repleo Loc: Boston

(Original Poster) WOW! I never thought I would get so many and such varied responses to what I thought was a simple or even dumb question. Thank you all, even if some folks are more confused than me. I think the takeaway is that if you are in a Priority mode (or AutoISO off), adjustments to EC will be accompanied by auto adjustments to the other settings. If you are not watching your settings you could easily find yourself with more ISO or slower shutter than you anticipated. Worth keeping an eye on.

Apaflo Loc: Anchorage, Alaska

It is not at all rare that many replies are at least as confused as the OP...

But it is very rare that at the end of the day, so to speak, the OP flat got an understanding that is as correct as now yours is!. Unfortunately most of the confused folks that replied will probably remain confused... That's life. (Which used to be a magazine, but if you take a picture of it we call it Street Photography. There's section on UHH for Street Photography!)

mcveed Loc: Kelowna, British Columbia (between trips)

The camera would slow down the shutter speed.

Edia Loc: Central New Jersey

Great Answer.

Tracy B. Loc: Indiana

Thanks Apaflo! I see the light (pun intended).

Allen Essek

In your 2nd paragraph, you state:

" If EC is changed to -1 EV the light meter will say the Light Value is 16.6 EV. If EC is set to +1 EV the light meter will say the Light Value is 14.6 EV."

HOWEVER, WOULDN'T THIS ACTUALLY, BE:

* If EC is changed to -1 EV the light meter will say the Light Value is 14.6 EV. If EC is set to +1 EV the light meter will say the Light Value is 16.6 EV.

INSTEAD? Please explain; (if you had reversed the two figures,) or, else, WHY, do the two EV Values, end up, as they do?

***Why would, -1 EV EC, on a 15.6 EV, yield a 16.6 EV?

This, doesn't make sense, to me! Please, explain this! Thanks!

NoSocks Loc: quonochontaug, rhode island

:thumbup: :thumbup:

Jrhoffman75 Loc: Conway, New Hampshire

If you select -1 EC it means you want to subtract one stop of light to what the camera is measuring (underexpose by one stop). In order to do that you need to tell the camera there is one stop of light more than it is really measuring. Thus you would tell the camera instead of 15.6 EV there is 16.6 EV of light.

Apaflo Loc: Anchorage, Alaska

Lets take the common example that comes up every fall about how to get pictures of scenes with a lot of snow.

The light meter in the camera is calibrated to provide "correct" exposure if the average of the entire scene is something like 18% gray. A scene with grass, trees, a road and some sky with a few clouds works out to about that, and it works. But if it snows, and most of the image is now reflecting about 75% of the light things go wrong. The light meter says there is a lot of light, so the Auto Exposure modes stop down the aperture and/or makes the shutter speed shorter, thus providing only enough light to hit the sensor to make everything appear 18% gray rather than 75%.

How do we correct that, and get it back to making the picture look white instead of murky gray? Exposure compensation.

EC is set to +2 EV to make the light meter cause exposure to be increased by 2 fstops. It does that by indicating there are 2 fstops less light than is actually being measured. The aperture or shutter speed is changed to allow 2 fstops more light, and the picture is no longer 18% grey, it is now 72% grey. Close enough. Now the pictures produced look normal.

Now lets be more specific. With EC set to 0, the light meter might measure a Light Value of 16 EV on a bright sunny day. When EC is set to +2 EV, the light meter still sees the same bright light, but it reports only 14 EV.

A quick look at the chart in a Nikon D7200 manual (it is in every Nikon DSLR manual) on page 327 says that a LV of 16 at ISO 100 would match an aperture of f/11 at 1/500 shutter speed. That setting would cause everything in the image to be grey rather than white. By setting EC to +2 the exposure in increased by 2 EV because the meter reports a LV of only 14. The chart in the book of course says that at an LV of of 14 the aperture needed would be f/8 and the shutter speed 1/250, or a two f/stop increase in exposure.

Decrease the meter reading to increase the exposure.

repleo Loc: Boston

Brilliant Apaflo! Great explanation. I was a little confused by your first post too and was going to question you until I looked at your gorgeous pictures from Barrow Alaska and realized you must know what you are talking about.

repleo Loc: Boston

"Scale the output". That's a new term for me. Does it mean changing ISO? I googled it and found a reference under sensor fundamentals in industrial applications. How would you you scale the output in everyday photography?

ballsafire Loc: Lafayette, Louisiana

:thumbup: :thumbup: :thumbup: :thumbup: :thumbup:

ballsafire Loc: Lafayette, Louisiana

Yes, see your point(s) -- i.e. it doesn't make much sense. All I know is that when I use EC, the positive (+) obeys or the negative (-) obeys…and that is what I want. I find it hard to understand when a positive is a negative and vice versa.

Macronaut Loc: Redondo Beach,Ca.

Your kidding.....right? :|