What is ISO? ISO Has NOTHING To Do With Exposure! (Page 2): That's a rather bold statement. So, since you made it and then stepped in it, perhaps you'd like to suggest "someone with...

rmalarz Loc: Tempe, Arizona

That's a rather bold statement. So, since you made it and then stepped in it, perhaps you'd like to suggest "someone with authority".
--Bob

davidrb wrote:

Utube has NEVER been associated with truth or honesty. Whatever gave you the idea it did? Children with video cameras do NOT make an honest association. Try someone with authority.

rmalarz Loc: Tempe, Arizona

I believe the ISO setting, in digital, is related to the amplification of the reaction of the sensor to the light striking it. It's somewhat of an after-effect.
--Bob

srt101fan wrote:

I'm not an expert, but my understanding, based on comments by the experts, is that ISO has nothing to do with sensor sensitivity.

Ysarex Loc: St. Louis

selmslie wrote:

That's not just the most common case. It's the way that all cameras create the default JPEG.

I take it you've never heard of the camera manufacturer Sigma then. The existence of Sigma cameras proves my statement was accurate and you are wrong.

Provide documentation from any of the camera manufacturers that indicates the existence of a "default JPEG" as opposed to some other JPEG.

selmslie wrote:

In-camera processing to create a non-standard JPEG does not "implement an ISO increase".

Provide documentation from any of the camera manufacturers that indicates the existence of a "non-standard JPEG" as opposed to a "default JPEG." No such dichotomy exists, that's just you making up lame BS.

ISO can be implemented using analog amplification of the sensor signal which alters raw values.
ISO can be implemented using digital scaling in the ADC which alters raw values.
ISO can be implemented in the camera's image processor which does not alter raw values.

Any one or any combination of those methods is an acceptable implementation of ISO. If a change in ISO is implemented in the camera image processor the raw values are not altered.

We've been through all this before and you've been proven wrong before and you remain proven wrong: https://www.uglyhedgehog.com/t-609317-1.html

jackm1943 Loc: Omaha, Nebraska

In my camera at least, if I'm in anything other than full manual, when I change the ISO it changes the shutter speed and/or the aperture, thereby changing the amount of light hitting the sensor. Apparently his camera works differently?

Racmanaz Loc: Sunny Tucson!

jackm1943 wrote:

In my camera at least, if I'm in anything other than full manual, when I change the ISO it changes the shutter speed and/or the aperture, thereby changing the amount of light hitting the sensor. Apparently his camera works differently?

Who are you referring?

Ysarex Loc: St. Louis

jackm1943 wrote:

In my camera at least, if I'm in anything other than full manual, when I change the ISO it changes the shutter speed and/or the aperture, thereby changing the amount of light hitting the sensor. Apparently his camera works differently?

No his camera doesn't work differently. The point he was making, which is correct, is that exposure, defined as the amount of light reaching the sensor, can only be altered by changing the shutter speed or the lens aperture or the scene illuminance. ISO plays a role as it influences the exposure we or the camera's metering system select since ISO affects the final image lightness.

sippyjug104 Loc: Missouri

I find it helpful for me to think of the digital cameras as, "Digital Computers (microprocessors)". Each setting has an effect on the processing of the data as well as the functions of the camera. Those of us in the CB Radio days can relate to the 'squelch' adjustment on the clarity of the signal and the amplification of the signal of the ISO setting is much the same. In terms of the radio, the squelch amplifies or retards the processing of the signal and the ISO amplifies or retards the processing of the signal generated from the light striking the photosites on the sensor.

The squelch has nothing to do with the transmitted signal coming into the radio itself nor does the ISO setting have anything to do with the light itself coming into the camera striking the sensor.

Longshadow Loc: Audubon, PA, United States

jackm1943 wrote:

In my camera at least, if I'm in anything other than full manual, when I change the ISO it changes the shutter speed and/or the aperture, thereby changing the amount of light hitting the sensor. Apparently his camera works differently?

Remember, the digitals use a two part process to create the final image, but the second is still "connected" to the first.
So yes, it will alter the first part. Cameras are "smart".

letmedance Loc: Walnut, Ca.

In my mind ISO plays an important part in exposure, ISO indicates the gain of the processor which corresponds to the speed of the film. The amount of light hitting the sensor is changed by adjusting the ISO setting and increasing it will require changing your exposure just as raising ASA requires different shutter speed and aperture settings. The gentleman is correct about the ISO being a gain setting but is wrong about it not being being part of the exposure settings.

jackm1943 Loc: Omaha, Nebraska

Ysarex wrote:

No his camera doesn't work differently. The point he was making, which is correct, is that exposure, defined as the amount of light reaching the sensor, can only be altered by changing the shutter speed or the lens aperture or the scene illuminance. ISO plays a role as it influences the exposure we or the camera's metering system select since ISO affects the final image lightness.

That's not what I heard, but if that's what he was trying to say, why didn't he do it as concisely as you just did?

jackm1943 Loc: Omaha, Nebraska

Racmanaz wrote:

Who are you referring?

Oops, sorry. I was responding to the poster's video.

rmalarz Loc: Tempe, Arizona

The amount of light hitting the sensor is not changed by adjusting the ISO setting. The amount of light hitting the sensor is governed by the aperture and the duration of the shutter being open. The ISO governs how the sensor will react to that light.
--Bob

letmedance wrote:

In my mind ISO plays an important part in exposure, ISO indicates the gain of the processor which corresponds to the speed of the film. The amount of light hitting the sensor is changed by adjusting the ISO setting and increasing it will require changing your exposure just as raising ASA requires different shutter speed and aperture settings. The gentleman is correct about the ISO being a gain setting but is wrong about it not being being part of the exposure settings.

Longshadow Loc: Audubon, PA, United States

rmalarz wrote:

The amount of light hitting the sensor is not changed by adjusting the ISO setting. The amount of light hitting the sensor is governed by the aperture and the duration of the shutter being open. The ISO governs how the sensor will react to that light.
--Bob

And in doing so, will adjust the EV to meet the needs of the ISO setting so it can do the job correctly.

Ysarex Loc: St. Louis

letmedance wrote:

In my mind ISO plays an important part in exposure, ISO indicates the gain of the processor which corresponds to the speed of the film. The amount of light hitting the sensor is changed by adjusting the ISO setting

The amount of light reaching the sensor is not changed by changing the ISO. Given a constant scene illuminance the two camera settings combinations below produce the same sensor exposure.

1/250th sec. shutter speed
f/5.6 aperture
ISO 200

1/250th sec. shutter speed
f/5.6 aperture
ISO 800

The ISO difference in the two settings combinations above does not alter the amount of light reaching the sensor.

letmedance wrote:

and increasing it will require changing your exposure just as raising ASA requires different shutter speed and aperture settings. The gentleman is correct about the ISO being a gain setting but is wrong about it not being being part of the exposure settings.

"Gain" gets used pretty loosely in many descriptions of ISO. ISO can be and is most often implemented using hardware amplification which certainly qualifies as gain. ISO can also be and is frequently implemented simply by multiplying/scaling numbers in software. Some people become uncomfortable using "gain" to describe a software only process and sometimes call it "digital gain." The ISO standard does not specify the in camera implementation so we want to be careful not to fall into the habit of defining ISO by how it gets implemented.

Ysarex Loc: St. Louis

rmalarz wrote:

The amount of light hitting the sensor is not changed by adjusting the ISO setting. The amount of light hitting the sensor is governed by the aperture and the duration of the shutter being open. The ISO governs how the sensor will react to that light.
--Bob

How the sensor exposure and ISO setting get processed is up to the camera manufacturers to implement as they see fit. ISO governs the lightness of the camera's final output image (JPEG) relative to a measured exposure.