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Pookeyhead submitted a new resource:
Everything you need to know about exposure theory but were afraid to ask 101. - Everything you need to know about exposure theory but were afraid to ask 101.
Read more about this resource...
Written by me for a local Car Forum, but every bit as useful here.
--------------------------------------------------------------------------
I think it's a good idea if I start typing up some tutorials that cover the basics in Photo theory on here, as once you understand these, it all becomes SO much clearer, and you'll no longer be scared of that manual setting
There's no way to avoid some of the more technical issues, because they're the foundations of photographic theory, but I'll try to keep the maths and stuff a bare minimum.
The following rule however, is the cornerstone of exposure theory, and should be learned. I've used some analogies that make it easier to understand, so hopefully even those new to the hobby can get to grips with using a camera manually.
----------------------------------------
Reciprocity Law
The trick to exposure, is understanding something called reciprocity law. Basically, you can't just use any shutter speed you want, because the relationship between shutter and aperture are linked... it's reciprocal.. hence the name. Basically, think of a lens as a tap, but instead of letting water in, it lets light in. There are two ways you can control the amount of water (light) that flows through your lens (tap).
Aperture (the amount you open the tap). Basically, this is the size of the hole that lets the light in. The bigger the hole, the more light flows through.
Shutter (the amount of time you open the tap for). The more time the shutter is open for the more light flows through.
So thinking of a tap: If tap A is open halfway for 1 second it will flow X amount of water. Tap B however, is open all the way for 1/2 second.... that also flows X amount of water. The result is that the bucket (your film or chip) contains the same amount of water (light).
Start thinking about it as the water analogy until you get your head around it.
The amount of light received by the film is referred to in "stops". The name comes from the "stops" on the lens aperture ring (most modern cameras no longer have this), but the same name applies to shutter speed as well because they both control the same thing: The flow or amount of light (water). Get it?
Aperture stops:
F1
F1.4
F2
F2.8
F4
F5.6
F8
F11
F16
F22
F32
As a diagram, it would look like this
Here are some images of a real camera lens showing the aperture blades in action at various settings.
Shutter speed stops.
These are just fractional numbers denoting time.
1 second
½ a second
¼ second
1/8
1/15
1/30
1/60
1/125
1/250
1/500
1/1000
1/2000
Etc
Your camera may not have all the same f numbers or shutter speeds, but dont worry about that.
Modern cameras are also capable of using values in-between stop as well, such as f13.6 or 1/235th sec. Dont worry about this for now either.
Any given amount of light is called a Exposure Value, or EV. Because the reciprocal nature of aperture and shutter speed, an EV can be made up in many different Combinations of shutter speed and aperture. This is the main concept behind Reciprocity Law.
Increasing by one stop doubles the amount of light, and decreasing halves it. This is true for both shutter speed and aperture (and ISO which we will deal with later when you've mastered this).
With that in mind if we increase aperture from f8 to f5.6 (made the hole bigger by one stop) then twice as much light entering. Because of this, we then need to increase the shutter speed by one stop, which HALVES the light entering, thus cancelling out the first change: The result is, the exposure is the same.
For example:
EV0 = a shutter speed of 1 second @ f1. So thinking back to the tap analogy, can you guess another way to get EV0?
If its 1 second at f1, then 2 seconds at f1.4 will give the same amount of light, and therefore the same exposure.
If you make the aperture smaller (larger f number), you use a longer shutter speed (bigger number), and vice versa. Just like the tap. If you want to fill the bucket (expose the film) in half the time (twice the shutter speed), you need to open the tap more (use a wider aperture smaller f number).
Just remember, that with aperture, the higher numbers mean less light (smaller hole), and shutter speeds with larger numbers are shorter because they're fractions . 1/30th second is longer than 1/60th for example.
The only thing to remember, is if you go longer than 1 second then the numbers will start going up again the other way 1 sec, 2 seconds, 4 seconds etc. For now though, until you get your head around it, just assume that 1 second is the longest youll ever use, and 1/2000th of a second the shortest.
So if a light reading is saying we need 1/125th @ f8 reciprocity states that we can also use the following
1/2000th @ f2
1/1000th @ f2.8
1/500th @ f4
1/250th @ f5.6
1/125th @ f8
1/60th @ f11
1/30th @ f16
1/15th @ f22
1/8th @ f32
Look at the relationship between those numbers!
As shutter speed increases (higher number), we have to stop down (open up the lens smaller number) by a corresponding stop.
All those combinations will result in EXACTLY the same exposure.
Thats Reciprocity Law.
Practice this, until someone can say to you Sixtieth at F8 and you can then recite all other combos that give the same EV. When you can, then you've cracked it, and well move on to WHY there are so many settings that give the same EV and WHAT the effects of each are. While they give the same exposure, they do however, give lots of different effects.
Just remember the relationship.
Exercise .
Your meter suggests 500th sec @ f4
What aperture do you need for 1/60th of a second.
NB. Your camera may not display as a fractional number it may say 500 instead of 1/500th.
Next up . Light Meters: Why they're god damn bare faced liars!
Everything you need to know about exposure theory but were afraid to ask 101. - Everything you need to know about exposure theory but were afraid to ask 101.
Written by me for a local Car Forum, but every bit as useful here.
--------------------------------------------------------------------------
I think it's a good idea if I start typing up some tutorials that cover the basics in Photo theory on here, as once you understand these, it all becomes SO much clearer, and you'll no longer be scared of that manual setting
There's no way to avoid some of the more technical issues, because they're the foundations of photographic theory, but I'll try...
Read more about this resource...
Written by me for a local Car Forum, but every bit as useful here.
--------------------------------------------------------------------------
I think it's a good idea if I start typing up some tutorials that cover the basics in Photo theory on here, as once you understand these, it all becomes SO much clearer, and you'll no longer be scared of that manual setting
There's no way to avoid some of the more technical issues, because they're the foundations of photographic theory, but I'll try to keep the maths and stuff a bare minimum.
The following rule however, is the cornerstone of exposure theory, and should be learned. I've used some analogies that make it easier to understand, so hopefully even those new to the hobby can get to grips with using a camera manually.
----------------------------------------
Reciprocity Law
The trick to exposure, is understanding something called reciprocity law. Basically, you can't just use any shutter speed you want, because the relationship between shutter and aperture are linked... it's reciprocal.. hence the name. Basically, think of a lens as a tap, but instead of letting water in, it lets light in. There are two ways you can control the amount of water (light) that flows through your lens (tap).
Aperture (the amount you open the tap). Basically, this is the size of the hole that lets the light in. The bigger the hole, the more light flows through.
Shutter (the amount of time you open the tap for). The more time the shutter is open for the more light flows through.
So thinking of a tap: If tap A is open halfway for 1 second it will flow X amount of water. Tap B however, is open all the way for 1/2 second.... that also flows X amount of water. The result is that the bucket (your film or chip) contains the same amount of water (light).
Start thinking about it as the water analogy until you get your head around it.
The amount of light received by the film is referred to in "stops". The name comes from the "stops" on the lens aperture ring (most modern cameras no longer have this), but the same name applies to shutter speed as well because they both control the same thing: The flow or amount of light (water). Get it?
Aperture stops:
F1
F1.4
F2
F2.8
F4
F5.6
F8
F11
F16
F22
F32
As a diagram, it would look like this
Here are some images of a real camera lens showing the aperture blades in action at various settings.
Shutter speed stops.
These are just fractional numbers denoting time.
1 second
½ a second
¼ second
1/8
1/15
1/30
1/60
1/125
1/250
1/500
1/1000
1/2000
Etc
Your camera may not have all the same f numbers or shutter speeds, but dont worry about that.
Modern cameras are also capable of using values in-between stop as well, such as f13.6 or 1/235th sec. Dont worry about this for now either.
Any given amount of light is called a Exposure Value, or EV. Because the reciprocal nature of aperture and shutter speed, an EV can be made up in many different Combinations of shutter speed and aperture. This is the main concept behind Reciprocity Law.
Increasing by one stop doubles the amount of light, and decreasing halves it. This is true for both shutter speed and aperture (and ISO which we will deal with later when you've mastered this).
With that in mind if we increase aperture from f8 to f5.6 (made the hole bigger by one stop) then twice as much light entering. Because of this, we then need to increase the shutter speed by one stop, which HALVES the light entering, thus cancelling out the first change: The result is, the exposure is the same.
For example:
EV0 = a shutter speed of 1 second @ f1. So thinking back to the tap analogy, can you guess another way to get EV0?
If its 1 second at f1, then 2 seconds at f1.4 will give the same amount of light, and therefore the same exposure.
If you make the aperture smaller (larger f number), you use a longer shutter speed (bigger number), and vice versa. Just like the tap. If you want to fill the bucket (expose the film) in half the time (twice the shutter speed), you need to open the tap more (use a wider aperture smaller f number).
Just remember, that with aperture, the higher numbers mean less light (smaller hole), and shutter speeds with larger numbers are shorter because they're fractions . 1/30th second is longer than 1/60th for example.
The only thing to remember, is if you go longer than 1 second then the numbers will start going up again the other way 1 sec, 2 seconds, 4 seconds etc. For now though, until you get your head around it, just assume that 1 second is the longest youll ever use, and 1/2000th of a second the shortest.
So if a light reading is saying we need 1/125th @ f8 reciprocity states that we can also use the following
1/2000th @ f2
1/1000th @ f2.8
1/500th @ f4
1/250th @ f5.6
1/125th @ f8
1/60th @ f11
1/30th @ f16
1/15th @ f22
1/8th @ f32
Look at the relationship between those numbers!
As shutter speed increases (higher number), we have to stop down (open up the lens smaller number) by a corresponding stop.
All those combinations will result in EXACTLY the same exposure.
Thats Reciprocity Law.
Practice this, until someone can say to you Sixtieth at F8 and you can then recite all other combos that give the same EV. When you can, then you've cracked it, and well move on to WHY there are so many settings that give the same EV and WHAT the effects of each are. While they give the same exposure, they do however, give lots of different effects.
Just remember the relationship.
Exercise .
Your meter suggests 500th sec @ f4
What aperture do you need for 1/60th of a second.
NB. Your camera may not display as a fractional number it may say 500 instead of 1/500th.
Next up . Light Meters: Why they're god damn bare faced liars!
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