Camera metering modes

[Colin Southern]

I tend to use a hand held incident light meter (with difuser cone) wherever possible as this is really the only way to get a truly accurate reading of the light falling on a subject.

Hi Mike,

Welcome to the forums

I'm a big light meter fan too - but for landscape I'm mostly using it's spot-metering capability, which (apart from being profiled to the camera), isn't much different to regular in-camera spot metering.

In camera spot-metering is still very accurate though - so long as people remember to shift the exposure to allow for the reflectance of the object they're metering off (-2 for blacks -> +2 for whites).

PS: If you get a chance, pop a reply onto the welcome thread so that we can all welcome you properly

[Zephyrize]

Something confuses me with metering modes.

If I understand, metering is basically a way to set a correct exposure which is controlled by Shutter Speed and Aperture. (Assuming that the ISO is constant)

For one scene, a too slow shutter or too fast shutter will result in a over and under exposed image. The same goes for too wide or too small aperture. So there's only a limited range that the settings can go. The metering mode is there to help you choose the right 'spot' within that range right?
What I don't get is why different metering modes are that helpful. It only gives an approximate value that you have to adjust afterwards. Since the camera meter is here to correct either shutter speed or aperture depending if you're using Av or Tv, metering is then completely useless with Manual mode, since you have control over everything?

That's what confused me when Colin said "using spot metering in conjunction with Manual mode".

I mean, at the end, what to picture will look like only depends on two number and if any combinaison of the two settings can't give you a satisfying exposure, there's nothing else to do..

[Alis]

ok Canon users, please then don't complaint about the horrible, dificult and I don't know what else adjectives else might describe the interface your camera has

And to be clear, I was not complaining about the user interface, my problem was that there are options that I don't understand and need to learn the concept behind them before I can use them.

The UI may be complicated but I was not complaining about that...

Sedali

[Dave Humphries]

metering is then completely useless with Manual mode, since you have control over everything?

Hi Zhiyao,

Well I wouldn't go that far!

The camara will still indicate by some means when it thinks it you have manually set the exposure it would have chosen had it been in auto exposure mode.

Let's go back to first principles, and for the moment, we will forget those metering modes.
You are correct in as much as a scene that is correctly exposed at f8 and 1/125 will also be correctly exposed at f4 (2 stops wider) and 1/500 (2 stops shorter), for the same ISO.

If you are using Shutter Priority (or Tv) and set 1/250, the camera will automatically give you what it thinks is a correctly exposed shot as long as this falls within the lens' aperture range for the prevailing light conditions and ISO set. If it can't, it will warn you somehow.

Similarly, in Aperture Priority (or Av), if you set f11,the camera will automatically give you what it thinks is a correctly exposed shot as long as this falls within the camera's shutter speed range for the prevailing light conditions and ISO set, but this may give camera shake if too low - they usually give a warning of speeds below say, 1/30 for this reason. If it can't at all, it will also warn you somehow.

In Manual mode, as you say, the camera will happily let you take an under or over exposed shot, so you have to pay attention to what the metering says, sometimes this indication is merely a colour change of the figures in the viewfinder, possibly with an arrow or two to indicate which way to turn the shutter speed or aperture ring to get it more right. So the metering IS still doing something useful, even in Manual.

In all the above, we have assumed the camera's meter is going to get it right, as we know, it sometimes doesn't; for example when taking sunsets, snow scenes, or similar things where the picture content is largely quite light or very dark.

In these cases, there are two things we can do:

1) set an exposure compensation (EC) factor to tell the camera to offset, or move, what it thinks is correct exposure by a 1/3, 2/3, 1, or more, stops above or below it's metered calculation.

2) change what the meter "sees", so it stands more chance of getting the exposure calculation right - this is what the metering modes are all about.

Why would we want to do this, well think of this;
A) If you take a wide angle view of a landscape from a hill or mountain (that isn't snow covered!) with the sun behind you, the meter, in matrix or average mode is hopefully going to get this right.

B) If you now turn around and try to take a picture of a person standing behind you, they will have the sun behind them, shining into the lens with their face in shadow and the result WILL be an under-exposed face on the matrix or average metering mode.

However, if you select Spot metering mode under these conditions, i.e. use 2) above, and center up on their face, it will be more correctly exposed.

A) and B) are the two extremes to demonstrate when the spot metering may and may not be useful. Note this has nothing to do with the actual results in terms of the shutter and aperture values, just how they are achieved and optionally modified in 1).
It may be that in addition to spot metering, you may also need to set an EC offset to get a well exposed face, but the sky would be vastly over-exposed in this example. You wouldn't really do this.

Hope that helps and apologies if I have told you lots you already knew,

[Davey]

I actually find metering as useful in manual to in auto. Even more useful if that's possible since I never like the way my shots work in auto, sometimes they are fine, sometimes they are blown or (more often) darker than ideal. Even when I use appropriate mode (only have 3, average, spot and multi) in some situations it gets it wrong, sometimes unforgivably wrong. Sometimes it's ok but I stick in manual exclusively to be safe.

The other thing is in auto my cam choses too much for me like the iso and my camera suffers from noise. Well I'm the one actually suffering from the noise but my camera is the source of it so I like to stay in iso64, or 100, usually no higher than 200 if I really need it. The flexibility of manual mode coupled with metering is ideal for me. Although P, A and S priority modes improve on full auto overrides of factors I'd like to keep constant they basically do what I can do easy enough in manual so I don't see the point since if it works full auto is fine, but since it often wont (to my taste or in scene where lighting is not usual, usual for me) if I am going to fiddle with anything it might as well be both shutter and aperature rather than just one of them (since I shoot in raw I don't worry with wb etc).

I quite like my camera despite it's auto mode not being reliable (but I find automation of most kinds is not preferable from cooking to computers) and suspect it's the same for higher priced cameras. I have little probs with it's metering (admittedly it's not as good as a more expensive camera but for it's very low price range it's much better than I expected). In fact the metering is just as important because to get the shot I want I meter in appropriate manner (ie spot the brightest point when setting to stop something clipping) and set ap and shutter accordingly. Then I take a test shot, if it works I use that setting, if not I adjust slightly (since metering always gets me closer than ballpark).

[Dave Humphries]

Hi Davey,

As an aside; thanks to Colin's recommended book, I have just discovered how powerful the noise reduction is in ACR (I use 4.3.1). I believe we have similar cameras, possibly even the same 6MP sensor, and I shoot upto 800ISO on many occasions.

Due to Neat Image (previously) and now ACR, I can get rid of most of it in day shots, although I will admit, your nocturnal shoots might give a little more trouble.

Just something to try; I have luminance and chroma noise settings almost maxed out though to get a good result.

Cheers,

[Davey]

I might give increased iso a try then thanks for that. If you don't mind me asking what do you do to reduce it.

I do blitz it n acr and find it does one hell of a job but if there is more I can do to remove it would be great. At moment I have both lum and chrominance noise reduce sliders at 100% (with hardly any discernable sharp loss). Coupled with few other things such as repeated filtering, blending and selective sharpening the final result doesn't show much noise.

I also tried blackframeNR but I think acr automatically deals with it if I'm not mistaken. I notice the difference between shots developed no processing (as possible that is from raf to tiff) in finepix tool to acr ones is the acr pics don't have hot pixels on, or seem to have less at least. Do you find this too since you use similar cam and same apps?

Oh I use finepix viewer 5.4.11e with exif v2 (and fuji raw and fps upgrade so my raf files have thumbnail preview in windows) and acr 4.5 (if emember correctly as that update was a while ago) and 5.2 (2 different as on different machines with different ps versions you see).

[Dave Humphries]

Ok, it sounds like you're already doing what I was suggesting.

The other tool I use is Neat Image, this comes as a stand-alone and with a plug in for PS Elements (and presummably PS CS3/CS4 too). This works by sampling a small area of picture that has no discernable info in it, then uses that to subtract noise from across the image without knackering fine detail. Costs about $50 for what I got (Home+).

It's very configurable, not wonderfully intuitive, but once you know how to do it, it's easy, I normally use the auto + defaults, occasionally moving the sample box, or changing the strength of the effect.

It does the job for me, although I'll probably use it less now.

We're in danger of a moderator extracting this aside to a new thread, especially as I wound one up earlier!

Cheers,

[Colin Southern]

Something confuses me with metering modes.

If I understand, metering is basically a way to set a correct exposure which is controlled by Shutter Speed and Aperture. (Assuming that the ISO is constant)

Yes. The problem is though that the metering often gets it wrong because it can only determine the range of brightnesses in a scene; it has no knowlege of whether tones in a scene are supposed to be shadows or highlights - so it assumes that the brighter bits are supposed to be highlights, and that the average scene reflectance is a medium gray - and that where things can start to go wrong.

With metering modes like partial, you can tell the camera to ignore things around the edge that might throw the exposure calculation off (like a window) - but spot-metering is a bit different; because it's so precise it doesn't "average" the readings that it gets - so you have to feed in a bit of human intelligence to get the right exposure. If you use spot metering - point it at something white (like a bride's dress) it'll under-expose it by around 2 stops; point it at something black and it'll over-expose it by around 2 stops

Make sense, or still confused?

[Zephyrize]

Thanks guys
It cleared up most of the things I wasn't sure
so even in manual mode, I have to rely on the suggested settings and adjust to acheive what I'm looking for.
So let's say that I want to correctly photograph a snow covered open field with a few trees; I better use Spot and aim at the tree, then recompose and shoot?

also, in Dave Humphries example of a subject backlit by the sun...logically there are two results possible:
- evaluation metering will get a underexposed subject face
- spot metering will get a blown out sky
In such case, there's no other solution than change the shooting location to get both subject and background sky correctly balanced.

I guess all these elements will get clearer once I'll be able to go shoot outside in spring, and get to experience under different conditions
I'm also thinking of getting Bryan Peterson's book Understanding Exposure, a lot of ppl seem recommending it

[Davey]

thanks Dave for recommendations @ me, I came across neat image a while ago (from seans tutorials in fact), and someone I met told me about noise ninja too.

I'd personally spot meter the snow and expose just under white clipping point. This might not be standard practise though. Usually the meter gets you close but sometimes I find I can go a bit over or have to go a bit under (more usual). The way mine is I adjust ap/shutter until I get the metering point on the exposure bar registering just under the the right then I knock it down a touch. Then a test shot. Then gauge from this whether to adjust shutter, or aperature depeding on scene, or both. Sometimes mine clips something wicked until I get the balance to around the centre of the bar, depends on the scene etc. Obviously how sensitive metering is, lighting and scene elements, or how wide the "spot" is and the actual meter in the camera (and of course it's different modes) and so on will affect what you find yourself.

I personally find snow is ok and not too bad unlike skies. Aside from GND filters (I don't own nevermind use so someone like colin is the man to ask there but can guess his answer will be singh-ray) the only way I get round this is either

1. HDR. I'm not "there" myself but it's getting more familiar. 2 (or 3) exposures needed.

2. Taking more than one exposure and blending together. One for sky detail/highlights, one for mids that's just right (aside from blown highlights). I don't bother with shadow detail for this method. My prefered method, kind of similar to above but more long winded and without the loss of contrast. Not ideal for high volume of images though. Can get away with no tripod when you're blending manually.

3. Bit of a dirty cheat but a few times I have done this. Mask off sky with paths/selection tools and simply just add a pretty gradient to it. Blend a few in to get a natural look or whatever you like. I added a small amount of natural looking noise once to stop the plastic-like fake look. Basic tweaks to achieve perfect "imperfection" and no-one knows. Not one most photographers would like since it's a complete lie but it's one I can sleep soundly over

[Bill44]

also, in Dave Humphries example of a subject backlit by the sun...logically there are two results possible:
- evaluation metering will get a underexposed subject face
- spot metering will get a blown out sky
In such case, there's no other solution than change the shooting location to get both subject and background sky correctly balanced.

There is another solution, in most cases balanced fill flash will let you capture the lot. Have I opened up a lot more questions?

[Davey]

ah yeah I remember colin posten an example of portrait into sunset sky. I guess it get's difficult in landscape scenes or is there a way (short of having a flash that throws light silly distances)?

[Colin Southern]

Thanks guys
It cleared up most of the things I wasn't sure
so even in manual mode, I have to rely on the suggested settings and adjust to acheive what I'm looking for.
So let's say that I want to correctly photograph a snow covered open field with a few trees; I better use Spot and aim at the tree, then recompose and shoot?

If you wanted full control then I would use spot-metering in manual exposure mode - meter off some snow - and then adjust the exposure so that the meter was showing 2 stops over centre (unless there was something even brighter in the scene that had to be retained.

also, in Dave Humphries example of a subject backlit by the sun...logically there are two results possible:
- evaluation metering will get a underexposed subject face

Adduming Av or Tv modes, and without adding exposure compensation, yes.

- spot metering will get a blown out sky

If in Av or Tv mode then yes - if you're in manual mode (which I think is almost mandatory when spot metering) then it's going to depend on where you shift the metered value to - if I shift it to about +1 then it'll look pretty much OK (but the sky will be nuked to kingdom come).

In such case, there's no other solution than change the shooting location to get both subject and background sky correctly balanced.

As I think Bill mentioned, flash is the answer - but that's an entirely different discussion.