Exposure triangle explanation please.

Started Jul 9, 2013 | Questions
Tan68
Tan68 Veteran Member • Posts: 5,778
Re: Not exactly

TTMartin wrote:

You're forcing your photographic technique on the definition of photographic exposure. You camera isn't ISOless you just don't use other ISOs.

In my previous post, I said I understand 'ISO-less' cameras. It is a confusing term to me and I better say I believe I understand it.

ISO camera = my K20 where it really was better to raise ISO in camera; in some situations, I got lower noise using a higher ISO.

ISO-less camera = K5 where the noise levels are about the same whether use ISO in camera or in PP. I am still not convinced this is true through the entire range... My K20 only showed benefits to 1600 and after that, PP was the same.

So, yeah, they choose to not use other ISO. I still prefer to lift as little as possible in PP. Maybe it makes no diff, but I figure if I have to apply gain somewhere... may as well be in the camera. Anyway.

ADDED: and for anyone wondering why I wouldn't add exposure (Tv/Av-style), I mean a situation where I no longer care to increase physical exposure by lengthening shutter or whatever.  The constraints of the image require the depth of field or shutter I have set.  So, gain must be applied.  Or, ISO increased.

... Without a photographic medium you can't have an exposure.

How can you have any exposure if you don't load your medium ?

Your definition of exposure works for a film camera with no film in it.

mmm... You sound like a true Table 2 guy instead of a Table 1 fellow.

All of the things you say are photographic exposure can be done, shutter speed and aperture, etc. And yes, the empty back of the camera was exposed to light, but, there was NO PHOTOGRAPHIC EXPOSURE. You can not have photographic exposure void of a photographic medium.

Why not ? It's digital :^|

- - - - PS - loved the flux thing

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JTC111 Contributing Member • Posts: 505
Re: Not exactly
2

texinwien wrote:

I predict that ISO will mostly go away within a decade. For some of us, it already has. I, for instance, have a mostly ISO-less camera. I shoot RAW and almost always at base ISO, then apply the appropriate amount of gain in my post-processing step.

You're defeating your own argument.  A "mostly ISO-less camera" is an ISO camera.  You shoot "almost always at base ISO..."  Both of those statements indicate that you, like most everyone else that has a good working knowledge of photography, adjusts their ISO when necessary.  Like you, I like to keep my ISO at the base number, 100 in my case.  I only increase it if the amount of available light is insufficient for me to get the shot I want.  I don't know anybody who has a preference for a high ISO setting if a lower one is up to the task at hand.

ISO has been a factor in photography for a long time.  The nice thing about ISO on a DSLR is that we no longer have to make a commitment to a particular ISO for 36 shots.  But without the ability to adjust ISO, there are many pictures for which we'd have to sacrifice artistic sensibilities or we wouldn't be able to take at all.

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texinwien Veteran Member • Posts: 3,326
Re: Not exactly
1

Guidenet wrote:

I read the article several times and though I respect the writer, I think it is another regurgitated explanation using the Wiki article. I think it analogous with the "The Emperor's New Clothes" tale.

I would like to say that I disagree, but it's stronger than that. This is a question of right and wrong, not a question of opinion, and the writer of that article is simply right, whether you agree/understand or not.

Note, I'm not trying to be disrespectful or in any way rude to you - just telling it like it is.

I think we try to take definitions from physics and try to apply it to a different scenario in photography.

The physics is written in stone and was written in stone long before humans, let alone cameras or artificial concepts like ISO came along.

The idea that it quacks and has webbed feet makes it a duck, might be closer to the mark. When I use my camera, I can use the control of the ISO dial in such a way as to change the saved RAW file.

Assuming nothing else changed when you used the ISO dial (i.e., neither shutter speed nor aperture changed), and that the only change wasn't the ISO value that was saved in the EXIF, your camera is not an ISOless one.

As soon as you switch to an ISOless camera, changing the ISO dial alone (not allowing it to affect any other settings on the camera) will no longer change the saved RAW file, other than the ISO value saved in the EXIF information.

That's a duck, call it what you will. I can also change EV-L or scene brightness and all else being equal, I also affect the RAW capture. I realize this might be brightness applied after the event, but the overall effect is the same. It quacked again. I'm sure it's a duck.

Please clarify.

The idea of ignoring ISO as one of the tools to control exposure seems to be a poor way to both explain it to novice photographers and to understand it in general use as well. Fair enough?

I don't think so. Let's assume the novice can't control scene luminance (he has no flash and isn't in a studio with adjustable lighting).

If he forgets about ISO, he can now focus on the two remaining variables under his control. How is it harder to focus on just two variables rather than on three? I can tell you - it's not. I shoot this way. I ignore ISO and only have to keep two variables in mind. I leave the application of gain (i.e. ISO) until after the fact. That is, rather than the novice juggling three variables before he captures his exposure, I juggle only two and leave the third until later.

Leaving the third until later also means I'm not stuck with a bad gain decision I made at the time of exposure. There is no reason to force the user to choose the necessary gain before he presses the shutter release button. Forcing him to do that makes the act of taking a photograph MORE complicated, not less.

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Tan68
Tan68 Veteran Member • Posts: 5,778
Re: Not exactly
1

Tan68 wrote:

mmm... You sound like a true Table 2 guy instead of a Table 1 fellow.

The only use I can think of for Table 1, EV, without describing sensitivity of the medium or gain applied in PP is as a shortcut way of describing exposure parameters.

Alone, it tells me nothing about your shooting environment.  If I told you EV 0, you would know I shot at an equivalent to f/8 and 60 seconds.  The parameters.

However, without sensitivity or gain, there is no information about what makes a properly exposed image for the environment I was in...

My shot at EV 0 parameters may be exposed right or under exposed.  No real way to know.  To obtain an image for viewing, a photographic exposure, ISO/gain must be involved.

I suppose ISO/gain could be truly ignored if I always 'shot at base' and applied no gain, but the reality is sometimes I need a faster shutter than would allow for a properly exposed image so I must apply gain.  etc.

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JTC111 Contributing Member • Posts: 505
Re: Not Necessary
1

texinwien wrote:

It's already not necessary on some cameras. On my current camera, I almost always shoot at base ISO. I ignore the ISO completely.

Add this capability to the ability to quickly adjust an exposure's gain in-camera, and ISO is simply thing of the past. Good riddance

Two questions:

If you " almost always shoot at base ISO," as you've stated in at least two different posts, then you occasionally do adjust your ISO setting, right?
If you rarely adjust your ISO setting, why are you acting like the availability of ISO adjustment, which is of great use to many of us, is akin to a festering boil on your butt cheek?
I don't understand why the existence of this tool is such an issue for you.

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texinwien Veteran Member • Posts: 3,326
Re: Not exactly
1

JTC111 wrote:

texinwien wrote:

I predict that ISO will mostly go away within a decade. For some of us, it already has. I, for instance, have a mostly ISO-less camera. I shoot RAW and almost always at base ISO, then apply the appropriate amount of gain in my post-processing step.

You're defeating your own argument.

I'm not. I'm being honest here. My camera is barely ISOful. It makes sense for me to use ISO 200 and ISO 400. My camera goes to ISO 28,800.

A "mostly ISO-less camera" is an ISO camera.

No, there is a difference between a truly ISOful camera and a mostly ISOless camera. The important thing, however, is that more and more cameras are truly ISOless, and my argument is that when all cameras are truly ISOless, it will no longer make sense to talk about ISO.

You shoot "almost always at base ISO..." Both of those statements indicate that you, like most everyone else that has a good working knowledge of photography, adjusts their ISO when necessary. Like you, I like to keep my ISO at the base number, 100 in my case. I only increase it if the amount of available light is insufficient for me to get the shot I want. I don't know anybody who has a preference for a high ISO setting if a lower one is up to the task at hand.

No, you're off here. I use three ISO settings on my camera. I use ISO 200 in abundant light and ISO 400 or 800 in lower light. This means, in lower light, that I end up with underexposed images that I have to brighten in post processing. Basically, my camera is ISOful at ISO 200, 400 and ISO 800 and is ISOless above that.

I do not use ISO like you do most likely. My camera goes to ISO 28,800. Because my camera is ISOless above ISO 800, though, I ignore all of those higher ISOs and often end up with 'underexposed' images to which I must apply gain in post processing.

ISO has been a factor in photography for a long time. The nice thing about ISO on a DSLR is that we no longer have to make a commitment to a particular ISO for 36 shots. But without the ability to adjust ISO, there are many pictures for which we'd have to sacrifice artistic sensibilities or we wouldn't be able to take at all.

The last sentence is wrong. On an ISOless sensor, you can leave the sensor on base ISO ALWAYS and apply gain in post processing, if you're shooting RAW.

Eventually, this is how cameras will work - they will be completely ISOless, the ISO setting will go away, and you will be able to apply appropriate gain after you've taken the photo, allowing you to focus only on shutter speed and aperture.

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Jeff Veteran Member • Posts: 5,091
could also be called auto ISO ...

texinwien wrote:

Limburger wrote:

It's a matter of formulae and definitions. But photographically by whatever ISO will be replaced it will be in relation with shutterspeed and aperture just in the fashion it is now.

You need not know how the internal combustion engine works in order to drive a car.

It's already not necessary on some cameras. On my current camera, I almost always shoot at base ISO. I ignore the ISO completely.

I focus only on the aperture and shutter speed necessary to get the desired DOF and the desired freezing of subject movement, always trying to get as much light on my sensor as possible. In low-light situations, I just choose the aperture and shutter speed I need for artistic purposes, knowing that I'll end up with a noisier image.

Later, I apply the necessary gain to my photos to make them as bright as I want them.

You see, I'm able to forget about ISO, completely. I focus only on the 3 actual variables that are a part of the exposure equation - scene luminance, shutter speed and aperture. No need to confuse the issue with the ISO, since it's just applying gain. Why should I choose the gain applied before I take the photo? There's no good reason to if you're shooting RAW and applying the gain yourself later on.

Once this is possible in-camera for JPEG shooters, the concept of ISO is simply confusing baggage that can be jettisoned.

Furthermore, my camera, the OM-D E-M5 has a function that shows me, in the live few, which highlights I'm about to blow. This allows me to quickly adjust shutter speed and aperture to get the optimal exposure (most light possible without blowing important highlights - leads to the least visible noise in the resulting exposure) in situations where light is abundant.

Add this capability to the ability to quickly adjust an exposure's gain in-camera, and ISO is simply thing of the past. Good riddance

There's a lot that agree with in this post. What you're relying on, of course, is that your camera has enough dynamic range that you can postpone the determination of {gain|ISO|image brightness} until PP. With modern sensors in larger formats that can work as you've indicated within reason. Depending on tolerance for noise in your images, you'll have 4-5 stops of head room to work with. In effect, you're working in an auto-ISO mode where gain is determined at the end to produce the final image.

I've been fooling around a lot lately with iPhone photography (don't judge, I enjoy the challenge and am having fun with it) where dynamic range is very limited. Shooting base ISO is basically forced because there is so little head room on the sensor. The f-stop is fixed, too, so effectively the only knob left to control image brightness is shutter speed. The point is that the small sensor format forces a different approach to exposure than the one you describe. At least for me, controlling {ISO|gain} at the time of exposure is still a very important aspect of creating the final image.

When the day comes that sensors -- both small and large -- have as much headroom as we encounter in typical photography situations, say 12-15 stops of headroom, then we can chuck {ISO|gain}. Until then, I'd rather hang onto the knob, or some proxy of it.

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TTMartin
TTMartin Veteran Member • Posts: 7,304
Re: Not Necessary
1

texinwien wrote:

Once this is possible in-camera for JPEG shooters, the concept of ISO is simply confusing baggage that can be jettisoned.

Furthermore, my camera, the OM-D E-M5 has a function that shows me, in the live few, which highlights I'm about to blow. This allows me to quickly adjust shutter speed and aperture to get the optimal exposure (most light possible without blowing important highlights - leads to the least visible noise in the resulting exposure) in situations where light is abundant.

Add this capability to the ability to quickly adjust an exposure's gain in-camera, and ISO is simply thing of the past. Good riddance

So the definition of photographic exposure should be changed because of the way you use your OM-D?

Even if you say that all gain is done in camera, there is still a base sensitivity of your cameras sensor. And that sensitivity is expressed in internationally standardized number.

Someone gave the example of images in wood. Even the sensitivity of wood could be calculated, and expressed as an internationally standardized number.

So, if you wanted to put an object on a piece of board, and leave it exposed to light, you would know how much light the board would need to be exposed to before the shape of the object was recognizable as an image on the board. Now one person might like there to be more or less contrast to that image, and they could determine the amount of light required to do that.

So if you want to take a natural light photo of a couple standing in a rose garden with your OM-D, would you do that on moonless night?

Of course you wouldn't because you know sensor doesn't have enough sensitivity to pickup enough light in that situation, and no amount of in camera gain is going to change that.

But, how would you know that before you purchased the camera? Because the sensitivity of the sensor and the in camera gain available has been expressed by the manufacturer in an internationally standardized number.

You can not divorce the sensitivity of the photographic media to light, from the photographic process. And for photography that sensitivity is expressed in an internationally standardized number called ISO.

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texinwien Veteran Member • Posts: 3,326
Re: Not Necessary
2

JTC111 wrote:

texinwien wrote:

It's already not necessary on some cameras. On my current camera, I almost always shoot at base ISO. I ignore the ISO completely.

Add this capability to the ability to quickly adjust an exposure's gain in-camera, and ISO is simply thing of the past. Good riddance

Two questions:

If you " almost always shoot at base ISO," as you've stated in at least two different posts, then you occasionally do adjust your ISO setting, right?

As I posted elsewhere, my camera is ISOless above ISO 800. It has ISO settings up to 25,600, but since it's ISOless above 800, I ignore the higher settings.

If you rarely adjust your ISO setting, why are you acting like the availability of ISO adjustment, which is of great use to many of us, is akin to a festering boil on your butt cheek?

Because it leads to confusion. You, for example, are confused about what ISO does on an ISOless sensor, a fact that is made clear by your questions here.

I don't understand why the existence of this tool is such an issue for you.

What you don't understand is that the existence of this 'tool' is useless to you, assuming you have a camera with an ISOless sensor. And eventually, when all cameras have ISOless sensors, this 'tool' will be useless to everyone.

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Tan68
Tan68 Veteran Member • Posts: 5,778
Re: Not exactly
1

texinwien wrote:

TTMartin wrote:

Whether the plane is photosensitive is the entire point of PHOTOGRAPHIC EXPOSURE.

Practically all planes are photosensitive. Some are just more sensitive than others.

Again, you have defined exposure, just NOT photographic exposure.

There is only exposure. There is no special photographic exposure.

This is becoming a tit for tat argument of semantics.  I don't mean that with a negative connotation.  I mean it literally.

One adhering to 'physics' and pin hole cameras made from granite and tree trucks while the other insists we discuss exposure within the context at hand, photography performed with cameras as popularly defined.

The esoteric concept that the shadow of a picture frame on the wall after that picture from has been hanging for 10 years is actually a form of photography is interesting, though.

...  And again, if changing the ISO setting on your camera doesn't affect the sensitivity of the light-gathering medium (the sensor), of what use is ISO as a concept?

Do you apply gain in PP ?

So, I decide I will not adjust ISO in camera and, in the end, that means what?  Really?  Gain must be applied somewhere...

If ISO doesn't have any relation to the sensitivity of the medium, what good is it to us?

Darn ISO.

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JTC111 Contributing Member • Posts: 505
Re: Not exactly
1

I think you've boxed yourself into a ridiculous argument and now you're committed to trying to win it through some silly semantics game.

texinwien wrote:

JTC111 wrote:

texinwien wrote:

I predict that ISO will mostly go away within a decade. For some of us, it already has. I, for instance, have a mostly ISO-less camera. I shoot RAW and almost always at base ISO, then apply the appropriate amount of gain in my post-processing step.

You're defeating your own argument.

I'm not. I'm being honest here. My camera is barely ISOful. It makes sense for me to use ISO 200 and ISO 400. My camera goes to ISO 28,800.

A "mostly ISO-less camera" is an ISO camera.

No, there is a difference between a truly ISOful camera and a mostly ISOless camera. The important thing, however, is that more and more cameras are truly ISOless, and my argument is that when all cameras are truly ISOless, it will no longer make sense to talk about ISO.

This is like that old adage about how you can't be a little bit pregnant.  A camera either lacks the ability to adjust ISO or it doesn't.  This nonsense about "mostly" ISO-less is a semantic invention you've come up with.  It's rubbish.

You shoot "almost always at base ISO..." Both of those statements indicate that you, like most everyone else that has a good working knowledge of photography, adjusts their ISO when necessary. Like you, I like to keep my ISO at the base number, 100 in my case. I only increase it if the amount of available light is insufficient for me to get the shot I want. I don't know anybody who has a preference for a high ISO setting if a lower one is up to the task at hand.

No, you're off here. I use three ISO settings on my camera. I use ISO 200 in abundant light and ISO 400 or 800 in lower light. This means, in lower light, that I end up with underexposed images that I have to brighten in post processing. Basically, my camera is ISOful at ISO 200, 400 and ISO 800 and is ISOless above that.

I do not use ISO like you do most likely. My camera goes to ISO 28,800. Because my camera is ISOless above ISO 800, though, I ignore all of those higher ISOs and often end up with 'underexposed' images to which I must apply gain in post processing.

Now here you are contradicting your previous statements.  You say you use ISO 100, 200, 400, and 800.  Why do you use 800 on occasion?  That's a rhetorical question; we both know why.  You use it because without its availability, you wouldn't be able to get the shot you want the way you want it.

ISO has been a factor in photography for a long time. The nice thing about ISO on a DSLR is that we no longer have to make a commitment to a particular ISO for 36 shots. But without the ability to adjust ISO, there are many pictures for which we'd have to sacrifice artistic sensibilities or we wouldn't be able to take at all.

The last sentence is wrong. On an ISOless sensor, you can leave the sensor on base ISO ALWAYS and apply gain in post processing, if you're shooting RAW.

Eventually, this is how cameras will work - they will be completely ISOless, the ISO setting will go away, and you will be able to apply appropriate gain after you've taken the photo, allowing you to focus only on shutter speed and aperture.

If I can't adjust ISO on the camera, I can't always get the shot I want how I want it.  I adjust my ISO upwards from 100 for the same reasons you do.  It that adjustment isn't available, we don't get the picture.  It's that simple.  Stop trying to be clever.

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texinwien Veteran Member • Posts: 3,326
Re: could also be called auto ISO ...
2

Jeff wrote:

texinwien wrote:

Limburger wrote:

It's a matter of formulae and definitions. But photographically by whatever ISO will be replaced it will be in relation with shutterspeed and aperture just in the fashion it is now.

You need not know how the internal combustion engine works in order to drive a car.

It's already not necessary on some cameras. On my current camera, I almost always shoot at base ISO. I ignore the ISO completely.

I focus only on the aperture and shutter speed necessary to get the desired DOF and the desired freezing of subject movement, always trying to get as much light on my sensor as possible. In low-light situations, I just choose the aperture and shutter speed I need for artistic purposes, knowing that I'll end up with a noisier image.

Later, I apply the necessary gain to my photos to make them as bright as I want them.

You see, I'm able to forget about ISO, completely. I focus only on the 3 actual variables that are a part of the exposure equation - scene luminance, shutter speed and aperture. No need to confuse the issue with the ISO, since it's just applying gain. Why should I choose the gain applied before I take the photo? There's no good reason to if you're shooting RAW and applying the gain yourself later on.

Once this is possible in-camera for JPEG shooters, the concept of ISO is simply confusing baggage that can be jettisoned.

Furthermore, my camera, the OM-D E-M5 has a function that shows me, in the live few, which highlights I'm about to blow. This allows me to quickly adjust shutter speed and aperture to get the optimal exposure (most light possible without blowing important highlights - leads to the least visible noise in the resulting exposure) in situations where light is abundant.

Add this capability to the ability to quickly adjust an exposure's gain in-camera, and ISO is simply thing of the past. Good riddance

There's a lot that agree with in this post. What you're relying on, of course, is that your camera has enough dynamic range that you can postpone the determination of {gain|ISO|image brightness} until PP. With modern sensors in larger formats that can work as you've indicated within reason. Depending on tolerance for noise in your images, you'll have 4-5 stops of head room to work with. In effect, you're working in an auto-ISO mode where gain is determined at the end to produce the final image.

It's even better with my current camera, since my camera tells me which highlights will blow before I release the shutter. When light is abundant, this allows me to maximize the amount of light that hits the sensor without blowing important highlights, leading to the absolute best possible exposure (with the highest SNR possible) given the scene's luminance, plus the aperture and shutter speed dictated by my artistic goals.

I've been fooling around a lot lately with iPhone photography (don't judge, I enjoy the challenge and am having fun with it) where dynamic range is very limited. Shooting base ISO is basically forced because there is so little head room on the sensor. The f-stop is fixed, too, so effectively the only knob left to control image brightness is shutter speed. The point is that the small sensor format forces a different approach to exposure than the one you describe. At least for me, controlling {ISO|gain} at the time of exposure is still a very important aspect of creating the final image.

Why, though? How does it help to set the gain before you take the image, and to not be able to adjust that after the image is taken? Switch to your idea of auto ISO and an ISOless sensor, and let the user adjust the gain after the fact, if they want to. This is better than forcing the user to choose the gain before taking the photo, then not making it possible to change the gain after the photo has been taken.

In short, the gain is applied AFTER the exposure has been captured. Why force a user to make a permanent, unchangeable decision about gain before the exposure is captured, if the gain won't be applied until afterwards, anyway.

When the day comes that sensors -- both small and large -- have as much headroom as we encounter in typical photography situations, say 12-15 stops of headroom, then we can chuck {ISO|gain}. Until then, I'd rather hang onto the knob, or some proxy of it.

Again, if your camera shows you which highlights will blow given a scene's luminance and your shutter speed and aperture choices, you need much less headroom.

Even in cases where your camera doesn't do this, you only need to know the 'saturation ISO' of the sensor, if the sensor is ISOless. I know that the saturation ISO on my sensor is ISO 107, so I can calculate safe exposure values even if the function that warns me about highlights that are about to blow is turned off.

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JTC111 Contributing Member • Posts: 505
Re: Not Necessary
2

texinwien wrote:

What you don't understand is that the existence of this 'tool' is useless to you, assuming you have a camera with an ISOless sensor. And eventually, when all cameras have ISOless sensors, this 'tool' will be useless to everyone.

If it's useless, why do you occasionally adjust your ISO to 800?

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Jeff Veteran Member • Posts: 5,091
You're fixating on one idea of photography ...
2

texinwien wrote:

The last sentence is wrong. On an ISOless sensor, you can leave the sensor on base ISO ALWAYS and apply gain in post processing, if you're shooting RAW.

Eventually, this is how cameras will work - they will be completely ISOless, the ISO setting will go away, and you will be able to apply appropriate gain after you've taken the photo, allowing you to focus only on shutter speed and aperture.

We're not there yet, and you're fixating on only one form/style of photography.

First, not all of us want to shoot images at ISO 28,800 with dslrs.  We may prefer to constrain ISO to lower values to keep down noise, and are glad to accept the creative constraints to do so.  We want to know and perhaps constrain the {ISO|gain} at the time of exposure to have control over DR and noise in the final image.

Perhaps dslr sensors will have 20 stops of dynamic range in the not-so-distant future.  But that will be a longer time coming for the smallest format sensors which also have their creative uses.  For those folks ISO|gain will continue to be an important consideration at the time of exposure.

Guidenet
Guidenet Forum Pro • Posts: 15,748
Great Job Texinwien but,
2

texinwien wrote:

Jeff wrote:

There is confusion, no doubt. But just replacing ISO with gain is rather minor tweak. It'd be nice, sure. But recasting it all in terms of what's happening at the sensor plane might not be the best way to resolve the confusion for most people.

What I really care about are the image attributes, like image brightness relative to scene brightness, depth of field, motion blur, perspective, dynamic range, color. That we control them in terms ISO, sensor size, saturation, sensor efficiency, f-stop, focal length, etc., are all artifacts of the equipment and medium.

One of these things is not like the others. On an ISOless sensor, ISO has no effect on anything but the image brightness relative to scene brightness. That is, it's simply gain, and it's something that you should be able to simply adjust after the fact.

Being able to adjust gain after the fact allows you to focus on the only parameters that really matter, shutter speed, aperture and scene luminance. ISO just muddies the water on an ISOless camera.

If you're going to restructure the camera interface, why not do it terms of final image attributes. Sort of a stripped down version of the Lightroom Develop panel where I can set brightness, shadows, highlights, color and tint, clarity, etc. Now that would be truly useful, imho.

Sure - it's already possible in some cameras. Still, my point is that you shouldn't have to choose your gain BEFORE you take the picture. It's an extra, unnecessary variable that you shouldn't have to keep in mind when choosing settings. Given static scene luminance, the only variables you should think about are shutter speed (freeze motion) and aperture (DOF). Why throw the third variable into the mix, when it can just as easily be changed after the fact? Let the camera choose the gain automatically, for all I care, and allow the user to adjust it easily after the fact.

No need to force the user to choose the gain before he takes the picture.

Tex, good morning.

I think most of us truly understand what ISO is today. You've done a good job of clearing up some questions I had. I understand it better because of your excellent explanations.

On the other hand, ISO is a handy way of discussing brightness with regards to adjusting gain up front. In fact, when I'm adjusting it up front, I'm really not. I'm still after the fact, I suppose, but the information is stored in the RAW file and had an effect on the viewed image. It gives me an idea as to the default RAW view maybe helping me to guess as to how far I can push it after the fact.

Also, as Jeff says, what's wrong with using the existing ISO model to describe this effect regardless on when it takes place? It seems to me the only confusing part is introduced when you wish to change the model and how it describes it.

I think there is no need to change the current model application except to benefit prominents of smaller, more noisy sensors. By only being able to describe a sensor's ability to take gain in post and by considering it to be strictly a post applied process, we not only change the way we describe the process, but we alter a way to easily measure the ability of a sensor to output data that can accept increased gain without noise.

I note the demand every year or so to lose the ISO description is often led or spearheaded by 4/3rd owners and other crop sensor proponents. Not always, because there are often a lot of wannabes willing to jump on any bandwagon in order to look clever (Please believe and I promise I'm not describing you). After a month, this phenomena seems to dissipate and we continue on with our typical description of gain as ISO. People who own cameras that handle noise better seem to have no issue with the current ISO usage. So is there an alternate motive? Probably only subconsciously. One would naturally support something which has recognizable benefits to them. People who don't see an issue, would not. As a user of mostly three full fame cameras, including a Nikon D3S, I see no issue with the current method of describing gain.

So, for most people, I don't see any reason to change how we describe an effect which looks and acts the same for both sides.

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bobn2
bobn2 Forum Pro • Posts: 58,622
Re: The explanation of the triangle
5

Sir Carrington wrote:

The triangle itself is a visual representation of exposure.

No it isn't

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 has two values that affect exposure - the f-number and shutter speed, and leaves off the other part, which is scene luminance. It's popularity leads to a misunderstanding the 'exposure' means 'output image brightness'. It doesn't.

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Bob

texinwien Veteran Member • Posts: 3,326
Re: Not Necessary
2

TTMartin wrote:

texinwien wrote:

Once this is possible in-camera for JPEG shooters, the concept of ISO is simply confusing baggage that can be jettisoned.

Furthermore, my camera, the OM-D E-M5 has a function that shows me, in the live few, which highlights I'm about to blow. This allows me to quickly adjust shutter speed and aperture to get the optimal exposure (most light possible without blowing important highlights - leads to the least visible noise in the resulting exposure) in situations where light is abundant.

Add this capability to the ability to quickly adjust an exposure's gain in-camera, and ISO is simply thing of the past. Good riddance

So the definition of photographic exposure should be changed because of the way you use your OM-D?

On the contrary - the definition of photographic exposure (photometric / luminous exposure) will never be changed, since it's based on incontrovertible laws of physics

Even if you say that all gain is done in camera, there is still a base sensitivity of your cameras sensor. And that sensitivity is expressed in internationally standardized number.

This is true - that is the only sensitivity that's important on an ISOless camera, and it doesn't have to be expressed in ISO numbers. When every camera has a single real ISO, the concept of ISO is just garbage. Talk about the sensor's sensitivity and jettison the outdated and confusing concept of ISO.

Someone gave the example of images in wood. Even the sensitivity of wood could be calculated, and expressed as an internationally standardized number.

I gave that example, and you're right, it could. It could also be expressed in some other way. The point is, having an ISO dial and having to set ISO before you take a photo doesn't make sense on a camera with an ISOless sensor (even if the sensor is made of wood, which I suspect would not have a variable sensitivity to light)

So, if you wanted to put an object on a piece of board, and leave it exposed to light, you would know how much light the board would need to be exposed to before the shape of the object was recognizable as an image on the board. Now one person might like there to be more or less contrast to that image, and they could determine the amount of light required to do that.

What? I was with you up until the last sentence. What does that last sentence have to do with ISO, exposure, or anything else we've discussed here?

So if you want to take a natural light photo of a couple standing in a rose garden with your OM-D, would you do that on moonless night?

Well, if I was out on a moonless night and the opportunity presented itself, I might. Of course, the laws of physics dictate that I would probably end up with a very noisy image, whether I kept the ISO at base and applied my gain later on, or upped the ISO to the max of 25,600.

Of course you wouldn't because you know sensor doesn't have enough sensitivity to pickup enough light in that situation, and no amount of in camera gain is going to change that.

No amount of adjusting the ISO is going to change it, either, so, what is the point?

But, how would you know that before you purchased the camera? Because the sensitivity of the sensor and the in camera gain available has been expressed by the manufacturer in an internationally standardized number.

That's actually not true. The manufacturers don't usually share the sensitivity ISO of the sensors. You have to wait for someone like DXOMark to test the sensors out. Olympus says the base ISO on the OM-D is 200. DXOMark says it's 107. I've found that DXOMark is correct, in this case.

You can not divorce the sensitivity of the photographic media to light, from the photographic process.

No, you can't.

And for photography that sensitivity is expressed in an internationally standardized number called ISO.

I would like to invite you to read up on the definition of ISO - I have spent a lot of time doing just that over the past year. Feel free to quote the part of the standard that you consider to be proof of your last sentence above.

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texinwien Veteran Member • Posts: 3,326
Re: Not exactly
2

Tan68 wrote:

texinwien wrote:

... And again, if changing the ISO setting on your camera doesn't affect the sensitivity of the light-gathering medium (the sensor), of what use is ISO as a concept?

Do you apply gain in PP ?

I do, as I have said multiple times in this discussion

So, I decide I will not adjust ISO in camera and, in the end, that means what? Really? Gain must be applied somewhere...

It means, why should I be forced to pick the gain before I record the exposure? It's an artificial thing to force a photographer to choose the gain before he activates the shutter, and to, furthermore, apply the gain in a permanent and unchangeable way.

It made sense when cameras were ISOful. When cameras are no longer ISOful, what sense does it make to force the photographer to choose how much gain to apply before he takes the photo?

None, is how much, in my opinion

If ISO doesn't have any relation to the sensitivity of the medium, what good is it to us?

Darn ISO.

Darn ISO, indeed.

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bobn2
bobn2 Forum Pro • Posts: 58,622
Re: Not exactly
3

TTMartin wrote:

texinwien wrote:

clack wrote:

texinwien wrote:

For starters, ISO is not a variable in the exposure equation. The three variables in the exposure equation are:

  1. Scene Illuminance
  2. F-stop (actually T-stop, to be 100% correct)
  3. Shutter Speed

APEX camera exposure equation:

A: relative aperture (f-number)
T: shutter speed in seconds
B: average scene luminance ("brightness")
Sx: ASA arithmetic film speed (ISO goes here)
K: light meter calibration constant

K is a constant, B is not part of the camera settings.
This leaves the camera operator - or, camera control chip - with A, T and Sx.

Voila, the exposure triangle is part of 'the' exposure equation...

That's the wrong formula. It's an artificial formula built specifically to tell the photographer how to adjust the exposure values (aperture, shutter speed, scene luminance) to match the ASA / ISO.

Exposure (photography)

In photography, exposure is the amount of light allowed to fall on each area unit of a photographic medium (photographic film or image sensor) during the process of taking a photograph.

Note: Nothing about ASA or ISO above, and neither ASA nor ISO have any effect on the amount of light allowed to fall on each area unit of a photographic medium.

Exposure is measured in lux seconds, and can be computed from exposure value (EV) and scene luminance in a specified region.

What's EV, and how do we calculate it? Let's see:

Exposure Value

EV corresponds simply to a combination of a shutter speed and an aperture setting, independent of any ISO setting—independent even of whether there is film in the camera or any light available.

...

So, Exposure can be computed from scene luminance and EV (which, in turn is computed from the shutter speed and aperture setting). This leads us back to my previous post - the only 3 variables involved in the equation used to determine photometric exposure are scene luminance, shutter speed and aperture setting (or t-stop to be extra technical).

From the Exposure article linked above, this is the equation (photometric / luminous exposure) you need:

Hv is the exposure, Ev is the image plane illuminance (determined by the scene luminance and aperture setting) and t is time (aka the shutter speed).

et voila, APEX isn't the equation used to determine photometric exposure. It's simply a formula that photographers can use to adjust the three variables that make up the photometric exposure equation - shutter speed, aperture and scene luminance (where possible) - based on a given ASA or ISO.

Interesting how that Wiki article has been manipulated through the years, to imply that photographic exposure has nothing to do with the photographic medium. It has been changed from a definition of photographic exposure. To simply one of light exposure, which is incorrect.

No, it's correct. The definition now used concurs with all the classic sensitometry texts, including my old Focal (Ilford) Manual of Photography, which I had before the Web existed. the present definition is definitely not something thought up by Wikipedia, it is the correct and science based definition of exposure.

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Bob

TTMartin
TTMartin Veteran Member • Posts: 7,304
Re: Not Necessary
1

texinwien wrote:

JTC111 wrote:

texinwien wrote:

It's already not necessary on some cameras. On my current camera, I almost always shoot at base ISO. I ignore the ISO completely.

Add this capability to the ability to quickly adjust an exposure's gain in-camera, and ISO is simply thing of the past. Good riddance

Two questions:

If you " almost always shoot at base ISO," as you've stated in at least two different posts, then you occasionally do adjust your ISO setting, right?

As I posted elsewhere, my camera is ISOless above ISO 800. It has ISO settings up to 25,600, but since it's ISOless above 800, I ignore the higher settings.

So analog gain of the sensor changes the sensors ISO, but, digital manipulation of the image of the image after capture doesn't?

I can agree with that.

As a RAW shooter, I also only use ISOs that are created by analog amplification of the sensor. I have partial ISO steps disabled in my camera, and do not enable the expanded high ISO.

But, in order for a photographer to determine the optimum exposure they desire, they need to know both the sensitivity of the sensor and digital gain available (if they choose to use it).

Without knowing the sensitivity of the sensor, you can not determine how long to leave your shutter open, or how large an aperture you need.

Do you propose requiring all manufactures to use the same sensor sensitivity?

If a manufacture came out with a sensor with 23EV of dynamic range, should they be required to set the base sensor sensitivity at ISO 100?

Or should they be free to choose what base sensor sensitivity that they felt appropriate?

If you rarely adjust your ISO setting, why are you acting like the availability of ISO adjustment, which is of great use to many of us, is akin to a festering boil on your butt cheek?

Because it leads to confusion. You, for example, are confused about what ISO does on an ISOless sensor, a fact that is made clear by your questions here.

I don't understand why the existence of this tool is such an issue for you.

What you don't understand is that the existence of this 'tool' is useless to you, assuming you have a camera with an ISOless sensor. And eventually, when all cameras have ISOless sensors, this 'tool' will be useless to everyone.

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