Difference in exposure latitude Kodak Portra 400 and 160

Hi All,

I was wondering if somebody knew why there seems to be a great difference in exposure latitude with Portra 160 and Portra 400.

When exposing Portra 400 I have found it to be quite resilient to overexposure (up to 6 stops usable results). Portra 160 has always given me very variable results, sometimes overexposed quite easily and sometimes just being very contrasty and "dark".

Are they not a very similar emulsion?

Why do Portra 160 and Ektar 100 behave so differently?

Don't they have the addition of the special "KODAK VISION Film Technology"?

Would love to get some scientific explanations on this from somebody in the industry.

The main reason for the exposure latitude of color negative films is the low gamma, which allows for larger exposure variation for the density range.

It then requires compensating higher gamma in printing, which requires more accurate exposure. That is, low exposure latitude when printing.

A printing exposure meter, and even better, color balance meter is very useful in color negative printing.

As well as I know it, and maybe not so well, some films have chemistry such that development of one color layer inhibits development of other layers, increasing the color saturation. I don't know any details, and especially how it differs between films.

Mostly I prefer my colors not oversaturated, and have liked using VPS, and then Porta 160, for that reason.

Now with scan and print, it is easy to adjust to make them look however you want them to look, a little easier to increase contrast and saturation than to decrease them.

I was wondering if somebody knew why there seems to be a great difference in exposure latitude with Portra 160 and Portra 400.....Why do Portra 160 and Ektar 100 behave so differently?

- Which film are we comparing with Portra 160? Portra 400 or Ektar 100?

Whichever; if you download the datasheets from Kodak-Alaris, you'll see the difference in their Exposure-Density curves.

Portra 400 has a very long 'straight'* curve with an exposure range exceeding 3 decades, while Portra 160 has a red curve that starts to droop after only 2 decades. This means that overexposed highlights will have a tendency to a red or orange tint.

*Not really straight, because we're looking at a log/log graph.

Without measuring its curve exactly, Ektar 100 appears to have a slightly greater contrast than Portra 400, and a tendency to yellow highlights.

Portra 400 definitely shows the better resistance to overexposure of the three.

Here are links to their datasheets:

Ektar 100

Portra 160

Portra 400

"Don't they have the addition of the special "KODAK VISION Film Technology"?"

- Pure marketing hype!

All three films are different. Portra 160 and Ektar are low grain films. Portra 400 has low grain, but more than the other two. The palettes are slightly different.

What do you mean by "latitude"? Do you mean the range of values within a scene, or the ability to handle exposure at lower than box speed? Are you exposing Portra 400 at EI 6? Or are you exposing a high contrast scene at EI 400?

Please post some examples of what you are seeing. It will help the discussion.

In the days when film was it, the photo magazines used to do comparisons of the "usable" range of exposure for different films.

Some of the reasons for differences are discussed above, but for most of us it's a matter of empirical testing:

 

Modern Photography 1988-04

Color Negative films generally speaking have the widest usable latitude.

Ahh! Scotch film. That takes me back.

I tried it once.... and once was enough!

I think they (3M) confused it with the 60 grit sandpaper they also made.

(snip)

 

Whichever; if you download the datasheets from Kodak-Alaris, you'll see the difference in their Exposure-Density curves.

 

Portra 400 has a very long 'straight'* curve with an exposure range exceeding 3 decades, while Portra 160 has a red curve that starts to droop after only 2 decades. This means that overexposed highlights will have a tendency to a red or orange tint.

 

*Not really straight, because we're looking at a log/log graph.

 

Without measuring its curve exactly, Ektar 100 appears to have a slightly greater contrast than Portra 400, and a tendency to yellow highlights.

 

Portra 400 definitely shows the better resistance to overexposure of the three.

 

Here are links to their datasheets:

Ektar 100

Portra 160

Portra 400

 

It looks to me that all three are pretty straight over three decades (10 stops), but the graph stops while they are still straight.

Yes the red has a little droop, but not all that much.

So we really don't know how much farther before they start to curve, and then flatten out.

There are stories about some of these films being designed to make flesh tones look better,

though I don't know any details about that.

(snip)

Color Negative films generally speaking have the widest usable latitude.

And also C41 process black and white films.

When exposing Portra 400 I have found it to be quite resilient to overexposure (up to 6 stops usable results). Portra 160 has always given me very variable results, sometimes overexposed quite easily and sometimes just being very contrasty and "dark".

I don't have much experience with the 400 version, but had plenty with early Portra 160 NC. As well as its predecessors, VPSIII and II. These films all had tremendous overexposure latitude, at least in studio portraiture. In the large studio chain I was involved with, it was not uncommon (before going to digital) for a studio to botch up and shoot half-a-week's worth of portraits overexposed by 4 to 5 stops. Not much problem, except for the longer printing times.

One of our standard tests when each of those films was new was to shoot a long exposure series in studio lighting conditions (electronic flash). We would use 4 or 5 models, with complexions ranging from pretty pale to pretty dark. We had a standard set of colored fabrics that we'd include in the scene. Then we'd optically print the exposure series. The "normal" exposure was color corrected for a "best" print, then everything else was hand balanced to match an aim flesh tone in the highlight areas. Within 01 cc color, which is about as stringent as any lab could do.

To the best of my recollection, comparing the normal exposure vs 3 or 4 stops overexposed prints were essentially a dead match in a color correction booth. If we laid some of the colored fabrics in the color booth on top of the print, the colors were a very close match. At roughly 5 stops over, as I recall, some of the stronger colors would get something of a "creamy" appearance, so someone who had studied the series would be able to recognize the look, but no normal customer would.

Now, it's been maybe a dozen years since my last experience with Portra 160, so maybe it's changed for the worse, but I doubt it.

I sort of suspect that your problems with the 160 are really coming from the scanning stage, or possibly the film process.

Ps, the plots you see on the film data sheets are status M densitometry, pretty narrow spectral slices. They are not strictly representative of what happens when optically printed onto pro papers, or even seen by most scanners.

And also C41 process black and white films.

Yes, although it may not be for exactly the same reasons, Ilford XP2 is incredible!

XP2 Super has very wide exposure latitude, making the film easy to expose even under challenging conditions. XP2 SUPER can be used as EI 50 – 800 ASA with no adjustment to the process, making it an extremely versatile film.

from the data sheet (emphasis added, JDM)

Yes, although it may not be for exactly the same reasons, Ilford XP2 is incredible!

 

 

from the data sheet (emphasis added, JDM)

Having a similar gamma makes it easy to print on machines designed to print color negatives.

The Kodak equivalents have the same orange mask as color C41 films.

I suspect that it is a little harder to get the color (gray) balance right with XP2, but never tried it.

The wide exposure latitude was important in the days of cheap (one shutter speed, and maybe two aperture settings) cameras, and people that would use them under a wide variety of lighting conditions.

Thank you everybody. And thank you for the data sheets.

Please excuse my many different questions - next time I will try to keep my question clear.

What I am really wondering is this:

If Kodak claims their new films Portra 160, Portra 400 and Ektar 100 have gained better quality by incorporating cinema technology (vision 3 etc.), then why does only Portra 400 have that large exposure range?

Why can we expose Portra 400 6+, but not Portra 160 or for that matter Ektar 100?

Kodak's decision to keep the orange contrast mask in their BW400CN film was a market-driven attempt to widen the appeal of B&W to the colour-loving amateur masses, and to streamline minilab workflows. It made no sense at all from a professional user's or technical viewpoint, since it couldn't be printed on high-quality silver-gelatine paper. Well, not unless you bought Kodak's panchromatic paper and worked in near total darkness.

I think Ilford actually got it right by dropping the stupid orange mask. This makes both scanning and traditional wet printing a much more straightforward process.

In view of the fact that most film users now seem to perversely scan their film to a digital file; does the contrast mask even make sense for colour negative film any longer?

I'm old enough to remember when Agfa's colour negative stock had no contrast mask, and seem to remember getting perfectly good (for the time) prints from it.

The mask is there supposedly to correct deficiencies in one or more of the dye-couplers. Well, couldn't Kodak et al simply make their dyes a bit better? After all, there's no mask in reversal film, and nobody complains about the colour accuracy of that.

"Why can we expose Portra 400 6+, but not Portra 160 or for that matter Ektar 100?"

- The answer is all there in those Density-versus-Exposure graphs. What looks like a 'slight droop' in the log/log space used, is actually a massive deviation in linear space.

What I am really wondering is this:

If Kodak claims their new films Portra 160, Portra 400 and Ektar 100 have gained better quality by incorporating cinema technology (vision 3 etc.), then why does only Portra 400 have that large exposure range?

The very large "exposure range," by which I mean a roughly 9 f-stop scene-recording range with a roughly 5 f-stop overexposure tolerance on top of that, existed even prior to Portra 160, on VPSIII film. (I had a great deal of experience with this, including time as QC manager overseeing process control, etc., for a studio chain using these films exclusively.) So the huge exposure tolerance is not attributable to the key "Vision 3 technologies," in my view.

I take the main "Vision 3" technologies to be what they call "antenna dye sensitization" and "two-electron sensitization," which both increased "sensitivity" of the films (technical papers published in 2004, that I know of). Now, since Portra 160 continued to have a speed of 160 after that, then the obvious assumption would be that Kodak used these technologies to improve "graininess." (I can't say for sure, as I had little experience with Portra after that time frame.)

I have essentially no experience with Ektar 100, as it was not as suitable for portrait work as the VPS and Portra lines of film. So I can't say much about it. (Note that we DID once do trials with Ektar 25; it carried tremendous detail, etc., but skin tone reproduction was much inferior to the portrait films, so we never explored further.)

As a note, I've been referring to a 5-stop overexposure tolerance. Let me be clear that I am not saying this is a hard limit. This is all the farther that we (on behalf of my employer) tested to, as it was not generally possible for our studios to exceed this.

You might also wonder how a "normal" exposure is determined. Well, in the film data sheets, density specs are given for both skin tone highlights and grey card. Additionally, Kodak used to supply printer setup negatives, aka slope negs (I don't use the term "Shirleys"), which includes a physical example of a "normal" exposure. So this identifies my definition of a "normal" exposure. I should point out that this is for a studio-style portrait with "properly color-balanced" light sources, etc.; I don't personally recognize a proper "normal" exposure outside of these conditions. It goes without saying that the film processing also has to be "proper;" this is only confirmed by the use of "process control strips" as supplied by the film manufacturer, etc.

I gotta repeat that I don't have (much) personal experience with the current Portra 160 so I can't be certain that the long exposure range still exists. But I would probably bet a lot of money that it does. And again, I feel pretty certain that your issues with it are somewhere away from the film itself (I'm guessing that scanning is the big thing, although it might be film processing; overexposure puts a heavy demand on the development stage, and if the chemical process is not well-handled, including monitoring with control strips, then this could be a problem.) I'd say to discuss it with your lab, if possible.

As a further note, I'm coming from a lot of actual experience, my department used to read about 50 control strips per day, and staffed an on-site chem lab with full analytic capabilities that even oversaw chemical regeneration systems. We also did extensive testing of the (limited selection) of films and papers that we used, including a lot of sensitometric testing and screening: probably well over 10,000 sensi wedges while I was there. So I'm not just tossing out off-the-top-of-my-head thoughts.

Portra 400 has a very long 'straight'* curve with an exposure range exceeding 3 decades, while Portra 160 has a red curve that starts to droop after only 2 decades. This means that overexposed highlights will have a tendency to a red or orange tint.

 

*Not really straight, because we're looking at a log/log graph.

Rodeo, the published curves for a color neg film generally use what they call "status M" densitometry. These are three pretty-narrow spectral responses that are probably pretty good at seeing the relative amounts of each dye (cyan, magenta, and yellow). But they're not necessarily a good reflection of how a photo paper "sees" the film. (They show generally how the film will act, but not precisely.)

In my real world experience, we never saw the tint that you are predicting; It's just never been there in huge quantities of studio portraiture handled under very stringent process control conditions.

In the industry there is a different kind of density, known as "printing density." This is how the photo paper "sees" the film, as opposed to how status M densitometry sees it. It's pretty well understood (or at least used to be; maybe not anymore) that the two are broadly similar, but can't be assumed to be precisely comparable. So what's going on is that you're trying to predict results based on status M density, whereas the actual results are "printing density."

Note that I'm sort of ignoring the modern method of dealing with film - scanning. But again, status M densitometry is only valid if using a status M - based scanner. Which I suspect is almost non-existent, but I don't really know.

Interesting Rodeo_Joe, I did not know there could be a negative film without the orange mask. That would make scanning it a lot easier.

I am relatively new to analogue film (I have been shooting film non stop for 3 years). But most films went out of production before my love for the medium started.

And thank you for your post BillC, I do admit I only shot 2 rolls of Portra 160, but they weren't handling the overexposure I was used to giving Portra 400 well. Perhaps I made a big mistake, perhaps they were stored wrong, perhaps the lab did not change their chemicals. I will buy some fresh rolls this week and give Portra 160 another shot.

Ektar100 I have shot a lot and it sure cannot handle overexposure very well. I feel it behaves more like one of Fujis slide films - you either got the exposure right or you are left with disappointing photos.

Unfortunately I am not able to print from my negatives as even the colour lab at the local academy of fine arts just closed down. I do scan my work for web on my Epson V700. For exhibitions I get them scanned again by a professional lab and they print it.

I admit to being surprised that Portra 400 has more headroom than the 160.

FWIW, Wally Pfister, the DP for Christopher Nolan's Batman films (and many others) overexposed Vision 3 by 5 stops for one scene in The Dark Knight. I imagine he could have gone further than 5 if he wanted.

The mask is there supposedly to correct deficiencies in one or more of the dye-couplers. Well, couldn't Kodak et al simply make their dyes a bit better? After all, there's no mask in reversal film, and nobody complains about the colour accuracy of that.

The dyes are produced during development in a way that restricts the type used and nature of the dyes and these dyes have color absorption issues that cannot be solved simply by making them better. A mask is the most practical way to correct them.

The dyes in reversal film have similar deficiencies or impurities as those in color negative film, but each one has a different purpose and treated differently. Reversal film is meant to be viewed directly or projected; negative film is meant to be printed. When viewed directly as in reversal film, the dye impurities are there, but hardly noticeable as they are only seen once. But in the case of a negative, it is printed onto paper that also has similar dye impurity problems, so the dye impurity problems would be seen twice, and the problem would compound, and the resulting degradation is quite noticeable if not corrected somehow. The correction takes place in the negative because of the mask, so only the dye impurity problems of the paper are seen, and as with the reversal film, they are hardly noticeable.

Now, if one tries to print reversal material onto paper, there is no mask and thus no correction in either the film or paper and color degradation is much more noticeable than a print from a masked color negative. Technically, a print from a masked negative is always better than a print from reversal film and is one reason why the motion picture industry generally does not use reversal film.

Now, if one tries to print reversal material onto paper, there is no mask and thus no correction in either the film or paper and color degradation is much more noticeable than a print from a masked color negative.

- And that's why Cibachrome prints were so good?

Apart from the restricted SBR, a Cibachrome print could easily match the colour accuracy of any neg-pos print.

"..is one reason why the motion picture industry generally does not use reversal film."

- I thought that was simply a traditional thing; that any number of distribution prints could be banged off from a master negative. Plus colour neg is easier to grade.

That's all moot with a modern workflow anyway. Most, if not all, print film used for still photography today will end up being scanned; and once scanned any dye deficiency can be easily corrected digitally. There really is no need for the mask any longer.

In my real world experience, we never saw the tint that you are predicting; It's just never been there in huge quantities of studio portraiture handled under very stringent process control conditions.

- That would probably be because studio portraiture doesn't (or shouldn't) push the film into the area where the curves separate. You'd likely be holding the SBR to 7 stops or less, and correctly metering the exposure. That's well within the 2 decade 'linear' region, and not where the curves start to separate.

A portrait studio that regularly overexposed by several stops most likely wouldn't be in business too long!

I agree that status M densitometry doesn't tell you everything about a film, but it tells you a lot about the difference between types of film.

I note that all these 'expert opinions' have stepped in to argue or nitpick with my response, while not offering a single answer to the OP's question.

"FWIW, Wally Pfister, the DP for Christopher Nolan's Batman films (and many others) overexposed Vision 3 by 5 stops for one scene in The Dark Knight."

- Any idea why he did that Karim?

It seems to me that if the film's response to exposure was truly linear, then there would be little point in deliberately overexposing it.

- And that's why Cibachrome prints were so good?

Apart from the restricted SBR, a Cibachrome print could easily match the colour accuracy of any neg-pos print.

 

"..is one reason why the motion picture industry generally does not use reversal film."

 

- I thought that was simply a traditional thing; that any number of distribution prints could be banged off from a master negative. Plus colour neg is easier to grade.

 

That's all moot with a modern workflow anyway. Most, if not all, print film used for still photography today will end up being scanned; and once scanned any dye deficiency can be easily corrected digitally. There really is no need for the mask any longer.

I have printed Ciba/Ilfochrome prints and they were not that good compared to prints from negatives. They looked good to many because they had high contrast and saturation that made them tend to pop compared to prints from negatives. But such pop does not mean accuracy, and prints from Cibachrome were not as color accurate as prints from negatives due to the dye impurity problems. In addition to my own experience, I have read much about this in the photographic literature. Many experienced Cibachrome printers would have to resort to masking techniques to fix this problems as well as contrast issues and doing so could produce very good prints. This was done extensively in the publication industry to improve color and contrast when printing from reversal film.

The motion picture industry has used negative film for several reasons. It has dynamic range recording capability superior to reversal film due to very low contrast. It is masked for dye impurity problems which means multiple generation copies can be made with little color degradation, important for production and distribution. Its low contrast means it can be transferred to print material with better contrast and highlight and shadow detail than reversal film. This would all be totally impractical with high contrast, unmasked reversal film. The print film used for projection has a much higher dmax than any reversal film for better projected dynamic range.

The mask is still necessary as there are still many out their who print color negatives optically so it is as important for them as it ever was. Those who scan still benefit from the mask because color will always be better with it than without it. I really can't see relying on it being fixed digitally. That in itself may present problem for users; I believe the best way is just to do it in the negative, and have it already done, for both optical printers and scanners.

Kodak's decision to keep the orange contrast mask in their BW400CN film was a market-driven attempt to widen the appeal of B&W to the colour-loving amateur masses, and to streamline minilab workflows. It made no sense at all from a professional user's or technical viewpoint, since it couldn't be printed on high-quality silver-gelatine paper. Well, not unless you bought Kodak's panchromatic paper and worked in near total darkness.

 

I think Ilford actually got it right by dropping the stupid orange mask. This makes both scanning and traditional wet printing a much more straightforward process.

 

In view of the fact that most film users now seem to perversely scan their film to a digital file; does the contrast mask even make sense for colour negative film any longer?

 

I'm old enough to remember when Agfa's colour negative stock had no contrast mask, and seem to remember getting perfectly good (for the time) prints from it.

 

The mask is there supposedly to correct deficiencies in one or more of the dye-couplers. Well, couldn't Kodak et al simply make their dyes a bit better? After all, there's no mask in reversal film, and nobody complains about the colour accuracy of that.

 

"Why can we expose Portra 400 6+, but not Portra 160 or for that matter Ektar 100?"

 

- The answer is all there in those Density-versus-Exposure graphs. What looks like a 'slight droop' in the log/log space used, is actually a massive deviation in linear space.

With negative film, the dye deficiency happens twice, (on the log scale), so the effect is much more than for reversal films.

Specifically, both on the negative and print.

It is, in general, hard to make dyes that absorb at some wavelength, but not at a slightly shorter wavelength. The other was around isn't as hard.

Film dyes have the additional complication that they are made by combining an oxidized developer molecule with a coupler to form the appropriate dye, where the same oxidized developer works for all three color dyes. (Except possibly for Kodachrome, where the three are developed separately.)

Yes with scanning one could matrix out such dye deficiencies.

More generally, there is no requirement for negative films to have dye absorptions matching the red, green, and blue that they are sensitive to, as long as the dyes match the color layer sensitivities of the corresponding print material. If you did it different now, though, you would be incompatible with all existing papers and scanners.

Since Cibachrome dyes aren't made from couplers and oxidized developer molecules, they don't have the same restrictions.

As well as I remember, the dyes are supposed to be more stable long term, I don't remember discussion of spectral accuracy.

There is evidence that they are indeed very stable.

My understanding is the dyes used in Cibachrome had similar color absorption problems as those used in negative papers but although improvements were made in later versions, the problem was never completely solved.

And whereas negatives have dye spectral characteristics that are designed to work well with matched color papers, reversal film dyes were not designed to be printed on to paper at all and one could sometimes see problematic differences such as varying degrees of crossover between the different types, Kodachrome, Ektachrome, Agfachrome, etc. when printed, in addition to varying dye impurity problems in the films. Also, C-41 films use DIR and DIAR couplers which give improved color correction, sharpness and grain whereas reversal films do not.

However, as stated earlier, many of these problems could be fixed to a high degree with masking by the user.

"FWIW, Wally Pfister, the DP for Christopher Nolan's Batman films (and many others) overexposed Vision 3 by 5 stops for one scene in The Dark Knight."

 

- Any idea why he did that Karim?

It seems to me that if the film's response to exposure was truly linear, then there would be little point in deliberately overexposing it.

It was, IIRC, the interrogation scene in the white room. I would have to go back to the ASC podcast for the reason why he did it.