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a new exposure triangle

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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? 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.

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.

Regards, Matthias
 
I see you have the attention of those with, well, let’s just call them different viewpoints. I tend to ignore them.

Your chart is an interesting concept. It’s got one problem, described below, that should be easy to fix. I can see it used as a teaching aid. I’m all for getting people to think of exposure in terms of EV.

Although not named in ISO standards any more, all cameras behave as described in the APEX system (Additive system of Photographic EXposure.) The equation for photographic exposure has aperture and shutter on one side of the equation, while scene luminance and sensitivity (or Responsivity, in the digital age) are on the other side of the equation (as opposed to the equation for photometric exposure, which the “viewpoints” like to push as the definition of photographic exposure…which is wrong.)

In the APEX system, the term Exposure Value means two things. First, it’s a combination of aperture and shutter. Second, it’s a combination of scene luminance and sensitivity. When the two EV values are the same, you have standard exposure.

The problem with your triangle is that as ISO increases, EV is supposed to increase. Obviously that doesn’t happen. You can probably fix the problem by changing the label slightly to something like:
Sunshine (EV 15 at ISO 100)

Now, your triangle describes a level of luminance (it’s no longer EV 15...it’s just “sunshine”) but also gives a reference point. The luminance triangles will then become the fourth parameter in the exposure equation. In the main triangle itself, on the ISO lines you can have “ISO 200 (+1 EV)” and “ISO 400 (+2 EV).” In this way, users of the triangle can easily calculate the actual EV.

I say create 20 of them and give them to some beginner's photography class somewhere as a teaching aid to see how they work out. If the teacher and students like them, then sell the idea to some producer of teaching aids

.
 
I like it.

The "Ev triangles" really should be "Lv triangles" though as EV = LV at ISO 100.

The point that needs to be made clear is what the LV values represent - The average reflected light of the scene - and that this average value will be recorded as middle grey in the resulting image. It's not necessarily the "right' exposure, but a starting point.
 
geoffire said:
I like it.
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Thanks!
geoffire said:
The "Ev triangles" really should be "Lv triangles" though as EV = LV at ISO 100.
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As I said earlier, my original german version said "Lichtwert", which is in fact LV, but I didn't know about this acronym when I translated the whole thing to english. I will replace EV with LV in the next version.

Regards, Matthias
 
masi1157 said:
As I said earlier, my original german version said "Lichtwert", which is in fact LV, but I didn't know about this acronym when I translated the whole thing to english. I will replace EV with LV in the next version.
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There's no such thing as an LV. Most usages of LV is the same as EV, but something called a Light Value has never been defined in any standard.

http://en.wikipedia.org/wiki/Light_value

.
 
Graystar said:
There's no such thing as an LV. Most usages of LV is the same as EV, but something called a Light Value has never been defined in any standard.

http://en.wikipedia.org/wiki/Light_value
Click to expand...
Ok, in that link you can see where my mistake came from (#6). And it also mentions, what I was trying to say with it (#2 and/or #3, which are numerically equal). So what would be the correct term here?

Regards, Matthias
 
sherwoodpete said:
Indeed.
Click to expand...
That may all be true, but what improvement does it bring to my triangles? I already admitted that "EV" on the transparent triangles was a mistake, that I will correct. Nevertheless my triangles reflect exactly what you do with any today's DSLR to control exposure depending on the light of the scene: You dial in shutter speed, aperture (or f-stop, if you prefer) and ISO. All three!

So what added value does this discussion about what is part of exposure and what is not, bring? I don't see any. Please google yourself for "exposure triangle". Virtually every triangle you will find has the same 3 parameters on it's ends and I believe every photographer will understand, what they mean. But all the other triangles an't be used to determine the values of the 3 parameters. And that is what I am adding to them with my triangles.

Best regards, Matthias
 
masi1157 said:
Graystar said:
There's no such thing as an LV. Most usages of LV is the same as EV, but something called a Light Value has never been defined in any standard.

http://en.wikipedia.org/wiki/Light_value
Click to expand...
Ok, in that link you can see where my mistake came from (#6). And it also mentions, what I was trying to say with it (#2 and/or #3, which are numerically equal). So what would be the correct term here?
Click to expand...
Like I said in my previous post, what you're representing is the scene luminance, and there's no common photographic term for it. Most people use EV (as you did,) which isn't exactly right. That's why I suggested simply calling it "Sunshine" and in parens "(EV 15 at ISO 100)".

.
 
Technically it should be luminance, but then you'd need to list the values in your triangles as cd/m2, or use Bv from the APEX system.

Av + Tv = Bv + Sv (aperture value, time value, brightness value, speed value)

Bv = Ev - Sv. The speed value of 100 ISO is 5, so you can subtract your "Ev" values by 5 to get Bv.

Listing both might be a good idea as showing cd/m2 would demonstrate how much light there is and Bv for readability. Bv 10 is 3508 cd/m2 and Bv 9 is 1754 cd/m2 (half as much light). It also really shows how little light there is a night, Bv -5 (your Ev 0) is something like .003 cd/m2, and considering that means f2, 1/8 sec, 3200 ISO (2 + 3 = -5 + 10) that's not really quite moonless night type dark.

Whatever units you want to use I don't think really matters much to get the point across. It's not like anyone is really going to bust out the calculators and do the math on this, thats what the triangles are for :)

Here's a good explanation of the APEX system, and the tables where I got those numbers from - http://dougkerr.net/pumpkin/articles/APEX.pdf - It's honestly too much info for most people though...
 
geoffire said:
Technically it should be luminance, but then you'd need to list the values in your triangles as cd/m2, or use Bv from the APEX system.
Click to expand...
Yes, I was thinking about Bv as well. And yes, cd/m² might also be a good idea, but I have to admit that I don't have any "feeling" for those numbers. But that might change, just from having them in front of me on those triangles.
geoffire said:
Whatever units you want to use I don't think really matters much to get the point across. It's not like anyone is really going to bust out the calculators and do the math on this, thats what the triangles are for :)
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I hope so, but nevertheless I would want the math to be correct.
geoffire said:
Here's a good explanation of the APEX system, and the tables where I got those numbers from - http://dougkerr.net/pumpkin/articles/APEX.pdf - It's honestly too much info for most people though...
Click to expand...
No problem, I studied physics, I'm used to that. My problem here was, that I simply didn't know the exact english terms in the field of photography (I have no such problem in acoustics, though :) ) My numbers were from a german site, where "EV0" was given for "Neumond" ="new moon".

Regards, Matthias
 
You don't address the point at all.

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

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.

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.

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.

--
StephenG
 
geoffire said:
I like it.

The "Ev triangles" really should be "Lv triangles" though as EV = LV at ISO 100.
Click to expand...
LV = EV at 100 ISO. LV is a measure of scene luminance. The ISO unit for LV is lux and



(from http://en.wikipedia.org/wiki/Exposure_value )

L = the scene luminosity in Lux and 'EV' = LV (the exact correspondence depends on meter calibration)

Exposure is



(from the Wikipedia article already cited) where Hv is the exposure Ev - not EV - is the image plane illuminance in lux and t is the exposure time. The image plane illuminance depends on the T (or F) stop and the scene luminance, so we end up with

Hv = k*L*N*t, where N is the T (or F) number and all the others are as before. If you work through the units, then you find that the units of Hv are lux.seconds, and if scene luminance is expressed in LV the exposure is
Hv = k*(2^(LV-3))*N*t
Note, no ISO in exposure.

--
Bob
 
sjgcit said:
You don't address the point at all.

You are attempting to exclude ISO from being a direct factor in exposure settings.
Click to expand...
exposure settings is not the same as exposure
Deleted1929 said:
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.
Click to expand...
then why are you defining things so outside the norm?
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.
Click to expand...
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
 
Graystar said:
masi1157 said:
Graystar said:
There's no such thing as an LV. Most usages of LV is the same as EV, but something called a Light Value has never been defined in any standard.

http://en.wikipedia.org/wiki/Light_value
Click to expand...
Ok, in that link you can see where my mistake came from (#6). And it also mentions, what I was trying to say with it (#2 and/or #3, which are numerically equal). So what would be the correct term here?
Click to expand...
Like I said in my previous post, what you're representing is the scene luminance, and there's no common photographic term for it. Most people use EV (as you did,) which isn't exactly right. That's why I suggested simply calling it "Sunshine" and in parens "(EV 15 at ISO 100)".

.
Click to expand...
It would be easiest if people just got used to expressing scene luminance in lux and exposure in lux seconds. They are neither unwieldy units, and it leads to a nice straight forward and clear relationship between scene luminance and exposure. The problem is that the 'EV', 'ISO' and 'LV' were established before the SI system was widespread. Now it is, it makes sense to use it in photography.
--
Bob
 
bobn2 said:
Note, no ISO in exposure.
Click to expand...
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. 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.

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

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

Regards, Matthias
 
Graystar said:
I see you have the attention of those with, well, let’s just call them different viewpoints. I tend to ignore them.

Your chart is an interesting concept. It’s got one problem, described below, that should be easy to fix. I can see it used as a teaching aid. I’m all for getting people to think of exposure in terms of EV.

Although not named in ISO standards any more, all cameras behave as described in the APEX system (Additive system of Photographic EXposure.) The equation for photographic exposure has aperture and shutter on one side of the equation, while scene luminance and sensitivity (or Responsivity, in the digital age) are on the other side of the equation (as opposed to the equation for photometric exposure, which the “viewpoints” like to push as the definition of photographic exposure…which is wrong.)

In the APEX system, the term Exposure Value means two things. First, it’s a combination of aperture and shutter. Second, it’s a combination of scene luminance and sensitivity. When the two EV values are the same, you have standard exposure.

The problem with your triangle is that as ISO increases, EV is supposed to increase. Obviously that doesn’t happen. You can probably fix the problem by changing the label slightly to something like:
Sunshine (EV 15 at ISO 100)

Now, your triangle describes a level of luminance (it’s no longer EV 15...it’s just “sunshine”) but also gives a reference point. The luminance triangles will then become the fourth parameter in the exposure equation. In the main triangle itself, on the ISO lines you can have “ISO 200 (+1 EV)” and “ISO 400 (+2 EV).” In this way, users of the triangle can easily calculate the actual EV.

I say create 20 of them and give them to some beginner's photography class somewhere as a teaching aid to see how they work out. If the teacher and students like them, then sell the idea to some producer of teaching aids
Click to expand...
Once again you caused me to learn something. Thanks
 
Mako2011 said:
exposure settings is not the same as exposure
Click to expand...
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?
Click to expand...
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.
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
Click to expand...
And your photos all look the same, no matter what ISO you have set?

Regards, Matthias
 
masi1157 said:
sherwoodpete said:
Indeed.
Click to expand...
That may all be true, but what improvement does it bring to my triangles? I already admitted that "EV" on the transparent triangles was a mistake, that I will correct. Nevertheless my triangles reflect exactly what you do with any today's DSLR to control exposure depending on the light of the scene: You dial in shutter speed, aperture (or f-stop, if you prefer) and ISO. All three!

So what added value does this discussion about what is part of exposure and what is not, bring? I don't see any. Please google yourself for "exposure triangle". Virtually every triangle you will find has the same 3 parameters on it's ends and I believe every photographer will understand, what they mean. But all the other triangles an't be used to determine the values of the 3 parameters. And that is what I am adding to them with my triangles.
Click to expand...
Your triangle is based around an idea of 'correct' exposure, and there is no such thing. Most people when challenged to define 'correct' exposure, if they can do so at all, say something like 'it's the exposure which gives the brightness the photographer wants', but exposure doesn't give any image brightness at all, it is solely the processing that determines the image brightness. So, if you think abou this, what the 'ISO' control is doing is selecting the processing (which is indeed exactly what it does, apart from making the meter relative to a target exposer dependent on the ISO).

So, what your triangle is doing, in effect, is predicated on a technique where the photographer selects which processing he will use then takes a picture. You could also work your technique the other way round, so that you take the picture then select the processing. I don't see any reason why amateurs should find that difficult.

--
Bob
 
masi1157 said:
Mako2011 said:
exposure settings is not the same as exposure
Click to expand...
Is that is the only problem, that you are having with "exposure" in my diagram? Oh my god.
Click to expand...
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.
masi1157 said:
Mako2011 said:
then why are you defining things so outside the norm?
Click to expand...
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.
Click to expand...
see....now you added "correct" to exposure
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
Click to expand...
And your photos all look the same, no matter what ISO you have set?
Click to expand...
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.

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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