Xjyuk

I can expose a scene based on EV compensation or spot metering. If I spot meter...can I achieve identical results with EV compensation? Or is spot metering more than just a generic EV adjustment based on your target area? So a photographer that is good with EV adjustments technically wouldn't need spot metering?

Is spot metering just an EV compensation?

Metering, regardless of type, and exposure compensation are different functions with different purposes. Metering is used to obtain exposure values (ISO, aperture, shutter speed), while exposure compensation is used to modify those values. It is basically the difference between nouns and adjectives.

There are different metering methods:

• Average – The entire scene is averaged and compared with some reference (usually middle gray).


• Center weighted – The scene is averaged with emphasis on the center of the frame. (It is given more "weight".) The result is compared with the reference.


• Spot – A small circle ("spot") is compared with the reference. It usually covers about 1-2% of the frame. In some cameras, it is always the center point. For others, it follows the focus point.


• Evaluative / Matrix / Multi / Etc – These are proprietary methods that vary by manufacturer. A commonly described method divides the frame into several parts that are evaluated separately. The pattern can be compared with entries in a database to find an appropriate exposure setting.

Exposure compensation takes results from any of the above metering methods and adjusts it to increase (+) or decrease (-) exposure. The amount of compensation to use depends on the desired result and photographers' judgment.

If I spot meter...can I achieve identical results with EV compensation?

While it is possible to obtain the same settings from any of the metering methods by applying an appropriate adjustment, exposure compensation would be determined on a scene-by-scene basis by comparing the settings produced by different exposure modes. There is no single EC setting that will transform results from one metering mode into that of another.

So a photographer that is good with EV adjustments technically wouldn't need spot metering?

Spot metering isn't needed (though some like to have it). A few cameras have only a single metering mode, so exposure compensation is the only way to control exposure.

Yes, you could match the spot metering result by some degree of EV compensation, if you knew how much compensation. We typically may not know, so we instead meter it to be able to manage that.

Spot metering only analyzes the light intensity in that small spot. Regular metering looks at a much larger spot, closer to the full scene. Suppose you are photographing a person in the shade, but with a very bright background behind them, like bright sky. The regular meter will see the sky and assume it is important, and will try to expose it to be mid-tone. This will greatly underexpose the persons face, to be dark. We must choose one of them.

So we might spot meter on the persons face. The purpose is that the small spot specifically excludes the troublesome bright background. So then the sky surely burns out to be blank white with no detail, which we expect, but we don't care if the important face comes out well. But of course, we ought to learn to choose a better background. Or to add fill flash. Or something that involves thinking a second about what we're doing.

Even then, it is very incorrect to imagine spot metering on anything will correctly expose that spot. That's not how reflected meters work. Reflected light meters (including spot meters) simply try to make all metered areas average out to mid-tone. We typically call that mid-tone "middle gray", but it could be bluish or greenish, whatever the color is. It just means mid-tone. But reflective metering is not about "correct", it is about mid-tone. It might be about correct if that spot should actually look mid-tone, but many things don't. Instead, Incident meters do the "correct" thing very much better.

All reflected meters simply strive for this middle gray result, however not all subjects are correct as middle gray. We would want a photo of a black cat in a coal mine to come out near black, and a white polar bear in the snow storm to come out near white. However, a reflected meter will make both of them be middle gray. That is how meters work. If spot metering a typical Caucasian face, we learn to increase exposure about one stop compensation to correct it, so it won't be middle gray. But when spot metering, our dominant idea should be "how much brighter or darker compensation (than middle gray) should this spot area have?" Otherwise, it should come out mid-tone, correct or not.

So the general concept of EV Compensation is to know to adjust the middle gray metering result to be the correct result that we desire. That's where the photographers knowledge comes in. The skill is easy with a little experience. It involves just looking at the subject, and thinking a second. It is NOT point and shoot, but beginners typically don't understand the concept of thinking a second. Light meters are not smart at all, they only know to try for a middle gray result, not too bright, not too dark, regardless of what it should be. The meter does not recognize what it should be, but the photographer's brain should have a good idea about it... if he uses it.

Is spot metering just an EV compensation?

No. Spot metering only measures a small area of the total image. It bases exposure calculations only on the small area which it measures and totally ignores the rest of the frame.

If I spot meter...can I achieve identical results with EV compensation?

It doesn't matter how one gets there. The same ISO, aperture value (Av), and time value (Tv - a/k/a "exposure time" or "shutter speed") will produce the same image of the same scene.

Or is spot metering more than just a generic EV adjustment based on your target area?

There is no EV adjustment inherent in spot metering. There is only an adjustment in the amount of the total frame that is being metered. The result of spot metering is based on what a correct exposure is calculated for the area of the "spot" being metered.

Assuming the "spot" being metered is in the center of the frame (a few cameras allow spot metering at other than the center of the frame, but most that even have spot metering do not):

• If the entire frame is uniform in brightness, there will be no difference in the result of metering regardless of what metering method is used.


• If the center of the frame is much brighter than the rest of the frame, spot metering will result in a darker exposure than other metering methods. This is because the camera wants the bright thing in the center to be exposed as a mid-tone (medium gray).


• If the center of the frame is much darker than the rest of the frame, spot metering will result in a brighter exposure than other metering methods. This is because the camera wants the dark thing in the center to be exposed as a mid-tone (medium gray).

So a photographer that is good with EV adjustments technically wouldn't need spot metering?

The best photographers typically use all of the many tools at their disposal at various times. One reason they are great photographers is because for a particular shooting situation they can look at the scene and recognize which tool will work best to give them the result they want.

Sometimes spot metering is the simplest and most effective way to get proper exposure of a specific area of the overall scene.

Sometime other methods are more useful for other types of scenes.

A Case Study

I shoot a lot of night sports outdoors under artificial lighting.

• Why uncompensated Evaluative Metering doesn't work: If I were to use Evaluative metering with no Exposure Compensation the camera would recommend exposing the scene too bright because a lot of the frame includes dark sky or areas outside the stadium that are much darker than the field of play. The camera thinks it needs to make these areas bright enough to see details. Well, except when one or more of the stadiums light towers are in the scene and the camera wants to expose too dark.


• Why uncompensated Spot Metering doesn't work: Most sporting events involve one team with white jerseys and another team with colored jerseys that are usually fairly dark. Spot metering on either would not give proper exposure. If the white jerseys were spot metered, the camera would expose them as medium gray and the entire scene would be too dark. If the darker jerseys were spot metered, the camera would expose them as medium gray and the entire scene would be too bright.


• Why Center Weighted Averaging doesn't usually work: Metering results will change, sometimes quit drastically, from frame to frame as different bright and dark things occupy the center of the frame. Again, when dark things dominate the center of the frame (say there is a receiver on the left side of the frame and a defensive back on the right side of the frame jumping in the air to catch a football - the center of the frame is very dark sky in the background that I want to be black in the resulting image) the meter will recommend overexposure. When there is a very bright thing near the center of the frame (like a light tower behind a player) the meter will recommend underexposure.

So what's a photographer to do? It depends on what the photographer wants the results to be.

In my case, I want the white jerseys to be on the verge of maximum exposure without blowing out. To get there I can start by:

• Spot metering the white jerseys using about plus 2-3 stops of EC.


• Use Center Weighted Averaging on an unoccupied area of grass (being careful to meter an area that is not a particular "hot" or"dark" spot compared to the rest of the field). If it's natural grass that is still mostly green, it should usually be right around that "medium gray" brightness the camera's meter is looking for. If it is artificial turf it can usually be anywhere from a stop darker to a stop brighter than natural grass. Dial in the appropriate amount of EC. If it's the smurf blue turf in Boise State's Albertsons Stadium, all bets are off!


• Use Evaluative Metering (with my Canon cameras - other brands and even models within the same brand will vary based on the proprietary algorithms used for their Matrix/Evaluative/etc. metering scheme) of a wider scene that includes the field, the dark sky, and some of the lights with about -1 stop of EC dialed in.

From there, I set all three exposure parameters manually and look at test images to see if the white jerseys are where I want them on the histogram. Overexposure warning "blinkies" are also useful. When I've got exposure where I want it, there are just a few small, isolated spots on the white jerseys blinking in the preview image, which is based on the jpeg preview image appended to the raw file and displayed on the camera's LCD screen. Adjust exposure as necessary and repeat until that is the result.

I do not know about modern cameras and how they are programed but in analog metering of the past Spot metering is exactly what is sounds like, metering a specific area or spot in the composition ( A percentage of the overall ) as opposed to the entire composition being averaged or even center weighted.

It doesn't matter how you arrive at the three exposure relevant parameters time,aperture, and ISO. Whether you set them manually or via any of the automatic modes doesn't change the final result.

EV compensation just tells the exposure automatic that you want it to set the values for a darker or lighter result than it thinks to be correct; Spot metering tells it to base its judgement only on a small part of the scene. If you choose the EC value rsp. the targeted spot accordingly, you'll get the same exposure values.

Which one you should choose depends, then, on which is more adequate / convenient for the situation.

Basically, yes. The problem is that if any dynamic curve or ISO adjustments come into play (automatic gain contrast system, i.Dynamics and whatever else they are called), the metering method might influence more and/or different parameters than just using exposure compensation would. So if you have switched off all automatisms (like you would for creating image stacks or panoramas), the effect of metering area choice should be equivalent to some exposure compensation. If you tend to correct your metering based on zebraing, there is little motivation to change the metering method providing the initial guess.