Why don't most cameras allow control of metering?

[carl1864]

While I've never used high end cameras, I've used many prosumer cameras that have full manual controls, and just a touch of experience with DSLR's.

One function that always seems to be missing is the ability to control the metering, beyond just choosing spot, center weighted, etc. Even when you have your ISO, Aperture, Shutter, flash, etc. locked in, the cameras still want to handle the metering automatically, Often in tough lighting situations leading to highlights being over exposed, or else shadows being underexposed, and you don't seem to have much choice or fine control over it except just aiming the camera around till the auto metering gets it right. Why not allow control over this?

 

[Virginia Bill]

I'm not sure what additional control you want. Spot metering lets you take the reading from a very small area of the screen or viewfinder; that's as precise as you can get. You can also set many cameras to expose at various degrees under or over the indicated reading; that's what the + - EV button does.

I suspect your question arises from not fully understanding what the various metering modes and exposure controls do. In other words, many cameras do what you claim they don't do.

 

[Aletheia]

I don't think you understand how "most cameras" (not sure what that means) work. Or else I don't understand your question.

You need to re-phrase things to make it more clear what specific kinds of cameras you are talking about.

--
Nothing is enough for the man to whom nothing is enough.

 

[beshannon]

Why not allow control over this?

The type of metering is the control.

Perhaps a read of this article would help you rephrase your question

http://www.cambridgeincolour.com/tutorials/camera-metering.htm

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[carl1864]

I understand how metering works, but there are times I would like to control it myself, rather than home the cameras algorythm does it the way you'd want it to. Spot metering can be good, but only if the area you want to base the metering off of is in the center of the frame, which it often isn't.

To me, relying on a camera to accurately meter automatically is about the same as relying on automatic mode to automatically select the correct shutter speed, sometimes it gets it right, but often it doesn't. I wish I had the option to lock in the metering exactly how I want so it does not ever change until I want it to, same way you lock in a shutter speed or anything else.

 

[Graystar]

If you're in constant-light conditions and you have a Nikon or Sony, you can lock exposure and the find tune it with the Exposure Compensation control. With any other camera you lock exposure and apply EC, but locking exposure for multiple images is usually a pain, or sometimes impossible.

If you're in changing-light conditions then you base your exposure off of your subject and use the Exposure Compensation control to correct exposure based on the tone of your subject.

In either case the photographer can have precise control over exposure.

.

 

[dradam]

I understand how metering works, but there are times I would like to control it myself, rather than home the cameras algorythm does it the way you'd want it to. Spot metering can be good, but only if the area you want to base the metering off of is in the center of the frame, which it often isn't.

To me, relying on a camera to accurately meter automatically is about the same as relying on automatic mode to automatically select the correct shutter speed, sometimes it gets it right, but often it doesn't. I wish I had the option to lock in the metering exactly how I want so it does not ever change until I want it to, same way you lock in a shutter speed or anything else.

You say you only have a touch of experience with DSLRs and it is quite evident from your comments that you have the very slightest of touches. All of this is available on even the most basic DSLR. The camera meter, when in spot mode, doesn't use any sort of algorithm, it simply exposes for 18% gray. There is an exposure lock button for when the subject you are metering is off center and you still wish to use the automated modes. There is an exposure compensation dial for when you wish to expose above/below what the camera reads. And there is always manual mode where you can set the parameters involved in exposure and leave them there.

The reason (I believe) that this is not available on many p&s type models is that this level of control is not desired by a majority portion of the intended market for those cameras.

 

[RobG67]

I thought that was one of the functions of Manual mode, to allow you to control what the light levels in the image are. Maybe I've been doing it wrong all this time...

--
Rob.

Free advice, freely given. If you don't like it, I'll refund you twice the amount you paid me.

 

[Aletheia]

I thought that was one of the functions of Manual mode, to allow you to control what the light levels in the image are. Maybe I've been doing it wrong all this time...

That is what Manual mode does. I think there is some very profound misunderstanding about what metering is, how it works, and what the "modes" mean.

Spot metering is a metering mode that uses only a very small part of the image from which to measure. You can use spot metering in any of the "automatic" modes like Av or Tv, and you can use it in Manual. You can also use Center Weighted Averaging, or a complex mode like "Evaluative" in Canon Cameras in any of the camera operating modes.

In manual YOU must change the shutter speed, aperture or ISO to control the exposure you are giving to the image (is that what you mean by light levels?) YOU can adjust the settings, using the moving meter level indicator as a guide, to whatever level YOU want the spot the Spot meter is reading to have. You can also lock that exposure so that you can recompose, focus elsewhere and shoot the picture as you wish. You can do that with any DSLR of which I am aware, if you know how to operate it.

I do not understand what the issue is, other than you do not know enough about the operation of DSLR cameras to appreciate the flexibility and control they provide.

--
Nothing is enough for the man to whom nothing is enough.

 

[carl1864]

The exposure lock, is something I was unaware of. None of the primary pro-sumer cameras I've used had it, and I guess I never used a DSLR long enough to find it.

But even spot metering is still pretty automatic. I mean, you point at what you want to adjust the metering to, and it "automatically" adjusts the metering based on that spot. Sure you can use exposure compensation, but thats just adding a slight bit of adjustment to the automatic choice it made for you.

Then it will probably re-meter for the next photo a few seconds later (I'm making a guess that the exposure lock only locks for one picture, or burst). I just think there should be a choice that you can set the metering exactly where you want it, and it will never change till you want it to. Same way you can set the shutter speed, or Aperture exactly where you want it. I mean, you don't choose the shutter speed by pointing at an object, letting the camera chose for you, and then use shutter speed compensation to adjust it up and down, that would be silly.

Perhaps I'm just way too picky (I also am extremely disappointed that hardly any cameras let you choose the flash output levels of their built in flash). So what if not many people use either of those things, they are both simple, can't be that hard to include, why not include them for the people that want them?

 

[Graystar]

The exposure lock, is something I was unaware of. None of the primary pro-sumer cameras I've used had it, and I guess I never used a DSLR long enough to find it.

Many cameras have exposure lock. Even my old Canon A710IS compact has an exposure lock. Every DSLR I know of has an exposure lock button either under or very near the right thumb.

But even spot metering is still pretty automatic. I mean, you point at what you want to adjust the metering to, and it "automatically" adjusts the metering based on that spot. Sure you can use exposure compensation, but thats just adding a slight bit of adjustment to the automatic choice it made for you.

You're looking at it the wrong way. The meter doesn't choose anything...it simply indicates. The meter measures the reflected light to determine the Exposure Value for the scene. The camera will then do what it does for that EV value. For example, you can look in the back of a Nikon DSLR manual and find the Program Mode chart. The chart shows all the EV levels and what shutter/aperture combinations are available. Whatever EV level the meter reports, that's what Program Mode uses to select aperture and shutter based on the chart. You can change both what the meter reports (using EC) and what Program Mode selects (using Flexible Program.)

Then it will probably re-meter for the next photo a few seconds later (I'm making a guess that the exposure lock only locks for one picture, or burst).

Whether the exposure lock remains depends on the camera. As far as I'm aware, Pentax and Olympus toss the lock after one shot. Canon will keep the lock if you press the AE Lock button within two seconds after taking the shot. Nikons default to tossing the lock after 6 seconds, but that can be extended in the settings, allowing you keep the same lock for as many shots as you want. Sony keeps the AE Lock until it's unlocked.

Of all the DLSRs I feel that Nikon provides the most flexible exposure functionality.

I just think there should be a choice that you can set the metering exactly where you want it, and it will never change till you want it to.

I've made that suggestion to Nikon...to allow the meter to be set via a Command Dial, and to set the desired EV. As it stands now you can never "set" the meter...you can only lock exposure at its current reading. However, that's still incredibly useful because you still need to meter your scene. If you want complete control over exposure you have to set your camera to Spot metering, then meter a neutral tone and lock the exposure. Now your exposure is correct. If the tone you metered wasn't neutral, then you dial in exposure compensation to correct the meter. So you can meter blue sky or the sunny side of green grass and your exposure is set. Or you can meter a white dress, lock exposure, and then set EC to +2. Again, exposure is set.

Same way you can set the shutter speed, or Aperture exactly where you want it. I mean, you don't choose the shutter speed by pointing at an object, letting the camera chose for you, and then use shutter speed compensation to adjust it up and down, that would be silly.

That's called Flexible Program on a Nikon, and it has its uses.

Perhaps I'm just way too picky (I also am extremely disappointed that hardly any cameras let you choose the flash output levels of their built in flash).

All Nikons (and I'm sure most other DSLRs) allow you to set the flash to manual mode and to set the flash power directly. And again, even my Canon A710IS compact has a manual flash power setting.

So what if not many people use either of those things, they are both simple, can't be that hard to include, why not include them for the people that want them?

I really don't see anything that can be done to improve exposure functions on a Nikon, and other brands have their own pluses and are very capable of setting a precise exposure. The only thing missing is the ability to set the meter directly, which is really of very limited usefulness. You'd have to know the current lighting levels to set the meter correctly...are you going to set your camera with a hand held meter?

You can actually turn your camera into an Incident Light Meter using an ExpoDisc, if you want a really precise meter setting.

.

 

[carl1864]

Very good and detailed answers. I was unaware the exposure compensation button could also be used as an exposure lock, that helps a little. I also do have a canon P&S that allows a tiny bit of control over the flash, but only 3 stages, and its the only camera I've ever seen to have it, from what I hear, most dslr's don't even have this ability besides a couple nikons. I think every camera should all have it standard.

I am a bit confused why some people seem to be relating the metering to shutter speed and aperture though. To my knowledge they are completely seperate things. For example I can go in manual mode, set aperture to 2.8, shutter speed to 1/500, and iso to 100. Those are set, and not changing, yet depending on what I point the camera at, whether its bright, or dark, the metering still changes the overall exposure.

I couldn't find the article again, but I believe the explanation was something like a full complete histogram has more than 5 brackets, something like around 10, but the camera can only capture 5 brackets. It cannot capture both very bright, and very dark at the same time, so it basically slides up or down the scale accordingly. So Its a bit confusing why people are saying metering has anything to do with shutter speed/aperture.

 

[gisle]

One function that always seems to be missing is the ability to control the metering, beyond just choosing spot, center weighted, etc. Even when you have your ISO, Aperture, Shutter, flash, etc. locked in, the cameras still want to handle the metering automatically,

I have read the entire thread, and I do not think you understand what the light meter does.

The light meter just tell you how much light there is in whatever area of the image frame you choose to meter (selecting spot, center weighted, etc.). An advanced hand-held can tell you this directly, using a single unit for illuminance, such as EV or Lux. The camera's meter do this indirectly, by going to "zero" when a specific combination of aperture, shutter speed, and ISO is set. If you know the math, it is trivial to convert a specific (aperture, shutter speed, ISO)-triple into a specific EV or Lux.

It is important to understand that the light meter only performs a measurement of a physical entity (the amount of light illuminating the scene you want to photograph). You do not want to "control" this measurement, any more than you want to "control" the markings on a yardstick.

Often in tough lighting situations leading to highlights being over exposed, or else shadows being underexposed, and you don't seem to have much choice or fine control over it except just aiming the camera around till the auto metering gets it right. Why not allow control over this?

If you've understood what a light meter is, and what it does, you would not ask this question.

The question you should have asked is the following: How can I control exposure , so that in tough lighting situastions, I get a different exposure than the exposure my camera set automatically based upon the light meter reading.

And any decent camera have features that gives you plenty control over exposure. For instance:

• Exposure compensation (EC). In the automatic modes (Program, Shutter priority, Aperture priority) you just dial in the exact amount you want exposure to deviate from what is determined automatically from the meter's reading, before taking the photo.
• Exposure Lock (EL). In the automatic modes (Program, Shutter priority, Aperture priority) you meter the part of the scene you think gets it right (usually using spot metering). Then you lock exposure and recompose before taking the photo.
• Manual mode (M). You completely override the automatic exposure derived from the meter's measurement with the settings you think is right before taking the photo.

Note that if your camera does not have EL, you can do the exact same thing by putting the camera in Manual mode, meter the part of the scene you think gets it right using manual mode to "zero" the meter. Exposure is now locked by manual mode and you can recompose before taking the photo. Also note that changing the shutter speed, aperture and/or ISO in Manual mode is equivalent to using EC in any of the automatic modes.
--
– gisle [ See profile/plan for equipment list ]

 

[Chikubi]

Ooooh, my head hurts from the misunderstanding and misinformation in this thread. (edit: Gisle knows exactly what's up, but posted while I was typing)

Manual mode is exactly what you're asking for, why you don't understand that is beyond me. If I go outside and take a pic in manual mode @ 1/125 f11 @ ISO 100 that gives a correct exposure and then walk inside and take a pic with those same settings the pic will come out pitch black. The meter will show the severe underexposure, but it will not alter the exposure to get a correct one, at least not on any DSLR or high-end compact that I've ever owned or used. I have a D3, D200, and a G12 and they all work this way. If you have a camera that is doing otherwise then check to make sure you don't have safety shift on or some similar settings that will adjust to a safe exposure irregardless of your settings as that will get in the way.

Otherwise, sure the meter may jump around in manual mode as you have varying light, but that doesn't mean you have to pay attention to it. The other night I was shooting long exposures for a project I'm working on and the meter was screaming at me about severe underexposure, but I set my settings in manual that I needed irregardless of the meter and took probably 20-30 shots. Every shot was consistent; the camera did nothing to force a correct exposure regardless of the meter reading. FWIW, it was the G12 I using.
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[gisle]

I am a bit confused why some people seem to be relating the metering to shutter speed and aperture though. To my knowledge they are completely seperate things. For example I can go in manual mode, set aperture to 2.8, shutter speed to 1/500, and iso to 100. Those are set, and not changing, yet depending on what I point the camera at, whether its bright, or dark, the metering still changes the overall exposure.

So Its a bit confusing why people are saying metering has anything to do with shutter speed/aperture.

The meter as such is not linked to anything. In fact, I perfer to use a handheld Sekonic light meter that is not even physically connected to the camera as my preferred light meter.

In Manual mode, the camera's built-in light meter just tells you how much overexposure or undrexposure it "thinks" you will get - given the aperture, shutter speed and ISO settings you've set manually. You can of course ignore this reading entirely if you want to. But you can also choose to "zero" the meter in manual mode (i.e. adjust shutter speed, aperture or ISO until the meter is at "zero", and not showing overexposure or underexposure). Then you are acting as an "agent" that is linking the meter's reading to setting the shutter, aperture or ISO.

In one of the automatic exposure modes (Program, Aperture priority, Shutter priority), the camera will automatically adjust aperture and/or shutter speed to "zero" the meter for you (that's essentially what the automatic exposure modes do). In the automatic exposure modes, the camera's computer becomes the "agent" that's linking the meter to the aperture and/or shutter speed settings (and if the camera has auto-ISO, also to ISO). I.e. in the auto-exposure modes, the light meter (instead of you) is by the camera put in charge of exposure (however, with most DSLRs, you can use EC or EL to override this, if you want to).

When people "link" the meter to shutter speed/aperture, thay are referring to how the "system" (meter + computer) behaves in the auto-exposure modes, not manual mode.
--
– gisle [ See profile/plan for equipment list ]

 

[gisle]

The exposure lock, is something I was unaware of. None of the primary pro-sumer cameras I've used had it, and I guess I never used a DSLR long enough to find it.

But even spot metering is still pretty automatic. I mean, you point at what you want to adjust the metering to, and it "automatically" adjusts the metering based on that spot. Sure you can use exposure compensation, but thats just adding a slight bit of adjustment to the automatic choice it made for you.

Then it will probably re-meter for the next photo a few seconds later (I'm making a guess that the exposure lock only locks for one picture, or burst). I just think there should be a choice that you can set the exposure (not metering - which is irrelevant) exactly where you want it, and it will never change till you want it to.

There is. It is called "Manual mode".

Put your camera in Manual mode. Point at what you want to adjust the metering to (use spot metering if that is what you want, or any other mode you're happy with. Adjust the shutter speed and/or aperture until the camera's light meter is at "zero". Now you've set the metering exactly where you want it, and it will never change till you want it to.
--
– gisle [ See profile/plan for equipment list ]

 

[RobG67]

If that was for me then I must apologise for the misunderstanding - I was being funny; I know exactly what Manual mode does, as well as when and how to use different metering methods. I guess humour doesn't always carry well in text.

--
Rob.

Free advice, freely given. If you don't like it, I'll refund you twice the amount you paid me.

 

[cberry]

While I've never used high end cameras, I've used many prosumer cameras that have full manual controls, and just a touch of experience with DSLR's.

One function that always seems to be missing is the ability to control the metering, beyond just choosing spot, center weighted, etc. Even when you have your ISO, Aperture, Shutter, flash, etc. locked in, the cameras still want to handle the metering automatically, Often in tough lighting situations leading to highlights being over exposed, or else shadows being underexposed, and you don't seem to have much choice or fine control over it except just aiming the camera around till the auto metering gets it right. Why not allow control over this?

besides all the good responses breaking down the functions of the camera into it's different components and showing you how one system feeds into another, you're asking for a feature that is there on many cameras and you're probably using every day anyway.

Some ways of accomplishing what you want are:
Exposure adjustment dial usually - + 2 EV compensation that can be dialed in.

AE lock - catching your exposure, re-framing your shot and firing with different metering modes.
Manual - adjusting exposure based on what you see in the histogram/display
AE lock with Servo focus enabled.
Separate AE and AF locks - set exposure here, focus there and then re-frame.

Using an external light meter to set your exposure manually is the most accurate way of setting an exposure.
Half-press of shutter also locks exposure in some models/programs.

I think your biggest problem is understanding that all modes except for manual compensate for light metering changes on the fly until you tell them to do otherwise.
cb

 

[PeterLeyssens]

Hi Carl,

I am a bit confused why some people seem to be relating the metering to shutter speed and aperture though. To my knowledge they are completely seperate things. For example I can go in manual mode, set aperture to 2.8, shutter speed to 1/500, and iso to 100. Those are set, and not changing, yet depending on what I point the camera at, whether its bright, or dark, the metering still changes the overall exposure.

Gisle mentioned his Sekonic meter, which is always a good investment (I have a Gossen but it's just as good, of course). Another thing you should check out is how the multi-spot meter worked on the Olympus OM-3/4 film cameras from the 1980s. Here's my short explanation of how I used it (which you can also do with a good separate multi-spot meter).

1) I look at the scene and decide which parts look brightest and darkest

2) Looking through the cameras, I put one of the dark areas in the center of the viewfinder and press the "spot" button. I can do this up to 8 times. The camera remembers all 8 values, shows them on a line (a bit like the zone metering system from Ansel Adams) and also indicates the average value of all 8. I then know what exposure I want for the dark areas.

3) I clear the spot values and restart with the bright areas. I then know what exposure I want for the dark areas.

4) I average these two values and I get an exposure value for the whole scene. If the dynamic range between dark and bright is too wide (7-8 stops), I can decide if I prefer black shadows or white highlights.

5) To determine my f-stop, I worked with the manual focus lens: focus on the nearest by object that I want to be in focus and note the distance on the lens' distance scale. Same for the most distant object. If I then turn the lens until it's focused right in between these two, I can see which f-stop gets everything in focus.

6) When I know my f-stop (step 5), my ISO (film: fixed, digital: depends) and my exposure (step 4), then the shutter speed is a simple deduction. Most separate light meters can do this for you.

You can imagine that I miss manual focus lenses sometimes: even the cheapest had a distance scale, but only expensive AF lenses have them.

Peter.

--
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[carl1864]

It is possible I may have gotten confused over some possibly bad info in the past. I tried to find this info again, but could not find it anywhere.

What I had read was that digital cameras cannot capture the entire tonal range, only a small portion of it, (the 5 stops shown on a histogram). But that the whole tonal range is actually larger than that, lets say 10 stops for the sake of example since I can't remember the actual number. So out of those 10 stops, the camera basically would slide its 5 stop histogram bracket up and down this scale. A darker image would perhaps use brackets 2-6, and a lighter image would perhaps use brackets 4-9. Effectively changing the range that the camera picks up, and altering the final picture.

Perhaps this was wrong info? Or perhaps it doesn't apply to manual mode?

90% of my picture taking is always in manual mode, and I had assumed this still applied because the picture preview on the lcd would still change dramatically depending on the brightness of the object you were pointing at, however I just did a test photographing a light bulb directly, and also indirectly, and although the preview did change drastically, the final picture was the same brightness. That's what I had always believed would be the case, until whenever I read that article that said elsewise. I think it may be a situation where I used to understand fully, until a misunderstood article may have changed my perception.

But if that's the case, then why is metering type even an option in manual mode if it doesn't change anything? Is the sole reason of choosing a type of metering in manual mode simply to determine what area of the image effects the readings of the little on screen light meter, but doesn't change photo composition at all?