ISO seems like global brightness - True?

[keano12]

I know how to work ISO, Shutter and Aperture. Thing to me is that I tend to view ISO as a global brightness. It makes the whole image brighter. Is this simple analogy close enough the way I view it?

 

[mostlyboringphotog]

I know how to work ISO, Shutter and Aperture. Thing to me is that I tend to view ISO as a global brightness. It makes the whole image brighter. Is this simple analogy close enough the way I view it?

Just to understand you better, what would be non-global brightness? Unless you are burning or dodging, most setting affect the whole image. ;-)

 

[Tom Axford]

I know how to work ISO, Shutter and Aperture. Thing to me is that I tend to view ISO as a global brightness. It makes the whole image brighter. Is this simple analogy close enough the way I view it?

In simple terms, yes.

However, you need to also be aware that because of the way ISO is implemented in the camera, as you increase ISO (keeping the same shutter speed and aperture), the brightness increases, but also the noise in the image increases. So, if you have the choice, the best image quality is normally achieved at the base ISO.

In other words, it is often better to increase the shutter speed or increase the aperture (decrease the f-number) instead of increasing the ISO.

 

[keano12]

I know how to work ISO, Shutter and Aperture. Thing to me is that I tend to view ISO as a global brightness. It makes the whole image brighter. Is this simple analogy close enough the way I view it?

Just to understand you better, what would be non-global brightness? Unless you are burning or dodging, most setting affect the whole image. ;-)

I'm sorry maybe I'm wording wrong LOL. What I mean is if I am using a flash and increase shutter speed the background gets darker and area ivy flash stays the same but ISO increases all light.

So if my flash was struggling outside I could increase the ISO to make it easier for the flash.

 

[cookedraw]

I know how to work ISO, Shutter and Aperture. Thing to me is that I tend to view ISO as a global brightness. It makes the whole image brighter. Is this simple analogy close enough the way I view it?

It is a very good analogy. Shutter speed and aperture change the captured image , motion blur, depth of field and sharpness.

ISO don't do that . It is very similar to the brightness setting on your tv. It is a good analogy . Thumbs up !

 

[keano12]

I know how to work ISO, Shutter and Aperture. Thing to me is that I tend to view ISO as a global brightness. It makes the whole image brighter. Is this simple analogy close enough the way I view it?

In simple terms, yes.

However, you need to also be aware that because of the way ISO is implemented in the camera, as you increase ISO (keeping the same shutter speed and aperture), the brightness increases, but also the noise in the image increases. So, if you have the choice, the best image quality is normally achieved at the base ISO.

In other words, it is often better to increase the shutter speed or increase the aperture (decrease the f-number) instead of increasing the ISO.

Right that I got. Cool thanks

 

[TacticDesigns]

I know how to work ISO, Shutter and Aperture. Thing to me is that I tend to view ISO as a global brightness. It makes the whole image brighter. Is this simple analogy close enough the way I view it?

Just to understand you better, what would be non-global brightness? Unless you are burning or dodging, most setting affect the whole image. ;-)

I'm sorry maybe I'm wording wrong LOL. What I mean is if I am using a flash and increase shutter speed the background gets darker and area ivy flash stays the same but ISO increases all light.

So if my flash was struggling outside I could increase the ISO to make it easier for the flash.

Yes. And No?

All 3 of those settings can "brighten" the image. But each one is tied to another aspect that can affect the look of the picture.

Aperture, if you open it up, can let in more light, but that affects the depth of field that is captured.

Shutter speed, if you slow it down can let in more light, but that affects the amount of motion blur (or lack of) as well.

Increase the iso can increase the brightness of the final image, but (as some one has pointed out) with the potential of more image noise and perhaps with reduced dynamic range?

Take care & Happy Shooting!



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[mostlyboringphotog]

I know how to work ISO, Shutter and Aperture. Thing to me is that I tend to view ISO as a global brightness. It makes the whole image brighter. Is this simple analogy close enough the way I view it?

In simple terms, yes.

However, you need to also be aware that because of the way ISO is implemented in the camera, as you increase ISO (keeping the same shutter speed and aperture), the brightness increases, but also the noise in the image increases. So, if you have the choice, the best image quality is normally achieved at the base ISO.

In other words, it is often better to increase the shutter speed or increase the aperture (decrease the f-number) instead of increasing the ISO.

This thread could max out but increasing ISO does not increase the nosiness. The reason for higher ISO is because there is not enough light, and less light means more noisy image. ISO makes it simply brighter at the rendering level. At the signal acquisition level, "ISO dial" plays additional functions.

You could keep the shutter speed slower to keep the ISO low for the subject that are static, that may not be viable, always.

ISO number simply tells the SW algorithm how to interpret the mid point of gray when rendering JPEG.

What complicates the issue is that digital cameras also uses the ISO setting to apply the signal gain that has the effect of increasing the sensor sensitivity somewhat analogous to the faster films.

 

[J A C S]

If you keep the aperture and the speed the same, the ISO makes the JPEG brighter, indeed, and clips the highlights if there are such for that exposure.

It is a bit more than that because the ISO setting for most sensors and ISO levels works on sensor/ADC level and affects the RAW before being converted to JPEG. Then it could add a different amount of noise, etc.

Contrary to the popular wisdom, raising the ISO (keeping aperture and speed the same)does not increase the noise (the noise-to-signal level). It actually decreases it somewhat, which is he whole point of having that control. It could clip the highlights, though.

 

[Tom Axford]

This thread could max out but increasing ISO does not increase the nosiness. The reason for higher ISO is because there is not enough light, and less light means more noisy image. ISO makes it simply brighter at the rendering level.

For those who are determined to be obtuse, increasing the ISO increases the visibility of the noise in the darker parts of the scene by brightening those parts (along with everything else in the image).

For practical purposes, this means that noise may become obvious at high ISO that was less much less visible at low ISO.

I suspect mostlyboringphotog already knows all this, but just wanted to show how smart he is.

I'm also sure he'll start throwing abuse at me for pointing this out, but I do not intend to respond further! This topic has been fruitlessly argued over many times in the past.

 

[mostlyboringphotog]

This thread could max out but increasing ISO does not increase the nosiness. The reason for higher ISO is because there is not enough light, and less light means more noisy image. ISO makes it simply brighter at the rendering level.

For those who are determined to be obtuse, increasing the ISO increases the visibility of the noise in the darker parts of the scene by brightening those parts (along with everything else in the image).

FWIW, I'll agree that higher ISO increases the visibility of the noise in the darker part. Similar effect occurs when the shadow is boosted. I have not thought of that as increase of noise but certainly would not disagree that higher ISO makes noise more visible. I think it's a good point.

For practical purposes, this means that noise may become obvious at high ISO that was less much less visible at low ISO.

I suspect mostlyboringphotog already knows all this, but just wanted to show how smart he is.

I'm also sure he'll start throwing abuse at me for pointing this out, but I do not intend to respond further! This topic has been fruitlessly argued over many times in the past.

 

[J A C S]

This thread could max out but increasing ISO does not increase the nosiness. The reason for higher ISO is because there is not enough light, and less light means more noisy image. ISO makes it simply brighter at the rendering level.

For those who are determined to be obtuse, increasing the ISO increases the visibility of the noise in the darker parts of the scene by brightening those parts (along with everything else in the image).

Right but irrelevant because what matters is the SNR (or NSR).

For practical purposes, this means that noise may become obvious at high ISO that was less much less visible at low ISO.

Not really because for practical purposes, our high ISO photos do not look brighter.

 

[Tom Axford]

This thread could max out but increasing ISO does not increase the nosiness. The reason for higher ISO is because there is not enough light, and less light means more noisy image. ISO makes it simply brighter at the rendering level.

For those who are determined to be obtuse, increasing the ISO increases the visibility of the noise in the darker parts of the scene by brightening those parts (along with everything else in the image).

FWIW, I'll agree that higher ISO increases the visibility of the noise in the darker part. Similar effect occurs when the shadow is boosted. I have not thought of that as increase of noise but certainly would not disagree that higher ISO makes noise more visible. I think it's a good point.

For practical purposes, this means that noise may become obvious at high ISO that was less much less visible at low ISO.

I suspect mostlyboringphotog already knows all this, but just wanted to show how smart he is.

I'm also sure he'll start throwing abuse at me for pointing this out, but I do not intend to respond further! This topic has been fruitlessly argued over many times in the past.

Thank you for a more gracious reply than I expected (or probably deserved)!

 

[mostlyboringphotog]

This thread could max out but increasing ISO does not increase the nosiness. The reason for higher ISO is because there is not enough light, and less light means more noisy image. ISO makes it simply brighter at the rendering level.

For those who are determined to be obtuse, increasing the ISO increases the visibility of the noise in the darker parts of the scene by brightening those parts (along with everything else in the image).

Right but irrelevant because what matters is the SNR (or NSR).

Well, I think Standard Deviation reflects the noisiness of the image file better than SNR.

SNR of the viewing image can be different depending on how the viewing image is derived.

For practical purposes, this means that noise may become obvious at high ISO that was less much less visible at low ISO.

Not really because for practical purposes, our high ISO photos do not look brighter.

Consider an M mode with lower ISO and higher ISO...

 

[cookedraw]

This thread could max out but increasing ISO does not increase the nosiness. The reason for higher ISO is because there is not enough light, and less light means more noisy image. ISO makes it simply brighter at the rendering level.

For those who are determined to be obtuse, increasing the ISO increases the visibility of the noise in the darker parts of the scene by brightening those parts (along with everything else in the image).

FWIW, I'll agree that higher ISO increases the visibility of the noise in the darker part. Similar effect occurs when the shadow is boosted. I have not thought of that as increase of noise but certainly would not disagree that higher ISO makes noise more visible. I think it's a good point.

For practical purposes, this means that noise may become obvious at high ISO that was less much less visible at low ISO.

I suspect mostlyboringphotog already knows all this, but just wanted to show how smart he is.

I'm also sure he'll start throwing abuse at me for pointing this out, but I do not intend to respond further! This topic has been fruitlessly argued over many times in the past.

Thank you for a more gracious reply than I expected (or probably deserved)!

You see above that brightness can be used to explain the visible noise too .

"I made a shot at night with brightness set too high. The image came out too bright."

Brightness explains it all by a simple and correct way without complication. Brilliant. Remember this cause it is a good analogy for the younger people that did not shoot film.

 

[baloo_buc]

In Canon world it is exactly as you described. In the other sensors increasing ISO is worse than keeping the ISO down and then brightening the resulting RAW in PP.

If I use Nikon D7200 at ISO 100 and the photo is underexposed 3 stops I get better results for noise in PP brightening than making the same photo at ISO 800 (so 3 stops). After 3 stops there are some penalties (some weird amp noise) so I try to stay quite within that range. The same applies to ISO 1600 and ISO 12800.

In all cases the DR is reduced.

@OP: The analogy with brightness is partially correct as it clips the highlights but it also increase the amount of perceivable noise.

 

[J A C S]

In Canon world it is exactly as you described. In the other sensors increasing ISO is worse than keeping the ISO down and then brightening the resulting RAW in PP.

If I use Nikon D7200 at ISO 100 and the photo is underexposed 3 stops I get better results for noise in PP brightening than making the same photo at ISO 800 (so 3 stops).

So Nikon engineers made a mistake by making ISO 800 hardware based instead of pushing ISO 100 by 3 stops?

See this, think of this as the situation you describe but both shots are pushed 2 stops more. The colors change when you shoot at low ISO. You may argue that you do not see much difference but to claim that it is better, except for the non-clipped highlights, is a big stretch.

 

[baloo_buc]

The friends that have Canon sensors are horrified by underexposure and recovering shadows. Perhaps it's another approach of applying ISO.

All Sony sensors lately behave like that. It seems also the newer Canon sensors are going in the same direction. In older sensor Nikon result was similar with Canon (If you used the right ISO not to get underexposure you got a much more clean image, from 2 stops pushing was a mess).

Maybe Canon is more profit driven and they preferred to keep the R&D cost at low level for years and keep using the similar design for sensors maybe adding some PDAF sensor on them but practically they used the same sensor from Canon 7D to Canon 700D (2009-2013). They started to change the policy when MFT caught them up.

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[Iliah Borg]

So Nikon engineers made a mistake by making ISO 800 hardware based instead of pushing ISO 100 by 3 stops?

See this, think of this as the situation you describe but both shots are pushed 2 stops more. The colors change when you shoot at low ISO. You may argue that you do not see much difference but to claim that it is better, except for the non-clipped highlights, is a big stretch.

It's a bit more complicated, the problem is the linearity in the deep shadows and black level drifting; IMHO ISO 400 and ISO 800 are a bit more stable than 3200, and much more stable than ISO 100 (processing on all - white balance from second grey, rather crude, linear brightness adjustment, no colour transforms, no anything else). If you want TIFFs, let me know and I will process and upload.









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[Iliah Borg]

The friends that have Canon sensors are horrified by underexposure and recovering shadows.

Wait a minute, I'm horrified with underexposure of more than 2 stops on any camera, and on my Nikon Df or D5 I'm horrified of not setting ISO right too