Proper exposure?

Question

I've searched all over the web and read countless pages on exposure, but I still don't understand it. I know that +2 +1 attracts more brightness, 0 has no exposure, and -1 -2 attracts more shadow. What I don't understand is why my digital camera on PASM mode wants me to have an exposure of +1 or +2 when working in well lit studio conditions. I have tried it at 0 exposure, and the picture is horribly dark when in reality it is not. When at +1 or +2 EV It sets the aperture to around 2.8 or 4, and a 1/30 shutter speed, as well as using an 80 ISO. My understanding is that in portraits, what I'm photographing, the exposure should be set to 0. But on my digital, 0 does a terrible job, and sometimes even +1 and +2 don't seem like enough exposure. Why is this?

I'm going to try out a 35mm Minolta X-700 SLR on Aperture Priority mode, and I want to make sure that I'm not setting the exposure too low at 0, because my digital camera says I am.

Help! Thanks!

I know I need to go and learn about it, but that isn't exactly possible at this point, so I'm doing everything basically by myself with the internet and a few books as guides. But in this case, for me, the rules I learned seem to not be as I was told they were. And that's where my problem is, trying to figure out how to readjust what I learned to my scenario.

Answer 1

Correct exposure is a combination of light, f-stop, shutter speed and ISO. Judging light using the human eye is extremely difficult compared to the way a camera "sees" light. Your eyes may perceive the studio as "well lit" but to your camera it may appear dim. Think of the last time you walked into the mall after walking across the parking lot in bright sunlight - at first the mall appears dimly lit but it quickly assumes a brightness level that you perceive as equal to the outdoors. Why? The pupils in your eyes have "opened up" to admit more light. Outdoors your pupils might have been at f22 but indoors they are at f2. Your brain also adds compensation, something the camera can't do.

Since you didn't specify your subject matter, its hard to know exactly what needs to take precedence - shutter speed or aperture. If you're doing still lifes such as products or floral arrangements you'll likely want smaller apertures for better Depth of Field (DOF). If you're working with the camera on a tripod with inanimate subjects shutter speed can be much slower. If you're shooting people, hand-holding the camera and moving around then you'll need more shutter speed. For a higher shutter speed you need either more light or a higher ISO at a given f-stop or both.

ISO is a measurement of sensitivity to light. The higher the ISO the more sensitive the film or sensor becomes, allowing higher shutter speeds and/or smaller f-stops. ISO 80 can work well with outdoor light or indoors with flash or in a studio with the camera on a tripod and a static subject. It may, however (especially in your studio), over-extend your camera's ability to produce correct exposure. This is especially true if you're shooting where the camera is choosing aperture and shutter speed.

When you allow the camera to set both f-stop and shutter speed, the camera will choose a faster shutter speed - to minimize camera shake - and a larger f-stop. When it has reached the limit of maximum f-stop and still isn't satisfied with the shutter speed, it wants more light. Your own example shows this - your camera is at 1/30 at f2.8 and is telling you to give it another stop or two - +1 or +2 EV.

This example is hypothetical and is based on ISO 100 in bright light.

f2, 1/1000
f2.8, 1/500
f4, 1/250
f5.6, 1/125
f8, 1/60
f11, 1/30
f16, 1/15

All 7 examples will produce the identical exposure. You will notice an improvement in image quality between f5.6 and f11. Lenses are designed to produce optimum resolution somewhere in that range. DOF will also improve from f5.6 on. If you use ISO 200 in the example above the shutter speed will double.

We use EV when we know that the lighting conditions will "fool" our camera. Suppose your subject is a person standing in front of a dark background in sunlight. Your camera's meter, which "sees" the world as 18% gray, will choose an exposure that will cause your subject to be "washed out". There will be little or no detail. This is where we'd use the EV to compensate. Take two exposures - one at -1 EV and one at -2 EV. *

Now lets look at the same subject standing in front of a brightly lit background. Your camera will set an exposure that will leave your subject as a silhouette. In this situation we'd try +1 EV and then +2 EV. *

Now lets go back inside your studio. First, we're going to increase our ISO to 160 (since I still use film I use Kodak Portra ISO 160). Next, we're going to choose the "A" or Aperture Preferred Mode to shoot in. Set the f-stop to f4 and see what shutter speed you get. If its one you can comfortably hand-hold you're ready to go.** If not, open up to f2.8. If you're shooting a group, you may have to stay at f4 for a little more DOF and use a monopod for added support. It may be necessary to increase ISO to 400, although I always try to change only one variable in any given situation.

Although you did not specify what lens you are using I'm going to guess its a fast zoom. What you need to realize is that a zoom at f2.8 may give a different meter reading than a fixed focal length lens at f2.8. This isn't because the lens designer is exaggerating the capibility of the lens. It is because of light transmission. A zoom has a lot of elements compared to a fixed focal length lens. You "lose" a little light as it passes through each element. If portraits are your main studio subjects it might be beneficial to invest in a true portrait lens. In 35mm photography a portrait lens is considered any focal length between 85mm and 105mm. Find a lens that is equivalent to one in that range and buy the fastest one you can afford. (I've used a Minolta 85mm f1.7 for decades.)

* In the olden days, when cameras didn't have EV settings, you'd either use a hand-held spot meter to meter your subject and set exposure or you'd move in close enough to meter from their face, set that f-stop and shutter speed and then move back, compose and shoot or you'd switch to a telephoto, meter off the face, set exposure and then switch back to your taking lens and shoot (now you could just zoom in) or you'd meter off a gray card, open up 1 stop and shoot or meter off your hand and open up 1 to 2 stops.

** Early photographers used the Rule of Thumb which stated: "To avoid blurring your photos due to camera shake always use a shutter speed that is the reciprocal of the lens length." In other words, when using a 300mm telephoto you'd keep your shutter speed at 1/250 or higher. With the advent of Image Stabilization or Anti-Shake this is less of a problem. I'd still urge caution, however, since IS or A-S does have limitations. Your experience with your camera and your own ability to hold your camera steady will determine your personal limits.

NOTE: I own 4 Minolta X-700 cameras. I shoot almost exclusively in "A" (aperture preferred) Mode because I like lots of DOF. Although it has a "P" (program) Mode which sets the aperture and shutter speed I've never used it.

Answer 2

Hello,

I don't think you are really understanding the numbers as you state it. + numbers mean you picture will be overexposed by that many stops. 0 means it is the correct exposure as determined by the camera and - numbers mean your pictures will be underexposed. It may be as simple as which part of the picture you are taking your exposure reading from. You might be better off taking a spot meter reading which only reads a small area when determining the meter reading. With this system you would point the center of your viewfinder to the cheek or whichever is the most important part of your subject to get a correct meter reading.

Another thing that could be happening is your meter is reading all the light hitting your subject and the background and it is giving you a false reading. If you are using evaluative metering it will read the whole scene and give take into account all of the light in that scene. If the light around the model is brighter than the light hitting the model then the scene would come out overexposed because the camera is reading all the light and exposing for that and not just the model. If the camera tell you a plus number, then it is telling you that you will be overexposing the subject unless you make changes in some of your settings or in your lighting. Have you looked at your pictures on the computer to make sure the exposure was correct or are you just looking at the viewscreen in the back? The viewscreen is not always the perfect indicator of how a picture will look on the computer or in print. You can also use a histogram to see if the exposure is correct.

Answer 3

Proper exposure can be tough to gauge on a digital. Are you measuring by looking at your LCD screen? If so, this could be a mistake, as your LCD may be set to be too low. If your digital has a histogram display, that's the proper way to judge exposure. A histogram measure brightness values in the color channels, with darker values on the left side of the histogram and brighter values on the right side of the histogram.

You don't explain which digital camera you have and there's other possibilities as to why you're not getting enough exposure. It may be that there's not enough light around so that your camera hits its limits even at zero. At that point, pushing it to +1 or +2 won't make a bit of difference.

What you need to do is pump up your ISO from ISO 80. That will increase the sensitivity of your sensor and thus gather more light, increasing your brightness.

It sounds to me like this is what's going on:

Your camera has a lower shutter speed limit of 1/30 of a second (probably set in a menu). You've set the ISO at 80. When the camera does its computation, it hits the limit at f/2.8 at 1/30. It's too dark. Then you pump it up with a +1. And nothing happens.

The X-700 is a 35mm film SLR. Film has fixed ISO settings, and if you're shooting digital at ISO 80, to get a match you'd need ISO 80 film. Well, film generally comes in ISOs like 100, 200, 400, 800 and 1600. So you probably should set your digital to match the film you're going to be using.

Answer 4

At 0 EV (Exposure Value) the camera will expose at the meter reading. At -1 EV the camera will expose at 1 stop below the meter reading . At -2 EV the camera will expose at 2 stop below the meter reading etc..
At +1 the camera will expose at 1 stop above the meter reading. At +2 the camera will expose at 2 stop above the meter reading etc..
Make sure the ISO is set correctly (film speed) and take a meter reading that has average reflective value.

READ THIS
http://www.photography.ca/phototips/meter.html

Answer 5

you need to go and learn about exposure, using appeture mode or the compensations is just shooting and wishing.

if you want good exposure, study reading light/exposure and learn about "manually" setting exposure. study flash also

its not the tool or the studio lghts its the photographer that makes or breaks an image

however the X700 is a masterpeice like the ae1 the f2 and f4, K1000, om1, etc

EDIT: ok the best way to learn while getting good exposure is buy and use a "Grey Card". use your camera in manual and set the exposure to the reading of the grey card.


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Answer 6

Maybe you should go back and read about lighting conditions. www.Photo.net has a good tutorial on exposure, lighting and other settings.

Do not use the ev setting on your camera too much, to get a desired effect, it is much better to experiment with the aperture and shutter speeds.

Answer 7

Shadows and highlights are controlled via adjusting your lighting conditions, not by playing with your exposure compensation settings.