What is the difference between increasing ISO and exposure compensation

Michael Firstlight said:

Lysdexic said:

If I have scene that is too dark, is it better to increase the ISO or use exposure compensation? What is the difference between the two?

Thank you.

Peter

Click to expand...

After reading all these posts I thought maybe there something ridiculously basic that I've missed in over 45 years of experience (I do that because i have an open mind and always consider points of view contrary to my own). Then I thought about it a little more and realized what I've been thinking for decades - that faster film speeds (ASA as we used to call it) or higher ISO (newer term for film and digital) is really about nothing more than increased light sensitivity of the recording material we can choose when we have nothing else to use when there isn't enough light and can't artificially manufacture more light.

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You need to be careful because digital ISO doesn't really affect the sensitivity of the recording media.

Remember, light is comprised of photons, and essentially the sensor is simply counting how may photons hit each pixel. The counts are not entirely accurate as there is noise in the system.

However, if there aren't any photons counted at ISO 100, then there won't be any photons counted at ISO 12800. If we are counting 10,000 photons at ISO 100, then we are still counting 10,000 photons at ISO 12800.

What the ISO setting does is inform how we interpret that count. At a low ISO setting we may map that count to a dark area. At a high ISO that same count may represent a bright area of the image. We really haven't changed the input sensitivity of anything.

Now in simplistic cases, thinking of ISO as affecting the sensitivity of the camera will give a reasonable prediction. However if you ever want to be able to predict difficult situations, or want to know what's really going on under the hood, you should realize that ISO is not a sensitivity control. It doesn't change the data we get, it changes how we process that data.

Michael Firstlight said:

For exposure compensation I've always seen it as simply a correction adjustment for the light meter that is is getting fooled by the existing light (like a backlit scene). Exposure compensation actual adds nothing in terms of additional sensor sensitivity to make up for lack of sufficient light when there is no other acceptable option via aperture, shutter speed or addition of more (real) light.

Why is it any more complicated than that?

Click to expand...

That is exactly what exposure compensation does. It alters the bias of the metering system.

The name "exposure compensation" is no longer an accurate name. This can be confusing when applied to digital cameras. In the old days, when you biased the meter, the camera's only option was to adjust the exposure (light on the sensor). Thus biasing the meter resulted in a change in exposure.

With modern cameras, the camera might have the option of adjusting the ISO. Thus when you bias the meter, it might leave the exposure the same, and simply adjust the ISO to lighten/darken the JPEG.

Consider a camera in shutter priority mode with ISO set to AUTO. You've set the shutter to 1/60, the camera has decided to open the lens wide open, and has selected ISO 200. If you now dial in +1 "exposure compensation" the camera will leave the exposure unchanged (f/3.5, 1/60) and raise the ISO to 400. The exposure (light on the sensor) stays the same (the camera has no available option to increase it), but the camera can select a higher ISO. This is a case of digital "exposure compensation," not changing "exposure."

Michael Fryd said:

My advice to you is:

• If your camera offers Image Stabilization (AKA Vibration Reduction), then turn it on. This will help reduce motion blur from camera shake.
• Open up the aperture to a wide value. However, as you open up the aperture, you get shallower depth of field. Make sure you don't open too wide, or your entire subject may not look in focus. There are online depth of field calculators that will help you determine high wide you can go and still maintain your needed depth of field.
• Use the slowest shutter speed that doesn't result in motion blur (either from camera movement or subject movement). If your subject is static (such as art in a museum) you will benefit from a tripod (if the museum allows it). For a hand held camera, the general rule to avoid blur from camera motion is to use a shutter speed faster than 1/(AFL * CF) where "AFL" is the actual focal length of your lens, and "CF" is your camera's crop factor.
• If you are setting aperture and shutter manually according to the above rules, put the camera into Auto-ISO mode. Your aperture and shutter speed will allow you to capture the highest exposure circumstance allows. Auto-ISO will give you a reasonable lightness in your JPEG.

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Boom.

This is the answer.

Michael Fryd said:

fishy wishy said:

Michael Fryd said:

When in manual mode, think of ISO as being a lightness control. Higher ISO yields a lighter result.

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No it doesn't. People use higher iso when they accept they are going to be exposing an image in a way that creates more noise..

You are wasting everybody's time trying to reinvent the wheel according to your own ivory tower worded specification.

Everyday photographers don't change the iso in manual mode to brighten the image. If you think that's what happens in the real world outside of your ivory tower theorising, you must have a piece missing.

Normal people will adjust aperture and shutter speed until they see the exposure come to about 0 in the viewfinder. Not over. Not under. They won't be using the iso to 'lighten' the image, 'brighten' the image, or even gaslighting it like you do. Even if they use auto iso, the auto iso only functions not to push the iso out of a preprogrammed limit or the shutter speed below a preprogrammed limit. It's not there to give ludicrously bright or dark images when you open them in your post-processing.

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Imagine you are in a dimly lit room. You are not allowed to use flash. Your camera is set to ISO 100. Your shutter speed is set to 1/30. Any slower and your subjects look blurry. Your lens is wide open at f/3.5. You are shooting JPEG.

Your camera produced JPEGs look too dark. You can't put more light on the subject, you can't open up the aperture any further, you can't use a slower shutter speed.

In such a situation I would use a higher ISO in order to make the camera produced JPEG lighter.

It sounds like you think this is not the correct solution. What would you suggest?

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I believe this is the relevant bit of the point that fishy wishy was making...

"People use higher iso when they accept they are going to be exposing an image in a way that creates more noise"

Michael Firstlight said:

After reading all these posts I thought maybe there something ridiculously basic that I've missed in over 45 years of experience (I do that because i have an open mind and always consider points of view contrary to my own). Then I thought about it a little more and realized what I've been thinking for decades - that faster film speeds (ASA as we used to call it) or higher ISO (newer term for film and digital) is really about nothing more than increased light sensitivity of the recording material we can choose when we have nothing else to use when there isn't enough light and can't artificially manufacture more light.

For exposure compensation I've always seen it as simply a correction adjustment for the light meter that is is getting fooled by the existing light (like a backlit scene). Exposure compensation actual adds nothing in terms of additional sensor sensitivity to make up for lack of sufficient light when there is no other acceptable option via aperture, shutter speed or addition of more (real) light.

Why is it any more complicated than that?

Mike

Click to expand...

At the risk of opening up the whole ISO vis a vis exposure horse that's been beaten to a rotting corpse, this may be beneficial reading for many: https://www.dpreview.com/articles/8...on-t-know-what-iso-means-and-that-s-a-problem

Michael Fryd said:

Michael Firstlight said:

After reading all these posts I thought maybe there something ridiculously basic that I've missed in over 45 years of experience (I do that because i have an open mind and always consider points of view contrary to my own). Then I thought about it a little more and realized what I've been thinking for decades - that faster film speeds (ASA as we used to call it) or higher ISO (newer term for film and digital) is really about nothing more than increased light sensitivity of the recording material we can choose when we have nothing else to use when there isn't enough light and can't artificially manufacture more light.

Click to expand...

You need to be careful because digital ISO doesn't really affect the sensitivity of the recording media.

Remember, light is comprised of photons, and essentially the sensor is simply counting how may photons hit each pixel. The counts are not entirely accurate as there is noise in the system.

However, if there aren't any photons counted at ISO 100, then there won't be any photons counted at ISO 12800. If we are counting 10,000 photons at ISO 100, then we are still counting 10,000 photons at ISO 12800.

What the ISO setting does is inform how we interpret that count. At a low ISO setting we may map that count to a dark area. At a high ISO that same count may represent a bright area of the image. We really haven't changed the input sensitivity of anything.

Now in simplistic cases, thinking of ISO as affecting the sensitivity of the camera will give a reasonable prediction. However if you ever want to be able to predict difficult situations, or want to know what's really going on under the hood, you should realize that ISO is not a sensitivity control. It doesn't change the data we get, it changes how we process that data.

Michael Fryd said:

For exposure compensation I've always seen it as simply a correction adjustment for the light meter that is is getting fooled by the existing light (like a backlit scene). Exposure compensation actual adds nothing in terms of additional sensor sensitivity to make up for lack of sufficient light when there is no other acceptable option via aperture, shutter speed or addition of more (real) light.

Why is it any more complicated than that?

Click to expand...

That is exactly what exposure compensation does. It alters the bias of the metering system.

The name "exposure compensation" is no longer an accurate name. This can be confusing when applied to digital cameras. In the old days, when you biased the meter, the camera's only option was to adjust the exposure (light on the sensor). Thus biasing the meter resulted in a change in exposure.

With modern cameras, the camera might have the option of adjusting the ISO. Thus when you bias the meter, it might leave the exposure the same, and simply adjust the ISO to lighten/darken the JPEG.

Consider a camera in shutter priority mode with ISO set to AUTO. You've set the shutter to 1/60, the camera has decided to open the lens wide open, and has selected ISO 200. If you now dial in +1 "exposure compensation" the camera will leave the exposure unchanged (f/3.5, 1/60) and raise the ISO to 400. The exposure (light on the sensor) stays the same (the camera has no available option to increase it), but the camera can select a higher ISO. This is a case of digital "exposure compensation," not changing "exposure."

Click to expand...

Question? Do you write these replies out fresh each time, or do you have a list of copy and paste replies saved.?

Krav Maga said:

Michael Firstlight said:

After reading all these posts I thought maybe there something ridiculously basic that I've missed in over 45 years of experience (I do that because i have an open mind and always consider points of view contrary to my own). Then I thought about it a little more and realized what I've been thinking for decades - that faster film speeds (ASA as we used to call it) or higher ISO (newer term for film and digital) is really about nothing more than increased light sensitivity of the recording material we can choose when we have nothing else to use when there isn't enough light and can't artificially manufacture more light.

For exposure compensation I've always seen it as simply a correction adjustment for the light meter that is is getting fooled by the existing light (like a backlit scene). Exposure compensation actual adds nothing in terms of additional sensor sensitivity to make up for lack of sufficient light when there is no other acceptable option via aperture, shutter speed or addition of more (real) light.

Why is it any more complicated than that?

Mike

Click to expand...

At the risk of opening up the whole ISO vis a vis exposure horse that's been beaten to a rotting corpse, this may be beneficial reading for many: https://www.dpreview.com/articles/8...on-t-know-what-iso-means-and-that-s-a-problem

Click to expand...

Yah, I had read that article too - a good one, and I get it, but I use these controls as a reference point to get the images I want - not as an engineering project. There are good points in the article and some good counterpoints in the comments as well, but with dozens of factors to consider when shooting I'd miss many shots if I thought through it all at that level of detail. I think that's where the OP was coming from - what's the operational difference in practical terms, not in the terms only an EE could appreciate LOL.

Mike

Michael Fryd said:

Michael Firstlight said:

Lysdexic said:

If I have scene that is too dark, is it better to increase the ISO or use exposure compensation? What is the difference between the two?

Thank you.

Peter

Click to expand...

After reading all these posts I thought maybe there something ridiculously basic that I've missed in over 45 years of experience (I do that because i have an open mind and always consider points of view contrary to my own). Then I thought about it a little more and realized what I've been thinking for decades - that faster film speeds (ASA as we used to call it) or higher ISO (newer term for film and digital) is really about nothing more than increased light sensitivity of the recording material we can choose when we have nothing else to use when there isn't enough light and can't artificially manufacture more light.

Click to expand...

You need to be careful because digital ISO doesn't really affect the sensitivity of the recording media.

Remember, light is comprised of photons, and essentially the sensor is simply counting how may photons hit each pixel. The counts are not entirely accurate as there is noise in the system.

However, if there aren't any photons counted at ISO 100, then there won't be any photons counted at ISO 12800. If we are counting 10,000 photons at ISO 100, then we are still counting 10,000 photons at ISO 12800.

What the ISO setting does is inform how we interpret that count. At a low ISO setting we may map that count to a dark area. At a high ISO that same count may represent a bright area of the image. We really haven't changed the input sensitivity of anything.

Now in simplistic cases, thinking of ISO as affecting the sensitivity of the camera will give a reasonable prediction. However if you ever want to be able to predict difficult situations, or want to know what's really going on under the hood, you should realize that ISO is not a sensitivity control. It doesn't change the data we get, it changes how we process that data.

Michael Fryd said:

For exposure compensation I've always seen it as simply a correction adjustment for the light meter that is is getting fooled by the existing light (like a backlit scene). Exposure compensation actual adds nothing in terms of additional sensor sensitivity to make up for lack of sufficient light when there is no other acceptable option via aperture, shutter speed or addition of more (real) light.

Why is it any more complicated than that?

Click to expand...

That is exactly what exposure compensation does. It alters the bias of the metering system.

The name "exposure compensation" is no longer an accurate name. This can be confusing when applied to digital cameras. In the old days, when you biased the meter, the camera's only option was to adjust the exposure (light on the sensor). Thus biasing the meter resulted in a change in exposure.

With modern cameras, the camera might have the option of adjusting the ISO. Thus when you bias the meter, it might leave the exposure the same, and simply adjust the ISO to lighten/darken the JPEG.

Consider a camera in shutter priority mode with ISO set to AUTO. You've set the shutter to 1/60, the camera has decided to open the lens wide open, and has selected ISO 200. If you now dial in +1 "exposure compensation" the camera will leave the exposure unchanged (f/3.5, 1/60) and raise the ISO to 400. The exposure (light on the sensor) stays the same (the camera has no available option to increase it), but the camera can select a higher ISO. This is a case of digital "exposure compensation," not changing "exposure."

Click to expand...

Yes, I can see how that is accurate that it is technically a matter of processing. I do recall reading that nothing changes the amount of photons hitting the sensor, and that increasing ISO increases the amplification applied to the sensor - enabling the sensor's wells to capture more of those available photons - not creating more of them, and that the resulting noise is an artifact of the impact on the adjacent pixels - hence when necessary, increase the ISO enough to capture the available photons but not too much or the adjacent wells get over saturated and increase noise. I'm over my head here and not sure if all of that is accurate, but it is how I interpreted some of the reading I did. One thing of which I'm fairly certain is the photons we fail to grab at the time of capture can't be manufactured later in post processing.

Mike

Mike

Lysdexic said:

If I have scene that is too dark, is it better to increase the ISO or use exposure compensation? What is the difference between the two?

Thank you.

Peter

Click to expand...

It depends on the photo you're making.
In many landscape photo situations, the photographer has the option of dialing-in an ISO (often at or near base) corresponding to an exposure that will maximize the camera's dynamic range. As a general rule, that's good. An f-stop delivering a preferred depth of field can be used and then a shutter speed that will maximize exposure without blowing out highlights.

If the metering mode the photographer likes to use is recommending a shutter speed producing an exposure more than 1/3-stop from what the photographer wants, EC can be used in the field to dial-in a compensation that will indicate being on-meter at a shutter speed producing the desired exposure. Or, make a mental note to ignore the meter and use the shutter speed that will deliver the goods.

When shooting sports or another fast action scenario, the photographer may want to use a fast shutter speed (1/1000 or faster) to freeze action. It's common in sports photography to use a fast f-stop as the large aperture blows out the background to better isolate the subject. If shooting wide open at 1/1000 (or faster) delivers a dark image at base ISO, I would recommend increasing ISO to at least a level where the sensor is ISO invariant.

An ISO invariant sensor has a range of ISOs within which, at the same exposure settings (shutter speed and f-stop) and with negligible impact on image quality, you can use an ISO in the field that will deliver a desired image lightness or use a lower ISO and brighten the photo in your image editing app of choice. Bill Claff's excellent site (http://www.photonstophotos.net/Charts/PDR_Shadow.htm ) is a great resource for identifying the range or ranges within which your camera is invariant.

Personally when photographing birds, sports or other fast action, I Iike to capture images within a half-stop or less of the final lightness. This is one reason I normally use auto ISO for birds and outdoor sports. Under the constant lighting of an indoor venue, I still shoot in full manual.

Of course, there is much more to photography than landscapes and sports. I chose these because they illustrate the diverse approaches one can take to making a pleasing photo. I guess what I'm saying is, there's no easy pat answer to your question. Every photographer needs to go through a process of trying and refining their use of these tools to find what works for them.

Lysdexic said:

If I have scene that is too dark, is it better to increase the ISO or use exposure compensation? What is the difference between the two?

Thank you.

Peter

Click to expand...

From my understanding, increasing ISO increases the sensitivity of the sensor which increases the exposure. Adjusting the Exposure Comp, changes the brightness of the outcome. Thus, could impact the sensitivity of the camera. And I suspect that will differ between camera's type and technology.

Badwater said:

From my understanding, increasing ISO increases the sensitivity of the sensor which increases the exposure.

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That is almost always incorrect. Until recently there has been only one sensitivity for any particular sensor, and changing ISO only causes changes in how a signal is processed downstream after the sensor receives it.

Some new cameras have dual sensitivity technology that kicks in at a specific ISO setting; but even so, all other ISO changes still only affect how the signals are processed downstream from the sensor.

Badwater said:

Lysdexic said:

If I have scene that is too dark, is it better to increase the ISO or use exposure compensation? What is the difference between the two?

Thank you.

Peter

Click to expand...

From my understanding, increasing ISO increases the sensitivity of the sensor which increases the exposure. Adjusting the Exposure Comp, changes the brightness of the outcome. Thus, could impact the sensitivity of the camera. And I suspect that will differ between camera's type and technology.

Click to expand...

Don’t confuse “image lightness” with “exposure”.

Image lightness is how light or dark the image looks. Exposure is how much light hits the sensor.

The same exposure can produce a dark or light image depending on the ISO setting. F/3.5 at 1/60 might produce a dark image at ISO 100 and a light image at ISO 6400. Same exposure, different ligthness.

If the camera is in an auto mode, raising the ISO usually results in a lower exposure. When you select the higher ISO, the camera’s metering system targets a lower exposure (less light)

Lysdexic said:

If I have scene that is too dark, is it better to increase the ISO or use exposure compensation? What is the difference between the two?

Thank you.

Peter

Click to expand...

My compensation changes shutter speed, not ISO.

stevo23 said:

Lysdexic said:

If I have scene that is too dark, is it better to increase the ISO or use exposure compensation? What is the difference between the two?

Thank you.

Peter

Click to expand...

My compensation changes shutter speed, not ISO.

Click to expand...

I thought it could work either way, dependent on your camera settings.

stevo23 said:

Lysdexic said:

If I have scene that is too dark, is it better to increase the ISO or use exposure compensation? What is the difference between the two?

Thank you.

Peter

Click to expand...

My compensation changes shutter speed, not ISO.

Click to expand...

Most cameras do offer that option. Generally you have a choice of allowing the camera to change any one, any two, or all three of aperture, shutter and ISO.

Michael Fryd said:

stevo23 said:

Lysdexic said:

If I have scene that is too dark, is it better to increase the ISO or use exposure compensation? What is the difference between the two?

Thank you.

Peter

Click to expand...

My compensation changes shutter speed, not ISO.

Click to expand...

Most cameras do offer that option. Generally you have a choice of allowing the camera to change any one, any two, or all three of aperture, shutter and ISO.

Click to expand...

Offer that option?

Good grief.

After using three different Canon DSLRs in mostly Av mode and a couple of Fuji cameras over the last 16 years, EC always changed shutter speeds.

Alex Ethridge said:

stevo23 said:

Lysdexic said:

If I have scene that is too dark, is it better to increase the ISO or use exposure compensation? What is the difference between the two?

Thank you.

Peter

Click to expand...

My compensation changes shutter speed, not ISO.

Click to expand...

I thought it could work either way, dependent on your camera settings.

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Not sure how I would change my compensation dial to do otherwise. I can set bracketing to do something differently.

Michael Fryd said:

stevo23 said:

Lysdexic said:

If I have scene that is too dark, is it better to increase the ISO or use exposure compensation? What is the difference between the two?

Thank you.

Peter

Click to expand...

My compensation changes shutter speed, not ISO.

Click to expand...

Most cameras do offer that option. Generally you have a choice of allowing the camera to change any one, any two, or all three of aperture, shutter and ISO.

Click to expand...

Not sure I see the point of bracketing with anything other than shutter speed unless it's not for exposure compensation.

I can do special modes in my camera that bursts with sets of iso or special effects. But compensation is shutter speed if I'm using my dial.

fishy wishy said:

Normal people use exposure compensation.

Advanced people use manual mode and maybe spot metering.

Argumentative people say there's no such thing as ISO.

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No they don't!

.

.

.

fishy wishy said:

Take your pick.

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rurikw said:

Lysdexic said:

If I have scene that is too dark, is it better to increase the ISO or use exposure compensation? What is the difference between the two?

Click to expand...

The way I think about it is that If you want to lighten up your image in camera the first thing is to check if you can increase exposure ie. lower shutter speed or enlarge the aperture.

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Yes!

rurikw said:

If that's not possible, raise ISO at the cost of a noisier photo.

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Noisier than what? It won't be noisier than a photo with the same aperture and shutter but lower ISO. It will be noisier then the photo you would have had if you could have increased exposure. Since your premise is that it wasn't possible to raise exposure, there is no noise cost.

rurikw said:

Using EC can do either depending on mode. I mostly shoot in aperture priority and use EC to adjust exposure with a fixed ISO. I have to keep watch on shutter speed and adjust ISO if It's getting too low. But I don't always remember that when things happen too fast so have lately started using auto ISO more. Which means the camera determines when the shutter speed can't be lowered and raises ISO to maintain output lightness.

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Good adaptation!

rurikw said:

The relationship between EC and ISO isn't quite straightforward. A more appropriate term might be lightness control.

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Agreed!

rurikw said:

The main thing IMHO is to be aware of what's going on with aperture, shutter speed and ISO and try to optimize without getting too caught up.

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Tony Beach said:

mamallama said:

Tony Beach said:

rapick said:

Just take care: here you might find incorrect, fallacious and misleading answers!

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Though likely challenged.

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with other incorrect, fallacious and misleading answers!

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Not everything you read is that.

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Oh! I thought Mama was volunteering to provide some!