Curious about EV settings - Benefits, when & why

We have the capability to set the EV plus or minus X amount. I have seen some Exif info where some have set the EV to say -1 ro +1, etc. When and why do you choose to set your EV to a plus or minus setting? Is it used to be able to use an aperture settings ie 2.8 to shorten the DOF which might overexpose so you compensate the exposure by a minus EV setting?

Another aspect of the +/- EV setting, is one better or easier to correct in PP and would there be a reason to use it for a certain effect?

Bracketing for HDR, I understand. I am asking about any other reason for it's use.

Thanks

Your camera evaluates your scene and determines exposure based on algorithms to average out the exposure to approximately 18% gray. What this does in certain circumstances is make your whites not bright enough and your blacks not dark enough. Have you taken a picture in the snow and the result was really flat? If you added positive EV, the whites would probably appear closer to what your eye is seeing. Have you taken a picture of people in a low lit room and it seems too bright? If you added negative EV, the dark areas and shadows would probably appear closer to what your eye is seeing. Bottom line is you should us EV to make the exposure closer to what you see. As you use this technique it will become second nature. This is a pretty basic explanation but hopefully helps you get started.

cwgrizz said:

We have the capability to set the EV plus or minus X amount. I have seen some Exif info where some have set the EV to say -1 ro +1, etc. When and why do you choose to set your EV to a plus or minus setting? Is it used to be able to use an aperture settings ie 2.8 to shorten the DOF which might overexpose so you compensate the exposure by a minus EV setting?

Another aspect of the +/- EV setting, is one better or easier to correct in PP and would there be a reason to use it for a certain effect?

Bracketing for HDR, I understand. I am asking about any other reason for it's use.

Thanks

Click to expand...

Compensation is Not about f/2.8 or DOF - it is instead about obtaining desired exposure. It's what Eduard said, if you want the cameras metering result to be brighter, you add + EV compensation. If you want result to be darker, you add - EV compensation. Same deal with TTL flash and Flash Compensation. And yes, RAW images do allow substantial leeway for this adjustment in post postprocessing, but it is always good to get it near right in the camera (more important for JPG). Meaning good for the picture, and good for developing our own skill level.

Reflective meters (camera meters) simply underexpose white or light colored subjects. And they will simply overexpose black or dark colored subjects. Just how life is. We can recognize this scene when we first walk up, and experience lets us often get the compensation about right before we take the first picture (this skill really helped with film). Or we can look at the digital result, and then compensate the second try. Digital skill seems often postponed until post processing.

Recommended practice: Get a sheet of white paper and a sheet of black paper (craft store, maybe 18 inches large). Use it for the background of a picture of a black camera lens standing on black background, and a white coffee cup on white background. See? This is one of the first things we have to learn about camera meters.

Here is WHY compensation is sometimes necessary: How Camera Light Meters Work

Something that's important to understand : EV Compensation isn't a direct component of the so-called Exposure-Triangle (Aperture, Speed, ISO). Rather, it's a command you send the camera telling it where to go with said triangle when it does it's calculations. As such, it only works in modes where the camera decides of the exposure. Auto, scenes, etc. (P)rogram, (A)perture. In (M)anual it will do nothing BUT change the on-screen meter because all of the exposure controls are under your uh... control.

In Aperture mode, for instance, EV will vary speed. If you set EV +1, it will double exposure time. In Speed priority, it will vary aperture. - If you've set ISO to auto, that will also factor in of course.

My D3300 coupled with 35mm F1,8DX, over exposes red by +1EV. So if I am shooting an image where red is at least 50% (as in red flowers), I set the compensation to -1EV. Then I do not have to correct the exposure in PP.

Similarly, there are times when I want the flash to fill but not dominate, there I set the flash -1EV to -2EV. Again when I am using a flash at night and want to extend the range of flash (the object is far away), a simple +2EV or +3EV does the job.

WayneF said:

Here is WHY compensation is sometimes necessary: How Camera Light Meters Work

Click to expand...

I had time to read the first part of this article. It explains it quite well. I will have to take the time to read it through and digest. I think you, WayneF must be the author. Nicely done and thanks.

The big thing to realize is that metering is an art to be learned, and which is the purpose of the compensation functions. Beginners never want to hear that, they want to imagine the camera is supposed to always get it right. It doesn't of course, but they will persist with that for a while, but then hopefully, most will eventually try to learn how reflected meters actually work. The meter is an excellent guide, certainly almost ballpark, but often our head is our best tool about using it.

So we tend to suppose that the camera meter exposes the portrait face this way, and the background that way, etc. But it doesn't. There is only one exposure for the entire frame, and the light meter is too dumb, with no clue what any of that stuff is, or how it should be. The meter cannot tell the difference in a black subject with much light on it, or a white subject with little light on it. It just sees some light, which it can measure, but then what? It has no clue what it is, or how it should be. In every case, the only possible metering goal is that the average of the scene should be about middle gray (a compromise for safety, not too dark, not too bright). And the simplest experiments always show that is very true.

But which does in fact work pretty well, at least for very many "average" scenes, scenes which do contain a wide mix of bright and dark areas and colors, some areas brighter, some areas darker, and the average is often in fact in the middle, so it often magically works. But there are many exceptions too, which is what compensation is for. It is not that hard, we just learn that when we walk up to a white background wall, or a dark open area behind our subject, the alarms will go off in our head, and we know we will need to tend to the compensation. Or at least digital shows us the result, and we usually have another chance. I suppose one difference in beginner and advanced, is that advanced expects this, and gives it proper attention.

Light meters were inexpensive and popular and built into cameras 50 years ago, and every photographer ever using them has needed to know this. So learning how the meter works really is about the biggest of the big deals.