eospaddy Loc: Liverpool UK

when you increase your E.V by say one whole stop where are we gaining that light from ? for instance I.S.O increase will give more light at the expense of noise, whats the trade off with E.V when you add more light ?

JoeB Loc: Mohawk Valley, NY

If you decrease your shutter speed by one stop, you are increasing the length of time that your sensor is exposed to light. The trade off, so to speak, can be blurred image due to subject motion or camera shake. On the other hand, if you increase your aperture (opening) by one stop, you are increasing the amount of light that strikes your sensor, in both cases you have doubled the light striking the sensor. Here the trade off is depth-of-field, as you open the aperture, the depth-of-field gets narrower. For every proper exposure, there are about 8 different combinations of shutter speed, aperture and iso that will give you "proper" exposure. What combination you use is up to you as to what you are trying to capture and what you want as and end result.

rpavich Loc: West Virginia

Good question...I don't know. It obviously has to adjust one of the 3 variables but which one is something I'd be interested to find out.

martinfisherphoto Loc: Lake Placid Florida

If you have your ISO Fixed in camera you gain depending on your camera mode, for example aperture priority your camera will decrease the shutter speed giving you a longer exposure to gain more light. In shutter priority you camera will open the aperture allowing more light in. If your camera is in Auto ISO most likely your ISO will adjust higher keeping the camera settings the same.

infocus Loc: Australia

You don't need to go any further than JoeB's answer to your question. It is spot on.

rpavich Loc: West Virginia

But joeb didnt' answer the question.

The question was:

"When in auto modes and you dial in +EV or -EV in the camera...which of the 3 exposure variables is it modifying to get the different EV value"?

eospaddy Loc: Liverpool UK

thanx for your detailed reply, just to clarify when i increase my E.V by a whole stop this is opening up the aperture and so the trade off here would be depth of field, i would have less the more i increase my E.V ?

Db7423 Loc: Pittsburgh, PA

:thumbup: :thumbup:

eospaddy Loc: Liverpool UK

i think joeb did answer the question, as he explains the aperture is changing when we increase or decrease E.V so depth of field would be the trade off as we increase E.V the aperture would open more to let in more light and the reverse for for decreasing ! what stumps me now is why not just do this by just increasing or decreasing the aperture or is the answer one third stop increments where as we can only double or half the light via aperture but with E.V we can make smaller changes ? if this is correct then i now understand E.V

chaprick

I will take a shot at this. I would say that changing the EV (exposure value) on full auto mode would vary the settings based on the type of camera and the type of lighting situation. All cameras use slightly different firmware these days. One may alter aperture and another may alter shutter speed based on the situation. It might even change based on the scene type chosen (landscape, action, portrait, night, etc.). The only way to be sure what it is changing would be to shoot some shots of different subjects and vary the EV each time. Then go look at the exposure values each shot recorded and see what the camera chose to adjust. Depending on the type of camera you may be able to see what it adjusts through the viewfinder without taking a picture. This answer is based on full auto mode. If you are set on shutter priority or aperture priority it will not adjust either shutter speed or aperture depending on the setting. The other consideration is whether or not you chose the ISO or let the camera choose it. I am assuming that full auto mode means you let the camera choose everything including ISO. I like to think of the 3 values as:

1. Shutter speed - length of time light is exposed to sensor or film
2. Aperture - The amount of light let through the lens determined by the hole opening size (f-stop) in the lens
3. ISO - the speed that the sensor or film can collect light as determined by the International Standards Organization. Film had a set speed. Sensors can be varied by programming making it as if you can change film types on every shot if you desire (how great is that!!!!).

Changing EV is just a quick way to make an auto camera make the changes for you. You could just change the Aperture or shutter speed yourself in manual mode.

Long answer to a question that I know may have already been answered better by someone else. Sometimes a different perspective helps. Hope I am not confusing anyone.

eospaddy Loc: Liverpool UK

is it shutter speed or aperture that will increase and decrease in E.V ?

eospaddy Loc: Liverpool UK

thanks for giving it a go, i did not mention auto but i suppose it does matter if you are in different settings as to what may change in camera when E.V is changed, i should of said the guys are shooting in program mode on point and shoot cameras on a course that we have put together, and in program mode they can adjust the E.V so my question IS what is being adjusted when they increase there E.V i don't think its the iso in this case as they can adjust that also so is it obviously going to be one of the other two attributes, Aperture or Shutter Speed that would be adjusted when they change there E.V in program mode ?

changing your iso instead of film is a excellent bonus over film as it can be done on the fly where as film would need changing for different lighting conditions.

joeB answer sounding plausible in that the aperture would change at the expensive of D.O.F but if i understand you right it could also change the shutter speed depending on your camera or mode settings ? thank you for your input !

JoeB Loc: Mohawk Valley, NY

Correct. As you open the aperture wider, the depth of field becomes narrower. Sometimes this can be what you are looking for, such as a blurred background, but it can, at times, make it more difficult to get the focus you re looking for.

GrahamS Loc: Hertfordshire, U.K

"Exposure value (EV) denotes all combinations of a camera's shutter speed and relative aperture that give the same exposure. EV corresponds simply to a combination of a shutter speed and an aperture setting, independent of any ISO setting—independent even of whether there is any light available."

Ref: Encyclopedia of Photography - Focal Press

Linda From Maine Loc: Yakima, Washington

eospaddy, in response to this question "i should of said the guys are shooting in program mode on point and shoot cameras on a course that we have put together, and in program mode they can adjust the E.V so my question IS what is being adjusted when they increase there E.V i don't think its the iso in this case as they can adjust that also so is it obviously going to be one of the other two attributes, Aperture or Shutter Speed that would be adjusted when they change there E.V in program mode ?"

ANSWER: You could do some easy tests in the field by taking photo of a subject with a background that's several feet behind. Doing "before exposure value adjust" and after, you should be able to see if depth of field is affected. You could also test by shooting something moving (to see if it is shutter speed that changes).

And lastly, if you can view the results of your comparison photos on the computer (and sometimes right on the LCD screen, but maybe not with those cameras), you can hopefully compare the exif data to see which of the 3 variables changed.

NOTE: the exposure value adjustment might be in 1/3 increments. Are there little notches/lines between 0 and 1? For testing, you might even want to go all the way to 2 so you can see the differences in the comparison results more easily.