iso as an exposure variable - not.

[Patrice]

This getting to be a bit of fun. Lots of participants thinking about the my statements and countering with well considered arguments. (Some are also just saying I've lost my marbles, but not really contributing.)

Let me say my piece in another way, if you will.

The camera creates an image by exposing the sensor to light. Aperture and shutter are the controls that vary the amount of light that can reach that sensor. I fully acknowledge that changing the response parameters of that sensor to the amount light it receives will entail changes in one or both of the two controls I'm talking about. Changing the iso does not vary the amount of light the sensor receives, only its response to that light.

An image requiring a large depth of field and a fast shutter speed certainly might necessitate a higher iso due to the lack of available light.
So we raise the iso so that we can use the aperture and shutter speed the image requires. We are still only using aperture and shutter speed to control the amount of light reaching the sensor.

Of course changing the iso will require a change in aperture and/or shutter speed to maintain the same exposure. But it's not the change in iso that is modifying the exposure, it's the resultant changes in shutter and/or aperture.

I'm gonna shut up now and go eat my supper.

 

[Overread]

So what you're really talking about isn't making an exposure but about light control within the photographic setup. At which point you're assuming that the photographer is working only with natural lighting. Otherwise its not just aperture and shutter (and I'll say ISO as well because the ability of the recording medium to react to light IS a part of the process - it has to be otherwise the concept of low or strong light is meaningless) but also the light controling elements as well - flash, diffusers, black screens, lens hoods, filters, reflectors etc... all come into play with light control and manipulation.

But this is moving away from the bare bones - the bare bones is you have a recording medium - film, sensor - which reacts to light. Changing how it reacts to light is just as big a part of making an exposure as changing the amount of light it has to work with.


darn it she types faster than me!

 

[Patrice]

Unless I am mis-reading your new post entirely (and someone please correct me if I am), I still say your claim is incorrect.

Enjoy your supper. :sillysmi:

You are not misreading my post. You said the same thing. If you don't have enough light for the aperture and shutter you want to use then you have to amplify the sensor output. You have not changed the amount of light at all. You can only do that with aperture and shutter.

 

[Overread]

Unless I am mis-reading your new post entirely (and someone please correct me if I am), I still say your claim is incorrect.

Enjoy your supper. :sillysmi:

You are not misreading my post. You said the same thing. If you don't have enough light for the aperture and shutter you want to use then you have to amplify the sensor output. You have not changed the amount of light at all. You can only do that with aperture and shutter.

But you have to factor in the ISO because otherwise the light that the aperture and shutter speed are affecting has no meaning. What is strong or weak light? Your recording medium defines it of course and be it film or a sensor that recording medium can vary its reaction to the light. This ability to vary its reaction is what makes it part of the exposure triangle. I agree if film/ISO were always a fixed value it wouldn't matter in the triangle because with no variation you would have no choice. But we do have the variation and be it with film or a digital sensor we can change that value and thus it becomes part of that triangle of camera settings that affects the resulting exposure we get.

 

[Josh66]

Unless I am mis-reading your new post entirely (and someone please correct me if I am), I still say your claim is incorrect.

Enjoy your supper. :sillysmi:

You are not misreading my post. You said the same thing. If you don't have enough light for the aperture and shutter you want to use then you have to amplify the sensor output. You have not changed the amount of light at all. You can only do that with aperture and shutter.

You can only do that by adding more light.

Aperture and shutter speed don't change the light either...

 

[Patrice]

Aperture and shutter speed don't change the light either...

.... only how much of it reaches the sensor.

 

[Josh66]

Aperture and shutter speed don't change the light either...

.... only how much of it reaches the sensor.

How is that different than changing the ISO?


No matter what settings you choose, the light is the same - all you can change is how you record it.

 

[Destin]

Funny, my old film camera has a control for setting the ISO.

Yes, and as I remember, you inserted a film with a fixed ASA/ISO value, and could not change that while using that film?

That has not always been the case, once the film was loaded you then only had aperture and shutter speed as 'on camera' controls

But, pushing the film speed by telling the camera it was a different speed than it actually is, was also a viable option in certain situations in the film days. So you could argue that you has iso control on film cameras, albeit in a different sense

 

[white]

Of course ISO has a "direct effect" on the content of an image. Portrait shooters in the 19th century had to ask their subjects to remain still for the duration of the photograph because the speed of emulsions at the time were so slow. Forget about getting crisp shots of moving objects at that time.

More recently, if 25 iso is all you got in the back of your camera, but you want to stop motion, is it going to happen? No, not even at the widest aperture.

ISO is a controllable feature that allows different aperture/shutter combinations to be used. It is the foundation on which a house is built. It is the recording medium. How much more of a "direct effect" can one ask for?

 

[Aayria]

Guess it's time to tell Canon and Nikon that their "jig is up" so to speak... They've been making a fortune producing cameras that can perform at higher and higher ISO's than ever..

But now photographers know the truth. ISO is all a ruse... No point in paying the extra funds for great ISO performance. Just give us fast glass, good FPS with high shutter speeds, and darn the ISO performance to heck. "Real" photographers don't rely on such piddly superficial nuances anyway.

 

[Aayria]

I was going to type the "hugging" smiley emote back.. but after the weekend we've had here.. I think this is far more appropriate!

:cheers:

And on that note, enjoy the debate, I'm cracking open some wine with the hubby and calling it a night!

 

[timbearden]

Guess it's time to tell Canon and Nikon that their "jig is up" so to speak... They've been making a fortune producing cameras that can perform at higher and higher ISO's than ever..

But now photographers know the truth. ISO is all a ruse... No point in paying the extra funds for great ISO performance. Just give us fast glass, good FPS with high shutter speeds, and darn the ISO performance to heck. "Real" photographers don't rely on such piddly superficial nuances anyway.

Hit it on the nose. I need to return all my equipment, as I can go to cheaper cameras who don't emphasize ISO.

I guess the new Ektar film that claims to have less grain at the same ISO is worthless to. Probably just digital silver anyway.

 

[Shane Anderson]

Your view is very sensor-centric. A camera is more than just the sensor, and an image is more than just the light hitting the sensor.

Tell me, how do you judge correct exposure? Isn't it a judgement of whether the image has too much or too little light? And doesn't that judgement use as two of its parameters whether there is lost shadow detail or blown highlights? And aren't those limits set by the sensitivity of the sensing medium, be it a photoelectric sensor in a digital camera or film in a film camera?

 

[Rekd]

Blah blah blah, me me me....

I have a ham sammich.

 

[Christie Photo]

Tell me, how do you judge correct exposure?

Well... everything relates back to 18% reflectance (or 12% luminance, depending on which school of thought you accept). That's the benchmark.

-Pete