Exposure and ISO

[lct]

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1 hour ago, DadDadDaddyo said:

[...] Even if operating under partial or full automation, we value the ability to intervene in the decision making with tools like "exposure compensation."
But if I have to start influencing the decision making of the automation to get the result I want, it starts to become less convenient. [...]

Or more convenient. In auto iso M mode, both apertures and shutter speeds can be set manually while iso settings are automatic. Hardly a practical issue for those considering iso as part of exposure, and even less so for those who deny that.

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[jaapv]

3 hours ago, lct said:

Or more convenient. In auto iso M mode, both apertures and shutter speeds can be set manually while iso settings are automatic. Hardly a practical issue for those considering iso as part of exposure, and even less so for those who deny that.

Better replace "deny that" by "are aware that exposure is the amount of light hitting the sensor"

[pgk]

5 hours ago, DadDadDaddyo said:

For many photographers, on the other hand, manual control is a straightforward and simple prerequisite to making the photographs one has visualized.

I never use the 'A' setting on my Ms (and extremely rarely on other cameras). Manual exposure is surprisingly effective unless lighting is shifting dramatically and continuously and under such conditions it is eaqually difficult for autmation to adjust as I might want it to either. With manual exposure I understand what is happening and the interaction between lighting and exposure. With automation this is less easy. I don't really understand the logic of many automated features. They can work reasonably but have a tendency to become a solution rather than increasing understanding of exposure and what works and what does not. Not sure that there's anything romantic about manual exposure control though.

[LocalHero1953]

13 hours ago, jaapv said:

Better replace "deny that" by "are aware that exposure is the amount of light hitting the sensor"

Does that precision in terminology help you take better pictures than those who in their ignorance assess the optimal balance of shutter speed, aperture and ISO setting?

[jaapv]

Yes it does. Exposure is one of the most basic photographic principles   Understanding it is one of the essentials on the road to a good photo. ISO setting is just amplification. further on in the process, nothing more. And yes, it influences the EV setting. But so does motion, for example, and DOF. 

[PhotoCruiser]

vor 3 Minuten schrieb jaapv:

Yes it does. Exposure is one of the most basic photographic principles   Understanding it is one of the essentials on the road to a good photo. ISO setting is just amplification. further on in the process, nothing more. 

I agree,
however it depends on what is the scenery to photograph.
I find Auto Iso very useful if i want a particular aperture and shutter time but in 90% ISO is set to 100 as i can set the correct exposure with aperture and shutter speed. Having Auto Iso always on while using a exposure program function can lead to unexpected results as Iso may interfere with cameras aperture and shutter decision as it introduces a third parameter for exposure decision how to expose correctly.  
Chris

 

[lct]

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15 minutes ago, jaapv said:

[...] Exposure is one of the most basic photographic principles   Understanding it is one of the essentials on the road to a good photo [...]

It is just a matter of words. For some people exposure is an amount of light, for others the amount of time the film or sensor is open to the light and this amount of time depends on aperture, shutter speed and iso.

[jaapv]

Sorry. No. It is a strictly defined process.” Some people “ simply lack photographic knowledge. Go back to film. ISO varies with development . That is not even in the camera. Twiddling ISO is equivalent to loading another film. Again an action outside the operation of the camera. 

[lct]

2 minutes ago, jaapv said:

Sorry. No. It is a strictly defined process. Some people simply lack photographic knowledge. 

My own knowledge is limited to the Cambridge dictionary according to which exposure is "the amount of time a piece of film is open to the light when making a photograph". Matches my digital experience entirely but we discussed this already so it is probably one of the few (?) matters on which we will never agree. YMMV.

[jaapv]

I would hardly call that dictionary a photographic textbook. It completely ignores the existence of an aperture, the other component of exposure.
It is controlling the amount of light that falls on the film/sensor. 
In a digital camera setting  to a higher value ISO is simply the amplification of an underexposed photo to facilitate further processing. For example to get a readable LCD output.

If you want to keep this up, no problem but I will have to split the thread. 

[pgk]

1 hour ago, jaapv said:

Sorry. No. It is a strictly defined process.” Some people “ simply lack photographic knowledge. Go back to film. ISO varies with development . That is not even in the camera. Twiddling ISO is equivalent to loading another film. Again an action outside the operation of the camera. 

The problem with exposure is that it can be seen as a purely technical process, which of course it is. But there is a proviso; which is that in order to be a totally objective process you have to understand and be in control of all aspects of it. So reproducing a grey card and colour checker chart as precisely as is actually possible, will require a high degree of precision and understanding of all the factors affecting tonality and colour shifts in order to ensure as accurate an exposure as possible for this task.

However for general photography, the desired outputs are often rather less well defined and the photographer is able to vary exposure on a rather more subjective basis. This may allow for highlight clipping if acceptable or blocky shadows as desired. Add in a degree of latitude and variability of light sources and colour plus post processing adjusments, and exposure becomes a rather less precise and objective process than it might initially appear.

So whilst I am tempted to agree technically, in practice its somewhat variable depending on many factors which a photographer's decision making process may take into account, and which may not be the same as those considered by another photographer. Each though, may achieve a desired aimpoint and consequently differing exposures may be deemed 'correct'.

[LocalHero1953]

2 hours ago, jaapv said:

Yes it does. Exposure is one of the most basic photographic principles   Understanding it is one of the essentials on the road to a good photo. ISO setting is just amplification. further on in the process, nothing more. And yes, it influences the EV setting. But so does motion, for example, and DOF. 

I have no problem understanding the difference between shutter speed, aperture, film sensitivity and digital sensor electronic signal processing, and where colour frequencies fit in. But that is not the same as how you set about choosing camera settings to take a photograph. You are welcome to call it what you like, but I will continue to balance shutter speed, aperture and ISO when taking photos. It works for me; you're arguing about problems I just don't have.

[DadDadDaddyo]

4 hours ago, jaapv said:

ISO setting is just amplification.

This is both technically correct and important to results in a non-semantic way. It's precisely because of the impact of amplification on image outcome (signal to noise ratio) that blurring these factors together can be problematic. 

Let me try it this way....

"Exposure" deals with the measurement of light, the number of photons, if you like, that the photographer permits to enter the sealed light box. Changing the ISO doesn't change the amount of light permitted to enter, only aperture and shutter speed do. 

Changing the sensitivity of the medium to achieve a desired target aperture or shutter speed doesn't change the fact of what "exposure" is. It changes the exposure required but not what "exposure" is. 

Edited Wednesday at 02:18 PM by DadDadDaddyo

[lct]

On 11/18/2025 at 5:03 PM, lct said:

Or more convenient. In auto iso M mode, both apertures and shutter speeds can be set manually while iso settings are automatic. Hardly a practical issue for those considering iso as part of exposure, and even less so for those who deny that.

Strange that i become the OP in a thread that has been derailed without my consent. My intent was not to open a redundant thread about exposure that has been discussed several times already.

[SrMi]

21 hours ago, LocalHero1953 said:

Does that precision in terminology help you take better pictures than those who in their ignorance assess the optimal balance of shutter speed, aperture and ISO setting?

Yes. It enables a proper understanding of the available camera settings, allowing the IQ to be maximized with the least effort.

Edited yesterday at 06:29 AM by SrMi

[LocalHero1953]

1 hour ago, SrMi said:

Yes. It enables a proper understanding of the available camera settings, allowing the IQ to be maximized with the least effort.

A proper understanding of the available camera settings does not depend on the precision in terminology discussed here.

[LocalHero1953]

I could argue (if I wished to be a pedant) that 'exposure' in photography is already an aggregate of two specific factors, shutter speed and aperture, which have their own distinctive effects on how a photo looks. Combining them into another abstract concept risks confusion. Far better to stick to an understanding of the separate components of shutter speed, aperture and sensitivity/amplification which must be considered together to achieve the desired image.

But, since I'm not a pedant, I'll live and let live, so others may use the term 'exposure' as they wish.

[SrMi]

To be pedantic: exposure consists of shutter speed, aperture and scene light.

Ideally, native ISO would be always fixed, or switch between the two "native" ISOs, and the brightening would be applied only in post or when creating JPGs. One can simulate that though with proper settings.

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[SrMi]

4 hours ago, LocalHero1953 said:

A proper understanding of the available camera settings does not depend on the precision in terminology discussed here.

For me, understanding leads automatically to precision in terminology, in professional area and photography.

[LocalHero1953]

4 minutes ago, SrMi said:

To be pedantic: exposure consists of shutter speed, aperture and scene light.

Ideally, native ISO would be always fixed, or switch between the two "native" ISOs, and the brightening would be applied only in post or when creating JPGs. One can simulate that though with proper settings.

I'm genuinely puzzled about your practice. With native ISO 100, say, and in low light with moving subjects, how do you choose shutter speed and aperture to avoid blown highlights or noisy shadows? A light meter would simply advise an unreasonably long shutter speed.

1 minute ago, SrMi said:

For me, understanding leads automatically to precision in terminology, in professional area and photography.

In photography getting hung up on the meaning of 'exposure' simply doesn't help set a camera for taking a photo: I don't set 'exposure', I set shutter speed, aperture and ISO,