EV constant or film speed dependent?

Christopher Walrath · Dec 26, 2007

I knew my original thread would come back out again. So . . .

Here it is a nutshell. EV11 is f5.6 @ 1/60th second (and all corresponding combinations). NO MATTER WHAT. For an on-camera meter, you set the ISO on the camera body. For a hand held meter you set ISO on the meter. The meter reading takes this into account and gives you the appropriate EV. Now where EV11 would be right for, say, ISO100, EV12 would be right for ISO200, EV13 for ISO400 and so on, but EV13 is EV13 (f2.8@1/1000 - f4@1/500 - f5.6@1/250 - f/8@1/125 - f/11@1/60 - f/16@1/30 - f/22@1-15). Exposure Value numbers are for a specific set of exposure combinations. Differing film speeds require different sets of EV's. But the EV itself is constant.

ISO only comes into play when also using Additive Light Values.
But that is another story.

Murray@uptowngallery · Dec 27, 2007

OK. CW, fix yer FROMERLY signature :O)

Steve Smith · Dec 28, 2007

"That's a perfectly crummulent word" Lisa's teacher in The Simpsons'

Steve.

Christopher Walrath · Dec 28, 2007

Oopsies. <backs out of room, twitching spasmodically>

BobNewYork · Jan 2, 2008

Sorry - can't resist. EV, (Exposure Value) is a measure of the brightness or intensity of light and, as such, is independent of film speed. A one unit change, up or down, of the EV indicates a doubling or halving of the brightness. I believe that EV 1 represented a brightness level that would require a one second exposure at f1 with 100 ASA film to accurately produce an 18% grey negative with standardized development. The linkage or converter dials or whatever merely translate a known, absolute brightness into a usable shutter speed/aperture combination for the film speed indicated. At least that WAS the original intent. A change in subject brightness of 1 EV would require a change in exposure of one full stop, (step?) to maintain image density. Today the term EV is widely used on modern cameras to indicate exposure compensation.

Yeah, I know, BORING. Just remember explaining it in my Dad's camera shop back in the sixties!! Sorry!!

JBrunner · Jan 2, 2008

EV is a simple method of expressing reciprocity. Other information must be applied and extrapolated, in order to draw a conclusion concerning exposure.

BrianShaw · Jan 2, 2008

JBrunner said:
EV is a simple method.

I'm now agreeing with Dave Miller (post #12) - there isn't anything "simple" about it anymore!

Richard Kelham · Jan 2, 2008

OK, one last heave....EV is constant for a given light level. What a given EV translates to in terms of shutter speed and aperture is film speed dependent. Punkt.

If the OP wants to practise estimating EVs fine, but for gawd's sake keep your meter set to ISO100.

Now where's that bloody corkscrew....

Richard

ITD · Jan 3, 2008

Richard Kelham said:
If the OP wants to practise estimating EVs fine, but for gawd's sake keep your meter set to ISO100.

That's the conclusion I'd come to! Thanks all for your replies, I've got it now

Chan Tran · Jan 3, 2008

In the original meaning EV is constant for i.e. set the camera to EV15. When EV is used to express a brightness level it should be accompanied with an ISO number i.e the camera autofocus system would work to EV1@ISO100. And then again sometimes EV is used to express the difference in either brightness level or exposure i.e. this subject is 1 EV brighter than the other or increase exposure by 1 EV. Strictly speaking, only the first meaning is correct but the term EV has been widely used to mean all three.

polaski · Jan 7, 2008

All I know is that after I used a Voigtlander Vito B, with a locking EV scale between the aperture and speed scales, EV is a measure of light. Using that camera pounds it into one's head.

goros · Jan 8, 2008

From my point of view, EV is clearly related to film ISO speed.

If EV stands for Exposure Value, the film speed is one of them and conditions the value of the other two, shutter speed and diaphragm opening and it is clearly visible when you get the EV in your lightmeter: it is not the same when the meter ISO is set to 100 than when it is to 400. So you could have 1 second at f/1.4 (EV1) at ISO100 but if your film is ISO400, you will get 1/4 second at f/1.4 (EV3) at ISO400.

If this is not related to ISO speed, then tell what is related.

Cheers

Steve Smith · Jan 8, 2008

goros said:
If this is not related to ISO speed, then tell what is related.

My understanding is this: EV (Exposure Value) is the setting on the camera. e.g. f16 at 1/125 is EV15 (as is f11, 1/250; f8, 1/500; etc).

This is true whatever ISO (or EI) of the film. On cameras such as my Rolleicord which have linked shutter and aperture dials, an EV value is indicated. As this is a manual camera, it does not know the film's ISO and you do not set it.

When the film ISO (or EI) is involved, it then becomes a Light Value (LV).

Steve.

Ian Grant · Jan 8, 2008

Steve's totally right. To quote "In photography, exposure value (EV) denotes all combinations of camera shutter speed and relative aperture that give the same exposure"

Back in the 50's and 60's many cameras had lenses with built in shutters where you could set the EV and then turn one ring which altered the aperture and shutter speed while maintaining the same exposure. I have an Ilford Sportsman, a Rollieflex and a Yashicamat with this function. Most light meter will give an EV reading, usually this is independent of the ISO setting.

It does not take into account any reciprocity failure or the EI of the film. But the BS/ASA standards later assumed a standard of 100 BS/ASA

Some cameras/light-meters have the EV ring coupled to an ASA setting.

Ian

noseoil · Jan 8, 2008

Can't we have a meter with the EV, reciprocity, bellows factor and filter factor on one little ring? That would surely help to simplify this thread. tim

Corkscrew hell! Where'd I leave my bong?

Ian Grant · Jan 8, 2008

Some of us already have one Tim, it's called a "Brain"

Ian

EV constant or film speed dependent?

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