Exposure?

[Saorsa]

I saw a tutorial where the tutor set the 'three elements' then he looked at the screen and said it was too dark. He then adjusted a dial (which I thought was an exposure adjustment) which enabled him to lighten or darken the image to his requirements. Is this not exposure?

Ahhh, that control is the Exposure Value (EV). It provides you a way to control the combination of factors that make up exposure based on the settings on your camera.

If you are in something other than manual control mode the EV control will cause a change to the aperture, shutter speed and/or the ISO depending on capabilities and other settings on your camera.

For example you might have auto-ISO set and that tells the camera that it is free to change the ISO as necessary. If that is the case then +1 EV will double the ISO. It can get pretty complex, basically you are allowing the computer in the camera to take control of the factors controlling exposure.

If you are in Aperture mode, the camera may change shutter speed or ISO to give a particular exposure.
If you are in Shutter Priority mode, the camera may change aperture or ISO to give you the identical exposure.

This control has limits however. You can't exceed the maximum or minimum aperture of a lens for example. You may have menu options to make for a maximum ISO or minimum shutter speed and the camera, of course has it's own limits like the lens.

[xpatUSA]

I don't have a technical background, but my understanding is that the basic concept of exposure has not changed since the earliest days of photography. There have always been three aspects: the sensitivity of the material the light is falling upon (whether it's metal, glass, paper, film or an electronic sensor), the amount of time the light is falling on that material and the amount of light being allowed to fall upon that material.

Can't agree, Mike, sorry.

Exposure has long been defined as, e.g., "the amount of light per unit area (the image plane illuminance times the exposure time) reaching a photographic film or electronic image sensor, as determined by shutter speed, lens aperture and scene luminance."

https://en.wikipedia.org/wiki/Exposu...photography%29

Please note that the sensitivity of the material is not mentioned as an aspect.

Getting silly: if I were to replace the sensor or film by a piece of toilet paper the exposure would not be changed a whit.

[Mike Buckley]

Exposure has long been defined as, e.g., "the amount of light per unit area (the image plane illuminance times the exposure time) reaching a photographic film or electronic image sensor, as determined by shutter speed, lens aperture and scene luminance."

This is a classic example of a scientific definition that contradicts other widely recognized definitions and explanations of the concept. It may be scientifically accurate but it is misleading in and of itself for those of us who don't have a scientific background.

[Dave Humphries]

I think Mike's take on the dial being EC (Exposure Compensation) is probably the most likely explanation of what Bertam saw.

Failing that Didace's thought on it being the view of a control in an image editor is another possibility.


Please let's all cease the off-topic/unhelpful discussions of word definitions.


Bertam, it would be useful if you could provide a link to the video you were watching, if possible, or tell us where you saw it, at least - a little more context would help us.

Thanks, Dave

[Mike Buckley]

Please let's all cease the off-topic/unhelpful discussions of word definitions.

Amen to that!

[xpatUSA]

Please let's all cease the off-topic/unhelpful discussions of word definitions.

Thanks, Dave

I will comply with the intent, Dave, while finding it difficult to understand that a correct definition of "Exposure" is off-topic/unhelpful in a thread titled "Exposure"!

In the manner of Galileo, I recant. Putting 400 ASA film in, instead of 100 ASA, does affect the exposure . .

[Dave Humphries]

Thanks Ted,

I guess it was me that started us all off down that line too


It is about getting back to the context of the initial plus follow up query (it being a 'dial' on something) that makes the definition discussion unhelpful to Bertam.

[Donald]

This is one of those threads in which I wish people would look at what a relatively new member has asked. If people want to take the discussion off into another related area to avoid the possibility of totally confusing and intimidating a new member who's trying to learn the basics, then that would be more helpful.

[MrB]

Please let's all cease the off-topic/unhelpful discussions of word definitions.
Thanks, Dave

Much confusion arises (in many areas of life) because words that have perfectly good and simple definitions are used incorrectly, and some people cannot be bothered to change their bad habits.

The definition of exposure is stated clearly and simply in Post #4, as is the effect of the ISO value. If people were to stick to correct definitions, and use the terms correctly and without any need to get technical, others might find it much easier to gain a useful and deeper understanding of the basics.

And even a CiC tutorial writing about the "exposure triangle" doesn't make it right - it is not an exposure triangle, it is an image brightness triangle.

Cheers.
Philip

[xpatUSA]

Ahhh, that control is the Exposure Value (EV). It provides you a way to control the combination of factors that make up exposure based on the settings on your camera.

If you are in something other than manual control mode the EV control will cause a change to the aperture, shutter speed and/or the ISO depending on capabilities and other settings on your camera.

For example you might have auto-ISO set and that tells the camera that it is free to change the ISO as necessary. If that is the case then +1 EV will double the ISO. It can get pretty complex, basically you are allowing the computer in the camera to take control of the factors controlling exposure.

If you are in Aperture mode, the camera may change shutter speed or ISO to give a particular exposure.
If you are in Shutter Priority mode, the camera may change aperture or ISO to give you the identical exposure.

This control has limits however. You can't exceed the maximum or minimum aperture of a lens for example. You may have menu options to make for a maximum ISO or minimum shutter speed and the camera, of course has it's own limits like the lens.

I looked on all my cameras and could not find an Exposure Value (EV) control or function anywhere but the use of caps does imply that such a label exists. While most of us probably realize what is meant by "Exposure Value (EV) control", I'm not convinced that inventing a new term for Exposure Compensation will help Bertam that much.

Perhaps I'm wrong . . does a Canikon have a so-named control? Fuji? Sony?

[george013]

Much confusion arises (in many areas of life) because words that have perfectly good and simple definitions are used incorrectly, and some people cannot be bothered to change their bad habits.

The definition of exposure is stated clearly and simply in Post #4, as is the effect of the ISO value. If people were to stick to correct definitions, and use the terms correctly and without any need to get technical, others might find it much easier to gain a useful and deeper understanding of the basics.

And even a CiC tutorial writing about the "exposure triangle" doesn't make it right - it is not an exposure triangle, it is an image brightness triangle.

Cheers.
Philip

You must distinguish between a measured quantity and a wanted quantity. You're talking about a measured quantity. In photography a wanted quantity is ment, based on the sensitivity of the film or the sensor/amplification. So the exposure trangle is right.

I don't think you can change the iso-setting in pp.

George

[Saorsa]

I looked on all my cameras and could not find an Exposure Value (EV) control or function anywhere but the use of caps does imply that such a label exists. While most of us probably realize what is meant by "Exposure Value (EV) control", I'm not convinced that inventing a new term for Exposure Compensation will help Bertram that much.

Perhaps I'm wrong . . does a Canikon have a so-named control? Fuji? Sony?

Yes, This is the top of Nikon D90


the +/- to the right of the on of switch with a green dot next to it is the EV control.

Canon calls theirs Av adjustment and use the same symbol



and here it is on the Merrill at top right most convenient for the index finger.



I see something similar on the Sigma as Av with a plus and minus

[xpatUSA]

Yes, This is the top of Nikon D90


the +/- to the right of the on of switch with a green dot next to it is the EV control.

Canon calls theirs Av adjustment and use the same symbol



and here it is on the Merrill at top right most convenient for the index finger.



I see something similar on the Sigma as Av with a plus and minus

Brian, we need to discontinue this. None of these buttons are called "Exposure Value".

For example DP Review says:



"Behind this are four buttons; metering mode, exposure compensation, drive mode and AF mode."

And my Sigma SD1M manual says:

" . . press the exposure compensation button . ."

If you want to confuse Bertam by calling these buttons something else, I can't stop you so I'll just shut up . . .

[MrB]

You must distinguish between a measured quantity and a wanted quantity. You're talking about a measured quantity. In photography a wanted quantity is ment, based on the sensitivity of the film or the sensor/amplification. So the exposure trangle is right.

I don't think you can change the iso-setting in pp.

George

The facts in Post #4 are plain, simple, and correct.

Trying to keep it simple, some simple examples, requiring no measurements, just simple observation of the information in the viewfinder or screen:

Exposure:

E.g. 1. I want to use f/11 for more depth of field for this scene; that small aperture will not allow enough light to the sensor for the camera to give a sufficiently bright image, but I can balance that by slowing the shutter speed down to 1/60s, opening the shutter for longer to allow more light to reach the sensor.

E.g. 2. I want to use a shutter speed of 1/500s to freeze the movement of this subject; that will not allow enough light to the sensor for the camera to give a sufficiently bright image, but I can balance that by opening up to f/4, a wider aperture allowing more light to reach the sensor.

Brightening:

E.g. 1. I want to use a shutter speed no slower than 1/100s with this lens, in an attempt to avoid image softening by camera shake. I also want to use f/8 to give a reasonable depth of field. However, these exposure settings will give an image that will be too dark. But I can increase the camera's ISO setting, so that the camera will brighten the image that it produces.

E.g. 2. I want to use a shutter speed no slower than 1/100s with this lens, in an attempt to avoid image softening by camera shake. I also want to use f/8 to give a reasonable depth of field. However, these exposure settings will give an image that will be too dark. But I can use my post processing software to brighten the dark image that the camera produces.

Cheers.
Philip

[DanK]

OK, I think the OP's question has been answered, so I am going to allow myself to respond to the back-and-forth about terminology.

I think Philip is exactly right. That's why, for example, EV (exposure value) is defined without reference to ISO. And while most of us will slip into a colloquial use of terms like "exposure triangle" without any harm being done, I think it is helpful to keep the concepts straight.

I'll give another example to extend Philip's. Suppose I take an underexposed image. Let's say its BADLY underexposed, say, by 4 stops. I then open the image in software and try to correct for this underexposure. Just for the sake of illustration, let's say it's photoshop, and the tool I use to compensate for my underexposure is the levels tool. I just crank up the brightness until it has the brightness it would have had if it had been properly exposed. Would anyone then say that it was a properly exposed image? I wouldn't. It wasn't properly exposed; I just compensated in software.

Increasing ISO is technically different, but it is in principle exactly the same: it compensates for underexposure by amplifying the signal from the sensor. In fact, in the case of ISO-less sensors, you will get pretty much the same result regardless of which way you compensate.

Sometimes this won't matter in practice, but sometimes it does.

[bertam]

What an interesting discussion! I've learned so much, even when we went a little off topic it was still beneficial. What I'm taking away from the discussion is this; having set the three pillars and still finding the image too light or dark, an additional setting (which has different names on different cameras) called EV overrides the original settings to lighten or darken the image. Thank to everyone your input is really appreciated. Sorry I couldn't provide the link as was requested. I tend to trawl the net without taking particular notice of the location.

[Mike Buckley]

And while most of us will slip into a colloquial use of terms like "exposure triangle" without any harm being done

For the record, I didn't "slip" into anything. Everything I've been taught about photography from my first days in the mid-1980s by a Kodak series of books about the basics of photography is that exposure is comprised of three values, exactly as explained in the CiC tutorial. To learn today for the first time that there is another definition is alarming. It's especially alarming to be artfully informed by Philip that "some people can't be bothered to change their bad habits." If he wants to include me in that group, that's very shamefully his problem, not mine. I didn't come to my understanding by a series of bad habits and I'm reasonably confident that there is an entire community of photographers that the same is true for them.

Not only there is no harm being done for using so-called colloquial terminology, it's actually extremely helpful to use it because such a large number of photographers if not the vast majority of photographers have been trained to use that terminology. If someone wants to use terminology that is so-called correct but understood by only 10% of the community of photographers as opposed to using terminology that is so-called incorrect but clearly understood for practical application by 90% of the community of photographers, that person in my mind is a LOT more interested in being able to stand in the camp of being so-called correct rather than in the camp of effectively communicating with photographers the practical application of the tools available to them.

Do I understand how to practically apply the tools of exposure in the real world of photography? You betcha! I knew how to do it with film photography and I know how to do it with digital photography. Do I understand the scientific definition of those tools? Apparently not. Do I care? Not in the slightest.

Pluto used to be a planet. Though Pluto didn't change, it's no longer a planet. Thank the scientists for those two "facts."

[xpatUSA]

Now that we've helped Bertam to the extent that he now understands that "an additional setting (which has different names on different cameras) called EV overrides the original settings to lighten or darken the image." (my emphasis) . . .

. . . I'll continue my recant, started earlier

ISO is an essential part of The Triangle, which would collapse and become meaningless without it.

There is no such Standard as ISO 12232 - the very definition of the acronym "ISO" used for The Triangle.

Even if there were such a Standard, it does not contain, in Section 4.2:

" . . . where Ha is the arithmetic mean focal plane exposure, expressed in lux-seconds (lx⋅s)"

Neither does this non-existent Standard make any other references to "exposure" on page after page after page after page . . .

So I must conclude that exposure is just the brightness of an image after all . . and rebut any suggestion that my Sigma raw data is not immediately affected by "an amplifier" in-camera any time I touch the ISO knob.

And the Earth, of course, is flat.

[DanK]

Pluto used to be a planet. Though Pluto didn't change, it's no longer a planet. Thank the scientists for those two "facts."

Whether Pluto is considered a planet is a classification, not a fact. What changed is the facts available to astronomers about Pluto and its environs, which led people to suggest changing the classification. One could use a different classification. That wouldn't change the facts. An explanation can be found here.

But we digress, as Gail Collins likes to write.

I don't think there is any need for acrimony here. Mike, I didn't accuse you of anything; if anything, I put you and me in the same boat.

And I don't think only 10% of people understand this. People are just inconsistent in their terminology. I'll wager than in the example I gave--underexposing by 4 stops and brightening in software--you too would not call the image properly exposed.

[Mike Buckley]

I don't think there is any need for acrimony here.

Agreed. I have no acrimony whatsoever.

Mike, I didn't accuse you of anything

Also completely agreed.