"EV" - is it a universal thing?

AgX · Oct 6, 2020

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

When the term "LW" rsp. "LV" was introduced, there was no ISO at all.
If you refer by ISO to film speed, then I do not get your point. By definition the LV was based on a film speed, and at different film speed settings at the meter a different LV showed up at the dial.

AgX · Oct 6, 2020

reddesert said:
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.

Isn't this hairsplitting on terminology? Thus the value at the meter is a LV value, as it is dependent on film speed, but the value on the shutter dial is a EV value ?

Even if so, the problem is that when that system was introduced in the early 50's, the term "EV" did not yet exist. The only term was "LW" resp. "LV" and that was used for both scales, at the meter and the shutter.

thuggins · Oct 7, 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.

This is not correct. Although I believe it is a longstanding misconception that was contemporary when the system was in active use. It seems a natural assumption based on the names; "Exposure Value" being related to the camera shutter speed and aperture, while "Light Value" being some independent concept of brightness.

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

This is correct. EV and LV are two terms meaning the exact same thing. I will defer to AgX's knowledge of German for the derivation of LV. But here is a quote from the instruction manual of a Walz meter from the '50's.

"EV Number and LV Number are exactly the same. The 'EV' nomenclature has been adopted by the A.S.A. as the standard 'Exposure Value' system. The 'LV' nomenclature is used on most foreign cameras for a standard 'Light Value' system. Both systems are identical."

reddesert · Oct 7, 2020

People keep saying that an EV 0 is 1 sec at f/1.0 at ASA 100. It isn't. It's just 1 sec at f/1.0. An EV is not a measurement of light.

http://camera-wiki.org/wiki/Light_and_Exposure_Values_(LV_&_EV)

AgX · Oct 7, 2020

Let's assume you are right. But still then it only would be academic hairsplitting about a term. Of even lesser implication than saying that something has a weight of x kg, whereas it should be mass of x kg.

And it does not make the OP wiser too...

MattKing · Oct 7, 2020

As I understand it, EV = LV, but when you make use of the system with a meter in hand and want to communicate information about light levels to others, you need to reference a film speed too.
In other words: "I set the camera to EV 6".
Compared with: "There wasn't much light - I used a camera setting of EV 6 with ISO 100 film".

Chan Tran · Oct 7, 2020

reddesert said:
People keep saying that an EV 0 is 1 sec at f/1.0 at ASA 100. It isn't. It's just 1 sec at f/1.0. An EV is not a measurement of light.

http://camera-wiki.org/wiki/Light_and_Exposure_Values_(LV_&_EV)

You're right! Even the APEX system said the EV is only the combination of Av and Tv (aperture and shutter speed). They use the term BV and LV for what we call LV although they based on ISO 0.33 instead of 100.

thuggins · Oct 7, 2020

reddesert said:
People keep saying that an EV 0 is 1 sec at f/1.0 at ASA 100. It isn't. It's just 1 sec at f/1.0. An EV is not a measurement of light.

http://camera-wiki.org/wiki/Light_and_Exposure_Values_(LV_&_EV)

WOW! It's on the Internet! It has to be true!

I'll see your wiki article and raise you a contemporaneous statement by one of the worlds leading manufacturers of photography accessories, that specifically and directly addresses this issue.

The misunderstanding that you are referencing in likely almost as old as the system itself. The fact that Walz felt the need to so clearly and forcefully correct the misconception is evidence of that. I suspect that it stems from Americans seeing reference to LV numbers and trying to reconcile them to EV numbers. "Hmmmm... they must be similar. But the can't be the same as they have different names."

(BTW, the bit about something on the internet being necessarily true was sarcasm. A great deal of what is on the internet is not at all true.)

reddesert · Oct 7, 2020

AgX said:
Let's assume you are right. But still then it only would be academic hairsplitting about a term. Of even lesser implication than saying that something has a weight of x kg, whereas it should be mass of x kg.

And it does not make the OP wiser too...

It may sound like hairsplitting, but the distinction between a shutter speed + aperture combination, versus a shutter-speed + aperture + film speed combination, is fundamental to understanding metering and exposure. Only the latter one actually tells you how much light is in a scene. I'm sure the experienced photographers in this thread all understand that, but blurring the distinction makes it harder to teach people, especially if they didn't grow up with manual cameras.

If you look around on the internet there are a ton of tables giving "EV" for various common scenes, like https://en.wikipedia.org/wiki/Exposure_value#Tabulated_exposure_values or https://photographylife.com/exposure-value or http://www.fredparker.com/ultexp1.htm#Light Intensity Chart , and they all have to indicate "at ISO 100", or put it in a footnote, or they leave it off and confuse the issue.

BradS · Oct 7, 2020

thuggins said:
WOW! It's on the Internet! It has to be true!

I'll see your wiki article and raise you a contemporaneous statement by one of the worlds leading manufacturers of photography accessories, that specifically and directly addresses this issue.

The misunderstanding that you are referencing in likely almost as old as the system itself. The fact that Walz felt the need to so clearly and forcefully correct the misconception is evidence of that. I suspect that it stems from Americans seeing reference to LV numbers and trying to reconcile them to EV numbers. "Hmmmm... they must be similar. But the can't be the same as they have different names."

(BTW, the bit about something on the internet being necessarily true was sarcasm. A great deal of what is on the internet is not at all true.)

Didn't you mention previously that Walz wrote this in the 1950's ? That would be prior to the ANSI standard (1961) and certainly prior to all the subsequent revisions of the ANSI standard that eventually resulted in the ISO standard. Clearly the ISO Standard must be accepted as Correct. It supersedes all prior standards...even the initial de facto industry standard(s) which the standards committee may have attempted to incorporate in the initial revision of the formal standard.

Luckless · Oct 7, 2020

reddesert said:
People keep saying that an EV 0 is 1 sec at f/1.0 at ASA 100. It isn't. It's just 1 sec at f/1.0. An EV is not a measurement of light.

http://camera-wiki.org/wiki/Light_and_Exposure_Values_(LV_&_EV)

But an EV without regard to sensitivity is an utterly useless concept for anyone attempting to make use of an exposure, and it directly becomes a measurement of light once you add that context. [Literally how every single light meter I own provides me a reading...]

I really can't understand the desire to maintain a notation that deliberately drops the context needed to actually utilize it, just to shoe horn on additional elements to the notation to then make it functionally identical, when EV[ISO] works so wonderfully well.

EV[100] 0 = 1 sec at f/1.0

Switch to [50] - You're now a stop lower, so in the same scene you would drop down and use EV[50] -1 = 2 sec at f/1.0 to equal the same relative exposure.

Using film at ISO 100 and add a 1 stop filter? Assuming you're not metering through the filter, then you compensate by measuring as EV[50], or take one off your EV[100].

EV/Sensitivity | Shutter Speed | Aperture - Three coupled values that work beautifully in lockstep by similar stop value. Move one value up or down, to lighten or darken, but adjust the other two by the same combined amount to keep the same overall effective light. It is a really beautiful and simple system, and it seems a shame to waste time with bothering to be 'more technically correct' for no great benefit.

Photographers have been improving and streamlining systems and scales since the beginning. I can't really see any good reason to stop this tradition at distinct LV and contextless EV.

Sure, it might be handy to be aware of, but I've gotten more mileage out of knowing about roman miles than I have the LV scale.

Sirius Glass · Oct 7, 2020

BradS said:
I think a close and careful reading of the Wikipedia article for APEX might help some folks clarify the confusion.

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

I think people need to understand the history that led up to the standardization....which the wiki article does touch on briefly.

It also makes clear that EV refers to an aperture and shutter speed pair only.
Other usages are common and mostly understood but, technically incorrect.

The magazine article written by Doug Kerr also goes over this in some detail.

No we do not need to understand the history. My Hasselblad and other cameras use the EV system. My light meters use the EV System. I have no use for LV.

AgX · Oct 7, 2020

reddesert said:
It may sound like hairsplitting, but the distinction between a shutter speed + aperture combination, versus a shutter-speed + aperture + film speed combination, is fundamental to understanding metering and exposure.

When teaching the LW systen I always hint at that it is based on film speed. And that in use as descriptor of scene luminance a standard film speed is used. I do not see why to emphasize this I need to substitute EV fot LV.

By the way, we got the same issue with guide numbers, even worse, as the reference film speed even changed over time, and other variables come into as metrical or imperial distance, or coverage. I do not know of a respective discussion there, let alone specific terms.

BradS · Oct 7, 2020

Sirius Glass said:
No we do not need to understand the history. My Hasselblad and other cameras use the EV system. My light meters use the EV System. I have no use for LV.

Ah...I think that you have misunderstood what I was trying to say. Re-reading that post of mine, it is easy to understand why you might have done so.

Your first post (post #21) in this thread is actually the best so far. It demonstrates the actual reality perfectly and is not inconsistent with the ISO standard. That could have been the beginning and end of replies to this OP. All the rest of this noise is just meaningless and comical when you think about it...no amount of fuss or shouting at each other here is going to change the ISO standard nor how one must interact with a Hasselblad (of certain vintage?)

Sirius Glass · Oct 7, 2020

Sirius Glass said:
No we do not need to understand the history. My Hasselblad and other cameras use the EV system. My light meters use the EV System. I have no use for LV.

BradS said:
Ah...I think that you have misunderstood what I was trying to say. Re-reading that post of mine, it is easy to understand why you might have done so.

Your first post (post #21) in this thread is actually the best so far. It demonstrates the actual reality perfectly and is not inconsistent with the ISO standard. That could have been the beginning and end of replies to this OP. All the rest of this noise is just meaningless and comical when you think about it...no amount of fuss or shouting at each other here is going to change the ISO standard nor how one must interact with a Hasselblad (of certain vintage?)

As usual, as soon as I clear things up, a bunch of people jump in and work to get the waters as muddy as they can.

jay moussy · Oct 7, 2020

Stepping away from the finer points of the whole thread, here, what prompted the sudden popularity and addition of EV scales on photo equipment in the late 50s early 60s?

Sirius Glass · Oct 7, 2020

jay moussy said:
Stepping away from the finer points of the whole thread, here, what prompted the sudden popularity and addition of EV scales on photo equipment in the late 50s early 60s?

1) "Starting 1954, the so-called Exposure Value Scale (EVS), originally known as Light Value Scale (LVS), was adopted by Rollei, Hasselblad, Voigtländer, Braun, Kodak, Seikosha, Aires, Konica, Olympus, Ricoh and others, introducing lenses with coupled shutters and apertures, such that, after setting the exposure value, adjusting either the shutter speed or aperture made a corresponding adjustment in the other to maintain a constant exposure." - https://en.wikipedia.org/wiki/APEX_system

2) It is more convenient to set the exposure and then rotate the shutter speed ring and the f/stop ring ganged together to adjust for the Zone System and filters as I stated in post #21.

thuggins · Oct 7, 2020

jay moussy said:
Stepping away from the finer points of the whole thread, here, what prompted the sudden popularity and addition of EV scales on photo equipment in the late 50s early 60s?

It came about with the advent of selenium light meters. Getting a reading of two values required a computer (we would dismiss it as some dials) that had to be set, adjusted and then read. It was much easier and mechanically simpler to display a single value. Especially on the tiny, shoe mounted meters this was pretty standard.

You will see references to "easily changing shutter speed and aperture while maintaining the same exposure". While this may be true, the real driver was to simplify the operation of the meters.

BradS said:
Didn't you mention previously that Walz wrote this in the 1950's ? That would be prior to the ANSI standard (1961) and certainly prior to all the subsequent revisions of the ANSI standard that eventually resulted in the ISO standard. Clearly the ISO Standard must be accepted as Correct. It supersedes all prior standards...even the initial de facto industry standard(s) which the standards committee may have attempted to incorporate in the initial revision of the formal standard.

The Walz manual specifically references the A.S.A. (American Standards Association). A.S.A. changed its name to ANSI in 1969.

BradS · Oct 7, 2020

thuggins said:
The Walz manual specifically references the A.S.A. (American Standards Association). A.S.A. changed its name to ANSI in 1969.

Ok so what Waltz wrote in the 1950’s was true when he wrote it and could very well have been made obsolete by any of the several subsequent revisions of the standard.

Whatever. I’ve lost interest and regret participating in this pointless discussion.

None of this minutia matters unless one is designing a light meter. Simple fact is we take a meter reading and transfer the aperture and shutter speed to the camera. A photographer interested in making photos need never know or care about EV or LV.

thuggins · Oct 8, 2020

Thru a happy coincidence, I just received this cute little bugger in today's mail. It is a selenium meter, so from the heyday of the EV/LV period.

Note that the Exposure Value scale is labeled LV, and the film speed selection pointer is labeled LV . ASA.

jay moussy · Oct 8, 2020

@thuggins I was also playing with the new-to-me Baldessa 1b rangefinder and its built-in (but not coupled) selenium meter, with only only EV labels, sadly!

BTW,what is the required care, or caution for a selenium meter?

thuggins · Oct 8, 2020

jay moussy said:
@thuggins I was also playing with the new-to-me Baldessa 1b rangefinder and its built-in (but not coupled) selenium meter, with only only EV labels, sadly!

BTW,what is the required care, or caution for a selenium meter?

I have a (ridiculous) number of light meters, varying from the early GE ones before there were standard exposure scales to one with a USB cord to charge it. Some observations (These are specific to hand held meters, not "modern" TTL meters):

- Selenium meters are much more robust than CdS. Nearly all of my selenium meters still "work", and nearly all of those are quite accurate. I believe two of my CdS meters work. One of these is a fairly new (<50 years old) Sekonic and the other is a top of the line Metraphot. Keep in mind that any selenium meter will be at least a couple decades older than a CdS, so that is a pretty remarkable track record.
- Keep them in the dark. Contrary to popular wisdom on the internet, selenium cells do not "wear out" like a discharged battery. But any circuit that has electricity running thru it is more susceptible to corrosion. This increases resistance and will cause the meter to read low and eventually not read at all. For the same reason it is best to store them in a dry place. Here in Dallas, humidity is not a major issue. But if you need to take special precautions against lens fungus, you may want to be mindful of your meters. For cameras that are displayed (perhaps like your Baldessa), I cut a piece from a business card that completely covers the cell.

This is my go-to meter. It has never let me down. I have several of this same model and they all work as good as the day they were made.

swchris · Oct 8, 2020

BradS said:
Ah...I think that you have misunderstood what I was trying to say. Re-reading that post of mine, it is easy to understand why you might have done so.

Your first post (post #21) in this thread is actually the best so far. It demonstrates the actual reality perfectly and is not inconsistent with the ISO standard. That could have been the beginning and end of replies to this OP. All the rest of this noise is just meaningless and comical when you think about it...no amount of fuss or shouting at each other here is going to change the ISO standard nor how one must interact with a Hasselblad (of certain vintage?)

Actually, this post is wrong for my Hasselblad and Gossen Profisix combination. On the ProfixSix the EV changes when I change the ISO setting. Therefore I can read out the EV value and just set it on the lens.

AgX · Oct 8, 2020

swchris said:
On the ProfixSix the EV changes when I change the ISO setting. Therefore I can read out the EV value and just set it on the lens.

This is so with all meters with a LV/LW/EV scale.
Otherwise the system would not work.

And of course Gossen put "LW=EV" on a meter.

BrianShaw · Oct 9, 2020

This question and the ensuing conversation seems to come up about annually, and always seems to have the same arguments and conclusion.

"EV" - is it a universal thing?

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