New to EV's
I received my grandfathers Kodak Pony II this weekend. Before I shoot my first roll, I have a few questions about EVís. First, Iíd like to note that the Pony II has a fixed shutter speed which is not specified by Kodak in the manual. Iíve read that itís 1/60 or 1/125 shutter speeds, again not from Kodak.
I understand that film speed was much lower then what it is today, and the slowest roll I had on hand was my Kodak MAX 200. I can adjust the EV ranging from 9.5 to 15. If my EV app is correct, set at 200 iso and 1/60 and 1/125 shutter speed, the equivalent f stop range is,
1/60: f/4.0 to f/32, EV13 is f/16
1/125: f/2.8 to f/22, EV 14 is f/16
The EV card is showing EV 11.5 for sunny shots so I can only assume that would be f/16 for the sunny 16 rule.
Do I have the right line of thought?
I dont know what speed of film was used to set the EV numbers. The card is for Kodachrome day and in the top right hand corner is the numer 10.
Hmmm. The camera was produced in 1957. Kodachrome was ASA 16 I think. So that would be four stops slower than 200 speed. So EV 7.5?
I think your best bet is going to be to shoot a scene at various EV settings and develop the film to see what EV settings are correct.
If the film used was ASA 16, then the f stop range would be from 1.0 to 9.0.
Plus-X's published speed when the camera was made was probably 80. Kodak removed a 'safety factor' in their published film speeds and so Plus-X became ASA 125, though the film didn't change.
The Plus-X 80 card specifies EV 15 for bright sun. So, maybe the card reflected the true film speed without a safety factor. EV15 is 1/125 @ f/16 = 'sunny 16' for ASA 125.
The shutter speed is 1/50th of a second, given EV9.5 for for its maximum f3.9 aperture lens and the formula EV = log2 (f^2/t), where t is in seconds.
Check out this link. http://www.fredparker.com/ultexp1.htm
For 16 speed film, EV 11.5 would equate to about f2.8 and shutter 1/100.
EV as used on old cameras and lenses does not depend on ISO, only on shutter speed and aperture. You can calculate EV as follows:
For shutter speed (at aperture f/1):
1 second = EV 0
1/2 = EV 1
1/4 = EV 2
1/8 = EV 3
1/15 = EV 4
1/30 = EV 5
1/60 = EV 6
1/120 = EV 7
For aperture, (at 1 second exposure)
f/1.0 = EV 0
f/1.4 = EV 1
f/2.0 = EV 2
f/2.8 = EV 3
f/4.0 = EV 4
f/5.6 = EV 5
f/8.0 = EV 6
f/11 = EV 7
f/16 = EV 8
f/22 = EV 9
To get the EV corresponding to a particular shutter speed and aperture, simply add the EV I've listed for the shutter speed (at f/0) to the EV listed for the aperture (at 1 second). So EV for 1/120" and f/16 would be 7 + 8 = 15. This corresponds to the "Sunny 16" rule for ISO 120 film (since the shutter speed is 1/120"). So when you set EV 16 on the camera, if the built in shutter speed is fixed at 1/120" then you are simply setting the aperture to f/16.
Originally EV ("Exposure Value") only referred to the factors affecting exposure (shutter speed and aperture) and not to the film sensitivity. Later on, EV was used as a measure of light intensity. In this case, ISO 100 is usually assumed. You have to figure out from context whether a use of EV refers to an exposure setting (as it does with the camera) or a light intensity (as is the case with light meters calibrated in EVs).
So if you have a light meter calibrated in EVs (referenced to ISO 100) and you put ISO 100 film in the camera, then you can simply take the EV reading from the light meter and put it into the camera for a "correct" exposure. However, if you use a different ISO film then you need to adjust the EV reading from the light meter to account for the difference between the light meter calibration (usually ISO 100) and the actual film speed.
For example, with ISO 400 film, you need to decrease the exposure by 2 stops compared to ISO 100. To do this you have to ADD 2 to the EV since increasing the EV by one reduces (makes darker) the exposure by one stop. If the light meter reads EV 10, then for 400 film you would set the camera to EV 12.
Of course if the light meter includes an ASA setting (typically found on the calculator dial) then you may simply be able to set this to the ISO of the film you are using and then read the correct EV for that ISO from the meter, and then use it without any adjustment.
The fact that your exposure cards specifies EV 11.5 for a sunny day suggests it was designed for film that is about 3.5 stops slower than ISO 120, hence somewhere around ISO 10.6 (calculated as 120 / 2^3.5). According to Wikipedia, Kodachrome daylight film in that era was ISO 10. The Type A film was ISO 16, for use indoors under floodlights (presumably for movies).
I believe the Kodak Pony II has a 44mm f/3.5 lens with a fixed shutter speed of approximately 1/60 second.
The aperture ring is marked EV 9.5 (approximately) to EV 15, so the aperture positions are likely:
First lens marking (roughly EV 9.5) corresponding approximately to f/3.5
EV 10 = f/4
EV 11 = f/5.6
EV 12 = f/8
EV 13 = f/11
EV 14 = f/16
EV 15 = f/22
This table should give you the approximate lens openings assuming a fixed 1/60-second shutter speed on the Kodak Pony II. This should allow using a standard light meter to accurately determine exposure by changing the aperture using the corresponding EV numbers on the lens scale.
You’d prioritize the shutter speed on the meter at 1/60 second and take the reading. For example, if you got a meter reading of, say, f/8, you’d set the aperture ring to EV 12 = f/8.
If EV is not effected by ASA, then how does ASA fit into the mix?
See http://en.wikipedia.org/wiki/Exposure_value for the relation to ASA
Originally Posted by zackesch