The ISO argument

[PaulR70]

I have followed this argument elsewhere so I decided to share my thoughts. One of the arguments is that ISO has nothing to do with exposure! For the sake of the argument do this test, if you have camera like a DSLR or any digital camera that can be set manually do this. Set the camera up on a tripod, set camera for manual, set ISO to 200, then set the shutter and aperture to get a good exposure and take a shot. Set ISO to 100 do not adjust shutter or aperture take the shot. Set ISO to 400 again do not adjust shutter or aperture and take the shot. Then tell me if it does not effect exposure!
I have three shots out my front window and the only thing I did in my software was to save them as JPEG's (I shot them in RAW format)

 

[Ysarex]

I have followed this argument elsewhere so I decided to share my thoughts. One of the arguments is that ISO has nothing to do with exposure! For the sake of the argument do this test, if you have camera like a DSLR or any digital camera that can be set manually do this. Set the camera up on a tripod, set camera for manual, set ISO to 200, then set the shutter and aperture to get a good exposure and take a shot. Set ISO to 100 do not adjust shutter or aperture take the shot. Set ISO to 400 again do not adjust shutter or aperture and take the shot. Then tell me if it does not effect exposure!
I have three shots out my front window and the only thing I did in my software was to save them as JPEG's (I shot them in RAW format)View attachment 171039View attachment 171040 View attachment 171041

In photography, exposure is the amount of light per unit area (the image plane illuminance times the exposure time) reaching a photographic film or electronic image sensor, as determined by shutter speed, lens aperture and scene luminance.

That's the standard definition of "exposure" set and finalized in our industry long before you were born. It has not changed in nearly 200 years. In the clause that begins with "as determined by..." please underline ISO for us.

It does matter and for good reason -- I have to go out right now but I'll be happy to explain it to you later. In the meantime you can look at these two photos; both the same exposure 1/6 sec. f/4 but one at ISO 1000 and the other at ISO 125. See the difference?



Joe

 

[Derrel]

[>>SNIP>>>look at these two photos; both the same exposure 1/6 sec. f/4 but one at ISO 1000 and the other at ISO 125. See the difference?

View attachment 171044 View attachment 171045

Joe

The two photos look quite similar to me.

Could you elucidate on the importance of using ISO 125 as opposed to ISO 1,000?

 

[Richard Hutchings]

I don't see any difference?

 

[Soocom1]

OK so were doing this again.

First some parameters:

ISO is an acronym for International Organization of Standards.
ISO - International Organization for Standardization

ISO being standards found in every industry including photography, medicine, government, etc.
ISO9000 is specific to manufacturing.
ISO for photography is a MEASUREMENT for light values. Ergo: STANDARDS.


ISO in film is wholly different for ISO in digital.
They represent the same thing... MEASUREMENT OF LIGHT.

The arguments recently made on ISO (in regards to photography) is mostly based on the arguments made by individuals who want to talk.

The arguments are akin to red cars are faster.

Its nonsensical.

But for the sake of argument, the argument of itself is based no the ability to modify the exposure based on modifying aspects of a program to achieve the same results.
ironically, the actions taken though digital and electronic in nature is the same as taken when one over or under exposes silver paper under an enlarger. Achieving the same results.

Its all a matter of understanding what exposure, light intensity and value are.

 

[Derrel]

I don't see any difference?

MOST viewers would, I wager, tend to agree with that...

 

[Soocom1]

Oh I can see it, but you have to have a trained eye for it.

 

[Richard Hutchings]

Please train me I did notice a highlight on the jars in one of them.

 

[Soocom1]

There is an extremely tiny variation in contrast, saturation and grain/pixilisation.

But you wont see it unless you focus away from the images and switch back and forth between them.

 

[vintagesnaps]

Now I see it, I had to click on each to enlarge and take my glasses off to see them closer.

So, there's a difference, are we done with this now?? lol

 

[Soocom1]

lets go back to the core of this whole ISO argument:
The SENSITIVITY of the capture medium (film or digital) to the light.

The original DIN numbers and then ASA were based on and intended to make a STANDARD for the sensitivity of film.

That sensitivity is based wholly on the size of the silver halide crystals. The larger the crystals, the faster the film.
But it also meant grainier film.

In digital its not size as it is the ability to record the light intensity striking the pixels as based on a mathematical computation.

The who intent of the ASA/DIN/ISO number was to make UNIFORM the ability to know what the sensitivity was of the film and the appropriate scale to set one's aperture and shutter speed to.

In digital the faster the ISO (ergo 125 v 1000) typically means more "noise" or pixles that infer the light intensity differently from one setting to another.
This can all be changed later in post processing, but it has essentially the same effect and "grainy" film.

The ISO number for film was standardized for good reason. Because those rules DO NOT apply to digital, the numbers become arbitrary and defined by the manufacturer. But typically is in close proximity to film so that photographers have a basis to work from.

 

[PaulR70]

I started this thread but I did not intend for it to become some long drama! I have been doing photography as a hobby off and on since 1968 and I understand some of differences between film and digital. I just understand that ISO can effect exposure in the digital camera period. Yes I am done with it!

 

[JonFZ300]

 

[The_Traveler]

I put one over the other in PS and set the layer properties as 'difference'
the difference is more visible on screen (obviously)

 

[Ysarex]

I started this thread but I did not intend for it to become some long drama! I have been doing photography as a hobby off and on since 1968 and I understand some of differences between film and digital. I just understand that ISO can effect exposure in the digital camera period. Yes I am done with it!

You're operating with a colloquial definition of exposure in which you mean how light/dark is the final image. That's not our industry's standard definition of exposure but it is arguably a popular common usage definition. The two definitions conflict. It matters because what data you record in your photo and the characteristics of that data are a function of exposure as I defined it. If you mix ISO in there you can start getting confused like folks for example equating higher ISO with more noise and claiming ISO is the cause. That relationship is spurious and not causal. I'm going to guess that you likewise believe then that raising the ISO on your camera makes the image noisier. So then how do you explain this photo shot at ISO 12800 on an APS sensor camera: socks?

You're right that ISO is closely related to exposure so it's a subtle distinction. When we change ISO on our cameras the camera's meter system is effected and calculates a new exposure. If we allow the meter to determine exposure then ISO is certainly playing a critical role. But it remains exposure that determines what we're going to capture or not. ISO's functions post exposure in the camera's electronics and software can only cause a loss of information if we allow it.

There's little harm in continuing with your definition of exposure -- the Exposure Triangle model is used by lots of people taking successful photos. It works but it will fray at the edges and if you push your camera toward it's edges the misunderstanding can bite you, or rather an insufficient understanding will leave you with a missed opportunity.

Joe