Center weighted metering

[Hlop]

Hi,

Many of us are using matrix metering for automatic exposure measurement, many are using spot for better control. Is anyone using center weighted metering and when and why? What's the best usage of it? Any tips?

[Onyx]

I only really use centre weighted when shooting through a circular polariser, and only because it recommends to do so. I've set the centre circle diameter to 12mm (largest possible) to try and emulate matrix as close as possible. (ie. I see no point in reducing the circle size, as the metering bias towards it wouldn't make sense IMHO, if I wanted a reduced circle to meter off, I'd switch to spot)

[Killakoala]

I used centre weighted today to take a bunch of high contrast images of ships at sea. Using matrix metering caused the ships to be underexposed with respect to the surrounding bright sea.

[Manta]

I used centre weighted today to take a bunch of high contrast images of ships at sea. Using matrix metering caused the ships to be underexposed with respect to the surrounding bright sea.

That's a good call Steve - I would imagine spot metering would cause headaches due to lots of mid and dark shadow areas on the vessels whereas centre-weighted would iron out the averages. Have you got yours set to 12mm? I just changed mine after reading Chi's post - makes sense to give it the maximum as 8mm is, for the most part, not much different to spot metering for many subjects.

[leek]

It's always confused me what the different radii actually mean... 12mm of what? the sensor, the view finder?

[Manta]

The radius refers to the viewfinder John. The circle inscribed in the centre (encompassing the top, centre and bottom focus brackets) is 8mm.

[james m]

also depends on the camera, 8mm for my D200 and 12mm for my F6.

[leek]

The radius refers to the viewfinder John. The circle inscribed in the centre (encompassing the top, centre and bottom focus brackets) is 8mm.

Aha... Well there you go... I can sleep soundly tonight now...

Funny thing is, I'd not really noticed that circle until you mentioned it...

[Manta]

Sorry James - I was, of course, referring to the D70 which Leek and I both have. I wasn't aware of the differences in the models though, so that was interesting.

[avkomp]

I quite often use centre weighted for shots of birds especially when in flight because of the tendency to underexpose these subjects in matrix mode.

most other stuff I use matrix or spot depending on what I am doing

Steve

[Gordon]

I pretty much leave my metering set to 6mm spot. I find it helpful to isolate what is brightest in a scene, and aim to avoid saturated pixels.

Gordon

[Grev]

I pretty much leave my metering set to 6mm spot. I find it helpful to isolate what is brightest in a scene, and aim to avoid saturated pixels.

Gordon

I thought you can only change the circle in centre weighed metering, not spot metering...?

I always put on the largest circle.

[Gordon]

I pretty much leave my metering set to 6mm spot. I find it helpful to isolate what is brightest in a scene, and aim to avoid saturated pixels.

Gordon

I thought you can only change the circle in centre weighed metering, not spot metering...?

ahh you are correct, here I was thinking 6mm = spot, but spot is actually a 2.3mm area, quite a lot smaller. It pays to have a look at the user manual every now and then
Anyway, 6mm CW has been working well

Gordon

[Aussie Dave]

Interesting topic. From memory, the biggest difference between centre-weighted & spot metering is that CW still uses the entire scene to work out the correct exposure (a la Matrix), however CW has a bias towards what is in the "chosen" size of the circle (be it 8mm or 12mm etc..).
I cannot remember the exact bias percentage, sorry. It's probably in the manual somewhere.

Spot metering only considers what is inside the little area in the middle, so performs much differently (and is therefore much harder to use).

Of course, Matrix looks at the entire scene and makes an average, whilst guessing at what type of scene you, the photographer, are trying to shoot. From this, it calculates what is likely to give you the best exposure.

THIS and THIS may be of interest to read.

[Hlop]

Huh! I've brought this up and have almost forgotten about it!!!

So, CW meter, if I understood it correctly, is the same as spot but wider, isn't it? And if I'm metering a sheet of white paper with CW meter and in manual mode, I have to set metering in viewfinder to +1.7 or 2 ev, otherwise, if I set it to 0, it will be grey on photo?

Or is it more complicated? How does it meter mixed situation when shadow and bright light in it's circle?

[Alpha_7]

Huh! I've bought this up and have almost forgotten about it!!!

So, CW meter, if I understood it correctly, is the same as spot but wider, isn't it? And if I'm metering a sheet of white paper with CW meter and in manual mode, I have to set metering in viewfinder to +1.7 or 2 ev, otherwise, if I set it to 0, it will be grey on photo?

Or is it more complicated? How does it meter mixed situation when shadow and bright light in it's circle?

My understanding Mikhail, is that No it isn't like spot but wider.

It is more like a hybrid between Spot and Matrix. It takes into consideration the entire frame and then correct exposure for the Centre area, and then combines the two suggested exposures with a weighting towards the centre exposure.

To put some pretend numbers into the example, imagine a scene with as Steve suggested of a darkish boat on a bright sunlight sea.


=======================================
Lets say Matrix suggests that under your manual settings that 0EV is correct.

Now in Spot metering off the darker boat suggests +1EV

Now in CW metering it does the maths of (0EV + X*1EV) /2 where X is the weighted factor and the end result is +0.7EV for the exposure.



I really don't understand it well so could be WAAAAY of the mark, and I dont' suggest the formula is that easy either just wanted to demonstrate the general idea.

[gstark]

So, CW meter, if I understood it correctly, is the same as spot but wider, isn't it?

No.

Centre weighting looks at the whole image, but pays greater attention to the nominated central region.

Spot metering ignores everything outside of the nominated spot region, and looks only at that nominated region.

[Alpha_7]

So, CW meter, if I understood it correctly, is the same as spot but wider, isn't it?

No.

Centre weighting looks at the whole image, but pays greater attention to the nominated central region.

Spot metering ignores everything outside of the nominated spot region, and looks only at that nominated region.

 LOL, that was much more concise them my attempt to explain it. Well done Gary!

[gstark]

Craig,

Every little bit, and every not so little bit, helps.

[Alpha_7]

Craig,

Every little bit, and every not so little bit, helps.

Never heard that one before, had be scratching my head for a moment, must be time for a coffee!

[Hlop]

Thanks, Gary, Craig

Now, I'm trying to understand how to use it in manual mode? Craig, where did you get that formula? Is it real formula or just assuption? Should I set it to 0ev in manual mode?

[Alpha_7]

Mikhail, I just made up the formula for demonstration purposes, it maybe be right, but I'm sure it's probably more complicated then I've indicated.

Your questions about setting it to 0 EV, well (please correct me if I'm wrong) but I'd say that's a good place to start, it means the camera is doing all the calculations, if once you've taken the shot you want to compensate one way or the other then change the EV to suit. (As.. well I would when shooting in either SM or MM modes.

[Aussie Dave]

Mikhail, I just made up the formula for demonstration purposes, it maybe be right, but I'm sure it's probably more complicated then I've indicated.

Your questions about setting it to 0 EV, well (please correct me if I'm wrong) but I'd say that's a good place to start, it means the camera is doing all the calculations, if once you've taken the shot you want to compensate one way or the other then change the EV to suit. (As.. well I would when shooting in either SM or MM modes.

I agree. It will also depend on if you are trying to expose for the highlights, shadows or mid-range. Using spot meter, if you point the centre of the viewfinder at what you want to concentrate on (say for instance the shadows), and manipulate your settings to get 0EV, then you will be exposing correctly for the shadowed areas. However, in doing this you will be severely overexposing the brighter areas. This is where "bracketed exposures" comes in handy....but that is going off topic.

Basically, spot metering allows you to target & expose for specific areas of your scene. As long as you know what effect it will have on the rest of the scene, you should be able to choose an appropriate area to meter and take a photo with an exposure you are looking for.

Clear as mud ?

[Hlop]

Hi Dave,

Absolutely clear but I understand how spot meter works and I'm using it quite often. Now, I'm trying to understand how CW meter works and how to use it in manual mode. Camera does calculations but I have to read these calculations (say decrypt them ) to apply them to my exposure

Just imagine, you're shooting film. Thus, you can't check result off camera, so, you have to set proper exposure once. Sure, you can bracketing but on 120 film, for example, you'll end up with just 4 properly exposed frames per roll of 6x6 frames. Bit expensive, isn't it?

Let's say we are talking about abstract camera, digital or film, with center weighted metering system only, and let's say metering system is independant (sitting on top of the camera like with some older models). So, you have to read what metering system says and set your exposure

[Grev]

One question, when using spot metering and I change the focus points, the exposure value seems to change as well, does that mean the "spot" moves to whichever focus points you select?

[gstark]

One question, when using spot metering and I change the focus points, the exposure value seems to change as well, does that mean the "spot" moves to whichever focus points you select?

Grev,

Yes.

Mikhail,

You need to assess the type of scene that you're shooting, and try to apply the values your meter is telling you to that scene. For instance, if you can see that the scene is heavily backlit, you should "know" that you'll need to override the meter's settings because your camera doesn't.

In theory, matrix metering should notice the backlighting, and while it doesn't do too bad a job, it's not foolproof.

With spot metering, you're actually taking a reading from a known, targetted location and you should already understand how that location relates to your meter and a grey scale.

In the case of shooting people I'll typically meter off a person's cheek, which, IME, comes fairly close to an 18% grey and thus is pretty good for this purpose.

At the beach or in the city, I might meter of the footpath (if it's concrete) for similar reasons.

[Hlop]

You need to assess the type of scene that you're shooting, and try to apply the values your meter is telling you to that scene. For instance, if you can see that the scene is heavily backlit, you should "know" that you'll need to override the meter's settings because your camera doesn't.

OK. That's clear as mud

Let's make it a bit more complicated. What I have to do if I'm shooting scene with no reflected light. Sunset or night scene with some brightly lit buildings? How will I meter it with CW meter?

[xorl]

Mikhail, I just made up the formula for demonstration purposes, it maybe be right, but I'm sure it's probably more complicated then I've indicated.

The Nikon D70 uses 75/25 Centre Weighted metering. That is, the centre circle counts for 75%, outside is 25%. So the formula is more like:

Code: Select all

(75 * inside_ev + 25 * outside_ev) / 100

.

[xorl]

Should I set it to 0ev in manual mode?

If you mean EV Compensation (+/-), I'd recommend having that set to 0 when in manual mode. That way you know exactly what the meter is recommending through the viewfinder and you can easily use it as a guide when choosing your exposure settings.

Let's make it a bit more complicated. What I have to do if I'm shooting scene with no reflected light. Sunset or night scene with some brightly lit buildings? How will I meter it with CW meter?

(I'm not sure what you mean by "no reflected light"..)

Centre weighted and spot metering are very simple and predictable metering modes. They assess the light in the scene to find an exposure which will give approximately a mid grey tone. You should assess the scene to make sure that a mid grey average is what you want.

For example, if you are shooting a snowy landscape the camera will pick an exposure which renders the scene an average grey. In this case you would choose to overexpose a bit to make sure the snow comes out white instead of grey.

The easiest thing is to meter off an object which is approximately mid-grey as Gary suggested. Another idea is to meter off an object which requires a known amount of compensation. Eg, Meter off the palm of your hand (make sure it is subject to the same lighting conditions) and then overexpose 1 stop.

In your example you would meter the brightly lit building (presumably this is the subject you interested in photographing). Then you can adjust your exposure as required. Chances are the building is approximately mid grey anyway and no compensation will be required.

[johnd]

I found an interesting difference between spot and centre weighted metering the other day. I had my d70 set to spot metering and had the SB800 on to get some fill flash. The SB800 wouldn't go into TTL BL mode when on spot metering. It would do TTL but not TTL BL. Once I changed to centre weighted, the SB800 was happy to let me do TTL BL.

Had me a bit worried for a few minutes, I initially thought the SB800 was malfunctioning.

Cheers
John

[gstark]

Let's make it a bit more complicated. What I have to do if I'm shooting scene with no reflected light. Sunset or night scene with some brightly lit buildings? How will I meter it with CW meter?

Do you want the bad news, or the bad news?

In this case you have a different situation altogether.

Let's start with the brightly lit building. Are you wanting the lights (a city lights shot) or the building under the illumination of those lights.

\For the latter, meter against the surfaces that you're concerned about.

For the lights .... ahhh here's wher the fun begins.

You're actually shooting a light source, and at this point, all bets are off. While matrix metering is best able to cope under that sort of situation, light meters are designed to read the light that is illuminating your subject, rather than the loght being the subject itself.

So, take your D70 along, and meter the scened with the D70 acting as your handheld lightmeter, and then transfer the readings to your MF camera.

Sunsets ...

Now that you've read a little about a couple of the difficulties involved in shooting a scene that includes the light source, can you guess what the sun, included in your scene, might be considered to be?

[Hlop]

Sunsets ...

Now that you've read a little about a couple of the difficulties involved in shooting a scene that includes the light source, can you guess what the sun, included in your scene, might be considered to be?

This one was captured with center weighted metering f/7.1, 1/500


I pointed metering circle near the sun and set to EV0 manually, but that time I just guessed and got successful picture from the very first try. I actually, don't know why I decided to switch to CW as I've never used it before

Back to night-city-scapes. I'm just wondering if it's possible to use light meter which can measure incident light, in case if I want a city lights shot? Using D70 as a light meter was very first idea, and it looks like easiest and reliable way but it isn't always comfortable to have 2, 3 or more cameras

[gstark]

Incident reading is my favourite way to get a reading, but the D70 doesn't really lend itseolf to that.

And using incident readings for a nigh shot, the problem (not insurmountable) is the you're going to be takling your incident reading ..... off what subject?

[Gordon]

Back to night-city-scapes. I'm just wondering if it's possible to use light meter which can measure incident light, in case if I want a city lights shot? Using D70 as a light meter was very first idea, and it looks like easiest and reliable way but it isn't always comfortable to have 2, 3 or more cameras

You could try the foam coffee cup over the front of the lens trick as an incident light meter, but you will have to calibrate it first, ie work out what EV compensation you need to set to give you the correct exposure.

I have a Gossen LunasixF sitting in the cupboard, but havent used it since I went digital...

Gordon