Expose for shadows or highlights?

Discussion in 'Exposure Discussion' started by film_guy, Feb 25, 2007.

  1. film_guy

    film_guy Member

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    With digital, I try to expose for the highlights. But with film, should I try to expose for the highlights too or should I focus on the shadows? Is there a difference in exposure for shadows/hights with B&W and color film? Especially fast film >iso 400?
     
  2. eddym

    eddym Member

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    The "quick answer" is to expose for the highlights if you're shooting slide film, but expose for the shadows if you're shooting negative film.
    The "long answer" is the subject of many books, workshops, and religious cults. The best I can recommend if you really want to understand what is happening when you expose film is Kodak's Publication F5, "Kodak Professional Black and White Film." Sadly, it's out of print, but you might just find one used on Amazon.com. And just because it's about B&W doesn't mean that it is inapplicable to color film.
     
  3. reellis67

    reellis67 Subscriber

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    I put a short article on my website explaining this principle. Go the site listed in my signature line, click on 'articles' and select the article link. It should at least get you started with this concept.

    - Randy
     
  4. wirehead

    wirehead Member

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    I dono, I think it's best to understand what happens in a given situation for underexposure and overexposure.

    Digital: Underexposure means you get more noise. Overexposure and you clip ("block") in a very ugly fashion. Especially with a digital SLR in RAW mode, you have absurd amounts of shadow detail to draw from, with increasing noise as you go along. The troubles with overexposure is where the expose for the highlights come from.
    Slide film: Underexposure means you clip ("block") the blacks. Overexposure means that you clip ("block") the whites. However, blocked whites on slide film still look better than blocked whites on digital. Velvia and Kodachrome can have shadow detail that require either projection, viewing on a light table, or a drum scanner to get out. You need to fit the entire picture within a very small range, maybe 5 stops or so, so you really can't expose for the highlights or the shadows and be assured good exposure. And, unless your subject is a mottled gray wall, you can't really afford to be off by a stop in either direction. Blocked highlights are much more pleasing and sparkly with slide film than digital. Most slide films worth shooting are sufficently grainless that you won't notice large amounts of grain if your exposure is off..... because it'll probably be unusably blocked up anyway.
    Print film: Underexposure means that you clip the blacks. Before the blacks go totally black, you'll notice a dramatic increase in grain. The increased grain will go away in your midtones and return in your highlights, although the C-41 black and white films don't always behave like that. You have a much larger range of values, maybe 8-10 stops, but most of that room is in the highlights.

    If you consider a "normal" scene as having 5-6 stops of range, this means that you can overexpose your print film by 4 stops and still fit within that range.

    The problem with simple maxims like "Expose for the shadows" or "Expose for the highlights" with film is that film response curves are not linear and usually in a not especially pleasing way. This is not generally regarded as a defect in film, as the results from a tweaked response curve will be more pleasing and a perfect scientifically calibrated straight linear curve... and is why digital photographers spend so much time in Photoshop.
     
  5. reellis67

    reellis67 Subscriber

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    That system has been used to make some of the most memorable photographs known today, so I can't really agree with your statement above. The 'maxim' you mention is the basis for more advanced systems like the Zone System and BTZS, and if it were flawed, these systems would surely have been found to be lacking as well by now. Not to mention the large number of people who use this method today who can, as I can, show you examples of how it *does* improve results. If you're going to try to refute this one, you're going to have to show some serious empirical data to back up your hypothesis.

    - Randy
     
  6. wirehead

    wirehead Member

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    I wouldn't call "expose for the shadows" or "expose for the highlights" flawed. It's more a general statement like "If you drop a hammer, it's going to fall" as compared to Newton's Law and general relativity. If you spend much time trying to figure out how things are going to drop ahead of time, you are going to have to get beyond the first statement.
     
  7. reellis67

    reellis67 Subscriber

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    Fair enough I then, although I think it is a bit more complex than your analogy - I've just never seen the need to go past that point in my own work.

    - Randy
     
  8. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    With slide film the highlights are the thinnest part of the image on film. With negative film the shadows are the thinnest part of the image on film. If you don't record them, then you lose them, and no amount of post processing will get them back. Whereas, if the highlights are too dense on a negative, you can usually burn them in or use a contrast mask to get that information into the print.

    With slide film, there aren't so many options, particularly if you consider the slide the final product (but if you blow out the highlights in slide film, you've lost them, even if you scan or use contrast masks), so you have to decide whether you want to lose the highlights, because something else is more important, or retain highlight detail.
     
  9. CPorter

    CPorter Member

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    There's really no if, ands, or butts on this one. If you are going to expose film, you have to provide adequate exposure to the shadowed areas that are important to you. Underexposure of the shadows with film is a far more critical error than overexposure of the highlights because you can't regain information in the important shadow area after the film is developed, as alluded to in an earlier response. Altering film development can always be employed to hold the highlights in check, so it is prudent to give the shadows "adequate" exposure.

    "Adequate" does not necessarily mean extra, but it simply means the necssary amount of exposure. You could make an important Zone II shadow placement (i.e., a deep tonality shadow area that reveals "the first suggestion of texture") that helps to keep the highlights within a printable density. By doing so, you have provided adequate exposure to the defining shadowed area in your print.

    Chuck
     
  10. Maris

    Maris Member

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    I use only B&W negative film and go for maximum usable exposure. Not maximum exposure flat out but rather the greatest exposure that permits the high values (high negative densities) to just record texture without blocking. To be able to hit this exposure every time means the effective film speed needs to be known. Since development has an effect on film speed some testing and learning is in order.

    The rationale behind this approach is that the negative is merely the collector of spatial and photometric information about the subject. The greater the exposure, up to the "blocking" limit, the more information is recorded and the greater the number of optional renditions for the final gelatin-silver photograph.

    Large format film offers remarkable opportunities for heavy exposure. I have sometimes (foolishly and neglectfully) forgotten to stop down when shooting 8x10. Even at 7 stops over-exposed all the tones are there in a very dark negative.
     
  11. Jim Jones

    Jim Jones Subscriber

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    I mostly agree with Maris. Exposure that raises shadow detail above fog and flare almost always suffices. Some shadow detail can be enhanceded by modest bleaching of the negative. If I weren't too cheap to use modern multicoated lenses and fresh film, these tricks might not be necessary.