Lots of references to the exposure triangle (ISO/Shutter Speed/Aperture). Now, I am comfortable with the relationship between the 3 elements, but has anybody got a good explanation of how to use the triangle to define the relationship and how to use the triangle?
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Exposure triangle explanation please.
- Thread starter AnthonyL
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yooperguy
Senior Member
Never try to define a relationship.
If you say you understand the exposure triangle, then you have your definition.
How to use it? Enter the values in your camera and shoot. It's that easy. Have fun!
Seen that and dozens like it, so you increase the shutter speed, what happens to the triangle? How does the triangle itself help? What am I looking at? What do the sides represent? What do the apexes represent? Which way is more or less?
Nothing happens to the triangle. Nothing at all. Something happens to your exposure.
It doesn't.
The exposure triangle!
Nothing.
Nothing.
More or less what? More shutter speed? Depend on how your dials are setup spin your camera dial one way, it will change in one direction. Spin it the other,and it goes the other way.
I think you are trying to read too much into the 'exposure triangle', they're merely the basic factors of exposure. If you are really interested in learning, then put your camera in P-mode and start shifting the various settings and watch the magic happen. Your camera can teach you. Good luck!
Once you know the value for one proper exposure you can easily choose other values.
For example if you are shooting volleyball in a gymnasium using an f/1.4 lens. You've got an exposure of Tv 1/800, Av f/1.4, and ISO 200.
You would like a greater depth of field, so you know you need to stop down your lens. You don't want to changer your shutter speed, and you don't want to shoot at over ISO 1600 because of noise.
So from ISO 200 to ISO 1600 is 3 stops (200 stop 400 stop 800 stop 1600), so you know you can stop down your lens to f/4 (f/1.4 stop f/2 stop f/2.8 stop f/4) and keep your shutter speed the same.
I wish there was a "Doesn't answer the question" button.
As I said I don't have a problem with the relationship between the 3 variables - I have a problem in understanding in how to understand what the heck the schematic called "Exposure Triangle" is supposed to do.
So far no-one is answering that question and neither have I found a good explanation via a google search.
As I said I don't have a problem with the relationship between the 3 variables - I have a problem in understanding in how to understand what the heck the schematic called "Exposure Triangle" is supposed to do.
So far no-one is answering that question and neither have I found a good explanation via a google search.
Please read my question again. How do you use the triangle to represent any of the above. Explain to me the above in terms of the triangle?
Seems to me as if the "Exposure Triangle" schematic should be scrapped.
I don't particularly care for the 'Exposure Triangle' either.
It doesn't explain exposure particularly well because it leaves out the amount of available light.
It's designed to be a simple way to explain that the 3 values ISO, Shutter Speed, and Aperture are all tied together.
Nothing more than that. No fancy math, no special values for the angles, and no perfect shape.
It simply is designed to show that those values are tied together.
The reason you feel people aren't answering your question, is you are looking for more to it, than there really is.
Guidenet
Forum Pro
There's no geometric concept to it. It might not even be a triangle. What they are is three out of four considerations that contribute to your choice of camera settings. For instant, At ISO 100, what combinations of shutter speed and aperture will give you the "correct" exposure. EV100 --> f/stops and Shutter duration stops with consideration to subject luminance in stops. Each full stop in one direction either lets in double the amount of light or effectively causes the sensor to be twice as sensitive to light for a simplistic method of explanation. Go the other direction and you're halving light.
To be able to effectively manage this you need to have memorized all full stops in aperture and shutter speed (actually shutter duration) also ISO, but that's easy.
Example: Lets say you've metered the scene and your light meter, whether in hand or in camera, reported a proper exposure would be attained if you chose to set the ISO to 100, shutter speed at 60th of a second and aperture of f/8. Those are all full stops. Now lets say you don't like that aperture. Everything else is fine, but you bought that nice 85 f/1.8 to blur the background in portraits and isolate your subject.
So you know you want f/2 which is the widest full stop your lens can do. You're at f/8 now, so you need to open up 4 full stops, right? Each full stop lets in double the light as the previous stop. So, you go:
f/8---> f/5.6---> f/4---> f/2.8---> f/2. That's letting in 16 times more light. Get it? You're doubling, doubling again, doubling again and doubling one more time. So that's 2, 4, 8, 16 times more light.
Now if you're going to let in 16 times too much light to get to the aperture you want and decided was the best for you, you need to let in 4 stops or 16 times less light somewhere else. You pick Shutter speed. You're at a 60th of a second now, remember. You want to move to a faster shutter speed four stops. That would be 16 times less light. That balances you opening aperture four stops. Let's do it
60th --> 125th --> 250th --> 500th of a second.
Your new exposure is ISO 100, f/2 at 500th of a second.
That's the exact same Exposure Value as you started with at ISO 100, f/8, 60th of a second. Exactly the same within normal errors. Also notice that isn't not always perfect between stops like when we went from 60th to 125th. We somehow got bumped that 5th of a second. That's ok.That's the way it is and is the reason for memorizing all full stops. If you don't, how will you know what to set the aperture at if you had to stop down three stops? Notice also that our new 80 f/1.8 is not a full stop. It's a third of a stop wider than the f/2 which is the full stop.I tend to round it out to the nearest full stop so whoever I'm teaching can get it easier. Calculating in half or third stops is a pain. Just memorize the full stops.
There's also scene stops and you can add light to a scene by stops with a flash. If you can't get to a shutter speed or aperture you want, you can add light or increase ISO or both. As long as you understand and balance the stops you open by the stops you close. Make sense
I hope I didn't over or under explain it all. Please let me know, Anthony. Have a great afternoon.
Exactly. The word triangle in this case simply represents the number three; the geometric shape has nothing to do with the processes or relationships involved, it just reminds you that there are three variables you can control with respect to the tonal values you will see in an out of camera JPEG. Just as with the term "love triangle," where the word triangle simply lets you know how many people are involved.
yooperguy
Senior Member
Maybe this book would help you?
http://www.amazon.com/Understanding-Exposure-3rd-Edition-Photographs/dp/0817439390
You should not focus on the triangle as though it were some kind of geometry formula. Put your camera in Manual mode, and take multiple photos of a single scene, but change one component of the "triangle" for each photo. I started my photography learning back in the film days, when nothing was automatic. Shooting in full Manual should give you the same kind of experience, so you observe what happens when you change one component. All the cameras I'm familiar with today will provide an indicator while in Manual to show you how changing a component will affect the exposure for the photo. Trying various settings and observing the results will be more beneficial than reading books, articles, or anyone else's descriptions. Learn by doing. Try stuff. You should also be able to observe what happens to the image on your LCD or in an EVF, as well as looking at the results on your computer in post processing.
Dennis
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dsjtecserv
Veteran Member
You are expecting far, far too much significance from the structure of the triangle. The triangle concept is used only to illustrate that there are three factors involved in exposure (or more precisely, in the final brightness of the image), and that they work interdependently. Beyond that, there is no particular magic to the triangle; it just a way to say "there are three things that matter".
So forget the triangle and concentrate on how shutter speed, f-number and ISO work together to determine how the image is exposed and how bright it will appear. There are lots of web resources on "exposure" and has been pointed out, you can see it in action by putting your camera in P mode and watching for (for any given scene), changing one parameter changes the other(s) to compensate and keep brightness constant.
Dave
Sir Carrington
Member
The triangle itself is a visual representation of exposure. Picture a dot in the centre of the triangle. That dot represents the correct exposure. If you want to increase your shutter speed and still maintain the correct exposure you have to move the dot toward the shutter apex and thus away from one or both of the other values. This means that you are increasing the shutter speed and will also have to increase aperture and/or ISO.
That's all that the triangle is, a visual representation of exposure that makes it easier to see that the three values that affect exposure are tied together. It symbolises that you cannot change one value without affecting another. The part that you were missing was the 'correct exposure' dot in the middle. It is nothing more. It is not a tool to be used. It is a learning aid for beginners. The reason that you keep hearing it referenced is because it is a quick way to refer to the three values that affect exposure. If you understand the values and their relationships, you understand the triangle and that's it. There is no further use for it.
That's all that the triangle is, a visual representation of exposure that makes it easier to see that the three values that affect exposure are tied together. It symbolises that you cannot change one value without affecting another. The part that you were missing was the 'correct exposure' dot in the middle. It is nothing more. It is not a tool to be used. It is a learning aid for beginners. The reason that you keep hearing it referenced is because it is a quick way to refer to the three values that affect exposure. If you understand the values and their relationships, you understand the triangle and that's it. There is no further use for it.
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confyushis
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based on the above comments:AnthonyL wrote:
Well thanks, that prompted me to think about it a bit more and I've come up with this as an explanation. Sorry for my poor graphics capabilities.
Middle point represents the desired exposure (which is entirely up to the photographer). I wouldn't consider just any random point in the triangle to be correct, necessarily.
Each apex is connected to the other two by a fixed length of string (not elastic) that passes through the middle point using something like croquet hoops or wickets.
If the photographer adjusts one apex by "pulling the strings" one (or more) apex will have to be adjusted since the desired exposure is fixed (by the photographer). So if you make your aperture smaller, you will have "pulled" either the shutter speed apex closer to "blur" or the ISO apex closer to "noise" or both.
Thanks. I considered the approach of moving the apices (apexes) but for me at least I found keeping them fixed conceptually easier. It's six of one and half a dozen of the other really. What is actually incorrect with my model? ie what doesn't work?
Tan68
Veteran Member
You got three things and a triangle has three sides. Peanut butter and jelly. Each one of the three exposure parameters occupies its own corner of the triangle. Each exposure parameter sits at the end of an arm of our triangle.
The amount of light you want to get to your sensor is the surface area of the triangle. Say the surface area of the triangle is defined by: f/8 , 1/60 , ISO 400 These settings make a good picture for you.
Say you want to open up to f/4
This larger aperture lets in more light so the triangle on the f-stop corner gets bigger. Bigger triangle = more light = too bright image = less good than the first image that makes you happy.
We know that first image was a good exposure; we like the surface area defined by that first triangle. If we make part of the triangle bigger, we got to make some other bit smaller so we have the same surface area / exposure.
The corners are measured in stops.
If I make my f-stop corner bigger by going from f/8 to f4, I have made it longer by 2 stops. My surface area is greater and that gives me an overexposed image.
To counter the extra surface area, I need to make one of the other two corners smaller by 2 stops. I can make the shutter speed faster so less light enters the camera. I can decrease the duration of the shutter 2 stops from 1/60 to 1/250. The shutter speed arm gets 2 stops shorter and offsets the longer aperture arm. The area of my triangle is now equal to that of my first triangle and I get a good picture.
Another option is shorten both the shutter speed and ISO arms by 1 stop. Together, they add up to 2 stops shorter in the arms and this offsets the 2 stops longer aperture arm. So, Shutter = 1/125 (1/60 - 1 stop) & ISO = 200 (400 - 1 stop) offset my increased aperture (from f/8 to f/4) and I get a good picture.
The amount of light you want to get to your sensor is the surface area of the triangle. Say the surface area of the triangle is defined by: f/8 , 1/60 , ISO 400 These settings make a good picture for you.
Say you want to open up to f/4
This larger aperture lets in more light so the triangle on the f-stop corner gets bigger. Bigger triangle = more light = too bright image = less good than the first image that makes you happy.
We know that first image was a good exposure; we like the surface area defined by that first triangle. If we make part of the triangle bigger, we got to make some other bit smaller so we have the same surface area / exposure.
The corners are measured in stops.
If I make my f-stop corner bigger by going from f/8 to f4, I have made it longer by 2 stops. My surface area is greater and that gives me an overexposed image.
To counter the extra surface area, I need to make one of the other two corners smaller by 2 stops. I can make the shutter speed faster so less light enters the camera. I can decrease the duration of the shutter 2 stops from 1/60 to 1/250. The shutter speed arm gets 2 stops shorter and offsets the longer aperture arm. The area of my triangle is now equal to that of my first triangle and I get a good picture.
Another option is shorten both the shutter speed and ISO arms by 1 stop. Together, they add up to 2 stops shorter in the arms and this offsets the 2 stops longer aperture arm. So, Shutter = 1/125 (1/60 - 1 stop) & ISO = 200 (400 - 1 stop) offset my increased aperture (from f/8 to f/4) and I get a good picture.
Tan68
Veteran Member
Yes, your explanation is good.
The corners don't need to move. Moving corners works if you want to consider surface area. Yours works just as well and you have graphics.
I understand why you used elastic. As you adjust one thing, others are pulled towards it. The elastic stretches because they must retain contact with each other.
I also agree anywhere in the triangle is a good exposure as you have defined it. Slop around anywhere in there changing parameters, one to offset the other, and you get the same exposure. Slide outside the triangle and you got troubles.
Of course the image will have different characteristics depending upon which corner of the triangle you favor. Different depth of field or blur or whatever. But the exposure will be the same.
So, yeah, I know you know all that. In other words, I think your model works fine.
The corners don't need to move. Moving corners works if you want to consider surface area. Yours works just as well and you have graphics.
I understand why you used elastic. As you adjust one thing, others are pulled towards it. The elastic stretches because they must retain contact with each other.
I also agree anywhere in the triangle is a good exposure as you have defined it. Slop around anywhere in there changing parameters, one to offset the other, and you get the same exposure. Slide outside the triangle and you got troubles.
Of course the image will have different characteristics depending upon which corner of the triangle you favor. Different depth of field or blur or whatever. But the exposure will be the same.
So, yeah, I know you know all that. In other words, I think your model works fine.
confyushis
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while i think it is correct in a general sense, it may be difficult to label discrete camera values on your elastic model along the axes (1/60s, f/3.5, ISO 1600) ... maybe not ...
with fixed "string" lengths instead of elastic, someone could make a real scaled mechanical model of this "exposure triangle" and see that if they widen their aperture to f/2.8 from f/4, they have enough "slack in their string" that they can increase their shutter speed from 1/200s to 1/400s, etc. ...
whatever floats your boat ...
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