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06/21/2004 01:39:21 PM · #1 |
I've been reading about Ansel's Zone System, and started thinking about the advice to ajust by X number of stops. Obviously this controls the amount of exposure - as does aperture and shutter speed.
In shutter speed, we control how long the light is allowed to reflect on the sensor. With aperture we control how wide a portal the light comes in through, thus affecting depth of field. Then there's exposure compensation. Is this controlling length of time the image is exposed, or is it affecting aperture somehow? Or is the exposure always the same, but put compensation pushes or pulls a bit more processing voodoo from it?
Main reason I'm curious is that if I want to use the zone system, and need to stop down by 2 stops, would I always change aperture, or would I achieve a similar effect by edjusting EC by +/- 2?
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06/21/2004 01:53:53 PM · #2 |
All exposure compensation does is adjust the setpoint where the light meter system indicates the "correct" exposure. Aperture and shutter speed are the only means of varying exposure.
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06/21/2004 01:54:01 PM · #3 |
Exposure compensation will adjust the shutter speed, not the aperture. (that's how it works on the cameras I have) This applies to all modes except full manual since in that mode you have complete control.
You can adjust either the shutter speed or the aperture to change the exposure. It just depends on what you want to achieve.
You can also change the exposure by adjusting the ISO.
Message edited by author 2004-06-21 13:55:12.
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06/21/2004 01:58:09 PM · #4 |
Originally posted by Spazmo99:
All exposure compensation does is adjust the setpoint where the light meter system indicates the "correct" exposure. Aperture and shutter speed are the only means of varying exposure. |
This is what I suspected... Thanks for the clarification!
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06/21/2004 02:05:33 PM · #5 |
The Zone system is a dual process - both in the camera and in the darkroom. It is used when there is too much variation in the lighting (too many stops between the lightest and darkest areas). So you expose the film for one end of the spectrum and then "make up for it" when you process the film. By leaving it in the developer (fluid) longer, you force more detail in the shadows.
It is primarily used for Black and White - and has little practical usage for color.
If you want to underexpose by two stops - you need to let less light in. That means either change the shutter speed or the aperture or both.
There is a recipical relationship bewteen aperture and shutter speed. Each 1-stop difference must be matched by an opposite 1-stop to maintain correct exposure.
So if the exposure is CORRECT for f8 and 1/125 it will also
be CORRECT for f11 and 1/60
or for f 5.6 and 1/250
In this situation to underexpose 2 stops you would need to shoot - using the first example f8 and 1/500 or f16 at 1/125 or f11 at 1/250.
Depending on your make of camera and the mode you are in - the exposure compensation does exactly the same thing - but it an "easier" way.
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06/21/2004 02:08:29 PM · #6 |
The problem with digital is that you can't really make it up in the darkroom. You need to make multiple exposures and overlay them.
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06/21/2004 02:14:47 PM · #7 |
| It is worth noting at this point that the characteristics of panchromatic film and digital sensors vary greatly. The "expose for the highlights" rule of thumb for film does not apply at all for digital sensors, in fact quite the opposite is the case. Digital sensors are much more susceptable to losing shadow detail rather than highlight detail, especially when shooting raw, which will often allow an extra stop of highlight detail to be recovered. So with digital sensors it is much more useful to expose for the shadows and bring out the highlights in processing. |
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06/21/2004 02:18:49 PM · #8 |
Originally posted by nathank:
It is worth noting at this point that the characteristics of panchromatic film and digital sensors vary greatly. The "expose for the highlights" rule of thumb for film does not apply at all for digital sensors, in fact quite the opposite is the case. Digital sensors are much more susceptable to losing shadow detail rather than highlight detail, especially when shooting raw, which will often allow an extra stop of highlight detail to be recovered. So with digital sensors it is much more useful to expose for the shadows and bring out the highlights in processing. |
Wait, I thought the opposite was true. According to this article:
//luminous-landscape.com/tutorials/expose-right.shtml
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06/21/2004 02:27:22 PM · #9 |
Originally posted by jmsetzler:
The problem with digital is that you can't really make it up in the darkroom. You need to make multiple exposures and overlay them. |
Setz is correct.
The most common term for this technique is Contrast Masking. Usually it is used for scenics where two or more shots are made using a tripod. Although if the range is not too great, you can do it by shooting RAW and using a program such as C1 to generate 2 different image files (tiff or jpg), one with correct highlight exposures and the other with shadow detail from the same RAW file and combine them in layers. In this case, you wnat to make sure that you do not overexpose the highlights.
Most significantly, at least for DPC members is the fact that this single exposure technique was deemed legal for member challenges when i brought it up in an earlier thread, whereas the two shot technique is obviously not legal for any DPC challenge.
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06/21/2004 02:30:08 PM · #10 |
Originally posted by BikeRacer:
Originally posted by nathank:
It is worth noting at this point that the characteristics of panchromatic film and digital sensors vary greatly. The "expose for the highlights" rule of thumb for film does not apply at all for digital sensors, in fact quite the opposite is the case. Digital sensors are much more susceptable to losing shadow detail rather than highlight detail, especially when shooting raw, which will often allow an extra stop of highlight detail to be recovered. So with digital sensors it is much more useful to expose for the shadows and bring out the highlights in processing. |
Wait, I thought the opposite was true. According to this article:
//luminous-landscape.com/tutorials/expose-right.shtml |
The expose to the right technique is not the same as exposing for the highlights, it is in fact exposing to maximize the overall amount of image data recorded by the sensor, particularly in the shadow areas. Because the amount of image data recorded decreases linearly from the brightest stop in the exposure range, the shadows get the worst end of the bargain, with only 128 levels of brightness availiable for the darkest tones, while the brightest have a full 2048 levels of brightness availiable. Exposing to the right pulls the shadows up into the brighter stops of your camera's dynamic range, doubling or even quadrupling the amount of brightness levels possible. Exposing to the right is typically done after a proper exposure is gained; the exposure is then "shifted" (increased by 1-2 stops) on the histogram towards the right. Granted, if you are exposing to the right it is often less likely you will have to worry about lost shadow detail, but if you image does encompass the entire 5-stop dynamic range of your sensor, it is more important to avoid losing shadow detail than highlight detail.
Message edited by author 2004-06-21 14:31:43. |
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