Is 1.4 really necessary for available light?

[Pherdinand]

In case of a proper light meter, the EV value shown SHOULD not be changed when you change the film speed setting on the meter. Only the transformation from the read-out EV value to the f/stop+sh speed values should change.

 

[ampguy]

depends

depends

on whose EV def. you're using. If you interpret from the ultimate exposure computer, then EV's change with ISO's. Same with my old mechanical Sekonic.

I have read your defn. below though, it probably started out as defined for 100, when reciprocity and other film factors made it simpler to deal with only 2 variables.

snip...Switching to 1600 does not rise the EV, it is still the same EV number because EV number is defined for iso100....snip.

 

[VinceC]

EV is supposed to be universal. "Sunny 16" depends on film speed, but outdoors on a sunny day would have fixed EV value.

 

[Crasis]

For me it means you have to expose your iso100 film for 1/15 s using f/8 to get "correct" exposure. It also means, if you use 1600 speed film, you have to decrease the exposure with 4 f-stops compared to the above setting. But when you tell me EV10, i don't have to ask "for what film?", i don't care what film you use, because EV is defined for ISO100.

I'd like to point out:
Switching to 1600 does not rise the EV, it is still the same EV number because EV number is defined for iso100.
Switchng to iso1600 means for correct exposure of the iso1600 film you have to increase the EV number with 4 stops.

So switching to 1600 does not change the EV.
But switching to iso1600 increases the EV by 4 stops?

You are confusing the hell out of me 🙁

 

[Pherdinand]

It's easy in fact.
It's like saying: The price of steak is 12 euro. That of course means you have to pay 12 euro for 1 kg of steak. If you need 16 kgs of steak to feed the family, the price is still 16 euro but to properly make the family happy you will pay 16 times more.

The ev value is just a number expressed in units of euro per kg. I mean, f-stop and sh speed per iso100.

WHat you have to remmber is, that a certain EV means a combination of fstop and sh speed for iso100 film. Anything you change from this triplet you have to change the other(two) as well, or you will have no correct exposure.

 

[Pherdinand]

By "you have to increase the EV number with 4 stops" i was meaning, you take the original EV number - the NUMBER - and increase it with four and then you get another number which will correspond to the cortrect f/stop and sh speed combination for exposing 1600-film.

 

[jonasv]

Actually Pherdinand that depends whose definition you're using. A very common definition is "Exposure Value zero (EV 0) corresponds to exposure time of 1 second and aperture of f/1.0". (ie http://www.chem.helsinki.fi/~toomas/photo/ev.html and others).

While the origin of the EV value may have been different, convention dictates that this way is also correct. A good example is that EV value can be set some cameras (Minolta 7s among others), and the EV value reading varies depending on the ISO set. The correct term used to be LV. LV is not unused as you suggest, it's just that the term EV now refers to both the original EV value and the LV value. Convention...

 

[Pherdinand]

you are right of course, jvx. But i've learned the above definition with the parenthesis "(for iso 100 film that means correct exposure, that is, an average of 18% gray).

 

[jonasv]

We could ask the Internation Standards Organisation to settle this dispute - only problem is that we'd end up with two different variables (film speed and EV value) both being expressed in ISO 😉

 

[VinceC]

The ISO already did that in 1982. Where do you think EVs came from?
http://www.iso.ch/iso/en/CatalogueDetailPage.CatalogueDetail?CSNUMBER=7692&scopelist=ALL

 

[jlw]

As said above, exposure valuye EV is always for iso 100. "EV whatever for iso1600" does not exist. Not trying to be a wise ass but EV is something expressing a correct exposure on iso100 film. If you switch to iso1600, you can still calculate a number that looks like EV but it's not EV.

My post was above yours, but I did NOT say that, and it's not really right.

An EV number all by its lonesome self just designates an f/stop + shutter-speed combination. It has nothing to do with light levels.

If you want to give a photographer-friendly number that indicates a light level, then you have to combine the EV number with an ISO sensitivity value, and by convention, that's 100. (I'm actually old enough to remember when the convention was to use 25, because that was the speed of the then-very-popular Kodachrome II slide film.)

Since people insist on using this number in different ways, a fairly safe guideline is:

-- If the discussion is about the low-light sensitivity of an exposure meter, or the brightness level of a scene, assume that when someone says "EV" s/he means "EV number needed with 100 ISO film." Example: "Boy, it was darker than a dragon's colon in that nightclub -- the light was only about EV 2."

-- If the discussion is about light-meter readings or about camera settings, assume that when someone says "EV" s/he just means a particular set of aperture/shutter speed settings. Example: "The meter said I should set the camera to EV 9, but I wanted a bit more shadow detail so I set it to EV 8 instead."

 

[Gabriel M.A.]

I'm sorry, but can't help but think about this:

Costello: I throw the ball to who?

Abbott: Naturally.

Costello: Now you ask me.

Abbott: You throw the ball to Who?

Costello: Naturally.

Abbott: That's it.

 

[Pherdinand]

that's a good (and useable) conclusion, jlw.