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Overexposing film


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<p>Until you are thoroughly familiar with film characteristics specific to each individual film, you are better off using box speed - otherwise you are introducing too many variables to effectively track down exposure issues. The guidelines for negative films in general are to meter for the shadows, for positive films meter for the highlights - those are general in nature and don't take into consideration the degree of saturation desired, the reflectivity of the subject, or the desired "look" of the image. A good book to read to help you understand lighting & exposure issues is "Light, Science & Magic". Ansel Adams' "The Negative" is also exsellent, but may be somewhat overwhelming for most people relatively new to the world of film photography.</p>
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<p>There are occasions where you would want to "overexpose" from what your light meter is telling you. In looking at the flickr photos you linked to, for example, if someone was wearing white clothes and standing by a white wall, you would want to increase exposure so the whites came out white and not gray. To do that, you could dial in a lower film speed, say one or two stops, and meter normally. If the scene has strong backlighting and you want detail in the shadows, you could just meter the shadows and not mess with the film speed setting. But like Stephen says, it would be best to practice these kinds of shots before starting an important project, so you know how the film responds.</p>
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<p>"For overexposing, I heard that I have to rate the film lower and then meter for the shadow. Is it correct?"<br /><br />No. To overexpose film you simply open up the aperture more than the meter indicates, or lower the shutter speed more than the meter indicates. That's all there is to it. But you don't want to overexpose film, you want to get correct exposure. Sometimes that means giving it more than the meter says -- Meters are calibrated to 18 percent reflectance. Therefore they will assume that a white rabbit on snow (close to 100 percent reflectance) is actually gray, and give you a reading that will result in that. Therefore if you want the rabbit and snow to be white, you "overexpose" compared with what the meter says. But, in that case, the overexposure is actually the correct exposure.<br /><br />Some photographers like to rate their film at a lower speed, which if everything else is equal results in overexposure. For some advanced photographers this can be a way of controlling contrast and tones. That may be what you're thinking of. But many (not all) who talk fancy about doing this are actually doing it to compensate for errors in their metering technique without realizing that's all they're doing. It's a tool in the toolbox, but best to master getting good negatives with standard metering and exposure first. Like Stephen says, you don't want to throw too many variables into the mix.<br /><br /><br /></p>

 

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<p>I prefer slight overexposure for b&w film but in effect I'm using exposure instead of development to modify contrast. PopPhoto often said they preferred results from most color neg films when they were overexposed by about 1/3 a stop. For transparency (slide) film a little overexposure gives the image a pastel feel while a little underexposure enhances contrast and color saturation. YMMV</p>

<p>Henry Posner<br /><strong>B&H Photo-Video</strong></p>

Henry Posner

B&H Photo-Video

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<blockquote>

<p>"For transparency (slide) film a little overexposure gives the image a pastel feel while a little underexposure enhances contrast and color saturation."</p>

</blockquote>

<p>Yup, I preferred that pastel look from slightly overexposed Kodachrome. First time I noticed it as a teenager in the early 1970s was probably due to setting the ISO dial incorrectly, about +1/3. It finally made those Long Island seascapes look in photos like they did to my eye.<br>

<br>

The contrasty, saturated look from slight underexposure seems to be the David Alan Harvey style from his film days with Nat Geo. I was always puzzled by that look. I liked it when he did it. But if anyone else tried the same technique they'd be lambasted by technician-minded critics for poor exposure and composition. If you have the right name and an understanding editor who groks you, it's a style. Otherwise it's a mistake.</p>

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<p>Overexposing color print film by at least a full stop is the trend for a lot of wedding/portrait photographers these days, I do it to some degree depending on subject matter. There's no right or wrong, it just depends on the aesthetic you're after.</p>
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<p>I overexpose my color negative film by 1 stop but never make my print or scan light. I prefer to render some of the details in the shadow almost black. That is the shadow area look black on the print but if you let light shine thru you can see details in it. </p>
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<p>For an automatic only camera, your only adjustment is the ISO setting. Yes, you overexpose by decreasing the ISO setting knob. </p>

<p>Most such cameras don't have a way to select where you are metering, most often the whole scene. </p>

<p>More expensive cameras have other ways to adjust the exposure. Some have a +/- dial that allows some amount of change in either direction. Some have a manual mode, where the camera suggests an exposure, but you still have to set the dials. Some have an exposure lock, where you point the meter at something that you want to expose for, press the lock button, then compose for the desired shot.</p>

<p>More usually, you would do one, not both. Either adjust the ISO setting, OR meter for the shadows. Usually not both.</p>

-- glen

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