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One question that I guess asked often is : How to I meter by eye? I’ve got an old film camera that doesn’t have a light meter!
Although light meters are everywhere nowadays in digital cameras, learning to meter by eye is still one of the most useful skills a photographer can learn. Yes, I know that your camera probably has TTL metering with all the fancy algorithms, but many of the world’s “best” cameras do not have one (I’m looking at you guys, Leica and Hasselblad). Not only will you be able to use a Leica M4 with ease, but even if you just own a digital camera, it surely doesn’t hurt to know how to meter by eye.
Assumptions that I’ll make in this guide
Metering by eye first requires you to know the basics of exposure. If not, don’t fret, a handy guide on the basics of exposure is coming soon on Photograph IO. But for this article, I’ll make the following assumptions :
- You know are familiar the basics of the exposure triangle : aperture, shutter speed, and ISO;
- You own a film camera without metering, regularly shoot in manual mode or simply want to learn to meter by eye;
- You shoot in a variety of conditions but do not like to carry an external light meter with you.
If all (or any, really) of the previous statements apply to you, then this guide might be useful to you 🙂
The basic rule for metering by eye is called the Sunny 16 rule, and you might be already familiar with it. Basically, it is a method of guessing any exposure during a sunny day, and the rule is as follows : When you set your aperture to f/16 on a sunny day, the 1/shutter speed and ISO setting will have to be the same in order to get a good exposure.
Here are therefore some examples of exposures according to the Sunny 16 rule :
- 1/100 sec @ ISO 100, f/16
- 1/200 sec @ ISO 200, f/16
- 1/400 sec @ ISO 400, f/16
- 1/800 sec @ ISO 800, f/16
However, it is very rare that people shoot constantly at f/16 in bright daylight. In fact, f/16 is nowadays the minimum aperture on many lenses, and not only will you have diffraction, and well, to get that bokeh you have to shoot wide open, or close to it.
It is therefore crucial to adjust the rule to different aperture speeds. We’ll use the exposure triangle for this. An aperture twice as wide needs a shutter speed twice as fast (e.g. twice as less light) to get an equivalent exposure. Therefore :
- 1/100 sec @ ISO 100, f/16
- 1/200 sec @ ISO 100, f/11
- 1/400 sec @ ISO 100, f/8
- 1/800 sec @ ISO 100, f/5.6
- 1/1600 sec @ ISO 100, f/4
- 1/3200 sec @ ISO 100, f/2.8
- 1/6400 sec @ ISO 100, f/2.0
- 1/12800 sec @ ISO 100, f/1.4
As you can see from the guideline above, you can only make reasonable exposures at a max f-stop of 2.8 in bright daylight on a typical camera (1/4000 max shutter speed, base ISO 100). Based on my personal (and typical) experience, this is pretty accurate. When was the last time you shot at f/1.4 in bright daylight? Of course, the solution to this is very simple : simply put an ND filter when shooting wide open in daylight. But that’s not the point of this article.
Thing is, you may not be able to shoot in bright sunlight all the time, and it means that the Sunny 16 rule won’t exactly apply. In fact, there are many stops of differences between shade, cloudy, and all the other weather conditions out there, so what to do? Make a Something f/Something rule for every situation out there? Well … the answer is kinda… yes. Sorry.
In fact, the Sunny 16 article on Wikipedia includes a variation table for several other weather conditions :
|Aperture||Lighting conditions||Shadow detail|
|f/22||Snow/sand||Dark with sharp edges|
|f/11||Slight overcast||Soft around edges|
|f/5.6||Heavy overcast||No shadows|
|f/4||Open shade/sunset||No shadows|
|Add one stop||Backlighting||n/a|
But aren’t things getting too complicated now? Learning all the sub-variants of the “Sunny 16” rule, plus adjustment for specific apertures, just to meter by eye? What if there was a more simple way of guessing any scene’s exposure?
Understanding exposure latitude
Fortunately, although the Sunny 16 rule is extremely accurate for daylight scenes, you don’t nearly have to nail a perfect exposure in order to get a great picture. In fact, most digital cameras nowadays have excellent exposure latitude, meaning that shots can be severly over or underxposed but still able to yield a very usable shot. Photographic film too, to a lesser extent, has the exposure latitude of digital; of course, it depends on the specific type of film used. C41 color negative and B&W film are both excellent choices, while E6 slide film is notoriously famous for blowing shots even within 1 f-stop of latitude.
Of course, you should never over or underexpose on purpose, but when it comes down to metering by eye, exploiting the photographic medium used (whether film or digital) might be necessary at times. Although the dynamic range of film or digital is quite great, it isn’t necessarily the case in both directions, or else clipping may occur.
Therefore, should you over or underexpose in case of doubt?
The answer to this all depends on the medium used. Film is much more tolerant to overexposure than to underepoxsure; the whites won’t ever clip unless shot a good 4-5 stops above a set exposure, while a 1-2 stop underexposure will totally ruin the whole shot. Digital is the opposite; while underexposing greatly increases noise, it is almost certain that detail can be recovered, however overexposing, while yielding a minimum of sensor noise, is a very risky tactic that will easily clip the whites and lose all detail.
To sum up : Underexpose with digital, overexpose with film.
Why is this important, though? The answer is simple : although your camera seems to have a huge variation in terms of shutter speeds, it isn’t that hard to miss. Yes, it may go from 30 sec all the way up to 1/4000 of a sec, but I’m pretty sure you’ll use your common sense.
For instance, a scene metered at 1/500 of a second at a set aperture on a digital camera can be exposed anywhere from 1/4000 of a second (-3 EV) all the way up to 1/250 of a second (+1 EV). Seen in this way, it’s pretty hard to miss, isn’t it (who is going to make a 1/8 second shot in such a situation?).
If you have a digital camera, you can simply guess your exposure, experiment and adjust your exposure accordingly after chimping your LCD screen. Hugely useful, but of course, this only works if you are shooting digital. Alternatively, you can use your digital camera as a basis for your Hasselblad next to you to expose properly (but isn’t that considered “metering”? :P)
Putting all into practice
Although metering by eye can only be perfectly mastered by practice (sigh), because of exposure latitude you can “miss” an exposure by quite a lot and still manage a good shot out of it. Therefore I’ll give you some handy guidelines in order to expose in a variety of situations.
Situation 1 : Fast aperture (aka f/2.8 and faster) in bright daytime (sunny or with slight clouds)
Use a ND filter. Period. Now calculate the relative speed (the T-stop, or light transmission, really) of the lens according to the ND filter used. (E.g. a f/1.4 lens with 2 stop ND filter becomes f/2.8) See equivalent cases below.
Situation 2: Moderate aperture (aka f/2.8 to f/5.6) in bright daytime (sunny or with slight clouds)
Any shutter speed between 1/1000 and 1/4000 of a second work. 1/1000 with film in case of doubt, and around 1/2000 for digital. Use the 1/4000 in the extreme cases (extremely bright sunlight, f/2.8)
Situation 3: Slow aperture (aka f/5.6 and slower) in bright daytime (sunny or with slight clouds) OR fast to moderate aperture (all the way up to f/5.6) in dimmer daytime conditions (clouds, overcast, shady, sunset)
Any shutter speed between 1/125 and 1/1000 of a second work. Yes, I know, there is a huge difference between 1/125 and 1/1000 of a second, but if you follow the general the guideline of underexposing with digital and overexposing with film, you should be fine. I decided not to split this category in multiple segments for the sake of simplicity.
Situation 4 : Slow aperture (aka f/5.6 and slower) in any condition other than bright daytime.
I’ll assume that you are doing some landscape work (or anything else that is non time-critical), therefore you should either calculate precisely your exposure using the sunny 16 rule, or simply use a meter. Of course, testing shots with digital also works.
Situation 5 : Fast aperture in bright evening/nighttime conditions (e.g. blue hour or city lights)
Although the definition of fast might be anything from f/0.95 (!) to f/2.8, you will generally obtain shutter speeds around 1/30 of a second (‘slower’ lens or less light) all the way up to 1/125-1/250 of a second (‘faster’ lens or lots of light). Don’t underestimate the power of lights though, I have exposed at 1/500 of a second at some of world’s brightest places at night (Times Square).
Situation 6 : Moderate aperture in bright evening/nighttime conditions (e.g. blue hour city lights)
Image stabilization (IS/VR/etc.) is critical here. Your shutter speeds will be anywhere around 1/5 to 1/30 of a second. Err on the safe side and shoot on the faster end of the scale. If you are shooting film, I strongly suggest you to put down your camera on tripod. Metering by eye is definitely possible, but it is a hit-and-miss.
Situation 7 : Any aperture in dark nighttime conditions (e.g. moonlight only)
Put your camera on tripod and set a slow shutter speed. Unfortunately, I can’t tell you precisely what that shutter speed is. Use a meter or test exposures if you are shooting digital. Metering by eye is hard here.
Situation 8 : Any aperture in a room
This one is the trickiest, because although rooms are generally dimly lit, every case is different. As a guideline, expose as in situation 6 or 7, but the main warning in regards to indoor photography is not with exposure, but with white balance, since there are endless possibilities of source of lighting used. Digital RAW doesn’t have that problem, but if you shoot analog, use filters or tungsten film (when appropriate of course!).
The bottom line
Metering by eye is not a simple thing to do. Although nearly all cameras have meters on them, many of the world’s best film bodies don’t. If, for whatever reason, you need to guess an exposure using your eye only, at least you know how to now.
To recap :
The sunny 16 is an extremely accurate method of metering by eye in daylight conditions… that is, if you have the time to do all the calcuations in your head. Use it as much as possible.
If the exposure is more complex (or not during daylight), your best bet is to guess using my situation guidelines (and your hunch) and let the dynamic range of the medium used do the heavy lifting.
If you have a digital camera, you can always chimp after each shot, and you don’t even have to bother with metering, really. If you are shooting large format, maybe the cost of the film will deter you from shooting without an exposure meter. Take shots with either a pocket meter or phone (there are many apps available for metering). A digital camera works too.
In the aviation world, it is common knowledge that you should always trust your instruments before your senses. But when it comes to photography, even the best incident light meters cannot beat a well-trained eye, because only you are the final judge of your pictures…
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