Exposure Compensation -- Why?

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Archive 2008 · Exposure Compensation -- Why?

mantdob
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p.3 #1 · Exposure Compensation -- Why?

Stripper wrote:
This is a great question and a lot of people have posted great answers. I guess I will take a shot at telling you why I use exposure compensation, at least in one situation.

... A great education, references to Ansel Adams, a few very descriptive charts, and 2 awesome race car pictures, where even the over exposed one I'd be incredibly happy with having taken ...

Thank you for this post! I really like how you described your thought process and how you apply it to exposure compensation. It really made sense to me, and I'll definitely keep it in mind as I shoot!

Sep 05, 2008 at 06:26 PM

DavidP
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p.3 #2 · Exposure Compensation -- Why?

Photon wrote:
Except that as I pointed out above, we set the compensation "manually". It was called exposure compensation even when the only in-camera meters were "match needle", and AE hadn't been introduced.

Well, true. YOU are compensating (making the meter read what you want it to, rather than dead center).

Sep 05, 2008 at 06:30 PM

Cableaddict
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p.3 #3 · Exposure Compensation -- Why?

snurresprett wrote:
Err... when shooting in Aperture Priority mode, you are basically telling the camera to set the shutter speed as it sees fit in order to achieve the metered exposure. It is not possible to explicitly set shutter speed yourself in AV mode.

Huh? Maybe it's different on other cameras, but on the 5D, in Av mode, the big wheel does indeed adjust the shutter speed, and hence the exposure. (assuming you put the "on" switch to the second position, not the first.) You don't HAVE to adjust it, that's what AV mode is for, but the compensation is right there at your thumb.

That's exactly why I think his question makes sense. Unless you have a fast-changing scene, as I and Stripper outlined, or are shooting snowboarders, etc, it is typically much faster to just use the big wheel. AV mode (or TV) still gets you to a "known" starting point, so it still saves time, but you have faster control over EC changes. You can also do a 3 or even 5 shot bracket, much faster than going back to the menu screen.

Edited on Sep 05, 2008 at 07:40 PM

Sep 05, 2008 at 07:29 PM

Rod T
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p.3 #4 · Exposure Compensation -- Why?

Cableaddict wrote:
Huh? Maybe it's different on other cameras, but on the 5D, in Av mode, the big wheel does indeed adjust the shutter speed, and hence the exposure. (assuming you put the "on" switch to the second position, not the first.) You don't HAVE to adjust it, that's what AV mode is for, but the compensation is right there at your thumb.

That's exactly why I think his question makes sense. Unless you have a fast-changing scene, as I and Stripper outlined, or are shooting snowboarders, etc, it is typically much faster to just use the big wheel. AV mode (or TV) still gets you to a "known" starting point, so it still saves time, but you have faster control over EC changes. You can also do a 3 or even 5 shot bracket, much faster than going back to the menu screen.

On the 5D (and the 40D, 1DmkIII, and every other recent Canon) the 'big wheel' is exposure compensation. When in Av mode the net result of the exposure compensation is changing the shutter speed. In Tv the result would be changing the aperature. Either way it is exposure compensation.

Sep 05, 2008 at 07:49 PM

snurresprett
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p.3 #5 · Exposure Compensation -- Why?

Cableaddict wrote:
Huh? Maybe it's different on other cameras, but on the 5D, in Av mode, the big wheel does indeed adjust the shutter speed, and hence the exposure. (assuming you put the "on" switch to the second position, not the first.) You don't HAVE to adjust it, that's what AV mode is for, but the compensation is right there at your thumb.

Well, the point was that you are not dicating shutter speed per se, you are telling the camera "use this particular aperture and give me a shot at your metered exposure plus or minus so and so much and I really don't care how you go about it". The camera happens to do this by adjusting shutter speed relative to what the meter would suggest. But there is no fundamental reason why it could not have achieved the same effect by juggling the ISO instead.

Sep 05, 2008 at 08:31 PM

Cableaddict
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p.3 #6 · Exposure Compensation -- Why?

True, but it doesn't. That would actually be a very useful mode:

Select aperture.
Select MINIMUM shutter speed.
-Then have the camera select the apropriate ISO.

I would LOVE that.

Edited on Sep 06, 2008 at 03:31 AM

Sep 06, 2008 at 03:29 AM

Photon
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p.3 #7 · Exposure Compensation -- Why?

Cableaddict wrote:
True, but it doesn't. That would actually be a very useful mode:

Select aperture.
Select MINIMUM shutter speed.
-Then have the camera select the apropriate ISO.

I would LOVE that.
A lot of us have asked for an auto ISO mode that works like that. Pentax has it.
Closest approach for Canon (at least this applies to the 1DIII) is to set the custom function that uses ISO for safety shift. What I don't like about that approach is that the camera will choose ISO in third stop increments (even when set to only allow full stop increments when ISO is initially set by photographer) to get an accurate exposure. This leads to slightly more noise than you get at the full stop ISO setting above or below. I'd like it to choose the nearest full stop ISO, then go ahead and jimmy the shutter speed or aperture a fraction of a stop.

Sep 06, 2008 at 03:57 AM

thepiecesfit
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p.3 #8 · Exposure Compensation -- Why?

thats because the camera takes anything you point it at and turns it into 18% grey. You compensate to help the camera. Most useful in spot metering setting. Read about the zone system.

Sep 06, 2008 at 05:13 PM

Patrick Cox
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p.3 #9 · Exposure Compensation -- Why?

In general, I prefer to shoot in Manual mode. Especially if I have fairly consistent light. To me this is clearly the best method for light levels that are fairly consistent. However, if I am dealing with quickly changing light and a moving subject, AV or TV mode with some compensation may be a better alternative. Let's say I am tracking a moving dark bear that fills most of my frame and as he moves he is going in and out of sun and shade, manual mode would be too difficult to manage. However if I set some negative compensation using the spot meter, the meter will adjust for the changing light. This is the biggest benefit for me in using exposure compensation.

Pat

Sep 06, 2008 at 06:01 PM

Littlefield
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p.3 #10 · Exposure Compensation -- Why?

I am glad you asked the question . Good thread with good info.
Don

Sep 06, 2008 at 06:04 PM

FiveD
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p.3 #11 · Exposure Compensation -- Why?

Using your AV mode example, the camera has metered the scene and choses a shutter speed to expose the scene correctly for the Aperture you have set. Let's say the scene you are shooting is a skier on a slope of powder snow nearly above treeline so there are just a couple of trees.

So now you have a frame that is nearly all white, you meter wants to make all of that white a light gray. Your meter doesn't know the snow is white, it just wants 18% or so gray. Your histogram will confirm this, there won't be any spikes toward the right. Your eyes also know better, snow is white! So you dial in +1.5EC so the snow will come out right. EC is compensating for your scene fooling your meter.

Sep 06, 2008 at 08:25 PM

GeneO
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p.3 #12 · Exposure Compensation -- Why?

I think the original poster has lost interest.

Sep 06, 2008 at 09:04 PM

poodlelvr
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p.3 #13 · Exposure Compensation -- Why?

This is a great thread...

Sep 15, 2008 at 04:29 PM

WilliamG
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p.3 #14 · Exposure Compensation -- Why?

Yep awesome thread. Keep it going.

Sep 15, 2008 at 05:42 PM

saaketham
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p.3 #15 · Exposure Compensation -- Why?

FiveD wrote:Using your AV mode example, the camera has metered the scene and choses a shutter speed to expose the scene correctly for the Aperture you have set. Let's say the scene you are shooting is a skier on a slope of powder snow nearly above treeline so there are just a couple of trees. So now you have a frame that is nearly all white, you meter wants to make all of that white a light gray. Your meter doesn't know the snow is white, it just wants 18% or so gray. Your histogram will confirm this, there won't be any spikes toward the right. Your eyes also know better, snow is white! So you dial in +1.5EC so the snow will come out right. EC is compensating for your scene fooling your meter.

I think this is a good example. The light meter will try to make whatever it is pointed at, a medium tone. So, you compensate for that with your own judgement, and what's more easier than dialing in a EC value, rather than changing the aperture and shutter speed.

Sep 16, 2008 at 02:52 PM

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