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ISO: Graphic Aid

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/10/2015 at 10:59
Skylar McMahon View Drop Down
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Nice graphic that I found to help explain ISO.
 
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Excellent graphic!
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/10/2015 at 14:07
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Grain is a holdover from film. Now more often called noise.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/10/2015 at 16:29
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It is incredible how differently everyone's brain works.

I am pretty comfortable with what exposure, ISO, shutter speed, etc are, but how that graphic explains any of that escapes me completely.

For the way I think about it, that is the single worst explanation I have ever seen.

Oh, and Lile is absolutely right on "grain", for modern digital photography that a singularly bad way of thinking about noise.

ILya
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/10/2015 at 19:27
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OOOOh Somebody was late for lunch. Big Grin Do you need a Snickers bar?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/10/2015 at 19:31
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It's just a visual aid to illustrate the linked relationship of one side of the "exposure triangle" to the other 2 sides, with pictorial representation of the effect of a given change in either aperture, shutter speed, or ISO sensitivity at each apex of the triangle. It's geared toward beginners, visually depicting the general idea of how changes to those 3 controls effect light reaching the sensor and therefore exposure.

Yes, "grain" is a poor choice of terminology for digital photos.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/11/2015 at 00:00
koshkin View Drop Down
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Ted, I understand what they were trying to do, but I can't for the life of me see how a triangle does it.

Or why higher ISO value is equated to more light, for that matter.

Is the exposure value some spot within the trianlge with each spot defined by a unique combination of shutter speed, ISO value and F/#?  

That can't be it.  Then, what deos the triangle have to do with exposure?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/11/2015 at 00:26
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uh, I think one needs to read the text in the original post.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/11/2015 at 09:23
RifleDude View Drop Down
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Originally posted by koshkin koshkin wrote:

Ted, I understand what they were trying to do, but I can't for the life of me see how a triangle does it.

Or why higher ISO value is equated to more light, for that matter.

Is the exposure value some spot within the trianlge with each spot defined by a unique combination of shutter speed, ISO value and F/#?  

That can't be it.  Then, what deos the triangle have to do with exposure?


You're over-thinking this. The "exposure triangle" is the most commonly used analogy in photography instruction to help beginners learn how changing the 3 main controls affect exposure, along with the secondary affects each of those 3 controls has on the image. It is not meant to be a graphing tool, where plotting a precise point corresponds to actual values to input into the camera. It's simply a mnemonic, meant to illustrate to a beginner the basic idea that the photographer has 3 controls ("3 sides of a triangle") that affect exposure -- aperture, shutter speed, and ISO sensitivity -- and once the mythical "ideal" exposure is found, changing any one of those 3 control values must also involve a change in one or both of the other two to get the same basic EV. A triangle is used only to illustrate that, just as a triangle has 3 sides, "correct" exposure is influenced by a combination of 3 controls, and also that those 3 controls are inter-related to obtaining an "ideal" exposure. If you shorten the length of any one of the 3 legs of the triangle (thereby reducing either the duration or amount of light reaching the sensor, or the sensor's sensitivity to light), you must correspondingly increase the length of one or both of the other two legs of the triangle in order to bring the EV back to nominal.

There are numerous examples of the "exposure triangle" graphic out there, some more useful than others. Here are examples of a few others:









Again, a way to explain a basic concept. As a tool to arrive at precise values, it sucks. But then, it isn't meant to be used that way. It's a simple mnemonic for helping beginners remember the 3 controls for obtaining optimal exposure. Different people react favorably to different methods of illustrating a point and aids for remembering concepts. You're an analytical person, so perhaps this would not have been an effective tool to help you learn about exposure when you were a beginning photographer.

Higher ISO does not "increase light" to the sensor as you correctly allude to. Again, think mnemonic here. Higher ISO value equates to "more light" only in terms of the effect on EV. Increasing the sensor's sensitivity to light moves the peak of the camera's histogram to the right, so less light is required to get more optimal exposure. If you can't bring in more light with the other two controls, you can always bump ISO up so that it has the same effect on exposure as increasing the amount or duration of light.  If ambient light is relatively dim, you're not using a tripod, you can't select a larger aperture (either because you don't want a shallower DOF or your lens won't open to a larger aperture), you can't lengthen shutter duration (your focal length is too long, the subject is moving, etc), and you can't provide more light to the subject via artificial means, your only move at that point is to increase ISO. Yes, it also increases noise, but it may mean the difference between getting the shot and not.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/11/2015 at 10:24
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Get Your Popcorn Ready Way over my head, but enjoy reading the different opinions. Big Grin
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/11/2015 at 11:49
koshkin View Drop Down
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You are probably right, Ted.

If it is intended as a mnemonic, it would explain why it makes no sense to me.  To me a mnemonic is not an aid in memorizing things: it is just one more thing to memorize.

None of these triangles make any sense from a technical standpoint.  Perfect exposure space is a  three dimensional construct.

I do not think collapsing it into a triangle is at all helpful, but to each his own.

ILya


Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/11/2015 at 13:11
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As an example, when I was learning US Geography in elementary school, I used the simple term "Mr. MIMAL" to remember the names and sequences of the states along the Mississippi River. It was an effective mnemonic for more than one reason. First, if you look at a map, the central states along the Mississippi River kind of look like a man standing in profile... From top to bottom, Minnesota looks like the man's hat, Iowa looks like his face, Missouri his upper torso, Arkansas his pants, and Louisiana his boot. Look at a map and imagine what I just described. "Mr. MIMAL" was much simpler for my young mind to remember, as I only had to remember a simple name, and the acronym "M.I.M.A.L." even put the states in the correct order from top to bottom:

M = Minnesota
I = Iowa
M = Missouri
A = Arkansas
L = Louisiana

Ergo... "Mr. MIMAL"

I used mnemonics all the time in school to trigger my memory when I had to commit a lot of facts to memory in a short amount of time. I frequently used the first letter of the first words of facts I had to remember to form words and acronyms. I made up little songs I sang to myself in my mind to remember key words and phrases. The "Mr. MIMAL" example shows how using an effective mnemonic actually means LESS to remember, if the mnemonic is cleverly constructed. People are more likely to remember song lyrics than trying to memorize the same words from a speech or a book, for example, because the tune helps you recall the words.

Likewise, the "exposure triangle" is intended as a starting place to help you remember that, like 3 legs of a triangle, there are 3 settings that are totally inter-related that the photographer has control over. It gives you the basic idea of what effect changing those 3 variables has on exposure and the resulting image. That's the full extent of its usefulness, as intended. If you didn't use something like the exposure triangle to graphically represent that basic idea, it would take a lot of words to describe the same thing to someone totally new to photography, and as the saying goes, "a picture is worth 1000 words." After that concept is cemented in one's memory, one then builds on the basics as they gain more experience. If we're just talking about how the settings on your camera relate to exposure only and not other aspects of the image, it doesn't require a 3D construct to describe how changing one of "the 3 legs of the triangle" affects exposure. From there, you learn that each "stop" of aperture change has a 2:1 correlation on amount of light reaching the sensor and every time you double aperture size, you quadruple light, whereas shutter speed has a 1:1 correlation. If you think of ISO in terms of "amount of light," rather than light sensitivity, then it too has a 1:1 correlation with exposure value. To a typical beginner with no prior experience or knowledge of photography or photography terms, long technical explanations are less likely to be retained than simple graphical representations. Some people just want to know what time it is, not how to build a watch.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/11/2015 at 16:46
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I just got a hernia reading this.

I'll continue using my iPhone or iPad to take pics and when I want to see quality pics I'll check out what Ted , Skylar, Matt and daveco post on our great forum.

I will continue to enjoy my National Gegraphic and Adirondack Life subscriptions also.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/11/2015 at 16:48
Peddler View Drop Down
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Originally posted by RifleDude RifleDude wrote:

As an example, when I was learning US Geography in elementary school, I used the simple term "Mr. MIMAL" to remember the names and sequences of the states along the Mississippi River. It was an effective mnemonic for more than one reason. First, if you look at a map, the central states along the Mississippi River kind of look like a man standing in profile... From top to bottom, Minnesota looks like the man's hat, Iowa looks like his face, Missouri his upper torso, Arkansas his pants, and Louisiana his boot. Look at a map and imagine what I just described. "Mr. MIMAL" was much simpler for my young mind to remember, as I only had to remember a simple name, and the acronym "M.I.M.A.L." even put the states in the correct order from top to bottom:

M = Minnesota
I = Iowa
M = Missouri
A = Arkansas
L = Louisiana

Ergo... "Mr. MIMAL"

I used mnemonics all the time in school to trigger my memory when I had to commit a lot of facts to memory in a short amount of time. I frequently used the first letter of the first words of facts I had to remember to form words and acronyms. I made up little songs I sang to myself in my mind to remember key words and phrases. The "Mr. MIMAL" example shows how using an effective mnemonic actually means LESS to remember, if the mnemonic is cleverly constructed. People are more likely to remember song lyrics than trying to memorize the same words from a speech or a book, for example, because the tune helps you recall the words.

Likewise, the "exposure triangle" is intended as a starting place to help you remember that, like 3 legs of a triangle, there are 3 settings that are totally inter-related that the photographer has control over. It gives you the basic idea of what effect changing those 3 variables has on exposure and the resulting image. That's the full extent of its usefulness, as intended. If you didn't use something like the exposure triangle to graphically represent that basic idea, it would take a lot of words to describe the same thing to someone totally new to photography, and as the saying goes, "a picture is worth 1000 words." After that concept is cemented in one's memory, one then builds on the basics as they gain more experience. If we're just talking about how the settings on your camera relate to exposure only and not other aspects of the image, it doesn't require a 3D construct to describe how changing one of "the 3 legs of the triangle" affects exposure. From there, you learn that each "stop" of aperture change has a 2:1 correlation on amount of light reaching the sensor and every time you double aperture size, you quadruple light, whereas shutter speed has a 1:1 correlation. If you think of ISO in terms of "amount of light," rather than light sensitivity, then it too has a 1:1 correlation with exposure value. To a typical beginner with no prior experience or knowledge of photography or photography terms, long technical explanations are less likely to be retained than simple graphical representations. Some people just want to know what time it is, not how to build a watch.



Ted, that's like ROYGBIV!
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/11/2015 at 16:49
Peddler View Drop Down
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Originally posted by Peddler Peddler wrote:

I just got a hernia reading this.

I'll continue using my iPhone or iPad to take pics and when I want to see quality pics I'll check out what Ted , Skylar, Matt and daveco post on our great forum.

I will continue to enjoy my National Gegraphic and Adirondack Life subscriptions also.


Semo also!
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