View Full Version : EXposure value on Weston Master meter and Co....
This is something that has made me think for quite some time and never dared to ask. It is obvious (at least to me) that the Exposure Value on those meters give a different reading for a different film speed, I am only talking of the EV value window here.
I find it quite confusing to explain so I will give some examples.
When setting the ISO value to 100 and turning the scale to EV 15, the meter will give a reading of 1/125 at f16, which is correct. However change the ISO value from 100 to 400 with the same settings and you will get a reading of EV 17 for 1/500 at f16, which as far as I know is false(the EV should still be at 15). This can be verified on this well known website:
http://www.fredparker.com/ultexp1.htm#Light%20Intensity%20Chart
So is the EV window on those meters only designed to be used with ISO 100 film or did I once again understood the whole thing the wrong way around?
Your meter is telling the truth.
EDIT: refer to Parker's Exposure Factor Relationship Chart B
This is something that has made me think for quite some time and never dared to ask. It is obvious (at least to me) that the Exposure Value on those meters give a different reading for a different film speed, I am only talking of the EV value window here.
I find it quite confusing to explain so I will give some examples.
When setting the ISO value to 100 and turning the scale to EV 15, the meter will give a reading of 1/125 at f16, which is correct. However change the ISO value from 100 to 400 with the same settings and you will get a reading of EV 17 for 1/500 at f16, which as far as I know is false(the EV should still be at 15). This can be verified on this well known website:
http://www.fredparker.com/ultexp1.htm#Light%20Intensity%20Chart
So is the EV window on those meters only designed to be used with ISO 100 film or did I once again understood the whole thing the wrong way around?
Well 500 is two stops higher than 125 or 17 vs 15 at f16 or am I missing something here?
refer to Parker's Exposure Factor Relationship Chart B
nikon_sam
12-02-2007, 15:34
The EV number for 100 asa and 400 asa will be different in the same lighting conditions...what you are reading is correct...
EV = Exposure Value...Film Speed (ASA) & Light Condition
So the same light for two different film speeds will be different...
Some of the older cameras had a EV scale on the lens so that you could set your camera quicker when wanting to play with either the aperture or shutter speed...all you really need to confirm is the EV number and any combination of aperture/shutter speed would be correct...
refer to Parker's Exposure Factor Relationship Chart B
I think you're wrong... Because if you look at the first chart, then EV 15 is sunny F16 which should stay the same no matter the film you're using.
Well, do care to explain if you know better?
ClaremontPhoto
12-02-2007, 15:47
[QUOTE=I find it quite confusing to explain so I will give some examples.
When setting the ISO value to 100 and turning the scale to EV 15, the meter will give a reading of 1/125 at f16, which is correct. However change the ISO value from 100 to 400 with the same settings and you will get a reading of EV 17 for 1/500 at f16[/QUOTE]
1/125 f16 for 100 ISO film would be 1/500 f16 for 400 ISO film. Two stops difference.
Two stops difference.
Which is EXACTLY what Exposure Factor Relationship Chart B says.
Which is EXACTLY what Exposure Factor Relationship Chart B says.
Your caps lock is obviously stuck, unless you are having problems to read which is further proven by the fact that you are having problems to figure out that chart B. Unless we are having problems to understand each others.
Anyway if you look closer at chart B, you will see that for EV 15 and ISO 100 you get 1/125 at f16, for EV 15 and ISO 400 you get 1/500 at f16.
I have explained in my first post what readings the Weston Master gives me....
You are new to that light meter. I have used a Weston for 30 years. What's more, if you don't want to listen to the correct wisdom given to you by Ully, Nikon_Sam, Claremont and myself... then you will continue to be confused.
EV is a short-hand for a series of equivelent exposures. If you change film speed, you need to make the equivelent change in your exposure, or EV.
AMF
EDIT. What's more - you have a very rude demeanor.
Well, I am doomed. Over the last year I understood how to use C, python, setup servers and recompile my own kernels. But I can't understand a little light meter,..,
Not to be rude Chikne, but do read the chart B once again.
At EV 15, for ISO 100 film, the exposure is 1/125 at f/16. However, the EV for ISO 400 film, at the same setting, is EV 13 (-2 or two stops under).
The settings for ISO 400, for EV 15 is 1/500 at f/16, corresponding to EV 17 for ISO 100 film.
:)
nikon_sam
12-02-2007, 16:54
Try this...
Set your ASA Dial to any number then set the EV to 15...it will always be 1/ 125@f16 or 1/250@f11 and so on...
So changing the ASA will also change the EV for the same light reading...
Trust what is being stated in this thread...go out and play with your meter...it will all come to light in the end...
Not to be rude Chikne, but do read the chart B once again.
At EV 15, for ISO 100 film, the exposure is 1/125 at f/16. However, the EV for ISO 400 film, at the same setting, is EV 13 (-2 or two stops under).
The settings for ISO 400, for EV 15 is 1/500 at f/16, corresponding to EV 17 for ISO 100 film.
:)
You're not being rude at all, thanks for giving me your explanation.
Try this...
Set your ASA Dial to any number then set the EV to 15...it will always be 1/ 125@f16 or 1/250@f11 and so on...
So changing the ASA will also change the EV for the same light reading...
Trust what is being stated in this thread...go out and play with your meter...it will all come to light in the end...
I do trust it I was just having troubles to understand it. There is 1 mention on fredparker's page that the chart A is actually for ISO 100 film, this was all I needed to know.
Anyway it is all making sense now, it shows how there is no need to use capital letters to explain things. Thanks for your patience guys!!
vBulletin® v3.6.8, Copyright ©2000-2008, Jelsoft Enterprises Ltd.