Today, we’re gonna be talking about one of the
many items behind me in this set. A set which, for some reason, some of you think isn’t real(?) Even as I reach for the item in question, a physical item in the physical set
that I physically sit in front of, a few of you will convince yourselves that this
is all an elaborate compositing effort because… well frankly I don’t know why. I mean, it should be obvious from my videos that After Effects is a program I open accidentally, stare at in terror,
and then feel guilty about never bothering to learn despite multiple new years resolutions. And yet some of you think me and Captain Disillusion are the same person – how? We sound nothing al- anyway I will now reach for the thing. That is a real dust spot, by the way. This is a Canon F-1, a 35mm single-lens
reflex camera introduced in 1971. Single-lens reflex, often shortened to SLR, means
that the view through the viewfinder is through the same lens that exposes the film. This is done with the aid of a mirror which redirects light from the lens onto a ground-glass focusing screen to allow the shot to be composed exactly as it will be captured on film, eliminating the parallax error from a separate viewfinder and allowing you to preview
the depth-of-field of a stopped-down lens.
When the shutter is released, the mirror is
swung up and out of the way, allowing the light from the lens to land on the film itself (after the shutter has opened, of course). I love this camera, though I haven’t used it
in quite some time, and we’re gonna talk a lot about analog photography as time goes on but this particular video is about one fundamental aspect of how you use it – its light meter. Now, quick side-note, there were plenty of cameras with automatic exposure available to the consumer when this was released. Like this Olympus Pen EES-2, which you better believe we’ll talk about
someday because it’s got all sorts of weirdness, but the Canon F-1 is entirely manual, and in fact
entirely mechanical. That’s a large part of why I love it. It’s built like a tank, weighing in at just shy of 850 grams or nearly 2 pounds.
That’s without a lens or film, mind you. Lightness was never a priority. By the way, despite its uncanny resemblance to some sort of
LCD screen, this thing is in fact nothing but a holder for the torn-off end of a box of film, to serve as a reminder of what ya put in it. Interacting with this camera is so delightful – everything is where it is because that’s where it needed to be. All the controls are physically
connected to the mechanisms they activitave which makes them delightfully chunky. You can see how turning the film advance lever cocks the shutter by moving the two halves of the shutter curtain in unison, and you can even hear the little clockwork mechanism that controls the shutter’s timing at long exposures.
Take a listen. [ticking sound] [clack; ticking stops] Still, even with the constraints in
place, Canon managed to make this brick of a camera decently ergonomic (for righties, anyway). Your thumb, index finger, and middle fingers rest naturally on the film advance,
shutter release, and front control respectively. My personal favorite thing is that front
control. Push the lever towards the lens and it closes the aperture so you can get
a depth-of-field preview in the viewfinder, but turn it the other way and you can feel
that you’re winding something up.
Well… [rapid high pitched ticking] Oh god, the suspense. CLACK I just love that. That’s its self-timer. Oh, and that little lever on the bottom? That is used to lock the aperture preview in place, and lift the
mirror for vibration-free long exposures. This camera requires no batteries to
function and yet it can do pretty much anything you can reasonably
expect a 35mm camera to do. Well, aside from auto-focus and motorized film
winding. I did say this was entirely manual. The F-1 was designed to be incredibly modular,
though, and you could accessorize it with all sorts of things from motor drives to different
viewfinders to bulk film backings. This one, though, is in its stock form. It has the
standard everything. And, while it does not need any batteries whatsoever to function, it
does have a battery compartment on the bottom. In here lies a small coin battery which powers
the light meter.
What’s a light meter? Well, it’s not a questionable astronomical
unit, it’s instead an information display. Alright, quick crash-course in basic photography. Almost every camera ever can control the amount of light that hits the film or image sensor in two ways: the lens aperture, and the shutter speed. Inside the lens is a multi-bladed diaphragm that
can, to put it in rather basic terms, reduce the size of the lens’s opening through constriction. Those are what the F numbers on a lens are, and the higher the number, the more constricted that opening becomes, thus the less light makes it through to the film or sensor.
A side-effect of this is that the depth-of-field, that’s the range of depths that are in-focus, becomes
deeper the more constricted the lens becomes. That means that more of the image is in focus,
much to the chagrin of bokeh fans, when a higher F number, and thus smaller aperture, is used. Note that for landscape photography and other scenarios where nothing is close to the camera, the depth-of-field becomes more or less irrelevant. The shutter speed, meanwhile, is
(in still photography) the amount of time the shutter remains open. Leave it open for longer and you can collect more light, hardly open it at all and you collect less of it. The trade-off here is that long exposures require very still scenery (and probably a tripod) as any motion will be blurred. Shorter exposures on the other hand will freeze motion, but they require more light through a wider-open aperture. Shutter speed is measured in fractions of a second, and this camera is capable of speeds from 1 second to 1/2000th of a second. B, short for bulb, will leave the shutter open
as long as the shutter release is pressed. There’s an inverse relationship
between shutter speed and aperture. Higher F numbers allow less light through the lens
which means the shutter has to stay open longer to collect the same amount of light.
And, if a shorter shutter speed is desired, the aperture has to open wider to allow more light through the
lens. In order for the exposure to be correct, the aperture and shutter speed must be an appropriate combination for the amount of light available in the scene and
the sensitivity of the film or sensor. However, once you know one combination that works, you can
adjust the shutter or aperture up or down so long as you adjust the other setting appropriately in
the opposite direction.
The F-numbers, by the way, are as weird as they seem to be because the number itself is a geometric ratio, but we want to have stops at each value that halves or doubles
the amount of total light going through the lens in order to correspond to the available
shutter speeds. We call those stops… stops. So now we've come to the metering bit. Every filmstock has a certain sensitivity to light, known as its film speed. The term speed comes from the fact that exposure time will vary based upon sensitivity, all else being equal. We now call that the ISO, though back when this camera was made it was called the ASA (the initialism for the American Standards Association, now known as ANSI).
See, back then, Germany was doing its own
thing with a logarithmic system they called DIN, the acronym for their standards organization, incidentally, but
in 1974 the International Standards Organization said “ya know we’re gonna just mash the ASA and the
DIN together, and now that’s the ISO” but nobody ever remembers the DIN half of it: the
ISO 100 should really be 100/21° so in a weird way we’re still using ASA but calling
it ISO. At least, outside of Germany. Anyway… Nope, one more tangent, I S O. I say the three letters. Why? Because ISO and "eye-so" are so close to each other that I
don’t think it makes sense to force the acronym. Does it matter? Of course not, it’s just,
like, my opinion but I will at least grant that it’s less atrocious than calling this
“Nitsah” which they’re trying real hard to make a thing in case you hadn’t noticed.
And I regret to inform you that… it’s working. Anyway, modern digital cameras have an ISO
setting because you can change the sensitivity of the image sensor, but back when we were using good ‘ol emulsions of silver halides on a clear plastic backing, you’d be stuck with whatever
the sensitivity was of the film you bought. Of course there are many kinds
of films from many manufacturers, and the film speed is itself something
of a trade-off – more sensitive films are usually grainier, so you’d want to pick
the appropriate film for your situation. But now… well how are you supposed to know
what shutter speed and aperture setting you should use? You have to get the exposure correct if you want
the resulting image to have decent dynamic range. Otherwise it will be blown out from overexposure,
or a dark mess without any detail.
Well, there are some general rules of thumb you can use
in certain situations. For example, on a clear sunny day you can use the Sunny 16 rule: set the aperture to 16, and the shutter speed to the value that most closely matches the film speed. So, if your ISO is 100 – one one hundredth of a second, or the closest available setting (on this camera, it would be 125). This works because a doubling in film speed
equals one stop in exposure – it requires half as much light, and at F16 the correct
shutter speeds happens to match the film speed numerically. If you need a faster shutter speed for a given shot, just open up the aperture an equal number of stops that you
increased the shutter speed to compensate. But, news flash, not every photograph is
taken outdoors on a sunny day. Wouldn’t it be nice to have something that can tell [clunk]
you the correct exposure for any given scenario? Enter the light meter. These devices are able to, with the aid of some sort of light sensor, provide the user with an appropriate exposure value.
These devices were originally hand-held, and were fairly crude. Generally they’d just have a needle-type readout which would point to the appropriate aperture value for a given film and shutter speed. To use them, you’d bring them to your subject
and point them at something which was close to a middle-grey in terms of brightness, then
you’d set your camera up appropriately. You can still buy handheld light meters today,
though they’ve been digitified of course. But before long they were integrated
into camera bodies themselves. And that’s why this otherwise mechanical camera
has a battery compartment. Now, keep in mind this camera was originally released in 1971
(though this example is a later revision). Its light meter will be limited to the same sort of analog tech
that was found in the handheld meters of the time. But, and this is why I wanted to make this video,
it was done in an extremely clever way that not only simplified its operation to the user, but
allowed for more flexible use of the camera.
The meter appears as a small display to the right
of the image in the viewfinder. Right now the camera doesn’t have a lens on it, but watch what
happens when I put one on. [clicky sounds of lens being attached] The small circle moved upwards. That circle is mechanically linked to
this little piece here. You can see that as I move it with my finger, the ring moves up and down. This engages with a small peg on the lens itself.
Once installed on the camera, moving the aperture
ring on the lens causes that ring to move. Now, in addition to the ring, there’s a small
horizontal line. Right now it’s sitting in the bottom red area. This is actually a needle that will move depending on how much light the camera sees. And this is where the battery comes into play. You may have noticed this power switch – all that does is turn on the light meter. That little blue mark in the meter’s display is used as a battery level check. You can see there’s a little sticker here reminding you that to check the battery level, the shutter speed should be set to 2000 and the ASA to 100. Then when you move the switch to the
check position, the needle should jump up to the blue mark and so long as it does – the battery’s OK! If it doesn’t make it to the blue mark, well it’s
flat and if it overshoots it… we’ll get to that.
When the meter is turned on you can see
the needle move with the amount of light that hits the camera. The brighter the image the higher it goes! But… where exactly is it measuring? You probably noticed the darker portion of the viewfinder towards the center. That is the sensitive area of the light meter. With a lens on, you can see that it’s only what’s in this area
that affects the needle’s behavior.
But… how is that possible? Where is the actual sensor? Surely we didn’t have transparent light sensors in 1971. Well maybe we did but that’s not what’s going
on here. Again, it’s extremely clever. One of the many things you could customize on this camera
is the focusing screen. To remove it, you simply remove the viewfinder by pressing in these little lock buttons and sliding it towards the rear. And… there’s the focusing screen. Kinda trippy, huh? That’s what we were looking at in the viewfinder, but now we’re looking… down at it. In fact all the viewfinder is is a prism, a roof pentaprism to be precise, there to redirect
your view from the eyepiece downard and flip the image horizontally. This creates the distinctive hump you see above the lens of all SLRs to this day, though I must say I much prefer these
sharp lines which don’t hide the nature of the thing to the blobular designs of today. Anyway, this is the focusing screen and it, too,
is removable.
Before I even remove it, though, something about it seems weird. That darker region appears to be… floating. Now, this is obvious in person thanks to
stereoscopic vision, but it might not come across well on camera. I’ll try my best, though. At the very least, you can see that the circular focusing aids in the center are actually separate from that darker region. If I pop the focusing screen out, you’ll get a clue as to why. See that little window there? Look through it. Weeeeird. That dark region is actually a semi-transparent
mirror that is floating in the middle of the glass somehow. I really want to see how these were manufactured. But anyway, it redirects some of the light coming up through the focusing screen out
this little window and if we look from the front you’ll see what lies behind it. The light sensor. From the looks of it it seems to be a simple light-dependent resistor or LDR, though it’s obviously a little fancier than the one in your garden variety night light. The amount of light that falls on this will, thanks to the battery and the simple electronics it powers, determine where the needle in the meter lands.
So, in the end, that rectangle is simply the
dark region left by a semi-transparent mirror embedded in the glass of the focusing screen at
a 45 degree angle so it can redirect a portion of light onto the sensor. That’s what I call
neat. Now that we know where the meter measures, how it works, and what it does… how does one use it? You may very well have figured it out by now. This variety of meter is called a match-needle
meter, and that ring? Well, it’s your target. To use this camera’s light meter, you
first point the camera so that something in the scene that’s not too bright or too
dark is within that metering region. Light meters in cameras are generally calibrated
to a middle-grey value, and this is no exception. Now, simply turn the aperture ring on the
lens until the ring surrounds the needle. You are now set to the correct exposure
setting so you can recompose your shot however you like, hit the shutter release, and you're done! One exposure down, 23, maybe 35 more to go! But what if that combination isn’t what I want? Maybe I have to stop the lens way way down in order to match the needle's position expose correctly.
I’ll lose my sweet
sweet bokeh! Well, nothing a little after-the-fact AI-powered image processing can’t fix… I mean… that’s no problem at all! Simply adjust the shutter speed so that it’s faster. Aha! The needle moved. Here’s where the other
part of this genius system comes in. The actual sensitivity of the light meter itself is
affected by both the selected shutter speed and also the film speed. Perhaps you noticed this little insert in the shutter speed dial. Rotate the dial while pulling up on it and you can change
the film speed setting which will make the meter more or less sensitive. And the shutter speed alone has the same effect. Increasing shutter speed causes the needle to fall down, which means you need to open the lens up to match.
Now, you could have worked this out in your head by just
counting the stops to, say, F2 and then increasing the shutter speed by the same number of stops. But having the meter work differently depending on the shutter speed offers a sort of sanity check. It also demonstrates the relationship between shutter speed and aperture beautifully. Each stop you move in shutter speed requires two clicks of the aperture ring to compensate. Two clicks because this lens has detents at half stops.
Most elegantly, though? The matching nature
allows for shutter priority or aperture priority exposure. Rather than just point the camera at the scene and find a combo that works, you can fix one of those variables ahead of
time and adjust the other as needed. Say you want a stopped-down aperture
of F16 for a deep depth of field. Well, set the lens to F16 and keep changing the shutter
speed until the needle gets in that ring. Or, perhaps you need a fast shutter speed to
freeze motion in action shots.
Simply set the shutter speed to 1000, and move the aperture
ring until the ring surrounds the needle. Easy! This metering arrangement is not only intuitive,
but it’s flexible and also just a great teaching aid to those learning photography. You see hints of it in modern interfaces, and then of course there’s even more powerful stuff these days like histograms and whatnot, but there’s just something about the way
this works that is… beautifully elegant to me. Should we talk about the weirdness, though? Let’s talk about the weirdness.
First, there’s a limit to its range of operation. Watch what happens as I approach a shutter speed of one second. At a quarter of a second, the meter turns red. It doesn’t exactly stop working, but it behaves erratically. If I increase the film speed to 1600, the meter goes red at a thirtieth of a second. And here, at really slow shutter speeds, the needle just… stops changing at all even when it should. Now the meter is definitely not working right. What’s going on here is that the
meter is a lot simpler than you may imagine. Changing the shutter speed setting simply
changes how sensitive the meter becomes. As you slow the shutter, you need to close the
aperture down in equivalent stops for the same exposure.
The meter needs to move the needle higher to indicate that, which means the needle becomes more sensitive to given amounts of light. But the same thing needs to happen
when you increase the film speed. If you doubled the film speed, you'd need
half as much light for the same exposure, so the needle needs to move one stop higher. Doubling the film speed demands that the sensitivity of the meter change exactly as if the shutter speed were cut in half. And the simplest way to do this?
Just shift everything over. The needle will indicate the same apertures for a doubled film speed as it would for a halved shutter speed, so if you can shift those sensitivities around, you
can adjust the meter for different film speeds. That’s exactly what changing
the film speed setting does, in fact that’s literally what it does because
we’re dealing with a mechanical contraption. Adjusting the film speed essentially relocates
the different sensitivities of the light meter independently of the camera’s shutter mechanism.
There are more meter sensitivities than there are shutter speeds on the high end, but there aren’t on the low end. The meter just isn’t sensitive enough to tell you how to expose
a low-light shot. So, as the film speed increases, the lowest speed settings become locked out because that sensitivity is now assigned to a higher shutter speed. Each doubling of film
speed locks out the next lowest shutter speed. In the end, the meter is just an analog device
that’s been finely calibrated to move the needle logarithmically. Each doubling of light landing on the sensor makes it move the same distance upward. I imagine each sensitivity level is just
adding a different resistor to the mix. Which brings us to the next bit of weirdness:
batteries. When this camera was made, we were still manufacturing mercury batteries because, ya know, we hadn’t yet come to grips with the fact that the garbage can isn’t a magic receptacle
that makes things harmlessly disappear forever.
The trouble is, mercury batteries produced 1.35
volts. That’s a weird voltage these days. While you can buy a replacement battery that fits
perfectly in the battery compartment, it will likely be a 1.5 volt alkaline battery. You might not think that’s enough to matter but remember this is an all-analog system which is calibrated to behave logarithmically. The voltage matters a lot, and those batteries simply do not work. They push the needle way too high and it will never give you an accurate reading. If you do a battery check with one of these alkaline batteries, the needle will end up all the way up here. Trust me, I know. That same sort of error makes its way into every metering scenario. However, there is a solution! Zinc-air batteries, which produce electricity through reacting with oxygen in the air, are commonly available.
They’re pretty neat all on their own, featuring a surprisingly large energy
density due to the nature of the reaction, but they have a time-limited life
because you can’t stop the reaction once you remove the adhesive pull tab. However, for some applications like hearing aids, this drawback is more than made up for by their energy density. And most importantly, the voltage they produce is close enough to 1.35 that they can be used in cameras like these. Now, you can buy a zinc-air drop-in replacement online for
about $5 but you’ll be quickly annoyed with that option since, as I said, they have a built-in time
limit. So, pro tip, get yourself some 675 hearing aid batteries. They’re about the same thickness as the PX625 battery this camera is designed to take, and although they’re not the right diameter, a simple loop of wire insulation will center it well enough. You may need to bend the camera’s negative tab up slightly, but this simple modification allows you to use batteries you can buy at Walmart for about a buck apiece. And as a happy accident, the battery compartment cover
has a couple of holes allowing air in, but they're small enough that in my experience a battery
will last a good couple months before it’s dead.
You might also have asked, where is
the meter’s display? And how is it lit? You can see it in the viewfinder quite clearly, but when you remove the viewfinder you find just a blank hole where it was. Well, the meter is actually right here. It’s tiny! And this piece of translucent plastic up here is what illuminates it. Old cameras are filled with all these clever,
intricate mechanisms. I mean, think about the linkage connecting the shutter speed dial to the tiny little indicator in the meter.
Hmm, it’s amazing. Oh, and you could purchase a different viewfinder which had its own battery and light source for the meter, but this was never really super useful since the meter doesn’t work in low light anyway. For outdoor photography that little window works surprisingly well. Speaking of, did you notice the “OFF”
position on the meter is also marked “FLASH?” How does that work? Well, it doesn’t. Remember there’s no automatic anything, and when this camera was made you’d use a chart on your flash itself to set exposure correctly based on film speed and distance to the subject.
Oh, and that’s why the shutter speed 60 is marked in orange. That’s the flash synchronization speed of this camera, or the fastest shutter speed where the entire shutter is open at once and thus suitable for use with a flash. Since this camera’s shutter curtain moves horizontally, its shutter is pretty slow and you can see even with a smartphone’s slow-mo that any speed above 60 doesn’t expose the film all at once. This can actually create distortion in certain scenarios, so in a funny way, this old camera
has a rolling shutter. Go figure. The shutter mechanism alone is just
incredibly intricate and also fascinating, I mean the curtains themselves are made of
titanium. And they’re flexible! They roll up into these little compartments here, and move as
one unit when you cock the shutter and advance the film. You can see the seam right here. But with the press of just one button, they move apart and come back together with precise control in a fraction a second [CLICK] all done entirely mechanically.
Amazing! This little thing here is
the old-style flash hookup, though up here by the film rewinder
you’ll find an older style of hot shoe. These little contacts here (along with those
inside the plug) are bridged right when the shutter is entirely open, signaling an electronic flash to… [CLICK] flash. But anyway, now we’re getting well into the nitty-gritty which we’ll save for later. I hope you enjoyed this look into the old-fashioned light metering systems of yesteryear. While it’s fundamentally very simple, a lot of ingenuity was built-in to make it usable, intuitive, and flexible. But we’ve just scratched the surface
on how this camera takes pictures. What about the film itself? How does that store
an image? And what about film development? How do film negatives become printed photographs? Oh, don’t worry.
There’s a lot more to explore with analog photography, and before long we’ll get there. See you in the darkroom! ♫ logarithmically smooth jazz ♫ Single lens reflux(?), also sort…
ahh already sca-rooooo-ewd it up and it’s great because I have to re-take the OTHER line, too! I don’ like how I said FUNdamental I forgot I need to.. Open that The more constricted that opening becomes. Thus, the let light… less light… That means that more of the image is in focus at once,
much to the chagrin of bokeh fans.
(the sentence shouldn’t have ended) When a higher F number… ugh dang yeah forgot. Forgot the delivery! [clears throat] So… So… ble ble bah buh… we’ll move it over there. How ‘bout that? But nobody eberdy… nobody ebedy bedu… it’s going so well…. But, in 1974, the International Standards Association said… Organization! Dang it… I'm aware that the ISO dictates from their righteous throne of meticulousness that it is "supposed to be" pronounced "eye-so" Just remember that the inventor of the GIF tried to steer the ship and look how that's working out for him.
Anyway language is dumb..