Jump to content

Is it possible to get wide gamut color out of Scanstation scans (color primaries wider than sRGB/REC709 locations)??


Larry Baum

Recommended Posts

  • Site Sponsor
12 hours ago, Phil Rhodes said:

One issue which springs to mind here is that this is, we're told, a scanner using RGB illumination and a monochrome sensor. Much as that's great with respect to getting no-compromise cosited RGB information, using LEDs to do this does raise a couple of concerns. There's a decent red emitter available, but most (not all) LED blue is more royal blue than the deep indigo we might prefer. Green-emitting diodes, in particular, are notoriously not a very deep green. I have never looked into this formally, but I would speculate fairly confidently that there are deeper greens in film negative than the green of the sort of LED that is likely to be used in this sort of application.

 

For what it's worth, the filters on a Bayer or other CFA sensor also tend to be rather feeble and that's one reason Bayer cameras struggled for years to produce workably accurate colour, until people got smart enough to apply a lot of matrixing. This probably wouldn't ywork so well with RGB LED scans because the problem isn't solely that the green is unsaturated - it's pretty saturated - it's just too yellow. There is not much ability to fix this sort of thing in post.

Does any of that make sense to anyone?

1. There are more expensive LEDs which are in the right color spectrum range for film scanning and also for LED high CRI lighting, so it is just a matter of cost and devices for the LED Lamp for any of these scanners.

2. There is allot Alooooottt of color channel cross talk with any Bayer mask sensor, the dyes used are not strong like a dichroic filter. So that is the big disadvantage with a fast CFA scanner, just like with the digital cinema cameras. A matrix or LUT or combo can tune the system back to better especially if the LED lamp if properly balanced for the film and the CFA of the sensor before a matrix transform is applied.

Edited by Robert Houllahan
typo
Link to comment
Share on other sites

  • Premium Member
26 minutes ago, Robert Houllahan said:

There are more expensive LEDs which are in the right color spectrum range for film scanning and also for LED high CRI lighting, so it is just a matter of cost and devices for the LED Lamo for any of these scanners.

If we're talking about CRI, we're talking about principally white light. Are they using white-emitting, phosphor-converted LEDs for these scanners, then filtering it green for the green flash?

Link to comment
Share on other sites

  • Site Sponsor
14 minutes ago, Phil Rhodes said:

If we're talking about CRI, we're talking about principally white light. Are they using white-emitting, phosphor-converted LEDs for these scanners, then filtering it green for the green flash?

No and LED fixtures like the Arri Skypanel or the Aputure LED do not either they use RGB LEDs similar to the scanners.

 

From Arri:

 

"

SkyPanel is a compact, ultra-bright and high-quality LED soft light that sets a new standard for the industry. With a design focused on form, color, beam field and output, SkyPanel represents the culmination of more than a decade of research and development of LED technology at ARRI.

Incorporating features of ARRI’s successful L-Series LED Fresnels, SkyPanel is one of the most versatile soft lights on the market, as well as one of the brightest. The SkyPanel ‘C’ (Color) versions are fully tuneable; correlated color temperature is adjustable between 2,800 K and 10,000 K, with excellent color rendition over the entire range. Full plus and minus green correction can be achieved with the simple turn of a knob. In addition to CCT adjustments, other control options are available such as: hue and saturation, gel selection, RGBW, source matching, x,y coordinates, and 16 professional lighting effects programmed into every fixture."

Edited by Robert Houllahan
More info
Link to comment
Share on other sites

  • Premium Member

Well, they use RGB plus white, or the colour quality would be horrible (and the colour quality on a skypanel isn't the best in the world anyway, but that's a topic for another day). The concern over the scanners using green LEDs for the green flash remains; is that what they're doing?

Link to comment
Share on other sites

13 hours ago, Phil Rhodes said:

One issue which springs to mind here is that this is, we're told, a scanner using RGB illumination and a monochrome sensor. Much as that's great with respect to getting no-compromise cosited RGB information, using LEDs to do this does raise a couple of concerns. There's a decent red emitter available, but most (not all) LED blue is more royal blue than the deep indigo we might prefer. Green-emitting diodes, in particular, are notoriously not a very deep green. I have never looked into this formally, but I would speculate fairly confidently that there are deeper greens in film negative than the green of the sort of LED that is likely to be used in this sort of application.

This would intrinsically clip the colourspace of the scanner in a way that you can't really do much about and that would be a shame.

They're using LED lights specifically designed for scanning film, not off-the-shelf products.

13 hours ago, Phil Rhodes said:

Alternatives would be to use a more full-spectrum light source and dichroic filters, which would end up looking rather like the part of a contact or optical printer that responds to colour timing numbers. I can fully understand that the designers of these things might prefer to avoid the cost, bulk and maintenance issues of a complex piece of mechantronics like that, and so an easier approach might be to use phosphor-converted white-light LEDs and filter their output green. This would be very inefficient, optically, but for the sake of a scanner that might be a worthwhile tradeoff.

You're describing the old lights used 20 years ago. Like this :

light-source-xenon.thumb.png.dc607502d3700afc9af3bc739022959b.png

Full-spectrum light with dichroic filters. If doing it this way was the best way to do it today that's how it would be done in the best modern scanners - but they don't because this is an old solution engineered prior to the LED technology available today. The solution was already engineered, the earliest Arriscan (launched in 2004) probably had a very similar light. It's also not all that complicated really, I cannot see this system significantly adding to the cost of production. I can think of one reason not to do it, and that's flicker. How do you eliminate the flicker inherent in Xenon lights? Another problem is brightness - Xenon lights lose their brightness and become dimmer over their lifespan, for projection that's not so important but for scanning you want a consistent brightness.

Link to comment
Share on other sites

  • Premium Member
9 hours ago, Dan Baxter said:

They're using LED lights specifically designed for scanning film, not off-the-shelf products.

Sure, fine, but in the end there are only so many arrangements of physics that actually create green LEDs. In the mainstream there's really two,  types based around gallium phosphide, which are the rather feeble grassy-yellow-green variety used in indicator lights, and types based around gallium nitride, sometimes called "pure green". It's not as if some designer somewhere has the ability to use the some kind of super-deep-green LED because it doesn't exist, just as very deep blues didn't until fairly recently (and are still rare and expensive).

Actual Xenon lights, at least of the type used in film projectors, are DC driven and don't flicker (otherwise they wouldn't work in film projectors). If we're talking about arc and discharge lights generically, a lot of scanners (certainly Spirit and Northlight) absolutely do use various types of short arc or metal halide light sources and presumably use flicker-free ballasts to avoid issues. Again, modern video projectors tend to use light sources of this approximate type and would suffer terribly if there were unsolvable flicker issues.

And yes, that's the sort of light box I had in mind. It could be driven by an LED source, although the result might lack deep indigo.

rgb-lights-color-printing-800x600.jpg.a00f111be3e20059402a1531916a7400.jpg

Presumably someone has actually done all the work on this and figured out whether film stock really does have a colour gamut larger than the one created by RGB LEDs. I haven't compared the output of either of the common green LEDs to the greens of film stocks and I'm speculating, but I wouldn't be too shocked if it presented a limitation.

Link to comment
Share on other sites

Well green light gets you the magenta emulsion layer with some limited (ideally nil) cross-talk from the others, I've never heard of magenta/green being difficult to capture it's usually yellow/blue that's difficult.

That looks like a photo from an optical printer?

Link to comment
Share on other sites

  • Site Sponsor

The Spirit (all versions) uses a Xenon lamp (700w on the newer 2K/4K) and it has a filter wheel and a few other filters auto drop in which alter the light before it hits the quartz rod to illuminate the line slit on the gate. These filters do not do RGB balance but are for different stocks like positive or negative etc. The color separation is done with dichroic filters on the CCD line arrays.

There was a telecine made by Sony called the Vialta that initially had a Xenon lamp and a dichroic box like the B&H printer and a F950 3xCCD camera image head. I know they eventually went to RGB LEDs for the lamp house in a version upgrade. As far as I know that early Vialta was the only Xenon RGB balance-able lamp house scanner made. Everything else has been a hot lamp Xenon or Metal Halide (Northlight) etc or eventually individual RGB+IR LEDs

The Arriscan has always been RGB+IR LEDs in a (beautifully made) integration sphere. The Northlight 1 and 2 eventually saw FilmLight make a RGB+IR LED replacement lamp.

I think with the right high end RGB LEDs (maybe a mix of 2 colors of R and G ?) that LEDs work as all the scanners running these days (except the Spirit 2K 4K) are running some form of LED lamps. I am not exactly an engineer but nobody is complaining about Arriscan or Scannity scans color fidelity as far as I know.

I was thinking that a newer daylight balanced Xenon equivalent LED film lamp might be a possible replacement for the Xenon lamp in the Spirit 2K/4K series scanners to keep these true RGB scanners relevant.

Link to comment
Share on other sites

3 hours ago, Mark Dunn said:

I'm afraid B&H has you beat on lamphouse porn. Unless you fire it up, maybe.......?.

 

Well, this isn't BH, this is the cine' forum where few members contribute photos. So, you must be grateful for any photo sent in. If and when I get a 4K+ scanner I will send you in gobs of photos and scans. I got close to 3,000 films and I like love visuals. 

Pretty interesting about the filters. Can you bring back faded red film as good as the Lasergraphics color correction Robert by filter adjusting?

You should start a blog on such things Robert showing various color corrections and showcasing your various scanner's abilities.

Start with these Robert and illustrate them...don't you have lacky interns to do such things Robert? You are an unusual character Robert, in that you talk about your willingness to experiment for clients. Maybe that is standard for the cine' industry, but it is not in other areas where people won't cater at all to change and tests. Illustrating your tests should be right up your alley Robert.

CINELAB FILM SCHOOL AND FAQ:

What’s the difference between a one-light workprint and a timed workprint?
When you get a One-Light Print, we determine the best average exposure at which to print the entire roll. For a timed print each scene is checked for density and is color corrected.

What is a PUSH or PULL process?
Push processing compensates for underexposed film by overdeveloping it. Pull processing compensates for overexposed film by underdeveloping it.

How many stops can film be pushed/pulled?
Two stops is the maximum this lab will push or pull film. We can only push or pull BW Reversal one stop.

What is the difference between best-light and scene-to-scene color corrected ?
A best-light telecine transfer is when the colorist in the transfer suite looks through the whole film and sets the times it to the best overall look. Scene to scene color correction is when the colorist times each individual cut for optimum color and sharpness.

Can I shoot old film and what might the results be?
In general dated film has lower contrast and increased grain - this is called base fog. You should always shoot a test roll to determine the state of the stock before you begin shooting your film. We advise that you do not use dated film if the footage is critical. Older forms of ektachrome or kodachrome may require an antiquated developing process and you should call the lab to ask if it is possible for us to work with it. If not we may be able to recommend a lab who can.

Can film shot without an 85 filter or exposed in fluorescent light be corrected in the printing?
Yes, the film is color corrected in the printing process. The lab needs to know of this condition ahead of time to be able to correct it.

What is the B&W reversal process?
Black and white reversal film is processed as a positive for projection. This is achieved by the exposed silver halides being developed up to a negative in the first developer tank. Then bleach attacks these exposed silvers as black silver, washes them away and leaves the unexposed silver halides alone. The emulsion is then neutralized in a salt bath before it inters the light. At this time it gets re-exposed and the leftover silver halides get subjected to another developer which turns all the silver remaining to black silver. Then the film enters the fixer tank to stabilize and clean the clears. It is now a positive and ready to project.
 

In what order are the color layers on film?
For color negative the color layers going from the base to the surface are cyan, then magenta, then yellow.

For print film the color layers from the base to the surface are red, then blue, then green.

How to Identify a Scratch if you are shooting Negative:
1) A white colored scratch is a scratch in the base.
2) A colored scratch is a scratch in the emulsion
3) A steady scratch going from the left to the right is caused by the camera 4) A wobbly scratch is caused by the lprocessor or the film magazine.

How to Identify a Scratch If You Are Shooting Reversal:
1) A white scratch indicates the emulsion has been scratched off
2) a black scratch indicates a scratch in the base.

What is Gamma?
Gamma is the slope of a plotted graph of gray scale from minimum density to maximum density. Higher gamma values result in more contrast in the film.

What is Sensitometry?
Sensitometry exposes a stock through a gray scale to determine gamma and proper color balance, a sensiometric control strip is run before each day’s processing to assure quality..

What is a densitometer?
The densitometer is a device which measures the density of grey in a color (red, green, blue).

What is Orange Base?
This is the color of the Color Negative base carrier. It is engineered by Kodak to control color layers for optimal printing.

What is Rem-Jet Backing?
This is the black layer on the base side of the color negative before processing. It’s purpose is for static control and anti-halation (light back scatter), and transport protection. Rem-Jet is removed from the base as the first step in ECN-2 processing.

What is Cross Processing?
This is when your Ektachrome color reversal film is developed as a negative using the ECN II process. After developing, the image comes out as a negative rather than a positive. The developed film must then be printed or transferred to video. With cross processed ektachrome, a very different image appears. The red/green/blue gamma lines will show some crossover causing different color relationships from shadows to highlights. Black and White Reversal can be cross processed as negative too, but the look of the film is not altereed other than the fact that it comes out as a negative instead of a positive.

What is an answer print?
An answer print is the first printed version of the film that has been color corrected and the sound synched.
What is a release print?
A release print is the final version after all necessary adjustments have been made.

Should I push/pull the film OR process normal and time the print?
In general, film should be pushed or pulled and then printed normal. If the film is underexposed definitely push. If the film is underexposed more than 2 stops you should re-shoot. If film is overexposed one stop, process normal and time the print. If film is overexposed more than 2 stops pull the processing and time the print.

What is wet-gated or liquid gate?
A process to print the film that helps to minimize and hide scratches on the base of the film.

What is a Keycode?
Film manufacturers embed numbers on the edge of the film. These unique to the film numbers are not visible until the film is processed. When the film is processed, the numbers are then visible and used to identify and count frames.

 

Edited by Daniel D. Teoli Jr.
Link to comment
Share on other sites

On 10/13/2022 at 7:29 AM, Phil Rhodes said:

Sure, fine, but in the end there are only so many arrangements of physics that actually create green LEDs. In the mainstream there's really two,  types based around gallium phosphide, which are the rather feeble grassy-yellow-green variety used in indicator lights, and types based around gallium nitride, sometimes called "pure green". It's not as if some designer somewhere has the ability to use the some kind of super-deep-green LED because it doesn't exist, just as very deep blues didn't until fairly recently (and are still rare and expensive).

Actual Xenon lights, at least of the type used in film projectors, are DC driven and don't flicker (otherwise they wouldn't work in film projectors). If we're talking about arc and discharge lights generically, a lot of scanners (certainly Spirit and Northlight) absolutely do use various types of short arc or metal halide light sources and presumably use flicker-free ballasts to avoid issues. Again, modern video projectors tend to use light sources of this approximate type and would suffer terribly if there were unsolvable flicker issues.

And yes, that's the sort of light box I had in mind. It could be driven by an LED source, although the result might lack deep indigo.

rgb-lights-color-printing-800x600.jpg.a00f111be3e20059402a1531916a7400.jpg

Presumably someone has actually done all the work on this and figured out whether film stock really does have a colour gamut larger than the one created by RGB LEDs. I haven't compared the output of either of the common green LEDs to the greens of film stocks and I'm speculating, but I wouldn't be too shocked if it presented a limitation.

 

Have they done any tests with RGB light for scanners versus white light scanners? 

Link to comment
Share on other sites

On 10/12/2022 at 6:26 PM, Phil Rhodes said:

If we're talking about CRI, we're talking about principally white light. Are they using white-emitting, phosphor-converted LEDs for these scanners, then filtering it green for the green flash?

 

You had better hope the companies still makes these crazy light sources when they need replacing.

Link to comment
Share on other sites

On 10/12/2022 at 1:43 AM, Robert Houllahan said:

Arriscan:

 

 

 

That's nice. Engine turning and all! You don't usually see such finishing nowadays. I will buy one as soon as the lotto hits!

Are you happy with it Robert? Although I think someone mentioned it is complex to run, so it may not be up my alley. 

Edited by Daniel D. Teoli Jr.
Link to comment
Share on other sites

On 10/12/2022 at 8:24 AM, Phil Rhodes said:

I hadn't had time to peruse this thread until today but it's quite an interesting question. I hesitate to say too much having not seen the files and not knowing much about how the scanner was set up. Even so, much as I think he was misunderstood early in the thread, I see what Larry means by his observation that the colours in the scanned files seem to clip against the edge of the sRGB/709 gamut. That's a reasonable concern and my immediate reaction would be to assume it's clipping the colour gamut.

One issue which springs to mind here is that this is, we're told, a scanner using RGB illumination and a monochrome sensor. Much as that's great with respect to getting no-compromise cosited RGB information, using LEDs to do this does raise a couple of concerns. There's a decent red emitter available, but most (not all) LED blue is more royal blue than the deep indigo we might prefer. Green-emitting diodes, in particular, are notoriously not a very deep green. I have never looked into this formally, but I would speculate fairly confidently that there are deeper greens in film negative than the green of the sort of LED that is likely to be used in this sort of application.

This would intrinsically clip the colourspace of the scanner in a way that you can't really do much about and that would be a shame.

Alternatives would be to use a more full-spectrum light source and dichroic filters, which would end up looking rather like the part of a contact or optical printer that responds to colour timing numbers. I can fully understand that the designers of these things might prefer to avoid the cost, bulk and maintenance issues of a complex piece of mechantronics like that, and so an easier approach might be to use phosphor-converted white-light LEDs and filter their output green. This would be very inefficient, optically, but for the sake of a scanner that might be a worthwhile tradeoff.

As I say, I'm speculating wildly here and much of what I've said might be utterly wrong, but feeble LED greens affect colour mixing lighting devices too, where they make it difficult to generate deep cyan and yellow-orange-red colours, which is exactly the concern Larry reports. The ability to render the deep, powerful turquoise of a tropical sea over white sand is often given as a motivation for the development of the Rec. 2020 colour gamut, which can handle those colours in a way that 709/sRGB just can't. 

For what it's worth, the filters on a Bayer or other CFA sensor also tend to be rather feeble and that's one reason Bayer cameras struggled for years to produce workably accurate colour, until people got smart enough to apply a lot of matrixing. This probably wouldn't ywork so well with RGB LED scans because the problem isn't solely that the green is unsaturated - it's pretty saturated - it's just too yellow. There is not much ability to fix this sort of thing in post.

Does any of that make sense to anyone?

 

No, sorry, too confusing for me. I would need practical application applied to the words aka I need actual comparison tests illustrating all this. 

On another topic, with all the crazy filters and colored lights you use...how does fading affect them? Do they have to be replaced regularly? Do you have tests to show when they need replacing or just do it by schedule?

BTW...I looked at Rober's Vimeo channel...he's got some weird stuff. One suggestion Robert - separate your personal material from your biz. Don't confuse the 2. It is more professional that way. 

 

Edited by Daniel D. Teoli Jr.
Link to comment
Share on other sites

  • Site Sponsor
1 hour ago, Daniel D. Teoli Jr. said:

 

Wow, you must have one of the biggest scanner collections around Robert!

Every lab I know of has a pile of scanners, Spirits and Scannity Northlights and Arriscans Golden Eyes and Oxberrys hanging around. Every lab I know of has at least one Scan Station.

Link to comment
Share on other sites

Listen up...and I'm only going to tell you this once. You need example / comparison photos on this type of thread. OK, maybe I've said it twice or ten times. Whatever...you need GD example photos!

Dye%20Transfer%20Printing%20from%20the%2

Selection from: Dye Transfer Printing from the 1950's

by

Daniel D. Teoli Jr. 

10 years ago, I was working on a project called the Encyclopedia of Photographic and Fine Art Ink Jet Printing Media. It turned out to be a massive project encompassing 12 volumes. (The reason I didn't spell ink jet as inkjet was my word processor was so old it didn't have inkjet in the dictionary and kept rejecting it!) In volume 12 I did a comparison of inkjet printing versus an Eastman Kodal dye transfer print.

For the tests I took 2 dye transfer prints, I scanned them on an Epson flatbed scanner and made 2nd gen inkjet prints from the scanned images to compare to the original prints. This tested 2 things. It compared how well a scan can reproduce an original as well as the color gamut or range of a pigment inkjet print compared to a dye transfer print. 

The notes to these tests are long gone, but I remember using invisible HDR to increase the range of the 2nd gen print.  I believe I used 0, +.5, -.5 for them. But that is not important. The question at hand was whether a pigment inkjet printer could reasonably reproduce the color gamut of a dye transfer print. While that question may not be answered 100%, my tests show that scanning can recover 85% - 90% of an original and pigment inkjet printing can reasonably reproduce the color gamut of a dye transfer print. 

Dye%20Transfer%20vs%20scan%20&%20inkjet%

The photo on the top is the original dye transfer print, the print on the bottom is the 2nd gen print made from a scan of the dye transfer print.

Dye%20Transfer%20vs%20scan%20&%20inkjet%

The photo on the right is the original dye transfer print, the print on the left is the 2nd gen print made from a scan of the dye transfer print.

Selections from: Encyclopedia of Photographic and Fine Art Ink Jet Printing Media

by

Daniel D. Teoli Jr. 

 

Edited by Daniel D. Teoli Jr.
Link to comment
Share on other sites

22 hours ago, Robert Houllahan said:

Every lab I know of has a pile of scanners, Spirits and Scannity Northlights and Arriscans Golden Eyes and Oxberrys hanging around. Every lab I know of has at least one Scan Station.

Who has the most impressive collection you ran across Robert?

Link to comment
Share on other sites

  • Site Sponsor
8 hours ago, Daniel D. Teoli Jr. said:

Who has the most impressive collection you ran across Robert?

These machines are tools for work and not classic cars I would not characterize them as "collectable" really.

Big post houses bought new scanners as new tech allowed for better and faster scans.

I think Co3 was running something like fifty scanners at one time. I know they had more than a dozen "classic" Spirit SDC2000 machines in a room with suites upstairs in NYC when they were uptown. They also had Spirit 4K and Arriscan and maybe Northlight machines in other rooms for DI work.

Postworks (used to be Technicolor-PW) in NYC has maybe ten spirits in the basement and two running along with a Scannity and Arriscan, if you watch "Succession" on HBO that is where it was scanned.

So IDK who has the biggest pile of machines it is not me.

Link to comment
Share on other sites

Unfortunately and shockingly, it's starting to seem like I was correct.

One scanner doing experiments and someone from another forum (apparently someone contacted some expert at film-tech and he seemed to come to the conclusion that it surprisingly outputted only REC709 color primary referenced data and simply clipped away all the extra rich, beautiful colors that 35mm film can record that go beyond that) seem to be reaching the same conclusion, that the Lasergraphics Scanstation 6.5K is absurdly appearing as if they remap the wide gamut output the hardware produces to the limited sRGB/REC709 color gamut in their software before outputting files. If they force the data to use REC709 primaries they seem to agree that the colors then look most natural and if they force the primaries to be interpreted as various wide gamuts it seems to come out over-saturated and/or odd. Nobody can seem to get a straight answer from Lasergraphics and they seem to be very evasive and stonewalling even to owner's of the machine who pay $$$$$$$ each year for service contracts. Honestly, they could simply add an option to allow for full native scanner gamut output and do it in less than a single afternoon but it seems they have no intention and maybe are afraid to do that since then they have to go tell everyone that all they scans they ever did, all the films archived by film archives and museums and so on had the color gamut clipped? It would seem a horrible shame to think of many films that got their one and only scan done without anyone realizing that the color gamut was clipped and that maybe for all time the original colors will be lost as the original film rots and fades and the digital archive failed to capture all the colors. I dunno how how a tens of thousands of dollar machine could do that when a $500 stills scanner over a decade ago could easily do wide gamut. And it's nothing to do with Bayer, almost every single DSLR has a Bayer sensor and even the 1st Canon 10D DSLR did wide gamut color. So does the camera inside of the Scanstation 6.5K.

I dunno, I wish I was wrong, but it is starting to seem like I was likely correct. I mean maybe I and some others now are wrong and I'm saying very unfair things about Lasergraphics, don't take this as 100.000000% proven gospel, but it's sadly sure looking like I was correct. I'll be able to judge more myself when I get some full scans back soon and also get a color chart scanned. Hopefully I'll be proven wrong, doesn't seem like it. We'll see. If so, it's kinda frustating. I think even Cintel likely allows full wide gamut color capture. But the Scanstation seems to be clearly better in every other regard so kind of a shame, why have it crippled for now reason (if it really is)?

 

Edited by Larry Baum
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...