Getting it right the first time
This article is not about making a photograph that ‘will do’, I try to discuss some aspects of mastering the craft of photography and get that technical work out of the way, in order to enable you to concentrate on the creative aspects.
I am not saying that a non-technical approach will not work, for some types of photography an open non-technical approach is the only way and I think that’s great.
I am looking at a photographic equivalent of the technical process behind the craft of artists like, let’s say masters in painting, without attempting one second to imply that mastering such a process will by default enable you to come even close to their artistic value. But without technical prowess you will not be able to reach into all the depths of any technical artistic craft or art form.
For instance, a relatively minor choice like selecting an aperture of f2.8 instead of f5.6 (with the corresponding shutter speeds) might result in a completely different end result.
Back to business:
One of the more complicated issues in photography is getting your exposure right, in other words allowing just the right amount of light to reach your camera’s film or sensor. If you want to know more, read on.
Scene
Why might there be a problem with using the camera’s automatic settings?
As an example, imagine a kitchen with a very large window and two persons having a conversation in front of that window.
You want to take a series of photographs.
All the light is coming from the window behind the two persons and this light will not change during the session.
Not Identical
When using auto exposure your light meter will receive varying information, due to the fact that in some photographs the persons will be covering a different part of the window, if at all, depending on your shooting angle, composition etc. Sometimes there are more dark parts in the scene and sometimes not.
Therefore most of your photographs will receive a slightly different exposure.
The camera’s build-in light meter will interpret the scene for every shot in a slightly different way due to the fact that the light meter, however sophisticated, is interpreting the scene as different objects for every shot. When you throw in some headshots the differences will be even more pronounced.
Identical
All this does not make sense. The scene did not change, the subject did not change, so the exposure should not change either.
Even worse, in processing the final pictures you would have a lot of work to make sure that all photographs end up having an identical look. When you only shot digital JPEG or analogue slide film you would be in real trouble, all photographs would look a little different and could not be used together as a series.
What is ‘exposure’
The technical terminology: what I mean by ‘exposure’ in this case is measuring the light and translating that measurement into the right amount of light energy reaching the film or sensor inside the camera.
The right amount of light energy creates the perfect condition to process the image in such a way that an optimal end result can be obtained.
Light metering modes
Most modern cameras have a built-in light meter, sometimes with the option to select different ways to measure the light, usually a multi-zone metering mode, a centre-weighted mode and maybe a spot metering mode.
Good, one problem solved, we have a light meter..
Yes, but unfortunately one that requires some knowledge from the user to be used correctly.
Let me explain.
The theory
Any light meter will measure whatever it is aimed at and will translate this measured amount of light into a result that will look like “18% grey”. Please check out the link to understand what 18% grey means and why it makes sense to use that standard.
This will work for the average subject, but there ar exceptions. Imagine measuring a black velvet cloth.
Any light meter that measures this black velvet wants to translate the dark black into this 18% grey and as a result will give you a measurement result that would over-expose the photograph, black becomes grey, receives to much light.
The same story for a white piece of paper, the meter will want to transfer it into grey, resulting in an underexposed picture.
If you try this with a centre-weighted or spot metering mode you will observe the above described results.
A good in-camera modern measuring system like multi-zone metering will compensate for this phenomenon, but the results are often not perfect and certainly unpredictable.
Conclusion: Any light measurement needs to be interpreted, preferably by an experienced human being.
Dynamic range
And that is only the first part of the problem. Now it gets a little complicated.
Your film or sensor can handle a certain difference between dark parts and light parts in a subject.
If the subject reflects or submits more light then the film or sensor can handle the result will be a light part without any detail.
If the subjects reflects or submits less light then the film or sensor can handle this dark part will have no detail whatsoever.
We want detailed dark and white parts in the image for most photographs to work, however minute these details may be.
We call this range between detailed blacks and detailed whites the dynamic range of a film or sensor..
This is a natural given property of a film and developer combination or the sensor design.
Dynamic range has nothing to do with what can be recovered from a digital RAW file in post-production other then that you cannot recover what is not there, so everything outside the sensor’s absolute dynamic range will be lost forever. Recovering a RAW file just means getting the full range out of the sensor. But that is advanced digital technique and not the subject of this article.
Luminance range
Your subject will also have some sort of ‘dynamic range’, a deepest black and a lightest white. It is called the luminance range.
Imagine the kitchen scene described earlier. The world outside the window will reflect a certain amount of light and the shadows inside will reflect a totally different, much smaller amount of light. The difference between the biggest and the smallest reflection of light or absence thereof, in other words the lightest and darkest part of the scene, is the luminance range of the subject.
In an ideal world you want to transfer that complete luminance range to your photograph.
Exposure Value
Now I need to introduce another phenomenon in photography, the exposure value (EV) or ‘stop’, and therefore we have to discuss aperture, shutter speed and ISO.
When you make a photograph you always use the aperture (in the lens) and the shutter (usually in the camera, sometimes in the lens).
You could imagine the aperture as an opening that can change it's diameter and the shutter as a timed device that allows the light to reach the film or sensor for a measured amount of time.
When the camera is in a fully automatic mode (sometimes called ‘program’ mode) it will set the aperture and shutter speed for you. In shutter priority mode you select the shutter speed and the camera will set the aperture. In aperture priority mode you select the aperture, the camera sets the shutter speed. Al these modes are automatic exposure modes.
If you set both aperture, shutter speed (and on digital cameras the ISO) yourself you are working in manual mode.
Example
A specific combination of shutter speed and aperture will result in a specific amount of light passing through the aperture and shutter to the film or sensor. Let’s call that value “10” for now, just a number as an example, there is no photographic significance.
If you open up the aperture by one value, e.g. from f5.6 to f4, you double the amount of light passing through. The value of light reaching the sensor is now 2 x “10” = “20”.
When you would now close the aperture one value, back to f5.6 again, the value of light passing through becomes “10” again.
You can do the same with the shutter speed. Change the shutter speed, like 1/125, one value, like 1/60, so that it opens for a longer amount of time. You have now doubled the amount of light passing through the shutter, changing the value to 2 x “10” = “20”.
To reach a value of “5”, what would you have to do?
- Open the aperture one value (stop) to allow more light through
or
- Change the shutter speed one value (stop) to allow more time for the light to reach the film or sensor.
ISO
The ISO value represents the absolute sensitivity of the film or sensor to light.
Double your ISO value and the film or sensor is twice as sensitive to light.
This difference of one value is sometimes also referred to as one stop or ‘click’.
EV
This number “10” I used for the examples does sort of exist in photographic technique, it is called the “exposure value” (EV) and any decent light meter will allow you to calculate it.
For instance, with an ISO of 100, an aperture of f4.0 and a shutter speed of 1/60 of a second the exposure value (or EV) is, surprise, 10.
With the same ISO, when setting an aperture of f4 to f2.8 (one click less light) and a shutter speed of 1/125 instead of 1/60 (one click more light), the EV remains the same,10, because the total amount of light being passed thru to the film or the sensor remains the same.
The only difference with the example I used is that doubling the amount of light means changing the EV value from 10 to 11, not to “20”. In other words, going from EV 10 to EV 11 on your light meter doubles the amount of light. On some cameras or lenses you can set the EV value directly, like on V system Hasselblad (Zeiss) lenses.
Each difference in EV is called a ‘stop’. Going from EV 11 to 10 is the same as one stop. That means that with an exposure of f5.6 and 1/125, opening one stop means using an exposure of f4 and 1/125 or f5.6 and 1/60.
Measuring the light
Back to our subject and the luminance range.
Let’s assume that the film or sensor of your camera can cover a dynamic range of 15 stops.
The subject of the kitchen scene will probably have a luminance range of more then 15 stops, imagine if you wil the world outside the window and the shadows inside. Let’s assume a luminance range of 25 stops.
Now we have a problem. Your film or sensor can never register the complete scene, it will always lose some detail somewhere, either in the dark or the light parts of the scene. You will somehow loose 10 stops.
A choice will have to be made. What part of the scene do we want to loose, the shadows, the world outside the window, a little of both? Remember, we can’t have it all.
This also means that when the luminance range is equal or less then the dynamic range of your film or sensor, a correct exposure is much easier. The chance that a measurement matches the dynamic range is more favorable when the luminance range is small.
It is not that difficult to make a correct exposure for a grey misted scene with a small luminance range of e.g. 5. In that case the dynamic range of 15 allows for three stops in exposure error without losing any information.
In other words: the more contrast (the difference between the darkest and the lightest parts) in a scene, the more demanding the exact exposure. You need to expose exactly right for a contrasty scene, the exposure is less critical for a scene with little contrast.
Different types of light meters in a camera
multi-zone metering
A multi-zone metering system will make this choice between luminance range and dynamic range for you.
It will measure all lot of little squares in the subject (a matrix) using the 18% grey method and will then compare the measured total result to a huge database of existing values in it’s memory. These values represent existing photographs translated into matrix values and the camera will automatically select the ‘best’ matching combination and expose accordingly.
It is very wel possible that the camera actually thinks it is looking at a sun-lit snow scene instead of a kitchen with a window.
When you change your composition the value of these measured zones changes and the camera will re-calculate the scene, maybe thinking it is now looking at something like a summer scene outdoors with people in it.
Therefore even the intelligent system of multi-zone metering can not be completely trusted, it might re-calculate for every photograph. It may calculate correctly, it may not. You have no idea what is measured and how that is translated into an exposure. What part of the luminance range is dropped? You don't know.
Average metering
Some cameras use average metering. The complete scene is measured but no intelligence is applied and no matrix is used. This system comes close to the theoretical 18% grey theory and can be found in many older types of camera. It can be very reliable when the photographer knows how to interpret the measured values.
Center-weighted metering
Some cameras allow you to set the light meter to center-weighted mode.
The camera measures the center of what is seen by the lens, usually about 60 to 80 percent of the total picture area. This will result in a predictable measurement. The photographer knows what part of the subject is measured. Very good.
But when used with auto-exposure, the measurement might stil change with every camera- or subject movement because the central part of the image as seen by the light meter changed. Therefore you stil have to check the exposure that the camera wants to execute, even more then when using multi-zone mode.
Even worse, if you have no experience the end result will probably be a photograph that is not as close to a correct exposure as the one with the multi-zone metering or the average metering.
Spot Metering
When you use spot metering you set the camera to measure a very small part of the scene. This will allow you to determine the exact luminance range of the subject by measuring the darkest and the lightest part of your subject. With this technique you can make a very calculated decision about the correct exposure. Spot meters are pre-set to measure angles like 8º or 1º etc., depending on the brand or type of spot meter.
You could use spot metering with an automated exposure setting but that requires extensive experience and a lot of user intervention. In general it is not a good idea.
Unfortunately, if you are not very experienced spot metering will result in very badly exposed photographs, it is a complicated technique.
Spot metering can also be used with a separate reflected light meter, either a specialized spot meter or a general reflected light meter. It takes time to measure the relevant zones of your subject and it requires some technical knowledge to translate the measurements in to a usable exposure combination.
Now what
Oh dear.
What to do? All metering modes seem to have an issue. Apparently you can not use the exposure that your light meter wants you to use.
There is an issue indeed. The light meter in your camera can not be trused ‘just like that’. If you use it in any automatic exposure mode or follow any indicated setting ‘just like that’ then you may experience some problems.
But there is a solution.
Choose
Let’s get back to the luminance range of the subject and the dynamic range of the film or sensor. They did not match. They usually don’t.
But do you really want to display the complete scene in your photograph? Is it that important that you show the outside world as seen through the window ánd have all the details in the shadows? You are photographing two persons who happen to be in a kitchen. The persons are probably the main subject, not their surroundings.
You as a photographer can choose what is important for you and set your exposure accordingly. That means that you don’t use automatic exposure settings or ‘follow the needle’ but set the exposure manually. You choose. It is your photograph.
A possible solution
As indicated, a possible solution could be to stop using auto on the camera and set aperture, shutter speed and, when working on a sensor, ISO by hand. Manually.
Select the average or, preferably, the center-weighted measuring mode and measure the two persons only. Now set your exposure by hand.
With a digital camera, you could make one test photo.
Check the result on the screen of your camera, the histogram may give you an indication. Do you like the result? If not, change the exposure to your liking (persons to dark = allow more light to enter the sensor etc.).
Take another test shot until you are happy with the result. When using film or when you don’t want to takt test shote, trust your initial light measurement.
Now keep the exposure settings like this for the entire session. Don’t change anything except the focusing distance. Do not use auto for any of your exposures.
Only when the light changes, i.e. because the persons moved into the garden, measure again, test again if you want, set the new exposure and again, change nothing during this new scene.
On a digital camera, only use your screen and histogram to check the exposure after measuring the light. Don't check any other photograph you make, don't ‘chimp’, you need to pay attention to your subject and have to forget about technique. You don't want to mis good photographs. Concentrate on the subject, not the camera. You tested your exposure, you’re good to go. I discuss focussing techniques here. There is no need to check every time. Build confidence.
With a film camera you can not check your exposure and will have to rely on your experience. You will see how it worked out after having developed the film.
Ownership
This is the most important part.
Measure the exposure using whatever method that works for you, set the exposure value manually on the camera using the aperture and shutter speed (and ISO on a digital camera). Don’t change these as long as the scene / subject / light does not change.
In technical terminology: you can only change aperture, shutter speed and maybe ISO as long as the resulting total amount of light reaching the film or sensor remains the same (open one, close the other etc., remember the EV value as discussed) .
After measuring the light once, only change an EV setting when the light changes.
This is very simple and with some experience becomes second nature. Don’t use auto anything. You should be in charge, not your camera.
When you master this technique it becomes easy and fast to meter and expose a subject. You could even use a hand held light meter: measure a scene once, set the camera, go. And change nothing until the scene or the light change. You could probably shoot for a big part of the day without changing any exposure setting.
Example
This might be the full luminance range of your subject. From the darkest shadows on the left side of this scale to the lightest parts on the right side
These red lines show the dynamic range of your film or sensor. Your film or sensor can only cover a smaller part of the total scale.
The photographer has to choose what part of the total luminance range of the subject wil be recorded on the film or sensor. In this case the central part of the subject’s luminance range was selected. We loose all detail in the subjects lightest and darkest parts.
The photographer might choose to record the lightest parts of the luminance range of the subject. Or any other part of the total range.
Here the photographer chose to expose for details in the lightest parts of the subject. As a consequence, all darker parts wil not show any detail in the photograph. These details are lost forever. The digital technique of recovering shadow parts in post production only ‘lightens’ the dark parts that were actually recorded on the sensor, the dark parts outside the red lines in the example are lost forever.
The photographer chooses what part of the subjects luminance range wil be transferred to the film or sensor.
If we allow more light to reach the sensor or film, we expose more dark details. We extend the exposure. But we loose the details in the lightest part of the scale. We ‘expose for the shadows’.
If we allow less light to reach the sensor, we expose more details in the lightest part of the scale. We diminish the exposure. In that case we loose detail in the darker parts of the scale. Now we ‘expose for the highlights’.
expose for the shadows, develop for the highlights
When working on film, there is a lot of science behind the relation between a subjects luminance range, the film dynamic range and the exposure that the photographer choses to use. With film photography we use this science. In general, we expose for the shadows in the scene. Then we develop the film in such a way that the highlights wil not lose detail. This combination is different for each subject. We call this ‘expose for the shadows, develop for the highlights’. With film we want a negative with detail in the light parts of the film (the shadows in the picture). if there is no detail there than we underexposed the picture.
The photographer Ansel Adams defined a systematic approach to this subject <> exposure <> final print challenge that he called the ‘zone system’. Even if you do not intend to take your photography technique that deep it might be very interesting to read about it.
Exposing for the highlights
When we use a ‘positive’ sensitive medium, like slide film, we have to protect the lightest parts of the image. We prefer to have some detail there. When measuring the light with an ‘18% grey’ measuring device, we have to underexpose a little.
When using a digital medium it is a little more complicated but as a rule of thumb we follow the same technique, we protect the highlights.
Different ways to measure the light
We have discussed the way a light meter in a camera translated the amount of light reflected by a subject into 18% grey.
We call this system of light measurement ‘reflected light metering’, the light meter measures the light that is reflected by the subject.
All versions of reflected light metering suffer the same issue, the measured subject should be 18% grey, and if not, how do we interpret the measurement?
There are some solutions though.
Grey card
One option would be to measure not the real subject but to substitute it with a special grey peace of plastic or cardboard that is indeed “18% grey”. You can buy these 18% grey objects.
With this artificial subject we do indeed measure 18% grey when we point our reflected light meter to the grey card. Now we know exactly what our measurement is worth.
A little warning: There are also grey cards that are designed to measure the white-balance of a scene. These cards are not necessarily 18% grey and cannot be used for this light measuring method. You need a special 18% grey card.
A Minolta IVf incident light meter. In this configuration the meter can only measure light falling on the subject but it can be adapted for reflected light metering with an accessory part.
Incident Light
Another option is to use a specialised separate light meter that does not measure the light reflected by a subject but measures the light falling on the subject. This is a specialised technique but the result is roughly comparable to the result of measuring a 18% grey card.
A drawback could be that this incident light metering can not measure the subjects luminance range, the difference between those blacks and whites.
This incident light metering is used extensively by professional photographers and film cameramen. It provides a quick and reliable measurement of the light on the subject.
Spot metering
This is a very specialised type of reflected light metering, but it is the most reliable when executed correctly.
When using spot metering, we specifically measure the luminance range of the subject and / or specific parts of the subject.
Extended spot metering is done with a specialised external spot meter.
You usually point the ‘spot’ in the light meter viewer at the darkest part of your subject, note te value and do the same with the brightest part of the subject. You now know the luminance range.
You can set the correct exposure if you know the dynamic range of your film or sensor.
All this takes some time to execute and you will need a lot of experience and trial and error to make this work.
Real life
How do we handle all this in real life, photographing our ever changing subjects?
The simplest way is to set the ISO in the camera, then measure the light using the centre-weighted metering once. Now set the aperture and the shutter speed by hand and leave it as-is. Re-measure from time to time, change the exposure settings only when the measured light changes.
This is actually a lot faster then auto-expose > chimp the screen for the result > compensate exposure using exposure compensation > do the same for the next photograph > repeat again and again.
The fastest way is to use an incident light meter (the one that measures light falling on the subject) and set exposure accordingly. Again, don’t change the settings etc.
The exception
Until now we looked at ways to set your exposure values for scenes or subjects where the light does not change very much. In those cases it is very much preferable to set your exposure settings once, manually, and keep them as-is. Only change anything when the light changes.
It becomes much more complicated when the light does change a lot or is very unpredictable. You don’t want to have to give all your attention to the exposure settings, you should concentrate on the subject. Technical perfection is much less important then an interesting photograph that relates a story, has ‘substance’, Artistic value is always much more important then technical perfection.
In those difficult light situations it can be a good choice to set the camera to automatic exposure.
But all auto settings creat lazy photographers that do not understand their camera or the photographic process behind all this automation. using auto settings can be useful but you need to understand what is happening first. Start with manual settings. Once you master that you can reliably start using automatic camera options because you have some idea about the logic that the camera applies.
Some tips
No change
Light does not change that often.
When the light does not change, your exposure does not have to change.
It is very wel possible that you measure the light once when starting your photography day or session and not change anything during the rest of the day or session, because the light remains the same. You can concentrate on the photograph.
Skin
For most people the skin inside the hand is one stop lighter then 18% grey.
You can measure the inside of your hand, compensate one stop (+1), done.
(subject too light = underexposure = now allow more light then measured)
Test this at home for your own skin and you are set.
Auto anything
Traditionally a lot of options are added to cameras to compensate for flawed techniques or uneducated users. Auto exposure & exposure compensation are part of that, autofocus is another. The cameras used to be very simple to operate. Then more techniques were invented but those did not always work as intended, so compensation options were added. And more options were added and did not always work etc. etc.
Having said that, automated functions can make life easy for us photographers. Why would you have to set your exposure by hand when the camera can do the same thing much faster? Auto exposure can make the difference between getting a near-perfect image or not getting it at all because you had no time to set the camera. It can be a great benefit and help us with the real thing, making photographs. But it should be a deliberate choice, choose auto settings when you need them, not because you don’t know how to operate your camera.
Guesstimate
In the old days photographers did not measure any light.
They would guesstimate the right exposure by looking at a scene. This is not very difficult but requires some practice. As does everything related to photography.
It is a very useful exercise: look at the scene that you want to measure. Now guess what the right exposure would be and then measure the light. How did you do?
Your results will improve rapidly when you repeat this exercise every time you measure light, the technique becomes very reliable with practice.
If you look at pictures of the earlier generations of photographers at work you will notice that they used camera’s without any light meter (Cartier-Bresson, Alfred Eisenstaedt, Robert Capa, Margaret Bourke White to name a few, actually everyone that photographed before light meters became available).
They all used this estimation technique and made great photographs, it really works. A variant to start with could be the ‘Sunny 16’ method, just look it up on the internet. But it is no more then a starting point, you should learn how do it by evaluating your subject.
Measuring light became normal practice around the Vietnam war era. Don McCullin says he did not want to risk his life for an incorrect exposed photo so he always measured light.
Documentary style
Multi-zone metering (and auto-focus) on professional cameras is there for the documentary stile of photography, like the photo journalism type of work. Sometimes there is no time to measure the light etc, the photographer just needs an image that is ‘as perfect as possible under the circumstances’. Multi-zone metering can be a great help, it is much better than other types of build-in licht metering when we have no time to go all the way. A good photograph is all about the content, not the technique.
More on digital exposure techniques
You might want to read 'inside raw files' on digitalphotopro.com for an in-depth explanation on RAW files
On the other hand
Having said al that, modern digital cameras offer some very distinct advantages. provided that we, the photographers, know what we are doing. With the good old film camera it was, and is, impossible to verify if our exposure was correct. Even worse, did we actually record the scene in the way we wanted to? With film we had to wait until after the whole event, when the material was developed and printed. Did we miss anything? Did we expose as we intended to? If there is a problem we have to begin all over again, if that is even possible.
With digital cameras we can check instantly. Exposure, focus, expression. Did we ‘get it’? Have we got the whole ‘story’? If not we can try to correct the issue and try to take another one. Some moments are unique and ‘getting another one’ might be impossible but ay least we can try.
And most mirrorless cameras have a viewfinder that gives instant feedback about exposure, focus, all that. If we are not sure about the exposure settings we only have to look through the viewfinder. If it looks ok, it probably is ok.
Do not chimp
There is one big issue hiding in the shadows here called ‘chimping’, checking every picture we take. Click > check > ok. Click > check > ok. Please don’t do that. Have some confidence in yourself. Don’t forget to photograph! If you think you have to check every picture you just took then there is an issue with your technique. Don’t you trust your auto focus? Then stop using it, see the blog Focus. Problems with your exposure? Stop using auto exposure. Measure the light, check, then stop checking and start taking pictures.
Concentrate on your subject, is your photograph ‘talking’ to you, are you getting the best photographs out of the scene in front of you? Only check your results from time to time, when there is a natural pause, when the event in front of you allows a small break.