Why EV numbers instead of f-stops?

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I have been a professional (and well published) photographer since 1984 and before that I assisted for a few top level national pros for three years; I understand and use a (modified) zone system to help previsualize the final image when evaluating the contrast range of a scene or a setup and I have never seen or felt a need in still photography for meter readouts in EV readings (much preferring to use the direct language of the camera, f-stops). So can someone tell me why you would want to read light in EV numbers and then translate that to f-stops? It seems clumsy and inelegant but maybe there is a reason I am unaware of.

-- Ellis Vener (evphoto@insync.net), September 25, 1998


I think this question has been asked before, fairly recently, but possibly not in this forum.

When I use a meter, I am initially concerned about the contrast in the scene. By switching the meter to EV units, it tells me the range in stops. If I metered in aperture units, I would need to do some mental footwork to convert, and I usually get such things wrong. Having determined the EV that I want to appear at Zone V, I press a button, and get a shutter speed/aperture combination.

This is what works for me. I wouldn't attempt to persuade an experienced photographer to change their method to mine.

-- Alan Gibson (gibson.al@mail.dec.com), September 25, 1998.

I agree with Alan. For me, the use of EV values will give me a quick numerical check showing the range of values from important highlights to shadow detail....without having to worry about f/stops or shutter speeds. From that I can quickly see if the range of values will fit within the films latitude. I can quickly interpolate the EV value to an appropriate exposure. Again...whatever works for you.

-- John Wiemer (wiemerjo@slcc.edu), September 25, 1998.

The only advantage of EV numbers is that you need only a single number to measure the amount of light, whereas if f-stops are used you also need the shutter speed. However, with flash meters the shutter speed is irrelevant, so that is why flash meters almost always use f-stops rather than EV numbers.

-- Stewart Ethier (ethier@math.utah.edu), September 25, 1998.

That "only" advantage of using EV values is an important one Stewart. On my spot meter, I can use that one single EV value, together with the ISO of the film, to determine a placement of values and then transfer that data to a dial that will give me a myriad of exposure combinations to choose from. I then just determine whether shutter speed or f/stop is more relevant for what I wish to accomplish. Also...a minor point, but it is much easier to explain to a new student in photography the relationship of EV values as representing a stop difference than the f/stop numbers or shutter speeds.

-- John Wiemer (Wiemerjo@slcc.edu), September 25, 1998.

Thank you for your answers. I now understand "EV" thinking. I am one of those guys who early on spent a lot of time memorizing the f-stop scale (back in the days when my only camera was a Nikon F) so I still find it easier to directly think/see the f-stop to shutter speed relationship, so I guess this is a matter of different ways of training the brain.

-- Ellis (evphoto@insync.net), September 25, 1998.

Actually the only difference is whether you use a 35mm slr/rangefinder or a camera that has no meter. Most hand held meters give information in EV numbers and you then choose shutter speed/aperture combinations to fit the scene. Most single lens reflex or range finder cameras have the meter built in and directly offer you a value in f-stops/apertures. Then you have to work out the contrast spread of the scene in your head. Depends on what system you use. Works either way. And I hate smart aleck spellers.

-- `james (james_mickelson@hotmail.com), September 27, 1998.


Sorry you don't like puns. Most handheld meters that I am familiar with-- Minolta, Sekonic, Gossen,and Sinar-- all present their readings in either f/stop & shutter speed combinations or, as an option in EV terms. I can't speak for the Pentax spot meters as I haven't used one in twenty years. I still think it adds an extra layer of "fiddling" but that is probably due to early training and now force of habit. If you learned how to expose using a method that centers around Exposure Value numbers than perhaps my method would seem difficult, either way the goal is the same: to get a properly exposed piece of film. "Proper" exposure to me can mean either a technically correct image or one that expresses the thought , emotion or feeling you are trying to convey. Sometimes these two ideals overlap and sometimes they don't. As Ansel Adams wrote in "The Camera" (and it has been a long time since i read "The Camera" so I might get the quote very slightly wrong) in the camera: "...if a man has something to say, he can say it with a pinhole camera, but it would probably be easier to express that idea with a 4x5 Sinar." The point being: don't get so caught up in the technology that you forget why you are making the photograph in the first place.

One last point: I do use EV numbers when shooting motion pictures or video. Since the shutter speed is fixed it is easier to compare and set contrast levels using EV numbers.

Once again thank you all for the enlightening answers. Can we put this thread to sleep now?


-- Ellis (evphoto@insync.net), September 28, 1998.

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