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03-05-2019, 09:52 AM - 2 Likes   #1
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Interesting article on EV

I just ordered an old film camera that uses displays EV(exposure values) in the viewfinder rather than aperture/shutter speed. My Gossen Pilot Light Meter also shows EV. Found an interesting article while researching the camera by Fred Carter on the subject. It also contains a lot of info that to a neophyte at film shooting I found interesting and useful. Thought I'd share just in case others have similar cameras/light meters.Ultimate Exposure Computer

03-05-2019, 10:59 AM   #2
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Oh yeah. I've seen that before. It has good info. My Zeiss lenses for my 500C/M have an EV scale on them in addition to f-stop. And of course my Pentax one-degree spot meter reads in EV.
03-05-2019, 11:00 AM   #3
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Interesting article.... .. using an incident light meter and camera in manual mode it works well to depict realistic exposures, although realistic isn't necessarily the best for an image to look good. Without a stand alone light meter, the camera light meter can be used when pointing the lens to a 18% gray card and locking the exposure (pressing the AE-L button). Exposure is a whole important topic, and raises questions: When to I exposure to preserve high light or should I get a correct exposure of the mid-tones and shadows while accepting burned high lights?
03-06-2019, 10:11 AM   #4
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QuoteOriginally posted by biz-engineer Quote
Interesting article.... .. using an incident light meter and camera in manual mode it works well to depict realistic exposures, although realistic isn't necessarily the best for an image to look good. Without a stand alone light meter, the camera light meter can be used when pointing the lens to a 18% gray card and locking the exposure (pressing the AE-L button). Exposure is a whole important topic, and raises questions: When to I exposure to preserve high light or should I get a correct exposure of the mid-tones and shadows while accepting burned high lights?
The 18% gray card method will work as long as everything in the scene has Lambertian reflectance (Lambertian reflectance - Wikipedia) and is lit by the same very distant light source (e.g., the sun) as the 18% gray card.

If there are different light sources illuminating the scene (e.g., shade and sun), then things get a little messy. (Exposing with the gray card in the brighter light helps.)

If the light source illuminating the scene is at very different distances to different parts of the scene (e.g., a single room light or a photoflash), then things get more messy. (Exposing with the gray card in the brightest area of the light helps but sometimes the ratio between the brightest and darkest parts of the scene are too much.)

If some of the objects in the scene are shiny, then things get messy. (Chances are the reflections will blow-out.)

If some of the objects in the scene are the light sources for the scene, then things may be almost impossible. (Blow-outs are unavoidable: the disk of the Sun is about EV 32 or 17 stops brighter than the sunlit ground.)

---

The more fundamental problem is that prints, slides, and computer displayed images all have a fixed and modest maximum brightness. The image of a "white" object in a scene needs to reflect, transmit, or display 100% brightness in order to look white. But if a scene contains both a white object and also the bright or reflected light source that illuminates that white object, then the print, slide, or computer image would have the impossible task of being BOTH 100% bright for the white object and then 1000%, 10,000%, or even 10,000,000 % bright to accurately replicate the image of the light source.

03-06-2019, 11:24 AM   #5
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Nice article you found there. Commenting for future reference.
03-06-2019, 11:44 PM   #6
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QuoteOriginally posted by photoptimist Quote
If there are different light sources illuminating the scene (e.g., shade and sun), then things get a little messy. (Exposing with the gray card in the brighter light helps.)
If the scene is outdoor, the shadow can be seen as a result of lack of light from the main source (the sun), exposing it by the sunny 16 rule or incident light metering lead to exposing for how the shadow really is and not how the eyes see it. Eyes will adapt to light level dynamically. I suppose there is no right or wrong exposure , as it depends on what kind of result is wanted.

---------- Post added 07-03-19 at 07:53 ----------

QuoteOriginally posted by photoptimist Quote
The more fundamental problem is that prints, slides, and computer displayed images all have a fixed and modest maximum brightness. The image of a "white" object in a scene needs to reflect, transmit, or display 100% brightness in order to look white. But if a scene contains both a white object and also the bright or reflected light source that illuminates that white object, then the print, slide, or computer image would have the impossible task of being BOTH 100% bright for the white object and then 1000%, 10,000%, or even 10,000,000 % bright to accurately replicate the image of the light source.
Yes. there is also the limitation of the image recording and displaying. The maximum range of light intensities may not fit into the range that can be recorded by the sensor. We have the choice to compress the high light with graduated filters, or underexpose shadows and raise shadows digitally, it's like compressing the real light dynamic range into a smaller range, hence less contrast. The end result is only a trade-off: between good contrast or more faded image having all of the image details visible.
03-24-2019, 12:34 PM   #7
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I first encountered Fred Picker's Ultimate Exposure Computer page several years ago. Probably the most important take-away is the fact that Exposure Value (EV) does not refer to a quantity or intensity of light. Rather, the numbers indicate powers of two expression of the amount of exposure* given the film/detector as determined by mechanism and fully divorced from the film/detector sensitivity. It is that last that provides a key insights into how one's camera works and how to figure exposure for both ambient light and flash.


Steve

* Think in terms of sunbathing.
03-24-2019, 01:02 PM   #8
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Most handheld light meters I have owned had an EV readout window,
and showed all combinations of shutter speed and aperture at the set film speed that will achieve it.
This can be a good learning tool; I wish I'd had one of these before I got my first adjustable lens camera.

In the late 1950's/early 1960's in an effort to simplify exposure many cameras had EV settings, some with coupled aperture and shutter speed selectors.
I had one such camera and found the EV system a bit of an annoyance, as it was hard to adjust those controls independently.

Chris

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