An alternative to Negative Lab Pro and Lr has to exist (C-41 reversal and orange mask removal)?!

Photo Engineer

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No, you are correct Adrian. You measure the densities of the mask to R/G/B and then set R=0. Once that is done, the G and B numbers become the needed offset.

The next thing we do in design is to add about 50R + a fudge factor for the average darkroom enlarging lamp and to give us some leeway to avoid any Cyan filtration.

If you do a raw sensitometric exposure of color paper to white daylight or tungsten you get a red step wedge that goes to black at Dmax.

PE
 

Adrian Bacon

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Ok. That’s what I thought. Thank you.
 
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Helge

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You only have to look at a non-demosaiced pre-RAW and/or a naively demosaiced images, to realize how much of a digital cameras final images are interpolation and "educated guesses".

I'm well aware that human sensory perception of unprocessed data is not to be trusted, but here the case is quite clear and can be backed up by actual numbers and delta data.
A good amount of the smooth look and high acutance (mistaken for sharpness or resolution in lay speak) that lured people to digital in the first place, and what is now the unfortunate normal, is due to demosaicing. Whatever implementation of it, that might be, there is still only the same basic kind if data to work with. And only so many things that can be done with it.
The effect demosaicing has on edges and fine, high contrast detail is basically close to what a sharpening algorithm does. You can of course roll the effect back, but that will just result in more guesswork.
Sensor shift and individual RGB sensors of course introduce a whole set of new problems.

WRT resolution, of course a large percentage of my images are just one shot frames done as a contact sheet equivalent or for web-use. But, it's always nice to have the option of high resolution.
You might want to crop, you might want to degrain with software on film you pushed hard, or you might once in a blue moon want to print really large.
 
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Adrian Bacon

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Film rolls contrast off as you record finer detail, which has quite a bit of clamping effect on the awful things you’d otherwise see if you originally shot the image directly into the bayer sensor instead of shooting it on film and “scanning” it with a bayer sensor.

A lot of the common visual artifacts introduced with a bayer array and related interpolation aren’t necessarily a 1:1 when scanning film with a bayer array. I’m not saying it doesn’t happen, it’s just not as unpleasant.
 
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Helge

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True. You'll still want to sharpen your file somewhat, just as you'd control various other parameters on RA4 in the darkroom though.
Bayer artifacting could theoretically get in the way of that.
"People", not you I know, often forget that a negative is the raw data, not the finished product. Often you hear naive "purists" proudly declare how little "manipulation" they've done to the inverted negative.
 
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Helge

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The whole role played by the orange mask talked about above, is something you'll see discussed a lot with a search. With wildly conflicting statements often by very cocksure people too.
It's something I've never quite been able to wrap my head around. IE how a varying mask (not a simple filter) can be can be satisfyingly "removed" with a simple linear filter.
But that seems to be what is happening in the color enlarger/RA4 process.

Some other questions never answered clearly is:

- Does the mask play a beneficial role outside of wet printing? That is, does it improve fidelity of the colours in the negative?
- Could C-41 film be made faster or otherwise better by not including the mask, if scanning only was the intent (you might even consider backing the film with an opaque retroreflector for really fast (at all costs) film)?

I'd very much hate to lose the option of high quality RA4 printing, since there is a clear difference in quality, and a very special magic about the IQ.
 
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Adrian Bacon

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Of course, but let’s be clear here: there’s a difference between manipulations done to get to something that you can see in LR/PS and manipulations you do after that point. The before is necessary stuff so you even have something, and the after is creative choices driven by artistic vision and what the final output will be.

I have plenty of images where my after point was a little spotting for dust, maybe an exposure tweak, a little cropping and output sharpen on the way to Instagram or jpegs for sharing.

On the other hand, if it’s going to be a print, a lot more work goes into it.
 

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All dyes have impurities in their spectra. You have a negative image of what you want plus the impurities. The mask forms a positive image of the impurities and is proportional to the density of each individual dye. Thus, as far as the paper or scanner is concerned, the impurities are removed or in effect, absent. I rarely need to manipulate a scan or a wet print. Except that in the case of a wet print I sometimes have to tweak the filter pack. My scanner does it pretty much automatically.

W. T. Hanson has written some articles and a book on this and Mees and James has a chapter on it.

PE
 
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Helge

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Thank you PE! Good to get a clear answer from a reliable source.
And as usual the right citations are golden keys to unlock a cascade of great stuff.
https://www.osapublishing.org/josa/abstract.cfm?uri=josa-44-2-129

Tadaaki Tani, Photographic Science: Advances in Nano-Particles, J-aggregates and Dye Sensitization Page 188 bottom, also has a brief but good and illustrated explanation.
 

Lachlan Young

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Having looked more closely at the way the 'divide' blend mode works, given that it's essentially taking the sampled colour & dividing by itself, producing white on the un-inverted negative rebate - thus we're probably ending up at a similar point from slightly different approaches.
 

Adrian Bacon

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I found a few other posts from you where you referenced using the divide blend mode and went and looked it up myself... the operation is basically divide the base layer by the blend layer. It’s better than using just the levels layer, but doesn’t have the same exact effect as a straight global raw multiplier, though if it works and creates the intended output in your color pipeline, then that’s all that really matters at the end of the day.
 

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I'll have to look at it but Tani is a very good source of information. He was head of the film R&D unit at Fuji. A few years ago, he was in Rochester for a conference and I had dinner with him and his wife along with another Kodak friend. Quite an interesting person. He was using an experimental slide film in his camera at the time. He had me take a few shots for him!

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RPC

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It's something I've never quite been able to wrap my head around. IE how a varying mask (not a simple filter) can be can be satisfyingly "removed" with a simple linear filter.
But that seems to be what is happening in the color enlarger/RA4 process..

It sounds as if you don't quite understand how the mask and orange color of a negative relate. They are not the same. The orange color of a negative is uniform, and consists of the non-uniform mask PLUS what it is masking: dye impurities.

The dye impurities form a negative image as PE has said, orange in color. The mask, formed during development, forms a positive orange image and its job is to mask, or cancel the dye impurity image.

Together, the two opposite images combine to form a UNIFORM orange cast all over the negative, overlaid over the main dye image. It is this uniform orange density that ends up being removed during printing or scanning, by simple filtering/color balancing, and along with it, the effects of the dye impurities.

The mask, cancelling the dye impurities of the negative, is beneficial for any use of the negative.
 

Adrian Bacon

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This has inspired me to do some additional poking around in photoshop, which I haven't regularly used for quite a while as most of my photo work is either in my own tooling or in Adobe Lightroom, and you might be able to do something like the global multiplier with the channel mixer tool/layer. Once that is done and the mask is registering a neutral grey or white, invert it with the invert tool/layer, then use the curves tool/layer to adjust the gamma of each channel and the global contrast. It'll probably get you pretty good results with 3 layers. Of course you still have to have an eye for color to dial out the color casts and such, and make sure you do it in 16 bit with a pretty large color space or you'll get a whole pile of other artifacts that you don't want.
 

lantau

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If the mask was cancelled out it couldn't do its magic.

Thinking logically I would say we cancel the orange value that can be observed at neutral density, ie the rebates.

Where dye has formed the mask is different/modified (am I right in my understanding there?) and that Delta of the mask is not cancelled out. Instead it masks the dye impurities, cancelling out these.
 
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Helge

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I knew there was a uniform orange filter to start with, in the undeveloped film, that affected the two underlying layers.
What I probably didn't quite get was how a positive image was formed, and how it (the mask) was actually left In the final image after canceling out the uniform filter, helping canceling out the uneven response of the two dyes.

The mask is really akin to a bandpass/low pass filter and the whole setup has some resemblance to Dolby noise cancelation or perhaps AC bias on analog tape, though the analogy is not perfect.
The guy(s) who came up with this sure had been thinking long and hard about the problem. It’s not immediately obvious how such a simple tool, an orange filter, can have such results in conjunction with the dyes.

Looking at the illustration in Tani mentioned above, helped to get a handle on it.
 
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RPC

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What I probably didn't quite get was how a positive image was formed...

As I understand it, the positive mask is formed by residual dye coupler, i.e., dye coupler that does not get converted to dye during development. (That is why you see it in the rebate area.) The dye couplers of the appropriate layers are colored during manufacture the same as the dye impurities, to mask those colors (collectively orangish) after the mask is formed.
 

Todd K

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Adrian, quick question about your scanning setup, if you don't mind sharing. What are you using for negative holders?

Adrian, quick question about your scanning setup, if you don't mind sharing. What are you using for negative holders?
 

Adrian Bacon

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Adrian, quick question about your scanning setup, if you don't mind sharing. What are you using for negative holders?

Enlarger negative carrier. If I'm going to make a print, it goes in the enlarger, if I'm going to scan it, it goes in the scanner. I can do single frames, or just run a whole roll through, and swap different carriers out for different film sizes, etc. Pretty handy, and quite gentle on the film.
 

GLS

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This approach also works very well for DSLR macro scanning. I use a glassless negative carrier for that.
 
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Helge

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The "guys" are Wesley T. Hanson and Paul W. Vittum. The former has co-authored a major text on the subject as noted above.

https://ethw.org/Wesley_T._Hanson

PE
I encourage anyone and everyone to watch the video in the link from PE. Most interesting piece of media I consumed in a long time.
The stories Mr. Hanson did tell, and could have told given no NDA and more time. Mind boggling!
Many of them I knew beforehand by it gives them a completely different flavour to hear them from the horses mouth.

Around 1:04 he tells of how he had the idea of the orange mask, as a flash of inspiration one night lying in bed.
And somehow you know he's not gilding the lily when you hear him tell it.

Also the story of abandoned single layer Kodakchrome is very interesting.
But all of this video is riveting!
 
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Helge

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This approach also works very well for DSLR macro scanning. I use a glassless negative carrier for that.
I find glassless holders and slide frames very overrated. It's far more important to have the negative as flat as you can. Glassless is never going to achieve that.
Use a drop of scanning fluid or just plain naphtha to get very little material to material optical loss or Newton rings.
 
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