"EV" - is it a universal thing?

jay moussy · Oct 6, 2020

Is EV universal across the different periods of photography equipment?

An example: A Kodak Pony II has an EV scale, a 1950s German Balda rangefinder has also an EV scale, and a lightmeter can give me EV values.
Are these EV values the same, and can be used interchangeably?

Note: We are ignoring the "U.S. System" exposure values, as found on early folders and such.

AgX · Oct 6, 2020

Universal.
EV0 = f1.0 @ 1 sec @ ASA 100 (the resting values are pure calculation

BradS · Oct 6, 2020

jay moussy said:
Is EV universal across the different periods of photography equipment?

An example: A Kodak Pony II has an EV scale, a 1950s German Balda rangefinder has also an EV scale, and a lightmeter can give me EV values.
Are these EV values the same, and can be used interchangeably?

Note: We are ignoring the "U.S. System" exposure values, as found on early folders and such.

The APEX (Additive Photographic Exposure) System is well described in thei document by Doug Kerr...

http://dougkerr.net/Pumpkin/articles/APEX.pdf

in a nut shell, the system assigns consecutive integers to consecutive F/ stops , shutter speed, film speeds and (measured) brightness values
and uses the equation
Sv + Bv = Av + Tv
where:
Av is the integer associated with aperture
Tv is the integer associated with shutter time
Sv is the integer associated with film speed (ASA or ISO, or even DIN)
Bv is the integer associated with measured brightness.

and Ev = Av + Tv represents an aperture and shutter speed pair.

All modern photo exposure calculators and light meters are based upon this system.
It is a fairly complex idea that is pretty easy to use in practice.
If old introductory "how-to' photo books used to describe it in fair detail.

so, I guess, to answer your question, yes. Ev is, in this sense, a universal thing.

BradS · Oct 6, 2020

AgX said:
Universal.
EV0 = f1.0 @ 1 sec @ ASA 100 (the resting values are pure calculation

it's an interesting thing...technically, the speed value for ASA100 is 5 but meters are not set up this way. Even so, on the Gossen Luna Pro SBC for example, if I set the ASA to 100 and rotate the calculator dial so that 1 second is exactly opposite f/1, then the EV readout indicates EV 0. Doug Kerr addresses this anomaly on page 10 of the document I linked in post #3 above.

AgX · Oct 6, 2020

EV's have three uses:

-) transferring meter readings to a shutter (with both meter and shutter displaying EV's)

-) speaking about scenery or set luminance

-) indicating the sensitivity range of light meters (not to be mixed up with possible scale readings)

jay moussy · Oct 6, 2020

A silly question: the only date I saw in the above-cited Doug Kerr Standards document is 1961.
Can we assume an early use of EV on 1950s cameras were based on same math and principle, or some variation?

BradS · Oct 6, 2020

AgX said:
EV's have three uses:

-) transferring meter readings to a shutter (with both meter and shutter displaying EV's)

-) speaking about scenery or set luminance

-) indicating the sensitivity range of light meters (not to be mixed up with possible scale readings)

did you read Doug Kerr's article?

Strictly speaking EV is ONLY a shutter speed and aperture pair.
The other usages are incorrect but common.

AgX · Oct 6, 2020

Never heard of him. (The problem is, there is a bug at Apug since some weeks, that does not show me all unread postings, thus I did not see your respective posting...)

Just take a german light meter from the 50's and you will see that it is the same already.

I do not see why other uses would be incorrect.

BradS · Oct 6, 2020

jay moussy said:
A silly question: the only date I saw in the above-cited Doug Kerr Standards document is 1961.
Can we assume an early use of EV on 1950s cameras were based on same math and principle, or some variation?

maybe, maybe not.
If it is but if it really matters you should state the specific lens/shutter.

BradS · Oct 6, 2020

AgX said:
Never heard of him. (The problem is, there is a bug at Apug since some weeks, that does not show me all unread postings, thus I did not see your respective posting...)

Just take a german light meter from the 50's and you will see that it is the same already.

I do not see why other uses would be incorrect.

Read the article I linked above. It is based upon the ISO Spec. He explains all of these things.

jay moussy · Oct 6, 2020

BradS said:
maybe, maybe not.
If it is but if it really matters you should state the specific lens/shutter.

Maybe this:
https://vintagecameralab.com/balda-baldessa-ia/

I am considering buying a similar camera, which prompted my question, that is, will the EV readings on my light meter phone app correspond the ones on the camera?

BradS · Oct 6, 2020

Here is the article if you have trouble with the link....

BradS · Oct 6, 2020

jay moussy said:
Maybe this:
https://vintagecameralab.com/balda-baldessa-ia/

I am considering buying a similar camera, which prompted my question, that is, will the EV readings on my light meter phone app correspond the ones on the camera?

I am not familiar with that camera but I see that one of the photos shows a top view and it appears that the shutter has ordinary f/stops and shutter speeds marked on it too...so, it would be a trivial matter to discover if the EV scale on the shutter conforms to the ANSI/ISO standard and even if the EV scale is different (which I doubt) it would be easy to set shutter speed and aperture in the usual way.

AgX · Oct 6, 2020

Brad, I am speaking of the german "Lichtwert" system (LW or LV). To my understanding and to all international literature I got at hand: LW (LV) = EV

You then are speaking of the Apex system (which did not even find its way into german literature...).

The Lichtwert system was introduced in the early 50's by the west-german shutter manufacturer Deckel.
The Apex system originates from 1960.

BradS · Oct 6, 2020

AgX said:
Brad, I am speaking of the german "Lichtwert" system (LW or LV). To my understanding and to all german literature LW (LV) = EV

You then are speaking of the Apex system (which did not even find its way into german literature).

Yes, I refer to the ISO standard. The article I linked in post # 3 and included as an attachment in post #12 describes and refers to the ISO standard.

I cannot speak to the German literature but if it disagrees with the ISO standard.... then who shall we say is correct? I'm inclined to go with the international standard.

AgX · Oct 6, 2020

The OP asked obviously about values found on those scales. You however refer to a most complex system from the field of sensitometry, that I could not even find at non-US literature other than two photographic encyclopediae. And even there it goes directly into mathematics, where even an engineer must sit down first...

BradS · Oct 6, 2020

AgX said:
The OP asked obviously about values found on those scales. You however refer to a most complex system, that I could not even find at non-US literature other than two photographic encyclopediae. And even there it goes directly into mathematics, where even an engineer must sit down first...

yes, and...what is your point?

The standard is the standard. The theory behind photography is complex.
Are you upset with me about it? I didn't make this shit up.

AgX · Oct 6, 2020

Kerr writes:
"We often see, especially in camera specifications, a factor that seems
to be scene luminance (brightness) described in terms of an Ev
number. Such a factor might be, for example, the lowest scene
luminance for which the exposure metering system of the camera is
able to function reliably.
This usage is unfortunate and technically inappropriate, as Ev is a
measure of exposure, not luminance. There is a perfectly good APEX
quantity for luminance: Bv. I suspect the motive for the practice is
that many photographic enthusiasts have heard of Ev but not Bv"

Which photographer would know that "perfectly good APEX quantity" ? And which photographer does know of an entity as Bv ?
Over here for practical reasons even a photoengineer would use EV to describe the luminance of a scene. And I cannot imagine a US collegue would do differently.

I am not upset with you at all. All I am trying to say is that your reply is inappropriate to the the OP's question.

reddesert · Oct 6, 2020

https://en.wikipedia.org/wiki/Exposure_value

EV alone refers to a shutter speed - aperture combination.

L or LV refers to a luminance value, a brightness of the scene.

BradS · Oct 6, 2020

AgX said:
Kerr writes:
"We often see, especially in camera specifications, a factor that seems
to be scene luminance (brightness) described in terms of an Ev
number. Such a factor might be, for example, the lowest scene
luminance for which the exposure metering system of the camera is
able to function reliably.
This usage is unfortunate and technically inappropriate, as Ev is a
measure of exposure, not luminance. There is a perfectly good APEX
quantity for luminance: Bv. I suspect the motive for the practice is
that many photographic enthusiasts have heard of Ev but not Bv"

Which photographer would know that "perfectly good APEX quantity" ? And which photographer does know of an entity as Bv ?
Over here for practical reasons even a photoengineer would use EV to describe the luminance of a scene. And I cannot imagine a US collegue would do differently.

I am not upset with you at all. All I am trying to say is that your reply is inappropriate to the the OP's question.

The OP asked a question about EV. I provided the most accurate and authoritative information on the topic that I knew of.
If you have issues with the information in the ISO standard then I suggest you take it up with the standards committee.
Your criticism of me personally is inappropriate, not helpful and not appreciated.

Sirius Glass · Oct 6, 2020

I learned when using the Pentax Digital Spot Meter set to other than ISO 100 to take NOT take the EV to set the Hasselblad lenses, but take the f/stop and shutter speed from the spot meter and set that on the Hasselblad lenses and then use the EV on the lenses to compensate for the Zone System and filters. That is because the spot meter is set for the ISO you set, in my case usually ISO 400, while the lenses do not have an input for ISO and assume an ISO 100 thus causing problems. I learned this from Alan Ross at his week long c

reddesert · Oct 6, 2020

I'm holding a Kodak Retina IIc. This camera has a Synchro-Compur shutter with EV markings (it's made by Deckel, who I believe invented the EV system). The shutter and aperture are linked so that for example, setting EV = 10 is about 1/60 at f/4. Setting EV=3 is 1 sec at f/2.8. This agrees with the definition that EV=0 is 1 sec at f/1.0.

This camera does not have a meter. It has no idea what the ASA/ISO of the film is. EV just means a shutter/aperture combination. It doesn't assume ISO 100. When you look at a meter that reads in LV (light values), that does assume an ISO value. EV and LV are the same for some ISO value, presumably 100, but it's not the camera's fault.

AgX · Oct 6, 2020

reddesert said:
https://en.wikipedia.org/wiki/Exposure_value

EV alone refers to a shutter speed - aperture combination.

L or LV refers to a luminance value, a brightness of the scene.

Not to my source, where it is repeatedly stated that LV=EV.
(a source that was edited by Agfa researchers).

Also camera- and lightmeter-manufacturers state the sensitivity of their meters in EV, not LV.

reddesert · Oct 6, 2020

A source that uses EV = LV without specifying an ISO to make the conversion is being sloppy.

Here's an example of lightmeter specs:
https://gossen-photo.de/en/sixtomat-f2/
"Ambient light measuring range (at ISO 100/21°): EV -2.5 to 18"

I didn't look up every light meter on the planet. But it is clear that:
- cameras without meters have EV scales, and that has to refer to shutter and aperture alone, since the camera has no ISO.
- once an ISO is specified, then EV can be transformed into LV.

AgX · Oct 6, 2020

First, let me apologize; still several preceeding posts only show up for me after repeatedly opening this thread, thus I have difficulties following it.

BradS said:
The OP asked a question about EV. I provided the most accurate and authoritative information on the topic that I knew of.
If you have issues with the information in the ISO standard then I suggest you take it up with the standards committee.
Your criticism of me personally is inappropriate, not helpful and not appreciated.

You don't get my point.
To my understanding (likely the OP is so overwhelmed by this all, that he did not confirm what he actually is inquiring on) the OP's question is on those LW/LV scales at cameras and lightmeters, and whether these scales are all the same.

I answered that (leaving here aside whether my reply was right or wrong). You though came up with a sensitometric system that for the OP's question not only is irrelevant, but also is most complex and practically unknown or ignored in parts of the world.

What I do not even understand at your reply is how a system published in 1960 can be of relevance on what happened about 8 years earlier. I mean, with a reference to the APEX system one cannot answer whether all these LW/LV scales from the preceeding years are the same or not.

"EV" - is it a universal thing?

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