Need help with exposure question

[Ysarex]

You two guys are funny (to be PC, I never said laughable ). How would you suggest taking a satisfactorily exposed picture without addressing the proper ISO to do it? (not speaking of relying on automation to do it for you).

Because I am not confusing exposure with brightness of final image. Your ISO setting affects the brightness of the final image, not the exposure. You can achieve the same thing after the shot is taken and the image file is downloaded to your computer. Lightroom has an "exposure" slider which will brighten or darken the image but clearly has no effect on what the camera has already done and so has nothing to do with the exposure.

So I guess you are saying you imagine your notion is somehow correct for digital, but that you are obviously wrong for film?

My own notion is about the histogram that I can see, and the usability of that image that I can see and access. Both film and digital satisfy the normal and accepted concept of exposure... for both, we just balance the three factors to produce the usable image.

But you failed to answer my question that you quoted. How do you take a properly exposed picture (the usable picture) without consideration of proper ISO?

Proper ISO? Anyway, you don't. ISO is an important consideration when making an exposure. That does not however make ISO an exposure determinant. "Exposure" has a definition that makes cause and effect clear. This old analogy is useful.

You're going to turn on the water and fill a beaker (ISO). You have constant water pressure at the time (scene luminance). The faucet handle is a little special and is equipped with click stops so that you can open it one, two, three, four, etc. clicks and each click opens the value more (aperture). You take an 8 ounce beaker and hold it under the faucet and open it two clicks for 5 seconds (time - shutter speed). The beaker nearly fills. Congratulations! Set that aside. Now reach up on the shelf and grab a 16 ounce beaker. Hold the 16 ounce beaker under the faucet and open it two clicks for 5 seconds. Which beaker has more water in it? The size of the beaker doesn't determine the volume of water.

Joe

That must be very tedious, and interesting to watch..

 

[Ysarex]

Joe, We understand that exposure is how many photons falls on the film or digital sensor. The the aperture and shutter speed control the photo quantity. But that's only of interest to engineers and camera designers. For average photographers, who are learning how to set proper exposure on their cameras, they have to input ISO as one of the variables to get the final picture to look exposed correctly. If ISO (ASA) wasn;t important, then you would have that control on a light meter. IF you set ISO wrong, you'll get an over or under exposed picture.

Beyond that we've entered the world of word games. So I'm out of here.

ISO is important -- never said it wasn't. Above I just confirmed it's needed to get a proper exposure. The problem shows up when you change ISO's roll and try to turn it into an exposure determinant. Read the water faucet analogy in my last post.

The exposure triangle is presented with three variables and they are all presented as determinants of exposure. They are then further presented as each controlling independent additional variables. Aperture = DOF, Shutter speed = motion/blur, and ISO = noise. Beginners read that and believe it. That's wrong and the beginners at that point become confused about cause and effect. ISO does not cause noise. If anything what ISO does suppresses noise. Ultimately their confusion leads them to making mistakes and taking worse photos than they otherwise could. Today with the arrival of ISO-invariant sensor a new twist gets added in and the triangle becomes more confusing.

Joe

 

[AlanKlein]

Joe, We understand that exposure is how many photons falls on the film or digital sensor. The the aperture and shutter speed control the photo quantity. But that's only of interest to engineers and camera designers. For average photographers, who are learning how to set proper exposure on their cameras, they have to input ISO as one of the variables to get the final picture to look exposed correctly. If ISO (ASA) wasn;t important, then you would have that control on a light meter. IF you set ISO wrong, you'll get an over or under exposed picture.

Beyond that we've entered the world of word games. So I'm out of here.

ISO is important -- never said it wasn't. Above I just confirmed it's needed to get a proper exposure. The problem shows up when you change ISO's roll and try to turn it into an exposure determinant. Read the water faucet analog in my last post.

The exposure triangle is presented with three variables and they are all presented as determinants of exposure. They are then further presented as each controlling independent additional variables. Aperture = DOF, Shutter speed = motion/blur, and ISO = noise. Beginners read that and believe it. That's wrong and the beginners at that point become confused about cause and effect. ISO does not cause noise. If anything what ISO does suppresses noise. Ultimately their confusion leads them to making mistakes and taking worse photos than they otherwise could. Today with the arrival of ISO-invariant sensor a new twist gets added in and the triangle becomes more confusing.

Joe

What confusion and how does it lead to mistakes?

 

[Ysarex]

Correct me if I'm thinking wrong....
So I need to think of ISO differently from film. Changing ISO on the digital camera does not really change anything about the sensor. Whereas different ISO or ASA films were physically different, changing ISO on the digital camera is about how the camera interprets or processes the light captured by the sensor.

Pete

Digital ISO is an amplification,

Wince! "amplification" and or "gain" have been used a lot especially in the past to describe what's going on. Those terms carry connotations with them from the audio industry that aren't quite right for digital photo. Problem is multiple methods are employed to "brighten" the image. The signal from the sensor is analog and in some cameras absolutely that signal is passed through amplification. However in more and more cameras now the signal goes straight to the ADC and the brightening of the image is done by digitally scaling the data. In more and more cameras now a hybrid combination of those methods are used.

but it changes anything that we can get out of the sensor or the raw file or the JPG file.
The only way to access the non-amplified data is to set ISO low to native value. I suppose that could be a misguided goal, but you still have to set ISO to achieve it.
That might be a technical issue, but to US users, it is just semantics.

Unless it's not a misguided goal but an appropriate way to get the desired image. In which case it can really help to understand what exposure is and what ISO is.

I don't see any reason to confuse the newbies with it. They have a lot more to deal with early on. Like learning to get aperture, shutter speed and ISO matched right.

No argument early on, but if you start them off confused and all twisted in a knot then later on it can be much harder to straighten them out when it might matter.

Joe

 

[Ysarex]

Joe, We understand that exposure is how many photons falls on the film or digital sensor. The the aperture and shutter speed control the photo quantity. But that's only of interest to engineers and camera designers. For average photographers, who are learning how to set proper exposure on their cameras, they have to input ISO as one of the variables to get the final picture to look exposed correctly. If ISO (ASA) wasn;t important, then you would have that control on a light meter. IF you set ISO wrong, you'll get an over or under exposed picture.

Beyond that we've entered the world of word games. So I'm out of here.

ISO is important -- never said it wasn't. Above I just confirmed it's needed to get a proper exposure. The problem shows up when you change ISO's roll and try to turn it into an exposure determinant. Read the water faucet analog in my last post.

The exposure triangle is presented with three variables and they are all presented as determinants of exposure. They are then further presented as each controlling independent additional variables. Aperture = DOF, Shutter speed = motion/blur, and ISO = noise. Beginners read that and believe it. That's wrong and the beginners at that point become confused about cause and effect. ISO does not cause noise. If anything what ISO does suppresses noise. Ultimately their confusion leads them to making mistakes and taking worse photos than they otherwise could. Today with the arrival of ISO-invariant sensor a new twist gets added in and the triangle becomes more confusing.

Joe

What confusion and how does it lead to mistakes?

I get it all the time from my students who have been "traingled." Confusion: ISO causes noise. Therefore if I raise the ISO that will make my photo noisier. Mistake: Stuck in a low light situation and need to take a hand-held photo. To get the shutter speed I'd like I'll have to raise the ISO to 6400. Yikes! I can't do that, that's too much noise! Ok, ok, I'll just set the ISO to 3200 and get within 2/3 to 1/2 a stop of a zeroed meter. I can probably get away with 1/60 sec. instead of 1/100. Click. They get a blurry noisier photo.

I waste a lot of time repairing that damage. ISO does not cause noise. If anything in many cameras it helps suppress noise. The triangle confuses cause and effect.

We're experiencing a slow but sure hardware change these past few years and certainly in the years to come. Many of us now are shooting ISO invariant sensors in our cameras and many more of us will be. To take maximum advantage of that it's going to help to have a good understanding of what's going on. The first fix to the exposure triangle if you're not going to dump it as a bad idea is to at least replace the ISO = noise side of the triangle with ISO = DR -- that could be useful.

Joe

 

[WayneF]

ISO does not cause noise. If anything in many cameras it helps suppress noise.

That is truly laughable. The gain required by digital ISO of course necessarily amplifies the noise as much as the signal. Visibility soon becomes an issue.
The camera amplification does have better ways to do it than in Lightroom (and Lightroom range is limited to only about 5 EV).
But the only way ISO lowers noise is an ISO lower than native, like ISO 50, which reduction does decrease both noise and signal (and dynamic range).

No one has answered my question about how you achieve proper exposure without considering ISO to do it.

If you do of course use ISO (as I strongly suspect), then this is just unnecessary semantics at any entry level suitable for the triangle. Trying to show off that you know something to beginners is in poor taste.
If you don't use ISO (and depend on Lightroom?), then that's just dumb, and you certainly did NOT achieve any proper exposure.
Either way, there is no point or any desire to continue this dumb stuff with you. Have fun.

I also wanted to tell someone else here today in another thread the classic "When all around you are wrong, maybe you should reconsider your own opinion". But I find no private messaging here, and I respect him too much to call attention to it online. And I do that sometimes too.

 

[Ysarex]

ISO does not cause noise. If anything in many cameras it helps suppress noise.

That is truly laughable. The gain required by digital ISO of course necessarily amplifies the noise as much as the signal.

So you agree then that ISO doesn't cause the noise -- amplifying the noise is not the same as causing it. Cause and effect is important. You seem very confused.

Visibility soon becomes an issue.
The camera amplification does have better ways to do it than in Lightroom (and Lightroom range is limited to only about 5 EV).
But the only way ISO lowers noise is an ISO lower than native, like ISO 50, which reduction does decrease both noise and signal (and dynamic range).

There are different sources of noise. Most of the noise that average photographers see in their photos is shot noise (not caused by ISO). ISO brightening makes that noise visible but does not cause it. Read noise comes from the camera electronics as the signal is processed and ISO analog amplification definitely suppresses read noise.

No one has answered my question about how you achieve proper exposure without considering ISO to do it.

I did.

And I see that you have failed to repost that definition of exposure with ISO underlined.

Joe

If you do of course use ISO (as I strongly suspect), then this is just unnecessary semantics at any entry level suitable for the triangle. Trying to show off that you know something to beginners is in poor taste.
If you don't use ISO (and depend on Lightroom?), then that's just dumb, and you certainly did NOT achieve any proper exposure.
Either way, there is no point or any desire to continue this dumb stuff with you. Have fun.

I also wanted to tell someone else here today in another thread the classic "When all around you are wrong, maybe you should reconsider your own opinion". But I find no private messaging here, and I respect him too much to call attention to it online. And I do that sometimes too.

 

[photo1x1.com]

I do have to defend Joes position. For us nerds who are able to take part in this advanced discussion, many things are somewhat logical. Of course, if the sun goes down it gets dark, and we have to compensate for that.
But some beginners don´t get that. From reading many facebook groups, here in the forum and also from people asking me when I´m out and about shooting, I know that some beginners usually don´t take the light situation into the equation. They only think in their exposure triangle, and that gets them confused. I for one have never used the phrase exposure triangle at all - having a triangle doesn´t really make it easier to understand, so it doesn´t add anything.

I for one will try to change my language from now on.
One thing that hasn´t been answered yet though is:
How would you call that brightness of the image, made up of "incomming" light, aperture diameter, shutter speed and ISO, that is commonly referred to as exposure?

 

[john.margetts]

I for one will try to change my language from now on.
One thing that hasn´t been answered yet though is:
How would you call that brightness of the image, made up of "incomming" light, aperture diameter, shutter speed and ISO, that is commonly referred to as exposure?

I call it brightness.



Sent from my 8070 using Tapatalk

 

[john.margetts]

What confusion and how does it lead to mistakes?

The confusion in the opening post where the poster could not understand why two photos with the 'same' exposure looked different. A later poster posted the histograms of the two photos concerned. The difference between the two exposures are clear. The larger exposure (taken at a lower ISO) has a different shape histogram to the smaller exposure taken at a higher ISO. The larger exposure contains more information which is more than just academic.


Sent from my 8070 using Tapatalk

 

[Ysarex]

I do have to defend Joes position. For us nerds who are able to take part in this advanced discussion, many things are somewhat logical. Of course, if the sun goes down it gets dark, and we have to compensate for that.
But some beginners don´t get that. From reading many facebook groups, here in the forum and also from people asking me when I´m out and about shooting, I know that some beginners usually don´t take the light situation into the equation. They only think in their exposure triangle, and that gets them confused. I for one have never used the phrase exposure triangle at all - having a triangle doesn´t really make it easier to understand, so it doesn´t add anything.

I for one will try to change my language from now on.
One thing that hasn´t been answered yet though is:
How would you call that brightness of the image, made up of "incomming" light, aperture diameter, shutter speed and ISO, that is commonly referred to as exposure?

Yep, you've zeroed in on the source of the problem here. When Alan first posted he used the term "proper exposure." He was never thinking of "exposure." In Wayne's first post (2nd sentence after throwing an insult) he uses the term "satisfactorily exposed." I quoted a definition earlier from Ilford's The Manual of Photography which is one of the most respected references in our discipline. They address this issue in the text and they solve it by carefully using two different terms. They explain why. "Exposure" they insist has a clear meaning and it's critical that it's definition not be confused with what they decide to call "camera exposure." "Camera exposure" includes ISO. They settle on "camera exposure" because the other options are too loaded with subjective land mines. Defining "exposure" is simple and it's settled. We settled it a long time ago. "Correct exposure" or "proper exposure" or "satisfactory exposure" is something else and if we set about trying to define that in this venue we're in for a much bumpier ride than we've gotten so far.

There are good reasons to keep these two concepts separate; Ilford found it necessary. But they both have the word "exposure" in them and it's really hard to get folks to understand the distinction and the need for it. When you tell everyone that ISO is not an "exposure" determinant they hear you saying ISO is not a "correct exposure" determinant and that they think is just crazy.

Unfortunately we're stuck here. "Proper exposure" was used by both Alan and Wayne. That's what most photographers mean when they say "exposure." It's a colloquial usage. What exactly is "proper exposure"? The next step sends you straight down the rabbit hole. Is it the translation of a specific gray value in the scene to a specific gray value in an RGB image? How is a light meter adjusted? In any attempt to try and define "proper exposure" it won't be long before someone comes along with, "it's whatever you want it to be, it's completely subjective!"

Ilford's solution feels unsatisfactory. By using "camera exposure" they decided to just go around the mine field -- not goin' there, ha! When it comes time to understand how our cameras actually work (throughout this thread I kept repeating "cause and effect") we need the established meaning of the term "exposure." We can't let that term and it's definition be changed. So we still have your question what term do we use when we mean; "that brightness of the image, made up of "incomming" light, aperture diameter, shutter speed and ISO, that is commonly referred to as exposure?" I think it's too established colloquially and we're stuck with it and we're stuck with the conflicting meanings. Just always use the adjective of your choice (correct, proper, satisfactory, etc.) in front of exposure when you don't mean exposure.

As for the definition of "correct exposure" -- I'm not goin' there, ha!

Joe

EDIT: The exposure triangle mess is unfortunate. Beginners need to learn to use and adjust their cameras. The ET as a model can be helpful at first. Many enthusiast photographers will never need to move beyond that and enough said.

The folks who spread the ET model around found it satisfying to create this balanced structure so that each side/vertice of the triangle has equal weight to the other sides. Each side adjusts exposure, oops "correct exposure" while at the same time also adjusting an independent variable. The independent variable they chose for ISO is noise.

For most of us the noise we see in our photos is shot noise. Shot noise is a function of exposure. The less you expose a digital sensor the more shot noise you're going to see. ISO correlates with this in that if we use the camera meter and raise the ISO then the meter recalculates a reduced exposure which gives us more shot noise. Correlation and cause are two very different things.

There is however a factor that ISO is causally responsible for. Increasing ISO reduces DR. Here's a graph of DR over ISO for a Nikon D7200: Photographic Dynamic Range versus ISO Setting. When ISO brightens the sensor output before or during ADC it's shaving DR straight off the top. Clipped highlights in a high ISO value image get clipped by the ISO brightening and may not be clipped in the exposure. The ET would make more sense if the independent variable associated with ISO were DR. At least in that case a causal relationship would exist. Then if they could just stop calling it the exposure triangle.....

 

[Designer]

No one has answered my question about how you achieve proper exposure without considering ISO to do it.

See post #29, above.

 

[Designer]

- having a triangle doesn´t really make it easier to understand, so it doesn´t add anything.

Unfortunately, we do seem to be stuck with the "triangle" idea, at least for now, but even when in use by well-meaning individuals such a concept actually makes a "good/proper/correct" exposure MORE difficult, not easier. Why wouldn't having only TWO variables (given the same existing light is the same) instead of three make anything easier? When one wishes to increase the light, he can use flash or wait for a sunny day, which of course introduces the third variable (if one needs three variables).

So where does the "confusion" come from? It comes from a fundamental misunderstanding of digital photography, and as long as beginners continue to rely on a "triangle" idea, they will continue to make mistakes. Just as the OP has illustrated; by plugging in known variables but getting different results yields confusion.

Now to the question of "what makes a "proper" exposure? In digital, I would say that getting the most information you can get without overloading your sensor would be the correct answer. Overloading an electronic sensor yields what we call "blown out", and is caused by such an overexposure that your camera's firmware cannot process the data to produce a viewable image. Considering the complete concept, this is how the socks photograph was made: Capture as much information as you can (in the low light condition), and boost the gain AFTER the data has been captured. Whether one has set the camera's ISO setting to a high value, or he does that on the computer later is irrelevant, the end result is the same.

One more thing: since there is no such thing as "photons", @alan Kline, the concept of the filling of a container with "light particles" is a bad analogy, and leads to more confusion, therefore should not be used. Inform the beginners how this stuff really works and you get less confusion, not more.

 

[WayneF]

No one has answered my question about how you achieve proper exposure without considering ISO to do it.

See post #29, above.

No, in no way. That just keeps on talking around it, intently trying to evade the specific question. He should be a politician (meaning, a politician of the worst kind). Along with his adding some really stupid stuff like: "ISO does not cause noise. If anything what ISO does suppresses noise. " Really laughable.

The question meaning was this: Suppose you want to take a picture of the crowd on Main Street, and you raise your camera to adjust for proper settings and do it. The Suns illumination does affect the brightness of the image you will see (as certainly also does the aperture, shutter speed and ISO selected), so there are the three settings necessary in an appropriate matched group for this proper exposure: aperture, shutter speed, and ISO. First Basics of photography. Each of the three requires selecting suitable choices for the situation (due to depth of field, motion blur, and sensor noise), or we could allow automation to chose something to do it (but other than exposure, it has no knowledge of the scenes actual requirements), but all three settings must absolutely be addressed. ISO is one of the settings we are required to make for a proper exposure (proper meaning so that we do get a usable image file with an acceptable histogram... there is no other way to get a proper image file out of the camera other than to select the three suitable settings). ISO is one of those extremely necessary settings to deal with, arguably one of the most important.

It is argued that digital ISO is just a gain amplification factor after actual instant of "exposure", which is just show-off clever in this context, but it is not useful in practice, or to newbies, since there is no other way to get the proper image file out of the camera without setting a suitable ISO too. Any image file and any histogram WILL have this ISO result in it. It is what the camera does. It is what ISO does. Setting ISO is one of the required ways we deal with situations, in order to get a proper and usable file out of the camera. The three basic essentials required for newbies (or automation) to get a proper image is aperture, shutter speed, and ISO. This was of course true of film too.

My question, still totally ignored, is: When standing on Main Street, how does one take any proper and usable image without concern for setting a usable ISO? It is not a question about semantics of terms, it is about when standing on Main Street, what does one do without setting ISO? Agreed, it is a stupid question (we all know the answer, we set ISO), but this has become a stupid thread.

 

[Designer]

..the image you will see ..

What you are looking at is the JPEG image that your camera's firmware has generated so you can view the data as a viewable image.

This is not like the analog process of emulsion-based film photography.