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

[Photo Engineer]

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]

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

Ok. That’s what I thought. Thank you.

 

[Helge]

There seems to be a fair amount of concern over using a bayer array and it causing problems with scanning film. As a user of a bayer array based scanning system, it's much less of an issue than what people probably think it is. A modern APS-C based camera has been at the 24MP mark for quite some time. At 240 pixels per inch print resolution, it will make a very nice looking 16x24 inch print of 35mm or 16x20 print of a 6x7 120 frame. Modern Bayer interpolation algorithms are very, very good. While 16x20 is not a large print by large print standards, it most definitely is not a small print, and based on the number of requests I get to make prints, is absolutely on the large end of what is generally printed. 5x7 followed very closely by 8x10 and 11x14 by a distant third is what I get most requested to print. Every once in a while I'll get a request to do something larger, but I easily print hundreds of the other sizes for every 11x14, and dozens of 11x14s for every larger request.

Don't get me wrong, I'm generally all for more resolution, but there seems to be a bit of a disconnect between how much resolution people want to scan at and how much resolution you actually need for common stuff. If you're worried about the bayer array causing weird aliasing artifacts with the film grain, you maybe might have to worry about that if the particular camera you're using doesn't have a low pass filter (like some Nikon models), but for pretty much everything else, there's a low pass filter that does a very good job mitigating problems without completely destroying fine detail. The camera manufacturers are not dummies when it comes to this sort of thing. Combine that with the somewhat random nature of the grains/dye clouds and the modern AHD Bayer interpolation and the whole "artifacts from the bayer array" thing hasn't really been much of an issue in my experience. Of course I get the occasional comment from a customer about how big the grain of some emulsion is when somebody takes one of my DNGs and looks at it at 1:1 or 2:1 in the LR develop module. I inevitably have to gently remind them that when they do that, they are effectively blowing it up to a giant print (by giant print standards) and looking at that with a magnifying glass, and that maybe a more realistic way to look at it is to put it full screen on their big 60-70 inch 4K TV and see what that looks like instead. Almost always, once they do that they comment that it looks a lot better that way and is pretty sharp. And that's with a 35mm frame size. A 4K TV is ~8MP and looks really good, even at the large end of the TV scale.

The point is, more resolution is generally better, but in reality, for most display purposes, you actually need a lot less than you think you do, and 24MP covers a really large swath of that. If you want to scan 120 and 4x5 with a 50MP Canon 5Ds, you can and it will look better than a 24MP scan at really large print sizes, but again, now we're getting into truly ginormous prints. Just some food for thought.

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.

 

[Adrian Bacon]

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

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.

 

[Helge]

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.

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.

 

[Helge]

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.

 

[Adrian Bacon]

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.

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.

 

[Photo Engineer]

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

 

[Helge]

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]

I’m interpreting “speed offset in the layers” as a global multiplier if done digitally, as the net result is the orange cast is effectively dialed out as a result of the multiplication that is effectively happening as a result of the layer speed differences.

If that is the case, then doing a raw global multiplier on each channel to dial the mask out isn’t totally wrong, as that produces the same effect as having each layer a different speed.

The mask itself still might have a response curve, but that doesn’t appear to be doing any harm to the image, at least in my setup.

Feel free to correct, as I’m finding this discussion to be very interesting

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]

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.

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.

 

[Photo Engineer]

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.

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!

PE

 

[Photo Engineer]

You may want to check out Evans, Hanson and Brewer, the go-to book on color photography.

PE

 

[RPC]

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]

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.

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]

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.

 

[Helge]

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.

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.

 

[Photo Engineer]

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

 

[RPC]

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]

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

I use a strobe diffused through a custom diffuser with enough separation between the film and the last diffuser stage that its completely out of focus and therefore a very smooth and diffuse light source. The strobe gives me very consistent and repeatable results, and I don't have to worry too much about light contamination because I'm operating at f/11 to f/16 at 1/250, which is easily several stops above the ambient room light. If the strobe don't fire, you get a black frame, when it does fire, you get the absolute minimum amount of anything that might introduce vibration induced blur. 35mm film can sometimes be a bit finicky with focus, especially if it's got a strong curl along it's longitude, but for that, I just go up to f/16-f/22 and turn the strobe power up. There's a little added diffraction, however, I'm using a very expensive macro lens, and with it, my setup is over 4000dpi for 35mm film. Jpegs scaled down to even a quarter of the resolution of the native sensor resolution have a *crazy* amount of fine detail. I'd rather have it in focus, than go for maximum sharpness and struggle with having frames in focus. For 120, there's close to 2 feet between the film and sensor. F/11 is plenty of DOF there. For me, going the DSLR route with custom software is a simple matter of speed. I can buzz through a freshly dry roll of 36 exposure film and be looking at the entire roll in LR in less than 15 minutes, with little to no retouching except for a spot of dust/fiber here or there, or the occasional scratch, and at most, some basic Develop Module touch ups if that.

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

 

[Adrian Bacon]

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]

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.

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

 

[PhilBurton]

How can I find out about NLP and how it makes better conversions then those you listed?

It took some creative searching, but I found the right link:

https://www.negativelabpro.com/
Looks interesting. But from what I learned scanning the GUIDE, it's really for post-processing a negative in Lightroom, not a replacement for scanning software.

Phil Burton

 

[Helge]

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!

 

[Helge]

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.