EV chart question

First off, sorry if this is in the wrong section. Mods may move at their discretion. Second, I am sure this has been hashed and rehashed on this forum and I regret that I didn't do my due diligence and search. But...

Am I understanding this correctly?

Let's say I am in P mode on my camera and ISO 100. The camera meters the scene and chooses to use F5.6 and 1/30 as it's aperture and shutter speed. Based on the attached chart, that gives an EV value of 10.

If I switch to M mode, will I then be able to go across the entire EV 10 range values and get the "same" exposure?

F1.4 & 1/500 to F22 & 1/2 if my lens has a max aperture of 1.4 and a min of F22?

If this is correct, then when I change my ISO from 100 to 200, or one stop, my EV would go to 11 and my exposure range would be F1.4 & 1/1000 to F22 & 1/4?

Thanks!

Chart can be viewed from here and it's located all the way at the bottom...

Moonshiner wrote in post #16948617
If I switch to M mode, will I then be able to go across the entire EV 10 range values and get the "same" exposure?

Yes

Moonshiner wrote in post #16948617
F1.4 & 1/500 to F22 & 1/2 if my lens has a max aperture of 1.4 and a min of F22?

Yes

Moonshiner wrote in post #16948617
If this is correct, then when I change my ISO from 100 to 200, or one stop, my EV would go to 11 and my exposure range would be F1.4 & 1/1000 to F22 & 1/4?

No. In the same amount of light, the EV value is unchanged, regardless of ISO value. However, that chart does publish EV as if it refers to an illumination level at ISO 100. So rather than f/1.4 with 1/1000 at ISO 100, you would use [f/2 with 1/1000, or use f/1.4 with f/2000] at ISO 200.

Wilt wrote in post #16948778
No. In the same amount of light, the EV value is unchanged, regardless of ISO value. However, that chart does publish EV as if it refers to an illumination level at ISO 100. So rather than f/1.4 with 1/1000 at ISO 100, you would use [f/2 with 1/1000, or use f/1.4 with f/2000] at ISO 200.

Ahh... I see... That makes sense... Thanks!

Moonshiner wrote in post #16948617
First off, sorry if this is in the wrong section. Mods may move at their discretion. Second, I am sure this has been hashed and rehashed on this forum and I regret that I didn't do my due diligence and search. But...

I don't think that on this forum "due diligence" would have yielded much, because that article and the charts he shows have some viewpoints that would be alien to most of us! For example, we (at list in our discussions) don't have a list of EV numbers from 1-10. For most of us, EV is about a couple things:

First, in the practical world, EV denotes the level of exposure you get from the combination of aperture, shutter speed and ISO. If you set those to what the camera considers "normal", such as your P-mode or another auto mode if don't apply any Exposure Compensation, then we typically refer to that as EV 0. If you do either apply some exposure compensation or change one of those three settings, then you change your EV, so if, for example, your camera is metering a scene/subject and giving 1/100 sec, f/4 @ ISO 100, then if you shoot with those settings, the meter/exposure is at "EV 0". But for many of us, we don't want that exposure, we want to either boost the exposure higher or lower, so we use one of the above approaches to do that, so say if you adjust your settings to 1/50 sec, f/4 @ ISO 100, you are doubling the amount of light taken in, meaning that according to the camera meter, you are pushing the exposure up to EV +1 (or +1 EV).

I'm putting this in these practical hands-on terms, because, well, most of us have likely not studied something like the article/charts you linked to, and our discussions will me more "hands-on"!

The second "scenario" in which it might come up is in the context of camera specs, regarding the "Metering Range" of a camera as it relates to the AF function, where it will give the range of a camera's effective metering in EV values. So, if you read the Specifications in your camera manual you'd come across that term! It has, though, to do with the ambient light, not your camera settings, although I don't have the expertise/understandin​g to delve into that topic!

Whether or not your EV changes based on ISO depends on how you are using/defining an EV.

My light meter spits out an "EV", and the light off my computer monitor right now gives me 7 and 2/3rd EV at ISO 800, and 9 and 2/3rd EV at ISO 3200.

So it depends on which direction you choose to approach the math, but it all ties back into the exposure triangle. The equation balances out four values, ISO, Aperture, Time come together to give you EV. And like any equation you can swap stuff around, EV, Aperture, Time giving you ISO, EV, ISO, Time giving you Aperture, etc.

If one changes, then at least one other value must be changed to maintain the balance.

By changing your ISO for the chart calculating out EV by f/stop to give shutter speed you either
- recalculate all shutter speeds,
- shift your f/stop values left/right by your ISO change,
- shift your EV values up/down by the ISO change.
- leave the chart alone and adjust your EV by your ISO change.

All of these options are mathematically equivalent of each other, and will result in your photo capture surface recording similar levels of light. (Due to various tolerances, especially with f/stops, it technically isn't perfect, but the difference should be so minimal that you're not likely to notice without lab level testing)

This all sounds like a mixture of APEX and "conventional" photography. For those who don't remember, or never knew, APEX stood for the "Additive System of Photographic Exposure.

APEX was such an abysmal failure that the terms left over from it have acquired new and/or distorted meanings. With Canon (and this is a Canon forum, after all), the leftovers are the "Av" and "Tv" on your mode dial and the "Ev" in exposure compensation. (Notice that the proper abbreviation is "Ev" and not "EV"; the Devil is in the details.)

So much has changed that one needs to define the terms carefully before attempting any meaningful discussion.

If you're curious about APEX, look here: http://dougkerr.net/Pu​mpkin/articles/APEX.pd​f

Guys,
EV is the quantification of the intensity of light falling on a scene. It has no ISO. It is an ABSOLUTE measure of the amount of light.
Light meters of old used to have an EV display. I still have one... It tells me something like EV10, and that value has no direct correlation to exposure until I [choose an ISO which then results in the shutter+aperture combinations (many of them)]!
Even modern meters have the EV display, but these assume ISO 100 correlation still. I have an Illuminance lable on the back of my Minolta Autometer Vf which says "EV0 = 0.31 footcandles of light, for the spherical diffuser, ISO =100, and C=31".
Have you notice that specs show, for the Canon 1D3 Mark III, "Metering range: 0 - 20 EV". That specifies the minimum level of light (and the maximum) which the camera's meter can respond to.

The EV charts like the one posted by digital paradise ASSUMES [a combination of f/stop and shutter speed which is based upon ISO 100 sensitivity] to the light. And uses of EV in a RELATIVE measure, such as what tonylong mentioned, allow us to give delta values from some arbitrary reference exposure. But fundamentally, EV is a fixed level of light (like the minimum amount of light that a meter can measure), but it also happens to be spoken of in a relative sense as well (+2EV, -1EV, etc.)

Honestly, this is all fascinating and informative... I am sure that I had sullied the waters initially by possibly using incorrect terms, abbreviations and expressions. That would be my inexperience showing through.

APEX seems to be pretty excruciating with so many variables.. With what tonylong is referencing, I guess I don't seem to understand as of yet. But I have a long road to travel yet to understand these things... I don't ever really plan on being a photographer (other than a generic hobbyist), but I am of the ilk that likes to understand how things work in order to manipulate the results...

I was merely trying to put the "exposure triangle" together in some quantifiable measure... The chart I referenced was the first (?) I found to help me better understand. There is lots of information out there (here included) and trying to discern what is accurate appears to be a challenge for even those with more experience then me (which isn't much since my first SLR was in 1991 and it never left full auto). With trial and error, over the last 5 years I have begun to understand how aperture and shutter speed correlate. How ISO relates to the "triangle (matrix)" was the last piece of the puzzle.

Thanks again to all!

"Exposure Value" is a mathematical quirk, and can be defined and used in multiple ways that work equally well. You must know how an "EV" is being defined as and used for so you can understand it. There is not just one definition that universally applies!

To declare that an EV is a strict measurement with only one definition would be to ignore the fact that other definitions exist and may be used differently. Such as on the light meter I own and use.

I select the ISO I'm working with on the meter, take a reading, and it spits back an "Exposure Value" for that ISO level. If I change my ISO selection then the EV I'm given in the same scene is adjusted up or down accordingly. From there I turn the rotating scale to that EV which then lines up my Time/Aperture combinations. (Finding ISO after picking an A/T combo is then a matter of counting.)

The definition of an EV is different with the meter I'm using because it calculates a value based on ISO before displaying it to the user.

I would assume that the meter takes a reading at its photosite over a standardized period of time, evaluates that from a baseline Exposure Value, and then scales it accordingly based on ISO. However as a user that internal EV level is useless and irrelevant to me as I have no way to see it.


To argue otherwise is to claim that every foot length of measurement is the same. There are different systems, and they can appear similar, and it is important to know that differences exist.

Not sure thus will help any.