did touch on colour crossover. Not sure I learned a lot about colour crossover except that it depends on a large number of factors and for most users it may never "show its face" which is what counts for most users.

I did learn or rather had reinforced my previous conclusions about certain members' willingness to engage in any open discussion if others ask for evidence or appear to disagree with their findings. Any mention of Ektar in one member's case and any hint of over-exposure act as "trigger words" which sets in motion predictable responses.Unfortunately this can quickly deteriorate into being talked at rather than talked to if you are judged to be less experienced and thus not really an equal.

On some threads you learn about things that help you but on a lot more threads I find you learn about people. So I am a wiser man in that sense but not necessarily one who has learned more

pentaxuser