what is the exposure latitude of Ektar 100?

Discussion in 'Film and Processing' started by weikle_chan, Feb 24, 2010.

  1. I have read some old threads in the forum,but a kind of confused,there are two different interpretations:
    First point:the ltitude is equal with film dynamic range,e.g.,Ektar 100 is -1~3,if i get a numberic value from exposure meter that F16 1/250 of highlight as well as F4 1/250 of shadow ,then get to take photo with F5.6 1/250(put shadow into -1ev and highlight 3ev),details both highlight and shadow will be recorded,otherwise it's impossible to get the most delicated details according to the principle of zone exposure which is well known.
    Second:the latitude of a film just represents a extension which is mainly applied by develop lab,it means the character of iso sensitivity(add/decrease)
    The two concepts is absolutely different,which is correct?Thanks in advance for any advice.
     
  2. The Kodak site has a wealth of related information:
    http://www.kodak.com/global/en/professional/products/films/ektar/ektarIndex.jhtml?pq-path=13319/1230/13328
     
  3. IMO, the term 'latitude' is somewhat misused, usually meaning "How much can I screw up the metering without ruining the image?" 'Dynamic Range' is more tangible and is taken to mean "Over what is the range of subject brightnesses will the film record usable detail?"
    Here's the best explanation I've found, although it doesn't offer a direct "9 stops" sort of answer.
    http://www.apug.org/forums/forum40/73019-negative-film-wheres-shoulder-data.html
    Follow the link HRST provides.
    In short, Ektar seems to record well down to -2.5 or so, and retains usable highlight details to somewhere around +5 and higher, although much depends on your darkroom skills or scanner's capabilities.
     
  4. Thanks Greg,i have already get the data from the characteristic curve of Ektar100
    The benchmark point of 18% gray is located near by (-1,1),i did not comprehend the relation between density numeric value and 18% gray before,so i can't get the individual EV range above/down 0EV.Dynamic range of any film can be figuered out by straight line part of Lux-Density curve ,but as what you have said,in the meantime,the final effect also depends on darkroom and scanner,otherwise,the whole range would not be revealed perfectly even though be exposured properly.Thanks again.
     
  5. The exp latitude is a standard characteristic of photosensitive material derermined by photometric test. The DR, usable details and the rest of it is a descriptive terms used among practitioners freely. EL for E1oo is about 3EV.
     
  6. I think dynamic range refers to the luminance range that can be captured by the medium - in this case, Kodak Ektar 100 - in a single take. It is important to know for those who routinely shoot high-contrast scenes without being in full control of the light (landscapists, street photographers). Latitude in my book refers to, as Greg said, the extent to which you can screw up exposure without irreversibly ruining the image. The two terms are related but do not mean the same.
     
  7. The other issue that most people ignore is linearity of color reproduction. For most films the luminance range over which color reproduction is more or less constant is significantly shorter than the range over which the characteristic curve is linear. This will vary from film to film, so there is no general answer for all films. Having been away from film design for awhile, I can't answer specifically for Ektar 100, but Kodak film designers try very hard to keep color reproduction as constant as possible.
     
  8. The dynamic range of film is the range of luminance in the subject which can be captured while retaining some detail in the high and low end. This is approximately 10 f/stops for Ektar 100, if you allow portions of the toe and shoulder of the characteristic curve.
    Latitude is the range over which the exposure can be varied and fall within the dynamic range of the film. If the subject has a smaller range of luminance over which you wish to see detail than the dynamic range of the film, you can vary the exposure by the difference and still "fit" it on the film. This is done at the expense of added grain and changes in color. The best exposure is still the best exposure.
    Exactly what "best" means depends on the subject and your goals. Likewise, the important range of the subject is a matter of judgement. Usually you can exclude deep shadows and specular highlights (typically using a spot meter).
     
  9. Hi,Les,thanks for your informative comparison,it looks as if appear it's unnecessary to worry about highlights with Ektar 100.
     
  10. As Les' example shows, Ektar 100 is more forgiving of overexposure than digital. It's inherent in the process - dark and darker on the negative, moving into the shoulder area of the characteristic curve. Digital behaves more like reversal film in this regard. At the low end of the scale, digital and Ektar exhibit comparable performance, and slide film is simply not in the running.
    Photos in the attached sample were taken three years apart*, from the same vantage point (Hasselblad, different lenses), the top with Reala, scanned with a Nikon LS-8000 and the bottom with a CFV-16 digital back. The colors are different and can't be matched, due to the vastly different sky conditions. It was a really dismal day in the bottom panel, and colors are extremely muted - accurately if I might add. My purpose is to show shadow detail. In both cases, the cropped panel was lightened using Photoshop Light/Shadow at 35%. Otherwise both areas are too dark to show details on the screen. The digital image was resampled to 8000x8000 pixels (2x) for comparision.
    * I'm sure I have similar shots under closer conditions, but not on my computer at this time. Scanned MF film files are simply huge - nearly 450 MB, and disks were much smaller when I was shooting film.
    00VsNf-224349584.jpg
     
  11. Here is another shot of the same bridge on an happier day. It was taken with the Hasselblad and CFV back, using a CF180. The upper left panel was exposed normally, but the detail panels were opened up with the Shadow/Highlight tool to reveal details to illustrate the enormous dynamic range. The previous example is typical of film's behavior in situations like this.
    00VsOa-224359584.jpg
     
  12. Les,
    In this thread, you stated "Compared to digicams, highlights you won't have to worry about with Kodak Ektar 100 as clearly shown below.", followed by an example comparing the dynamic range Ektar to digital. I show that it's basically a wash between negative film and digital with regard to exposure tolerance - give at one end and take at the other.
    Your example shows that Ektar (film) excels in a region where digital (and slide film) are weak - tolerance to overexposure. I followed by showing how negative film fails where digital tends to excel - tolerance to underexposure. The second example uses a high-contrast scene to reinforce this fact.
    I used a Reala example because Ektar has no special tolerance to underexposure - it is the nature of negative film just as overexposure is a problem with reversal film. That's easy enough to demonstrate, but not with the same subject. I gave up crayons a long time ago ;-)
    Is this sufficient to show the relevance of my posts?
     
  13. Les,
    Where is your test showing the effect of overexposure on reversal film? Where is your test showing the effect of underexposure on negative film?
    The control point in my examples is that each scene is well exposed, so that the overall results are comparable. Consequently it is legitimate to compare the behavior of film with a digital camera in the extremes of the same or similar situations.
    While your test may be reproducible, it falls far short of objective testing. Where is the densitometry? I admit images of Crayons are more appealing than density wedges, but no more objective than looking at a real world scene taken in situations we all encounter.
    Regarding your half-test of Ektar, the top two frames are photographically unuseable due to color distortions. You obviously compensate each frame for exposure. If there were a white patch in your test stand, it would appear grey in those frames. They may not be washed out like the digital example, but unuseable nonetheless.
    There are all kinds of engineers and all kinds of testing. I spent the last four years of my career as a senior engineer in Metrology. We calibrate the instruments you use in your tests.
     
  14. Les,
    If I take three successive frames of Ektar 100, taken at 1 stop increments, and scan them on my LS-8000 with my "hands off the wheel", I get a significant variation in density and color balance. Yet in your Crayon example, you vary the exposure over 6 stops with virtually no variation. How is this done without making adjustments (or allowing your software to make them)? Exactly how does this represent an objective and "scientific" test?
    I get similar results using a digital camera, only with very little color shift. Your digital exposures do not show a significant variation over a 4 stop range, until they begin to wash out in the top two frames.
    00Vsc1-224495684.jpg
     
  15. I've got to agree: How in Earth can random bridge pictures, take years apart and under wildly varying lighting conditions, be considered 'scientific' in any way? C'mon, dude!
     
  16. My intent is to show how an image can be "normalized" regardless of overexposure and clearly that is demonstrated in the first example.
    OK. I can go along with that. You can't say there are no adjustments, however, just because you let Nikonscan do it for you. That is the basis for my objection, which you have clarified.
    Your test is a reasonable way to demonstrate the latitude of film (or digital), but is only indirectly related to the dynamic range. That's because the test target (Crayon box) has a very small dynamic range, which makes it easy to fit inside the range of the medium. In my example, I turned auto exposure off as a prelude to doing an HDR merge. Similarly, you would not "normalize" patches in a step wedge - the scientific way to measure dynamic range.
    I hope you understand what I'm saying. A fair test of latitude would extend to the toe of the curve, where the density of negative film approaches the base and fog level. That's analogous to overexposing reversal film, where the image approaches the base density (or digital approaches pure white). Based on my "non-scientific" landscapes, I think you would find that film gets pretty grungy in this region compared to digital. Then too, not all digital is the same, which is partly why I bought the CFV back.
     
  17. Edward and Les,
    I think a third party might be needed here. I propose that Edward loan me his CFV back for a decade, and I'll do some extensive test to compare with film. I promise to return it. :)
     
  18. Did any of you guys factor in the narrower-then-film DR of the scanners when doing such tests?
     
  19. A good scanner, such as the Nikon 9000, has no problems with the dmax of color negative film. SilverFast offers the option of a double pass to handle slides. Trying this option on C-41 will show no visual improvement. At least that has been my experience.
     
  20. The variable that's been left out is that films are primarily designed to be developed and printed, not scanned, I get much better results with Ektar when it's printed in a darkroom than scanned, I find that it can be overexposed about three stops and underexposed about two and a half and still have a printable neg.
     
  21. James G. Dainis

    James G. Dainis Moderator

    Dynamic range is what you get on the negative; latitude is what you get on the print.

    Take a photo of a bride with a shaft of sunlight falling on her shoulder. In the print, the white dress shows lace and embroidery but her shoulder looks pure white. If you look at the negative with a loupe, you can see the lace and embroidery there, but it is as if it were drawn on a black paper with a black magic marker. You can give a lot more enlarger exposure to burn it into the photo paper but then everything else is much to dark. Or you can try to spot burn it in but then you get a gray blob with the lace and embroidery showing.
     

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