Latitude of Reversal film compared to Colour Negative

[Steve@f8]

It’s a question I’ve pushed to the back of my head, so to speak, why does Colour Reversal film have less latitude to exposure compared to Colour Negative?
Instinctively i would say it has to be the chemistry, but if asked to provide the detail I would hold my hand up high and say I haven’t got a clue. It’s a case of it just is, I’ve never thought to query it in the past.
I know there are some brilliantly knowledgeable individuals here and I’m hoping someone can explain.

 

[ic-racer]

If you are projecting it there is almost no latitude

 

[pentaxuser]

If you are projecting it there is almost no latitude

Can you expand on this? Does this mean that its latitude improves if it isn't projected? What would these ways be? I presume projection covers all ways in which the slide is viewed be that projection, on a light box with a loupe, holding up the light and using the naked eye etc

Thanks

pentaxuser

 

[Rudeofus]

If you use negative film, you create negatives with huge latitude, then print them onto a very high contrast medium to obtain pleasing, contrasty images. This allows for a wide range of exposure error, especially in the direction of overexposure. Slide film should be contrasty out of the box, so obviously there can't be much room for exposure error. Even slight underexposure will yield unacceptably dull slides, and overexposed slides will lose most of their highlight detail.

Note: if you use an ancient camera and try to guestimate exposure, you will likely get poor results with slide film. As soon as you use a modern light meter (either as part of a modern camera, think EOS 3, F6, or in form of a reasonably current external light meter), correctly exposed slides should be very easy to do.

 

[MattKing]

Wide latitude is a byproduct of low contrast.
If you project a film that has wide exposure latitude, you would be projecting a low contrast slide - yech!
Our film materials are designed with their use in mind. Film negatives are designed to be printed on to print material - that inherently increases the contrast of the final presentation result. If the negatives weren't lower in contrast, the prints would be too contrasty.
Still film positives - slide film - is designed to create a projectable, nicely contrasty image in one single step.
In the motion picture world, they shoot on low contrast negative film, then print on to projectable film, resulting in that same excellent projection print contrast.

 

[Steve@f8]

Wide latitude is a byproduct of low contrast.
If you project a film that has wide exposure latitude, you would be projecting a low contrast slide - yech!
Our film materials are designed with their use in mind. Film negatives are designed to be printed on to print material - that inherently increases the contrast of the final presentation result. If the negatives weren't lower in contrast, the prints would be too contrasty.
Still film positives - slide film - is designed to create a projectable, nicely contrasty image in one single step.
In the motion picture world, they shoot on low contrast negative film, then print on to projectable film, resulting in that same excellent projection print contrast.

Sounds like an excellent explanation.
I’m curios to know how the chemistry of the emulsion is adjusted to produce low and high contrast response, ie the transfer function.

 

[MattKing]

Sounds like an excellent explanation.
I’m curios to know how the chemistry of the emulsion is adjusted to produce low and high contrast response, ie the transfer function.

Contrast is something you tune the emulsion for - it is a target variable that every emulsion designer works with.
If you need more, you need to hear from those who do this, not me.
The emulsion making sub-forum would be a great place to ask your question in its own thread - I'd enjoy seeing the answers:
https://www.photrio.com/forum/forums/silver-gelatin-based-emulsion-making-coating.93/

 

[mshchem]

The modern color negative film is a thing of wonder. Kodak color negative film can be exposed 2 stops under and up to 4 stops over. The robot brain in your local minilab printing machine knows that you want perfect prints so it, scans the negative, adjusts the print exposure and filtration, replaces the red eye from the flash with a natural color, and does a few other things.
Cinema films, that are still made with a film movie camera, use a version of color negative film. This allows the skilled operator, in the lab, to, these days, scan each frame, adjust every variable that's conceivable, then this is scanned back onto a color print film for the rare theatre that still projects film.

Color reversal film, slide film, you get one chance to hit the nail on the head. Too much exposure (or development) you get a clear piece of film, to little it's dark or even black. The answer is to bracket exposure. My Nikon F5 camera can be set to take 3 shots in rapid secession, one at your chosen exposure then 1 a bit over and another a bit under. The values available are 1/3, 1/2, 1/7 th EV (simple terms slight adjustments, very slight more or less)

By bracketing like this it makes my 36 exposure, 18 dollar, roll of Fuji Velvia a 12 exposure roll (You pick the best of the 3). Yikes! That's a dollar and a half per slide. In the real world careful metering and some of the fancy cameras you can get 36 perfect slides.

Now the real scary part is who develops the slide film? People on this forum can reccomend the best, (Dwayne's in Kansas) it's going to cost. I process my own, that's another topic.

Back before the invention of most everything, slides were how people showed in real, amazing color, their kids, vacations, everything. Those of us that grew up with this still crave this experience, done right projections are wonderful!
I can still remember the sounds, the smell, and the colors. 60 years later I still have Kodachrome slides my Dad took when I was sitting in a high chair covered with spaghetti

That's what makes it special to me. Oh and medium format slides are like going to Imax.

Best Regards Mike

 

[lantau]

Looking at the film itself you will find that slide film has latitude similar to negative film. In practice it might be that such latitude has been more of a consideration in the R&D of negative films, because it is much used in the field. That is especially true for amateur films. Still, in principle there is no difference between E6 and C41 film in that regard.

First an example to prove my claim above: I was out shooting slide films, using Provia 400X (6x6) after a roll of Velvia 50 and forgot to set the meter from EI 50 to 400. When I noticed I was a bit upset and then adjusted the meter. The plan was to forgo the misexposed images. At home I eventually decided to develop the film into negatives in the ECN2 process (same dev agent as E6). Looking at the finished (negative) film strip I could hardly see a difference between the EI50 and EI400 portion with the naked eye. That is film latitude, I guess.

The reason why you won't have any latitude when going for a slide is that the E6 process is fixed in all its parameters. It means a certain exposure will lead to a certain result. It's a fixed relationship. If you use negative film and go to colour print in the dark room with such fixed and *predetermined* parameters you will have zero latitude just the same as for slides:

Use a roll of Portra 400 and take perfectly exposed images, e.g. incident metered in a studio. Develop in C41 and take the film strip to your enlarger. Find the parameters to make perfect prints. Then use those same parameters (exposure time of the paper, filter pack, column height, etc) unchanged for all your future printing.

Now if you overexpose your next roll of Portra 400 by two stops you will get negatives but not get a useable image on your colour paper from those. It might give a very faint image or just pure white.

The trick with negatives is that you can adjust the second half of the process to the needs of your negative, and hence of the original scene. Portra can record most of the information in the scene even when it is very overexposed. The negatives will be denser and so you'll have to increase the exposure time under the enlarger to punch through that. And you may have to adjust your colour filter pack, as well.

Slide film will also perfectly record the information when equally overexposed. But in the E6 process and with two stops under/overexposure you will develop away that information, because the first dev time has been set to obtain a certain density when the film was correctly exposed. Only that density will translate to a viewable image upon reversal.

To prove my point: When you *KNOW* that you (over/under)exposed by one stop (i.e. an intentional pull/push by one stop) you tell the lab and they will process the film accordingly by adjusting the time of the first developer. You'll get great results from that. Indeed I've heard that in the old day slide film was the way to go for pushing, because the results are better than with negative film. However, your exposure will still need to be spot on at the chosen, pushed E.I.

I have pushed Provia 400X by two stops. Gives very usable results. But the max density is slightly lowered. I don't like the look of that too much because, most of the time, I'm a contrast whore and I don't like the deep blacks becoming slightly off-black.

But pushing that film one stop to EI 800 is a no brainer. And if you digitise them you'll adjust the black point of a two stop pushed image and get a perfect result with very little grain. That being said, when digitising slides that have a slightly wrong exposure they can be fully recovered. I recently had one of those. Great sky, underexposed city. I could fully recover that in digital post. But that still leaves me with a very imperfect slide for analog presentation.

Now, you'll surely ask about dynamic range next. The contrast of the final slide is intentionally high for a brilliant result. It is like printing b/w negatives onto grade 8 paper for an incredible brilliance. A high contrast in the output medium, without the ability to cut out brightness ranges of the orginal scene (dodging, burning, masking) will reduce the maximum recordable dynamic range. It's how mathematics works...

In practice when printing in the dark room C41, too, is limited in dynamic range, unless you like burning and dodging. I don't like doing that with b/w film, let alone with colour film. My RA4 exposure times are too short to even try. And you may also run into colour shifts. If I'm lucky I will have masking equipment, eventually. In a few years, perhaps. Then I'd be able to print high contrast negatives, but with a lot of effort and extra cost of film for making masks.

The reason why many of us consider slides on a light table, or projected, to be 'nicer' than images from negatives is that brilliance of slides. The final image contrast is much higher than what colour paper or a computer screen can manage. C41 film is technically superior in its colour reproduction, but for the masses E6 will aesthetically look better than the technically near perfect C41 process.

I guess E6 vs C41 is like film vs digital (order intentional).

 

[Steve@f8]

@Iantau, brilliant explanation!

 

[Alan Edward Klein]

There's nothing like getting the exposure right in the camera.

 

[138S]

It’s a question I’ve pushed to the back of my head, so to speak, why does Colour Reversal film have less latitude to exposure compared to Colour Negative?
Instinctively i would say it has to be the chemistry, but if asked to provide the detail I would hold my hand up high and say I haven’t got a clue. It’s a case of it just is, I’ve never thought to query it in the past.
I know there are some brilliantly knowledgeable individuals here and I’m hoping someone can explain.

Color negative film has way more latitude than slides see this:



You may also see the sensitometric curves in the datasheets, each Log H unit in the horizontal axis is 3+1/3 stops

 

[Steve@f8]

Looking at the film itself you will find that slide film has latitude similar to negative film. In practice it might be that such latitude has been more of a consideration in the R&D of negative films, because it is much used in the field. That is especially true for amateur films. Still, in principle there is no difference between E6 and C41 film in that regard.

First an example to prove my claim above: I was out shooting slide films, using Provia 400X (6x6) after a roll of Velvia 50 and forgot to set the meter from EI 50 to 400. When I noticed I was a bit upset and then adjusted the meter. The plan was to forgo the misexposed images. At home I eventually decided to develop the film into negatives in the ECN2 process (same dev agent as E6). Looking at the finished (negative) film strip I could hardly see a difference between the EI50 and EI400 portion with the naked eye. That is film latitude, I guess.

The reason why you won't have any latitude when going for a slide is that the E6 process is fixed in all its parameters. It means a certain exposure will lead to a certain result. It's a fixed relationship. If you use negative film and go to colour print in the dark room with such fixed and *predetermined* parameters you will have zero latitude just the same as for slides:

Use a roll of Portra 400 and take perfectly exposed images, e.g. incident metered in a studio. Develop in C41 and take the film strip to your enlarger. Find the parameters to make perfect prints. Then use those same parameters (exposure time of the paper, filter pack, column height, etc) unchanged for all your future printing.

Now if you overexpose your next roll of Portra 400 by two stops you will get negatives but not get a useable image on your colour paper from those. It might give a very faint image or just pure white.

The trick with negatives is that you can adjust the second half of the process to the needs of your negative, and hence of the original scene. Portra can record most of the information in the scene even when it is very overexposed. The negatives will be denser and so you'll have to increase the exposure time under the enlarger to punch through that. And you may have to adjust your colour filter pack, as well.

Slide film will also perfectly record the information when equally overexposed. But in the E6 process and with two stops under/overexposure you will develop away that information, because the first dev time has been set to obtain a certain density when the film was correctly exposed. Only that density will translate to a viewable image upon reversal.

To prove my point: When you *KNOW* that you (over/under)exposed by one stop (i.e. an intentional pull/push by one stop) you tell the lab and they will process the film accordingly by adjusting the time of the first developer. You'll get great results from that. Indeed I've heard that in the old day slide film was the way to go for pushing, because the results are better than with negative film. However, your exposure will still need to be spot on at the chosen, pushed E.I.

I have pushed Provia 400X by two stops. Gives very usable results. But the max density is slightly lowered. I don't like the look of that too much because, most of the time, I'm a contrast whore and I don't like the deep blacks becoming slightly off-black.

But pushing that film one stop to EI 800 is a no brainer. And if you digitise them you'll adjust the black point of a two stop pushed image and get a perfect result with very little grain. That being said, when digitising slides that have a slightly wrong exposure they can be fully recovered. I recently had one of those. Great sky, underexposed city. I could fully recover that in digital post. But that still leaves me with a very imperfect slide for analog presentation.

Now, you'll surely ask about dynamic range next. The contrast of the final slide is intentionally high for a brilliant result. It is like printing b/w negatives onto grade 8 paper for an incredible brilliance. A high contrast in the output medium, without the ability to cut out brightness ranges of the orginal scene (dodging, burning, masking) will reduce the maximum recordable dynamic range. It's how mathematics works...

In practice when printing in the dark room C41, too, is limited in dynamic range, unless you like burning and dodging. I don't like doing that with b/w film, let alone with colour film. My RA4 exposure times are too short to even try. And you may also run into colour shifts. If I'm lucky I will have masking equipment, eventually. In a few years, perhaps. Then I'd be able to print high contrast negatives, but with a lot of effort and extra cost of film for making masks.

The reason why many of us consider slides on a light table, or projected, to be 'nicer' than images from negatives is that brilliance of slides. The final image contrast is much higher than what colour paper or a computer screen can manage. C41 film is technically superior in its colour reproduction, but for the masses E6 will aesthetically look better than the technically near perfect C41 process.

I guess E6 vs C41 is like film vs digital (order intentional).

Thanks for this comprehensive response, providing perspective on the differences.
Any thoughts (anyone) on how slide film responds in terms of exposure latitude when subject to XPRO?
Thanks.

 

[Helge]

Output media always has lower dynamic range.
Slide is it’s own output media.
You will hardly get better reproduction than an optimally exposed slide projected in the dark.
It’s a first generation image, with exceptional contrast and colour depth.
Only trouble is it’s ephemeral nature.

 

[Steve@f8]

I like the unexpected response from out of date slide, and XPRO’d slide. I get it now about slide being the output medium. But does XPRO’ing make difference (ie slide developed in C41)?

 

[lantau]

Thanks for this comprehensive response, providing perspective on the differences.
Any thoughts (anyone) on how slide film responds in terms of exposure latitude when subject to XPRO?
Thanks.

That was the top part of my reply. I accidently overexposed Provia 400X by 3 stops and, when I noticed, I changed exposure to box speed in mid roll. I processed in ECN2, which is a negative process for motion picture negative film. ECN2 and E6 both use the same development chemical (active ingredient, so to speak). That is why I prefer ECN2 over C41 when I have to cross process. I should, in theory, give better colours because it produces the chemically correct dyes i the emulsion.

Anyway, when cross processing you can expect a similar latiude to using C41 negative film. As I mentioned above, on the one film roll it wasn't that obvious that a few frames were overexposed by three stops. E6 development would surely have yielded clear frames.

 

[Steve@f8]

That was the top part of my reply. I accidently overexposed Provia 400X by 3 stops and, when I noticed, I changed exposure to box speed in mid roll. I processed in ECN2, which is a negative process for motion picture negative film. ECN2 and E6 both use the same development chemical (active ingredient, so to speak). That is why I prefer ECN2 over C41 when I have to cross process. I should, in theory, give better colours because it produces the chemically correct dyes i the emulsion.

Anyway, when cross processing you can expect a similar latiude to using C41 negative film. As I mentioned above, on the one film roll it wasn't that obvious that a few frames were overexposed by three stops. E6 development would surely have yielded clear frames.

So it was, I’m sorry, I didn’t intentionally repeat my question.
Thank you very much.

 

[DREW WILEY]

I thought "latitude" was a synonym for sloppy exposure. Amateur color neg films are designed for that scenario. Pro CN films vary with respect to contrast scale and saturation depending on the intended range of applications. A film like Portra 160, for example, has a longer engineered scale than higher-contrast more saturated Ektar 100. Color transparency films have even less usable scale; but they too differ to a degree. The point is to intelligently understand what that is range is, and learn how to correctly meter for it.

 

[138S]

I thought "latitude" was a synonym for sloppy exposure.

Also it is the capability of a film to record a very contrasty scene, conserving texture in the highlights , which is important to depict volumes as glares on the surfaces are important to tell to the human vision how the volumes are, even in portraiture.

A film like Portra 160, for example, has a longer engineered scale than higher-contrast more saturated Ektar 100.

Drew, Ektar 100 has an scale that is as long as the Portra 160 one, IMO it is a urban legend that Ektar has a shorter scale, you can insanely overexpose ektar and it will stand.

There is a difference with portra, Ektar is a more landscape oriented film (stili its footprint can be extremly great for portraits) and it has the effect to shift color in the extreme highlights, making a nice aesthetic effect. This effect would be undesired for portraiture as you want the glares in the skin neutral in general.

Simply see the graph provided in the datasheet:

We se that by +7 overexposure ektar is still working, not depicted but it still operates beyond +7 (Each H units in the Hor axis is 3+1/3 stops) , but ektar is designed to have some warming color shift beyond (say) +4 overexposure., while Portra is more neutral in the extreme highlights.

IMO Ektar has not a shorter "scale", but simply it has a design to treat extreme highlights in this way:


https://emulsive.org/wp-content/uploads/2016/11/Skokovic-BlueHourEktar-3.jpg
Source: https://emulsive.org/articles/blue-hour-with-kodak-ektar-100-by-toni-skokovic

 

[flavio81]

Looking at the film itself you will find that slide film has latitude similar to negative film. In practice it might be that such latitude has been more of a consideration in the R&D of negative films, because it is much used in the field. That is especially true for amateur films. Still, in principle there is no difference between E6 and C41 film in that regard.

First an example to prove my claim above: I was out shooting slide films, using Provia 400X (6x6) after a roll of Velvia 50 and forgot to set the meter from EI 50 to 400. When I noticed I was a bit upset and then adjusted the meter. The plan was to forgo the misexposed images. At home I eventually decided to develop the film into negatives in the ECN2 process (same dev agent as E6). Looking at the finished (negative) film strip I could hardly see a difference between the EI50 and EI400 portion with the naked eye. That is film latitude, I guess.

The reason why you won't have any latitude when going for a slide is that the E6 process is fixed in all its parameters. It means a certain exposure will lead to a certain result. It's a fixed relationship. If you use negative film and go to colour print in the dark room with such fixed and *predetermined* parameters you will have zero latitude just the same as for slides:

Use a roll of Portra 400 and take perfectly exposed images, e.g. incident metered in a studio. Develop in C41 and take the film strip to your enlarger. Find the parameters to make perfect prints. Then use those same parameters (exposure time of the paper, filter pack, column height, etc) unchanged for all your future printing.

Now if you overexpose your next roll of Portra 400 by two stops you will get negatives but not get a useable image on your colour paper from those. It might give a very faint image or just pure white.

The trick with negatives is that you can adjust the second half of the process to the needs of your negative, and hence of the original scene. Portra can record most of the information in the scene even when it is very overexposed. The negatives will be denser and so you'll have to increase the exposure time under the enlarger to punch through that. And you may have to adjust your colour filter pack, as well.

Slide film will also perfectly record the information when equally overexposed. But in the E6 process and with two stops under/overexposure you will develop away that information, because the first dev time has been set to obtain a certain density when the film was correctly exposed. Only that density will translate to a viewable image upon reversal.

To prove my point: When you *KNOW* that you (over/under)exposed by one stop (i.e. an intentional pull/push by one stop) you tell the lab and they will process the film accordingly by adjusting the time of the first developer. You'll get great results from that. Indeed I've heard that in the old day slide film was the way to go for pushing, because the results are better than with negative film. However, your exposure will still need to be spot on at the chosen, pushed E.I.

I have pushed Provia 400X by two stops. Gives very usable results. But the max density is slightly lowered. I don't like the look of that too much because, most of the time, I'm a contrast whore and I don't like the deep blacks becoming slightly off-black.

But pushing that film one stop to EI 800 is a no brainer. And if you digitise them you'll adjust the black point of a two stop pushed image and get a perfect result with very little grain. That being said, when digitising slides that have a slightly wrong exposure they can be fully recovered. I recently had one of those. Great sky, underexposed city. I could fully recover that in digital post. But that still leaves me with a very imperfect slide for analog presentation.

Now, you'll surely ask about dynamic range next. The contrast of the final slide is intentionally high for a brilliant result. It is like printing b/w negatives onto grade 8 paper for an incredible brilliance. A high contrast in the output medium, without the ability to cut out brightness ranges of the orginal scene (dodging, burning, masking) will reduce the maximum recordable dynamic range. It's how mathematics works...

In practice when printing in the dark room C41, too, is limited in dynamic range, unless you like burning and dodging. I don't like doing that with b/w film, let alone with colour film. My RA4 exposure times are too short to even try. And you may also run into colour shifts. If I'm lucky I will have masking equipment, eventually. In a few years, perhaps. Then I'd be able to print high contrast negatives, but with a lot of effort and extra cost of film for making masks.

The reason why many of us consider slides on a light table, or projected, to be 'nicer' than images from negatives is that brilliance of slides. The final image contrast is much higher than what colour paper or a computer screen can manage. C41 film is technically superior in its colour reproduction, but for the masses E6 will aesthetically look better than the technically near perfect C41 process.

I guess E6 vs C41 is like film vs digital (order intentional).

Thanks for this very good post.

 

[Mainecoonmaniac]

It’s really simple. If you overexpose transparency, the highlights get thinner or even blank. Color neg film builds density when over exposed. The shadows with transparency film gets denser when under exposed to the point where detail is so dense that shadow detail be not be recoverable. With negative film it’s the opposite the negative gets thinner with under exposure with the shadows. Detail is more recoverable through dodging when the neg is printed.

 

[138S]

Looking at the film itself you will find that slide film has latitude similar to negative film. In practice it might be that such latitude has been more of a consideration in the R&D of negative films, because it is much used in the field. That is especially true for amateur films. Still, in principle there is no difference between E6 and C41 film in that regard.

This is totally wrong, in post 19, Kodak graph shows that Ektar 100 has at least 10 stops latitude. Instead, if you explore the Ektachrome 1000 datasheet you will find that it has a way lower latitude, by a quite large margin:

 

[DREW WILEY]

Have you ever seriously worked with Ektar, Pere? Crossover kicks in pretty bad once you're more than one stop either side of what a typical transparency film does. You seem to be a person quite tolerant of crossover color artifacts. That's fine if it's what you're after. But it's rather misleading to categorize that kind of error under standard norms of acceptable range. Take care and stay well.

 

[138S]

Have you ever seriously worked with Ektar, Pere? Crossover kicks in pretty bad once you're more than one stop either side of what a typical transparency film does. You seem to be a person quite tolerant of crossover color artifacts. That's fine if it's what you're after. But it's rather misleading to categorize that kind of error under standard norms of acceptable range. Take care and stay well.

Drew, yes, I've been using Ektar extensively, by +3 overexposure for sure you have no shift, see the curves in the datasheet. I usually spot meter and placing the key at +2 (at least) in the cheek by routine.

Like Portra, overexposed Ektar has an slightly different footprint for contrast or saturation, but with Ektar I find no hue shift if not insanely overexposed, say +4 and beyond....

If you have glares at +7 then... yes... you'll you'll get some warming shift....

Anyway with a competent color edition you do what you want, today optical RA-4 is nearly extinguished and once you are in the hybrid you adjust color like you want, with 3D LUT Creator or the like you do what you want...

You may see many exposure Ektar exposure tests posted around, if you find an slight difference from +/-0 to +3 I'll show you how to get the same with a few clicks in PS.

 

[DREW WILEY]

Yes, indeed - I see many many Ektar images posted, and indeed tweaked despite significant exposure and filtrations errors - "I can correct anything in Photoshop " - and indeed looking awful ! This film is capable of much cleaner results if it is properly understood. And when output tweaking is needed, masking skills can do it in a darkroom for sake of RA4 printing just as well as PS qualitatively, maybe better - I didn't say faster. But once it's scanned, you have no choice but digital printing too, which I find rather disappointing compared to real darkroom prints, especially when the heavy artillery of large format film is involved.
Now ... the very curves you've posted have decent linearity only over a six stop range, or perhaps 7 stops fudged a bit, which is right around what actual experience with Ektar tells me too. But what you need to do is go to the tech sheet charts which show how the actual spectral sensitivity overlaps - where those three little dye mountains overlap down on the alluvial plain and create mud rather than pure Pyrenees tri-colored water. Once mud is mixed, it's tricky to unmix it.