Why use a light meter?

[DanK]

So, for me who is 99% of the time in Manual Mode, on tripod, in the garden, preparing to shoot a bright yellow flower in the morning light, a light meter would make the job of "exposing not too bright/dark right the first time?

No one has suggested shooting without a meter. You haven't said what camera you have, but virtually all modern cameras have a built-in meter, and most can meter in a number of different ways, e.g., spot, center-weighted average, and evaluative. The question is how useful it is to have another, hand-held meter. The camera meters from light reflected from the subject, while most hand-held meters are incident light meters, which you put near the subject so that they can measure light similar to that falling directly on the subject. The debate is whether you need the second type of meter.

I say probably not. I don't even own an incident light meter because the meters in my cameras are very good, and once one learns how to use the various modes well, it is not that hard to compensate for tricky lighting.

Re Andre's point about flash: if you use a modern, TTL or E-TTL flash, unless you set the flash in manual mode, you will automatically be using the camera's meter to turn off the flash when there is enough light. Under those circumstances, there is no need for an incident meter because you don't set the flash duration manually. I do all of my flash candids in E-TTL mode and pay no attention to metering at all, as it is automatic. This is one of the few circumstances where I let the camera do the thinking for me. I'll paste an example below. This was shot in ETT-L mode, using a flash bounced over my left shoulder, with a bounce card to give some direct light facing forward. I didn't meter.

[Loose Canon]

Hi Louise!

Maybe THIS would interest you.

If I were you and doing what you describe 99% of the time I don’t think I would bother with a hand held meter unless I just had the $$ and wanted one to play with.

I have used the White Towel method and it works if you really need it. I’d suggest since you are in your garden with plenty of time just watch the Histogram (color channels as well as luminosity), set the “blinkies” if your camera so allows and push it to the right as far as you can without clipping and you will get some killer, well exposed shots. Keep your eye peeled for the changing light as the morning progresses.

Maybe save the $$ or maybe a different piece of kit.

[ajohnw]

All your answers are different and helpful at the same time. In short it is all about understand how a camera sees the scene, be it reading in it too much light or not enough, or the difference between a pleasing picture or not so pleasing depending on the effect you where trying to accomplish? Right?
So, for me who is 99% of the time in Manual Mode, on tripod, in the garden, preparing to shoot a bright yellow flower in the morning light, a light meter would make the job of "exposing not too bright/dark right the first time?

1) Correct but the actual lightness or darkness can be corrected during post processing within the limits that are usually required.

2) No it wouldn't. In general terms the only really useful meter is a flash meters when multiple heads are used. The matrix/evaluation metering in the camera is more likely to make a decent job of it. Incident reading take no notice of reflectance, reflected reading using meters other than the matrix/evaluation types built into the camera will all meter what ever they see to the mid tone level. So for instance black would come out grey, dark yellow would come out light.

Out of curiosity I just took a shot of a yellow flower using northern light from a window, evaluation metering - it's called matrix metering on this camera. I don't use manual unless I am using flash. I use P mode and set aperture and speed to what I want so this was taken purely on the exposure the camera set. Normally I might apply maybe - 1/2 EV on something like this as it's a rather bright yellow but this is the result. It's the 1st time I have used this particular camera. It arrived a couple of hours ago. Hand held and insufficient depth of field but the exposure is more or less correct as are the colours, just a touch richer than reality.



Looks like I need to turn the cameras jpg noise reduction off but really with light available and the dof needed a tripod would be a must.

John
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[jcuknz]

I remember early on being told to take a reading off the back of my hand if I couldn't get close to the subject back in Weston Master days [ and then close down one stop if you are a caucasian with clean hands ] ... I don't remember using the camera's meter to do this but it is worth remembering the possibility for the occasion that requires it.

"I have not used a meter for yonks" is probably quite inaccurate as I use a meter for every shot I take, if only to tell me what the camera thinks so I can occasionally decide to do something different. I do not engage in demanding photography most of the time. I know the eye is very tolerant to changes in light intensity and so sadly not a good judge for exposure purposes. Though experience of various situations provides an answer when I think back to the B&W days when I never used a separate light meter and the cameras didn't have them either.... that changed when I got my first Pentax SLR.

So the answer is to know what and how what you have works and how with a bit of lateral thinking and interpretation it can provide you with the answer for the job in hand.

[William W]

. . . I am learning about photography a little more everyday, and new questions come up like: why use a light meter? I was reading an article from a pro in a magazine and he says he is never without a light meter. . .

At this stage I advise you should not consider buying an Hand Held Light Meter.

***

What camera do you have?

There will likely be a few, perhaps four, DIFFERENT Light Meter MODES on your camera. You would get great benefit seeking to understand two really important elements which many people never bother putting in time to understand:

1. how each Metering Mode interprets different scenes
And
2. how various BASIC COLOURS in any scene affect the Light Meter’s reading (for example a Black Cat / White Sheep)

***

Do you have suggestion for important things in a kit bag?

A Tripod, Head and a Remote Release - and make sure it is a good quality Tripod and Head: one of the two best purchases that you can choose, especially for the type of photography you indicated interests you.

WW

[William W]

. . . So, for me who is 99% of the time in Manual Mode, on tripod, in the garden, preparing to shoot a bright yellow flower in the morning light, a light meter would make the job of "exposing not too bright/dark right the first time?

A light meter and the knowledge of how the light meter works will indeed make the image exactly as you want it to be.

But the point is: you probably already have a light meter in your camera.

You need to learn how that light meter works and also how to best use it.

WW

[ajohnw]

If some one wants to get a grip on what metering and exposure is all about the best way is to study and think a little about this

http://en.wikipedia.org/wiki/Zone_System

Film is mentioned and grey scales are used to illustrate it. The problems are virtually identical using digital and when colour is introduced the grey scales can be any colour or mix of colours in the view.

Many cameras have spot metering and the behaviour of that is also accurately described in this linki. It also mentions reflectance problems and how this relates to metering system that average scenes or light levels for that matter. Sticking to just spot metering as that can be used it's a case of metering an area and then deciding which zone it needs to be in when the camera actually captures it. Not an easy thing to do or even learn to do accurately.

A camera's fancy usually default as it comes metering system benefits from many years of work by manufacturers to obtain perfect jpg's so it uses all sorts of data to decide which zone things should be in for you and also bears in mind how much dynamic range the camera can actually capture. Often on objects/buildings in landscape type shots for instance the light levels that are there will easily exceed that. Generally in this mode the meter will allow the sky/clouds to be clipped and concentrate more on the building depending on how large it is in the view. This is where manual intervention is needed if the photographer wants a different result. The nice thing about the metering system is that it's behaviour tends to be consistent and leaves easier guess work for the photographer to do.

On the flower shot I posted I mentioned that I might have applied some negative exposure compensation. This is because it's an olympus camera and I know that they don't leave much headroom in raw for high lights. I also intended to post the camera jpg so for various reasons shooting a little dark makes sense because of the characteristics of the camera. I can always brighten it up a little in PP. The point of mentioning this is that there is a learning curve associated with any particular camera. There is no way round that. Many initially seem to think there is - good luck. All metering methods have their catches and the best one is easily the preview after the shot has been taken especially if it shows areas that are clipped.

John
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[William W]

Part of my income is derived from tutoring High School Students. Previously, I taught Photography in Tertiary Institutions.

I have found that, when using a digital camera most Students respond better; understand easier and learn more quickly about how to use a light meter and the relationship between a light meter’s reading and the resultant image file, by using the camera in SPOT METER MODE and then recording a list of the exposure differences, in the same light, between a photographic GREY CARD and different key colours; for example: Green Grass; Building Concrete; Bitumen Road; Red Firetruck; Deep Blue Car; Caucasian Skin; Asian Skin; Indigenous Skin; Seaside Sand.

The 'Zone System' was and still is, part of some curricula as a sub-topic in the B&W, Film, Film Development and Wet Darkroom sections both in High School and in Tertiary Courses: though it has been a long time since I have noticed any questions that have been set on it other than it be required as a mention in an historical context. Nonetheless I have instructed on the 'Zone System' for many years, yet I found that many (most?) Students have difficulty in grasping the basic concepts of the ‘Zone System’ first up and moreover more Students have a greater difficulty in extrapolating and applying any usefulness of the knowledge of it, to Digital Photography and TTL Metering.

It is my opinion that spending time learning the ‘Zone System’ is not the best general course for either self learning or instructed learning for mostly all beginners.

WW

[ajohnw]

I don't Bill but have used lots of cameras. As presented in the wiki I find zones an easy way of grasping the difficulties with exposure in general. It's not a very large page and no doubt at some points in time loads and loads of other things have been added elsewhere by people. Where I feel it''s particular pertinent to digital is the idea that only certain levels of darkness can show detail and also why exposure compensation often needs to be used. The dark end problems are down to linear digital sensors and like wise displays, even printing to a certain extent. In some ways this is similar to film where exposure had to account for the dark end in order to clear the films sufficient to print. On the other hand digital has a definite highlight clipping level. The 2 technologies are remarkable similar in terms of trends apart from that.

The other point of course is that the wiki has far more lines than most people would be prepared to post on here - explains metering difficulties well and the effects of tone on detail. Also the idea of shifting exposure as you mention in relationship to spot metering in order for the camera to capture the tone as it actually is.

I wasn't suggesting that people learn the zone system either - just that they appreciates what it means in practice. There is another learning curve in this area too that Colin illustrated well in another post - Perhaps I might spot meter a bird in shadow and then guess what zone it needed to be moved into to record it correctly. That one word zone conveys rather a lot - where about on the tone curve it needs to be. A lot could be said about that.

My feeling about the wiki page and a beginner is that once they stop reading about this and that and actually use there camera it will go a long way to explaining the problems they encounter and the solutions. One of the biggest problems in this area started this thread - read some where or the other extolling something so starts wondering if they should buy it or slavishly follow the advice. Nine times out of ten the supposed solution wont help at all and the real problem is the need to use the camera and learn how to cope with it's limitations.

John
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[William W]

Given that the opening post describes a beginner questioning: how to use a light meter; what are the uses of a light meter; and the light meter's general relationship to exposure.

My feeling about the wiki page and a beginner is that once they stop reading about this and that and actually use there camera it will go a long way to explaining the problems they encounter and the solutions.

Thank you for the clarification of your opinion.

The clarification has a different meaning to and is not what these words below mean. I was responding to those words as they were written [my bold for emphasis of the meaning]:

If some one wants to get a grip on what metering and exposure is all about the best way is to study and think a little about this

WW

[ajohnw]

True but the Wiki entry is a decent way to get to grips with what it is about when just reading about it.

John
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[wlou]

Thank you for all your answers. You were so many to express your opinion. I see that when someone adopt a technique it becomes a way of doing things. I did some testing with mixed lighting, 2 speed lights, 1 table top light,and the ceiling light on to see how the camera would react. My Sony a77 on a tripod and using a black cardboard for background. The christmas cactus was on the table, it is a potted plant that grows in my house. I use Zone for focus area. What are your impressions.

[jcuknz]

Looks good to me though the stamens[?] look a little soft perhaps becuase of slight over exposure [ clipping?]
The color plus the black background makes for a luxurious image

If the mixing of light sources gives you a peculiar color mix then turn it into a B&W photo, or just ignore the error as I have done a couple of times when I add a tungstem anglepoise to daylight when shape and form are the key aspects of the shot.

[lukaswerth]

I couldn't find this coming up already:
Leaving flash aside, there is a principal difference between spotmeters which read reflected light and such meters which read the light which falls on the surface of the motive. In the latter case, you have to read in direction of the light source (whereas you hold a spotmeter on the motive). The benefit of reading the intensity of the light source is that the reading then is independent from the color of the motive (a light meter is color blind), and independent from the relative brightness of the motive. Portrait photographers often like to use this method.

Lukas

[tclune]

I normally use a light meter with flash. Beyond that, I tend to see different lighting in different ways. Commonly, I use spot metering in the camera because the thing driving the photo is a subject that "wants to" be middle-grey. Sometimes, an entire scene just seems to say that it sums to that. But sometimes the light seems divorced from the scene. For me, the natural way to meter that is with an incident light meter. I'm sure many folks would look at the same scene and meter it differently -- perhaps dialing in an exposure compensation as naturally as I would reach for my meter. My point is that folks are different in how they deal with these things, and there is nothing flawed or inappropriate about taking whatever approach is natural to you.

[ajohnw]

Thank you for all your answers. You were so many to express your opinion. I see that when someone adopt a technique it becomes a way of doing things. I did some testing with mixed lighting, 2 speed lights, 1 table top light,and the ceiling light on to see how the camera would react. My Sony a77 on a tripod and using a black cardboard for background. The christmas cactus was on the table, it is a potted plant that grows in my house. I use Zone for focus area. What are your impressions.

I don't know if this is a camera jpg or if you have processed it in any way.

This is the sort of shot where the posh metering mode in cameras can need a bit of help. Actually it's done a pretty good job of it. There is some red channel clipping in the staemen. I mention red channel as some pp packages only show clipping in luminance and ignore a single channel clipping as often that's the best guide to use to adjust shots. not this one though.

What's basically happened is that there are a lot of dark areas and a much smaller brighter centre area so the camera has biased the shot towards the dark end. There is a need to recognise this and apply exposure compensation. I would guess a 1/3 of a stop would have fixed this and would probably need a bit of brightened during PP.

An incident meter would give you an exposure for mid grey - no mid grey in this shot. Us it in reflected mode and it would make an even worse job of it. This where the zone system comes in to get some idea what needs to be done. In this case detail in the black background isn't needed so the reading could be adjusted to put it some where in that region but where as ideally the flower body needs to be well into the tone curve and the staemen unclipped. Spot metering via the camera has the same problem. The best option would be to meter the staemen and then make an adjustment to some point near the clipping level that will show detail.

A general comment. You might be past the resolution limit of the gear you used to show crisp sharp staemen detail. On the other hand you might just need to post a bigger image.

Hope this doesn't come up twice as thought I had posted it earlier. Thank heaven for the restore feature.

John
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[Manfred M]

Portrait photographers often like to use this method.

Also commercial product photographers.

[calexe]

...
Put a model with a very dark skin beside a model with a very light skin and try to use a reflective (i.e. in camera) matrix or spot meter to provide the the right exposure and you will be guessing and playing with exposure compensation to try to figure out the exposure. One reading with an incident light meter and you've got your exposure nailed. The same issue with a model that is back lit; a reflective meter result will need to be tweaked, but an incident meter will provide the settings to get the subject's face properly exposed.

A lot of people I know say that they can achieve the same results by using a trial and error approach using a histogram; and often they are right, but every so often I will have nailed the shot and they will have blown it...

...

Hello,
I need to interfere. Above underlined statements are deeply wrong!

First:
The reason for which a camera in matrix metering mode may not propose the "correct" exposure is the fact that the camera not only meters multiple zones of the image, but also applies additional exposure calculations weighting metered results with certain factors according to complex algorithms. These algorithms may take in account luminance o metering zones where focus was aquired, metering zones round focus-zone, background luminance, etc.. Algorithms are not documented (and actually do not need to be), but this happens e.g. in One Shot mode. Well, althogh complex, these algorithms are not smart enogh to resolve every photo scene and, besides that, they cannot guess what the photographer actually wants. Good examples where many cameras will mess exposure with matrix metering are scenes with large dark or light zones, backlit subjects, scenes with contrast range larger than the DR of the camera sensor, etc.. Just ask yourself "what is THE Correct exposure?" For this reason each dSLR has an exposure compensation mechanism to be used in shutter / aperture priority modes with matrix metering (and other modes / metering methods, of course). Thus, the reson for which the camera may propose wrong exposures with matrix metering is not necessary related to the fact that the camera uses a reflective lightmeter.

Second:
Spot metering is not to be used just by selecting this metering method in aperture / shutterpriority mode and shooting away, as you suggested. If one does so - of course results will be good only by (very much) luck. But do not blame the camera or its reflective spot-lightmeter! Blame the computer behind the camera! Spotmetering is most convenient to be used in manual mode. You may use the spot zone in the viewfinder to spotmeter various zones in the enviosioned scene. You set A/T@ISO such as to obtain what YOU want. E.g. you may set proper exposure for a medium tonality zone in the scene an then check light zones for potential overexposure. Or you may look to the most light zone in the scene, set exposure at clipping limit (e.g. +3 on certain cameras) and thus you obtain ETTR (=Exposure To The Right). Success guarranteed! No trial-error process! Each image will come out EXACTLY as the photographer wants. And be sure this process, with little bit training, is less than 1s long, thus much quicker than metering the scene with an external lightmeter device. Precision is limited to 1/3 stops - as the camera lightmeter offers. But that is enogh.

1. Disclamer:
M/Spot method works best with scenes where light on subject does not change quickly.

2. Disclamer:
I would like to state that I do not have any experience with external lightmeters and do not deny their usefulness for applications I may not use or understand. I just wanted to correct some wrong statements made here. I hope this to be useful to the community.

[ajohnw]

I often read comments about the processing power in cameras. As I have worked in related areas I do have some idea what microcontrollers are capable of. Going back rather a long time now as a for instance Canon used one which was extensively use in car abs systems that made rather complex braking decisions every 0.008 secs. These days they have moved on some way from that and then there are ASIC's and a number of other aspects. One of the interesting aspect of that early micro is could windows do that - not a cat in hells chance.

When people talk about noddy algorithms perhaps they should go talk to some one that hacks camera firmware. I can assure you they are far from noddy Many of them have years of work put into them and continue to evolve.

Spot metering problems are largely down to the user and the fact that they meter to mid grey. What ever is being metered that way needs a very careful consideration of just how much exposure compensation is needed. Given the exposure latitude available on film is some ways they were easier to use but still took rather a lot of experience.

John
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[DanK]

Thank you for all your answers. You were so many to express your opinion. I see that when someone adopt a technique it becomes a way of doing things. I did some testing with mixed lighting, 2 speed lights, 1 table top light,and the ceiling light on to see how the camera would react. My Sony a77 on a tripod and using a black cardboard for background. The christmas cactus was on the table, it is a potted plant that grows in my house. I use Zone for focus area. What are your impressions.

I think you are mixing two questions:
1. Can I get good metering information from the camera's meter for an image like this, and
2. If I let the camera make the decision based on some metering mode, will it get it right?

It's not clear to me what you did. If you were shooting in ETT-L mode, the ceiling light and table light shouldn't make much difference, since the light from the flashes would be much more powerful.

In this case (I do a lot of flowers like this--check my site), unlike candids of people, I wouldn't trust ETTL to get it right, but I also wouldn't worry about it much. I would control the exposure myself and change it if necessary. The flower isn't going anywhere, and digital images are free, so it is no big deal to re-shoot at a different exposure if you get it slightly wrong. I often re-adjust the exposure of flower shots after taking test shots, using the histogram as a guide.

I don't know what you mean by 'Zone for focus area.' Focus area isn't relevan. What is relevant is the metering mode, and which areas you took the reading from.

In this case, it looks to me like you have lost detail in the reds, meaning overexposure. It's too small for me to evaluate the anthers. Blown reds (that is, reds that are overexposed and "clipped," losing detail) are a very common problem in digital photography of flowers. The solution is to set your camera to show the histograms separately for the three color channels, and then set the exposure to avoid clipping the brightest color (hitting the right side of the histogram). If you shoot raw and the clipping is not too severe, you may be able to recover detail by pulling down exposure in postprocessing.