a new exposure triangle

masi1157 said:

bobn2 said:

Note, no ISO in exposure.

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I don't care how you call it. The rest of the world, and in particular the beginners whom this diagram is intended for, seem to call "exposure", what they control on their camera by dialling shutter speed, aperture and ISO, all three, and depinding on the light on the scene.

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If 'the rest of the world' does that, then the rest of the world is wrong. In fact, I know that my part of the world includes many expert photographers and physicists and photographers and also the ISO. The fact that your part of the world is intent on teaching 'beginners' incorrect facts is no reason to continue the practice. In fact, it's rather a good reason to argue against it. As an educator (among other things), I have never been of the opinion that someone's status as a beginner justifies them being fed incorrect information. Indeed, i have found that people fed incorrect information when beginners have great difficulty understanding more advanced issues when the inconsistencies in the stuff they were fed in the first place start causing problems.

masi1157 said:

In the world of exact physics that is different (I know, I live and work in this world). But I don't believe I can introduce the correct term here, when everybody else, incl. Bryan Peterson in his original "exposure triangle", uses exactly those.

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Bryan Peterson is one of the worst offenders when it comes to feeding beginners incorrect information.

masi1157 said:

What makes it so difficult to accept, that these triangles represent APEX formula
Av + Tv = Sv + Bv
in the form:
Bv = Av + Tv - Sv

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The APEX formulae are not a good place to begin an understanding of digital photography. It is a fundamentally misformed equation. The units on the RHS are log seconds and the units on the RHS are log lux.

masi1157 said:

Any problem with that? I will label the triangles with Lv and the problem simply disappears. Ok?

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One of the problems disappears.
--
Bob

bobn2 said:

Your triangle is based around an idea of 'correct' exposure, and there is no such thing.

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Then I wonder, why everybody has an exposure meter on his camera. Every modern camera that I know has one, and they have very sophisticated 3D-matrix-whatsoever algorithms to determine the "best" metering. Cameras are made like that, and that is what the triangles are intended to reflect.

And even if it is not the "correct" exposure, it might still be the "required", "optimum" or simply "desired" exposure. Remember, I don't say anywhere, how these BVs or EVs have been determined. When the triangle says "sunshine", it is nothing but an example, that a beginner will understand.

As I just said before, my triangles represent the usual APEX formula
Av + Tv = Sv + Bv
in the form
Bv = Av + Tv - Sv
What is wrong with that?

Regards, Matthias

Mako2011 said:

To a point....I can keep things at base ISO and use PP to up the exposure without bothering with ISO. That's that whole ISOless sensor thing which gives my brain a workout too.

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Another problem caused by people who play fast and loose with the terminology. PP talls commonly label the image brightness control 'exposure', when of course it has no effect on the exposure at all - that was set when you captured the image. What has happened is that the term 'exposure' has been conflated with 'image brightness', on a tacit assumption that the purpose of adjusting exposure is to adjust image brightness. in fact, that is a very poor use of the exposure controls in digital photography. Fundamentally, exposure controls image noise, not image brightness - it has nothing at all to do with that.

--
Bob

Mako2011 said:

I'm a beginner and your stated goal was to teach about exposure but you keep mixing up terms and that's what's making it hard to understand your diagram.

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Sorry, I am not a native speaker. Do you want me to write all this in german? I get the impression, that you are just searching for opportunities to misunderstand me.

Mako2011 said:

see....now you added "correct" to exposure

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And others tell me, there is no such thing as a "correct" exposure.

Mako2011 said:

To a point....I can keep things at base ISO and use PP to up the exposure without bothering with ISO. That's that whole ISOless sensor thing which gives my brain a workout too.

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And is that the usual way that a beginner would try? I don't think so.

Mako2011 said:

I do greatly appreciate the thread you started as it helps me see what little I know and make strides to correct that.

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Thanks. So please try to understand, what I am trying to say without nitpicking.

Regards, Matthias

masi1157 said:

bobn2 said:

Your triangle is based around an idea of 'correct' exposure, and there is no such thing.

Click to expand...

Then I wonder, why everybody has an exposure meter on his camera. Every modern camera that I know has one, and they have very sophisticated 3D-matrix-whatsoever algorithms to determine the "best" metering. Cameras are made like that, and that is what the triangles are intended to reflect.

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Cameras are made like that because their designs have been carried over from film days, when correct (ish) exposure was a more meaningful term. With digital photography it is still very useful to have an exposure meter, because you want to know what the exposure is in order to make decisions about noise. The way that the exposure meter is configured with film era cameras is not the most convenient fopr making those decisions.

masi1157 said:

And even if it is not the "correct" exposure, it might still be the "required", "optimum" or simply "desired" exposure. Remember, I don't say anywhere, how these BVs or EVs have been determined. When the triangle says "sunshine", it is nothing but an example, that a beginner will understand.

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The question would be, what is your reason for selecting a 'required', 'optimum' or 'desired' exposure? There is an assumption in your triangle and in the APEX formula that the reason is to control image brightness, and that is not a good reason for selecting an exposure in digital photography, exposure is about controlling noise, not image brightness.

masi1157 said:

As I just said before, my triangles represent the usual APEX formula
Av + Tv = Sv + Bv
in the form
Bv = Av + Tv - Sv
What is wrong with that?

Click to expand...

They make no sense, in an absolute sense. They only make sense if exposure is being used to control image brightness, which is non-optimum digital technique.
--
Bob

masi1157 said:

Mako2011 said:

I do greatly appreciate the thread you started as it helps me see what little I know and make strides to correct that.

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Thanks. So please try to understand, what I am trying to say without nitpicking.

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As an educator, I can tell you that when you say something like that to a student, you are in trouble.
If a student disagrees with what you are saying there are two possible reasons:

1. He's wrong
2. You're wrong

If a student pulls apart what you are saying, generally there is one possibility:

1. You're wrong

--
Bob

How about looking at distinct process stages of allowing light

onto sensor and of producing an image of appropriate

brightness:

Amount of incoming light is controlled - by size of lens

opening (aperture) and by the time (shutter speed) allowed for

light to impinge on sensor/film - this will constitute the

"exposure".

The brightness of produced image can be adjusted by

sensitivity/amplification (ISO settnig).

bobn2 said:

Mako2011 said:

To a point....I can keep things at base ISO and use PP to up the exposure without bothering with ISO. That's that whole ISOless sensor thing which gives my brain a workout too.

Click to expand...

Another problem caused by people who play fast and loose with the terminology. PP talls commonly label the image brightness control 'exposure', when of course it has no effect on the exposure at all - that was set when you captured the image. What has happened is that the term 'exposure' has been conflated with 'image brightness', on a tacit assumption that the purpose of adjusting exposure is to adjust image brightness. in fact, that is a very poor use of the exposure controls in digital photography. Fundamentally, exposure controls image noise, not image brightness - it has nothing at all to do with that.

Click to expand...

I totally agree. For me to gain understanding, it helps to have a solid standardization of terms to form a basis. Then the terms must be understood....and then learning can proceed. For example, when someone says they want to expose the scene correctly, I never care about ISO...give me a tripod and a stack of ND filters and I'll get it done even if my ISO is stuck at 100. But now my understanding of how ISO affects that is increasing due to this thread helping to define certain terms more factually. Thank you.

masi1157 said:

Mako2011 said:

I'm a beginner and your stated goal was to teach about exposure but you keep mixing up terms and that's what's making it hard to understand your diagram.

Click to expand...

Sorry, I am not a native speaker. Do you want me to write all this in german? I get the impression, that you are just searching for opportunities to misunderstand me.

Mako2011 said:

see....now you added "correct" to exposure

Click to expand...

And others tell me, there is no such thing as a "correct" exposure.

Mako2011 said:

To a point....I can keep things at base ISO and use PP to up the exposure without bothering with ISO. That's that whole ISOless sensor thing which gives my brain a workout too.

Click to expand...

And is that the usual way that a beginner would try? I don't think so.

Mako2011 said:

I do greatly appreciate the thread you started as it helps me see what little I know and make strides to correct that.

Click to expand...

Thanks. So please try to understand, what I am trying to say without nitpicking.

Click to expand...

I mean no disrespect. I really am the student here trying to gain understanding in a room full of respected teachers. (free lessons are something to be taken advantage of) My questions and comments are intended to further my own understanding and in that regard I can be a bit selfish. My apologies.

masi1157 said:

Mako2011 said:

exposure settings is not the same as exposure

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Is that is the only problem, that you are having with "exposure" in my diagram? Oh my god.

Mako2011 said:

then why are you defining things so outside the norm?

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Nobody is defining anything outside any norm. ISO controls the "correct" exposure of a photo, just as shutter speed and aperture do. Check it out with your camera.

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No, there is no 'correct' exposure, there is the exposure you may want to choose because of your photographic intent and constraints:

1. Aperture selected according to desired DoF (trading off with diffraction blur);

2. Shutter speed selected according to motion blur/camera shake considerations, minimizing noise by accumulating more light in the capture, etc.;

Note that ISO is not a part of exposure. Once you have chosen the exposure according to these criteria, there is an optimal choice of ISO depending on how you want to process the image, how much highlights you want to retain, camera noise, etc.

The problem with including ISO into a graphic such as the one in the OP is that it gets causality back-to-front. It gets people to thinking that 'raising ISO increases noise', exactly as your chart shows; however, it is not high ISO that causes noise, it is low exposure that causes noise (exposure in the correct definition of the term, which is independent of ISO), and high ISO simply brightens that noise to make it visible in the output image.

Furthermore, last time I checked every raw converter has an 'exposure compensation' slider that adjusts output brightness in exactly the same way that the camera's ISO control does (with the exception that it amplifies camera noise differently, on those cameras with ISO-dependent camera (read) noise). ISO is not part of exposure, in part because it can be changed arbitrarily after the fact during image rendering.

masi1157 said:

Mako2011 said:

As a beginner, I don't understand how ISO has anything to do with how the sensor is is actually exposed. The sensor/film is exposed exactly the same with a given sceneluminance/t-stop/shutter speed regardless of ISO

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And your photos all look the same, no matter what ISO you have set?

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In a camera with ISO-independent camera noise, yes, two images taken of the same scene with the same exposure (Tv and Av) will look the same when they are normalized to the same output brightness during raw conversion, assuming the raw converter is doing exposure compensation correctly. Except of course that the one taken at higher ISO will clip more highlights than the one taken at low ISO.

--
emil
--



http://theory.uchicago.edu/~ejm/pix/20d/

bobn2 said:

As an educator, I can tell you that when you say something like that to a student, you are in trouble.

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Do you want me to continue in german? It would be much easier for me and I could express myself much clearer. But I don't think it is too hard a request to try and understand what I am saying without nitpicking.

Gruß, Matthias

masi1157 said:

bobn2 said:

As an educator, I can tell you that when you say something like that to a student, you are in trouble.

Click to expand...

Do you want me to continue in german? It would be much easier for me and I could express myself much clearer. But I don't think it is too hard a request to try and understand what I am saying without nitpicking.

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I think what you see as nitpicking is my poor attempt at requesting clarification. I went to high school in Bitburg so I understand the language problem and am grateful your English is far superior to my German.

Mako2011 said:

I totally agree. For me to gain understanding, it helps to have a solid standardization of terms to form a basis. Then the terms must be understood....and then learning can proceed. For example, when someone says they want to expose the scene correctly, I never care about ISO...give me a tripod and a stack of ND filters and I'll get it done even if my ISO is stuck at 100. But now my understanding of how ISO affects that is increasing due to this thread helping to define certain terms more factually. Thank you.

Click to expand...

I developed these triangles for somebody, who still has difficulties to understand, that taking a photo of a bird in the dark wood with a 500mm lens at 1/60s and close to open aperture is not a good idea, and that increasing ISO from 200 (that he actually used) to e.g. 1600 could help him achieving a more appropriate shutter speed like 1/500s. We tried all the usual metaphors (filling glasses, sunbathing etc.), we tried simple formulae, but he didn't catch it. Today he sometimes seems to think that high ISO settings would be valuable by itself, not only to achieve higher shutter speed and/or more closed aperture. We are still working. The next attempt will be these triangles (in their german version, which appear to be easier understood, I never encountered the type of critcism I got here).

Regards, Matthias

masi1157 said:

I developed these triangles for somebody, who still has difficulties to understand, that taking a photo of a bird in the dark wood with a 500mm lens at 1/60s and close to open aperture is not a good idea, and that increasing ISO from 200 (that he actually used) to e.g. 1600 could help him achieving a more appropriate shutter speed like 1/500s. We tried all the usual metaphors (filling glasses, sunbathing etc.), we tried simple formulae, but he didn't catch it. Today he sometimes seems to think that high ISO settings would be valuable by itself, not only to achieve higher shutter speed and/or more closed aperture. We are still working. The next attempt will be these triangles (in their german version, which appear to be easier understood, I never encountered the type of critcism I got here).

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I don't see it as criticism as much as a limit of the text only format in a open discussion. It's hard to put inflection in the correct place when no visual/audio cues are possible.

In the bird example above....I understand that exactly. Your trying to convey how upping ISO can help get a proper composition (bird scene exposed well and bird not blurry). My comment would be that ISO didn't affect exposure as the blurry bird pic was exposed perfectly with regards to exposure alone but a change in ISO allowed for a different exposure that was useful in keeping the bird sharp. Looking at both final pictures (low and high ISO) I would say that each has the same exposure but differ in amount of noise and sharpness of subject. In that way I see ISO as a means to adjust the parameters of the original exposure triangle. I know that's not technically correct but I'm still trying to incorporate Graystars post in my understanding and help you come up with a good teaching tool for us exposure challenged folks. I will now put my hand down and listen for the rest of the class. Thank you for your patience.

sjgcit said:

You don't address the point at all.

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I directly addressed the point.

Deleted1929 said:

You are attempting to exclude ISO from being a direct factor in exposure settings.

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I said, and I quote:

http://forums.dpreview.com/forums/read.asp?forum=1018&message=39349826

The only role ISO plays in exposure is, as I said, how it indirectly affects an element of exposure in an AE (auto exposure) mode. For example, if you are in P mode, raising the ISO lowers the f-ratio and/or increases the shutter speed. The ISO setting doesn't change the exposure, the change in f-ratio and shutter speed does.

So, no, ISO is not a direct factor in exposure, but an indirect factor.

Deleted1929 said:

And you're doing this by using your usual tactics of simultaneously employing detailed arguments, your own redefinitions of common terms and demanding simplified answers from others when they would have to make complex answers to respond properly.

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I use the term "exposure" as it is correctly defined (as I linked earlier):

http://en.wikipedia.org/wiki/Exposure_ (photography)

and I explained it rather simply:

http://forums.dpreview.com/forums/read.asp?forum=1018&message=39349885

Exposure triangles for beginners.

Make an exposure triangle with the three elements of exposure:

• Scene Luminance
• t-stop (approximated with f-ratio)
• Shutter Speed

and explain how the metering mode, ISO setting, and flash power affect the three elements of exposure. Just not that hard. And if that's too confusing, well, hell -- just tell them to put the camera in Auto Mode, set Auto ISO, and be done with it.

Deleted1929 said:

I'm not interested in the minutiae of your arguments. My sole interest is in what the term exposure means to normal users who live in the practical world, and not your private world with your own view of everything that you are so keen to force on the rest of us.

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Your interest is in promoting ignorance.

Deleted1929 said:

You don't seem to care how much these views of your confuse beginners. Telling them to ignore ISO is just so misleading and damaging to their development.

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Another "holy man" who speaks for all beginners.

Deleted1929 said:

Happily for people like you, DPR have create a feature I find quite useful - the ignore list. I am happy to add you to mine.

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Great! Then I shouldn't have to deal with any more nonsense from you, while happily correcting yours.

masi1157 said:

Great Bustard said:

So, here's a quick question for you: do f/2.8 1/200 ISO 100 and f/2.8 1/400 ISO 200 have the same exposure? A simple yes or no will do.

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Are you really sure a beginner would even understand what you are asking him?

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If not, then they don't really need to know, do they?

masi1157 said:

He wants to know how to "expose" his photos correctly, and that he controls with shutter speed, aperture (or is f-stop the better term? In german we say "Blende", which implies the relative aperture) and with ISO, all these three parameters, depending on the the scene's luminance. And even if the physics behind it might be somewhat different, this is the way how a DSLR works.

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As I said before, if you wanted to say "how to control the brightness of the photo", I'd not have a problem with what you wrote.

masi1157 said:

So, for a beginner, and for every other photographer, the question is "do f/2.8 1/200 ISO 100 and f/2.8 1/400 ISO 200 make the same photo? They will have the same brightness, but different motion blur and noise. And that is, what my triangle is intended to visualize.

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And there it is in your very own words! Say "brightness" instead of "exposure" -- problem solved!

A beginner should know this even if these aren't the best scientific explanations.

1. The wider the aperture the more light hits the sensor making the image brighter. The wider the aperture the shallower the depth of field.

2. The faster the shutter speed, the less light hits the sensor making the image darker. The faster the shutter speed, the more movement will be frozen.

3. The higher the ISO, the more sensitive the sensor will be to light making the image brighter. The higher the ISO, the more noise the image will have.

Once they learn this, then they need to learn what the PASM modes do. Then they need to learn to meter off mid tones (or learn the modified zone system for metering off other tones) and either use exposure lock in A,S modes or how to zero out the light meter in M mode. Perhaps learn the theory regarding exposure to the right and how to read a histogram.

There is obviously much more to it than this, but it should give them pretty good exposure without blowing highlights.

gwlaw99 said:

3. The higher the ISO, the more sensitive the sensor will be to light making the image brighter. The higher the ISO, the more noise the image will have.

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Changing the ISO does not change the sensitivity of the sensor -- the sensitivity of the sensor is fixed, and that is one of the huge differences between film and digital (and why digital lets you change ISO on the fly, unlike film).

In an AE (auto exposure) mode, the ISO indirectly affects the f-ratio, shutter speed, and/or flash power. It also is linked to an analog gain with some cameras, and a digital push/pull in all cameras. But the sensitivity of the sensor does not change as a function of ISO.

Great Bustard said:

And there it is in your very own words! Say "brightness" instead of "exposure" -- problem solved!

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If that is the only problem you have with all this, why all this hazzle? Nevertheless every photographer and every beginner will see light, shutter speed, aperture and ISO all related to "correct exposure" (whatever that means). The first 3 control the amount of light falling on the sensor and the 4. controlling how much light is needed for this "correct exposure". And that is why I call it an "exposure triangle" rather than an "image brightness control triangle", even if that might be the better term. And as I said a couple of times before, my triangles represent the APEX formula
Av + Tv = Sv + Bv
in the form
Bv = Av + Tv - Sv

If you disagree with the principle of APEX or that formula, please discuss it with somebody else.

Regards, Matthias

Great Bustard said:

Changing the ISO does not change the sensitivity of the sensor

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Would you now please stop this? I presented my triangles to receive constructive critcism. You are just searching for opportunities to misunderstand everybody. Please do that in another thread.

Rgards, Matthias