The ISO argument

[beagle100]

There is a lot more to this than I had any idea. As an old film person I had thought getting started in digital that ISO was kind of like ASA.

In practice it can seem very much like film ISO/ASA but under the hood there are some substantial differences. Most notably that you can change ISO on a digital camera with the twist of a dial on a per shot basis.

This thread was started because the OP wanted to provide obvious evidence that ISO in part determines exposure -- a point of common confusion. We live with a "social phenomenon" (not sure what else to call it) in photography that can be a source of confusion. It's a really good thing that photography is practiced by so many people and it is likewise a good and welcome thing that many enthusiasts/amateurs get involved in photo. This large amount of non-professional participation however bolstered by the rapid communication options of the Internet can spread misinformation at an alarming rate (politics?). A term with a specific meaning or a process or phenomenon can become colloquially misunderstood and that misunderstanding can spread so that effectively the term-meaning or phenomenon gets changed. You'll run into the term bokeh at some point if you keep up your interest. What should we do now with bokeh? Should it mean what it originally meant or should we accept what it means now in the minds of the Youtube misinformation hordes?

So "exposure" likewise has a colloquial meaning that deviates from it's formal meaning in our discipline. Colloquially "exposure" means how light or dark your photo appears and when taking a photo with a camera you can alter that light/dark appearance by changing shutter speed, f/stop, or ISO. Therefore the factors effecting exposure must be shutter speed, f/stop and ISO. And then you get this:

View attachment 171201

(Notice the misuse of the word bokeh in that diagram -- it's a twofer!) The problem with that is ISO doesn't really causally effect exposure. It wouldn't be a big deal if it didn't matter but it does. And it's because it matters that our industry long ago defined exposure differently than the colloquial understanding. Exposure is the amount of light per unit area that strikes the film/sensor. There are three causal factors: the intensity of illumination in the scene, the time of the exposure (shutter speed) and attenuation of the light through the lens (f/stop).

So how does ISO fit in? It's obviously involved. You have to consider it when you make an exposure. Why isn't it a factor then? I explain it in class like this: We're in the lab and I can literally walk over to the sink and do this and I do. Turn on the water and let's call that light coming through the camera. I pick up an 500ml beaker and hold it under the faucet -- that's ISO. Turning the faucet on/off is the shutter speed and how much I turn the faucet is f/stop. Let's assume I can do this with precision. I turn the faucet on for two seconds with a 1/8 turn of the handle. I successfully fill the beaker. How much water do I have? That's the exposure and it's 500ml. Now I switch to a 1 liter beaker and make another exposure. I turn the faucet on for two seconds with a 1/8 turn of the handle. How much water do I have? 500ml just like the last exposure I used the same shutter speed and f/stop. Did changing the volume of the beaker change the exposure? No.

In practice however because ISO does in fact change the light/dark appearance of our final photo and because if we use the camera meter (nearly all of us do) then changing ISO causes the meter to recalculate exposure it certainly seems like ISO is an exposure factor. The triangle diagram above is commonly used and no question it helps beginners get a handle on using the camera. But it muddies the cause and effect of what's going on and that can be bad. Pretty soon you encounter beginners who believe that ISO is the cause of noise in a photo (it's not) and that misconception causes them to alter their behavior using the camera. The primary cause of noise in our photos is reduced exposure. What ISO does in fact tends to suppress noise. So caught up in a misunderstanding (and I see this in class all the time) a beginner resists raising ISO for fear of noise when the ISO function would have in fact made their photo less noisy. Understanding the cause of the noise is the first step in being able to control it.

Joe

seems reasonable
But always I use auto ISO

www.flickr.com/photos/mmirrorless

 

[Ysarex]

All you have to do is take the same pic with different ISO settings and pixel peep to see what it does for your camera. I don't understand what all the fuss is about regarding whether it's actually a component of exposure or not. In the end, it's about the images and image quality.

On my small sensor FZ300, it's irrelevant because I never take it off 100 ISO because I notice changes to IQ even at 200 and 400 is just ugly to my eye.

Wow. I have a similar 12 meagpixel compact with about the same size small sensor. I use it up to ISO 1600 and I'm happy with the results. Here's an example:

Sure ISO 80 is better but I don't see the above as ugly.

Joe

I'm definitely not anti-learning, but knowing the technicalities and science behind how a camera's ISO function works doesn't change the fact that the only way to exploit that knowledge is to change the ISO setting before taking the picture. And you should know what that does to the image from the test I mentioned above.

 

[Ysarex]

There is a lot more to this than I had any idea. As an old film person I had thought getting started in digital that ISO was kind of like ASA.

In practice it can seem very much like film ISO/ASA but under the hood there are some substantial differences. Most notably that you can change ISO on a digital camera with the twist of a dial on a per shot basis.

This thread was started because the OP wanted to provide obvious evidence that ISO in part determines exposure -- a point of common confusion. We live with a "social phenomenon" (not sure what else to call it) in photography that can be a source of confusion. It's a really good thing that photography is practiced by so many people and it is likewise a good and welcome thing that many enthusiasts/amateurs get involved in photo. This large amount of non-professional participation however bolstered by the rapid communication options of the Internet can spread misinformation at an alarming rate (politics?). A term with a specific meaning or a process or phenomenon can become colloquially misunderstood and that misunderstanding can spread so that effectively the term-meaning or phenomenon gets changed. You'll run into the term bokeh at some point if you keep up your interest. What should we do now with bokeh? Should it mean what it originally meant or should we accept what it means now in the minds of the Youtube misinformation hordes?

So "exposure" likewise has a colloquial meaning that deviates from it's formal meaning in our discipline. Colloquially "exposure" means how light or dark your photo appears and when taking a photo with a camera you can alter that light/dark appearance by changing shutter speed, f/stop, or ISO. Therefore the factors effecting exposure must be shutter speed, f/stop and ISO. And then you get this:

View attachment 171201

(Notice the misuse of the word bokeh in that diagram -- it's a twofer!) The problem with that is ISO doesn't really causally effect exposure. It wouldn't be a big deal if it didn't matter but it does. And it's because it matters that our industry long ago defined exposure differently than the colloquial understanding. Exposure is the amount of light per unit area that strikes the film/sensor. There are three causal factors: the intensity of illumination in the scene, the time of the exposure (shutter speed) and attenuation of the light through the lens (f/stop).

So how does ISO fit in? It's obviously involved. You have to consider it when you make an exposure. Why isn't it a factor then? I explain it in class like this: We're in the lab and I can literally walk over to the sink and do this and I do. Turn on the water and let's call that light coming through the camera. I pick up an 500ml beaker and hold it under the faucet -- that's ISO. Turning the faucet on/off is the shutter speed and how much I turn the faucet is f/stop. Let's assume I can do this with precision. I turn the faucet on for two seconds with a 1/8 turn of the handle. I successfully fill the beaker. How much water do I have? That's the exposure and it's 500ml. Now I switch to a 1 liter beaker and make another exposure. I turn the faucet on for two seconds with a 1/8 turn of the handle. How much water do I have? 500ml just like the last exposure I used the same shutter speed and f/stop. Did changing the volume of the beaker change the exposure? No.

In practice however because ISO does in fact change the light/dark appearance of our final photo and because if we use the camera meter (nearly all of us do) then changing ISO causes the meter to recalculate exposure it certainly seems like ISO is an exposure factor. The triangle diagram above is commonly used and no question it helps beginners get a handle on using the camera. But it muddies the cause and effect of what's going on and that can be bad. Pretty soon you encounter beginners who believe that ISO is the cause of noise in a photo (it's not) and that misconception causes them to alter their behavior using the camera. The primary cause of noise in our photos is reduced exposure. What ISO does in fact tends to suppress noise. So caught up in a misunderstanding (and I see this in class all the time) a beginner resists raising ISO for fear of noise when the ISO function would have in fact made their photo less noisy. Understanding the cause of the noise is the first step in being able to control it.

Joe

seems reasonable
But always I use auto ISO

And that's one of the things I initially do with my students. They all believe they should set the ISO and keep it as low as possible (bleepin' bleep YouTube). I tell them to put it on auto and let the camera set it. They're much better off paying attention to setting exposure which will really effect their photos.

Joe

www.flickr.com/photos/mmirrorless

 

[JonFZ300]

That's a nice looking shot. I shoot mostly birds and stuff outdoors in daylight and the FZ300 is a constant f2.8 through the full zoom range so I never really need to bump the ISO anyway.

 

[JonFZ300]

Here's my 1600 at full size in an indoor, low-ish light setting:

 

[Ysarex]

Here's my 1600 at full size in an indoor, low-ish light setting:

Your camera can save a raw file and should be able to do much better than that. I would expect your camera at ISO 1600 to at least equal what I posted.

Joe

 

[JonFZ300]

To be fair that's a a screen shot of the unprocessed raw file. Here's a jpeg of the full image after conversion to jpeg and a little bump in exposure in ACR. I guess I stand corrected. It's actually not that bad. The first thing I did when I got the camera was an ISO comparison and I wasn't happy at all. Looking at this, I'm not so upset anymore. It's bad but not that bad. My FZ200 was worse for sure, maybe that's where I got into the low-ISO mindset. Thanks for showing me your 1600 image. Cheers

 

[Ysarex]

To be fair that's a a screen shot of the unprocessed raw file. Here's a jpeg of the full image after conversion to jpeg and a little bump in exposure in ACR. I guess I stand corrected. It's actually not that bad. The first thing I did when I got the camera was an ISO comparison and I wasn't happy at all. Looking at this, I'm not so upset anymore. It's bad but not that bad. My FZ200 was worse for sure, maybe that's where I got into the low-ISO mindset. Thanks for showing me your 1600 image. Cheers

That's much better but, It can still be better than that. I suspect at least twice as good. I just stopped over at DPReview and looked over the specs for your camera.

Joe

 

[JonFZ300]

That's much better but, It can still be better than that. I suspect at least twice as good. I just stopped over at DPReview and looked over the specs for your camera.

Joe

Well, I'm glad I joined this discussion. This one was taken at ISo 400 and I think it looks pretty good. I opened the blind to let in some natural light. I think I'm still going to stick with 100 for my birds and well-lit stuff but it's good to know that I can use at least 400 and 800 if I need to and maybe even 1600 if I REALLY need to. Thanks again.

 

[Ysarex]

That's much better but, It can still be better than that. I suspect at least twice as good. I just stopped over at DPReview and looked over the specs for your camera.

Joe

Well, I'm glad I joined this discussion. This one was taken at ISo 400 and I think it looks pretty good. I opened the blind to let in some natural light. I think I'm still going to stick with 100 for my birds and well-lit stuff but it's good to know that I can use at least 400 and 800 if I need to and maybe even 1600 if I REALLY need to. Thanks again.

I suspect your camera at ISO 1600 can be this good or nearly this good.

Joe

 

[eja]

Here's my 1600 at full size in an indoor, low-ish light setting:

Your camera can save a raw file and should be able to do much better than that. I would expect your camera at ISO 1600 to at least equal what I posted.

Joe

I'm glad I'm still following this discussion. IF I'm still following the main points correctly, even a small sensor camera should be able to produce an image at high ISO with acceptable noise if it is exposed correctly.

I've included a picture taken with an older Olympus XZ-1. I was using off camera flash with the neutral density filter activated on the camera. That provides about a 3 stop underexposure. I wanted to underexpose the background, use a wider fstop to try and limit my depth of field. The flash was an old sb26 off camera. The image was shot in raw.

Now, I don't know why I ended up at iso 400. I was planning on using iso 100 so it may have been an accident. The point is, however, that you can see the image is noisy. My first thought was it was due to being at higher iso on a small camera with a small sensor. However, I did purposely underexpose the ambient and then set my Fstop at f 2.0. The flash exposure on the subject was 3 stops above roughly and measured with a light meter.

Assuming I got my exposure correct on the subject, what would attribute to the visible noise? Simply camera limits or I most likely didn't get my exposure correct?

The image was processed in DXO with all of the noise reducing stuff and contrast stuff turned off. It's pretty much out of the camera with only the distortion corrected.

 

[Ysarex]

Here's my 1600 at full size in an indoor, low-ish light setting:

Your camera can save a raw file and should be able to do much better than that. I would expect your camera at ISO 1600 to at least equal what I posted.

Joe

I'm glad I'm still following this discussion. IF I'm still following the main points correctly, even a small sensor camera should be able to produce an image at high ISO with acceptable noise if it is exposed correctly.

I've included a picture taken with an older Olympus XZ-1. I was using off camera flash with the neutral density filter activated on the camera. That provides about a 3 stop underexposure. I wanted to underexpose the background, use a wider fstop to try and limit my depth of field. The flash was an old sb26 off camera. The image was shot in raw.

Now, I don't know why I ended up at iso 400. I was planning on using iso 100 so it may have been an accident. The point is, however, that you can see the image is noisy. My first thought was it was due to being at higher iso on a small camera with a small sensor. However, I did purposely underexpose the ambient and then set my Fstop at f 2.0. The flash exposure on the subject was 3 stops above roughly and measured with a light meter.

Assuming I got my exposure correct on the subject, what would attribute to the visible noise? Simply camera limits or I most likely didn't get my exposure correct?

The image was processed in DXO with all of the noise reducing stuff and contrast stuff turned off. It's pretty much out of the camera with only the distortion corrected.

We need to look at the raw file for your answer. Put the raw file on something like Dropbox and post a link to it here and I'll take a look.

Joe

 

[eja]

Ok, thanks for the reply. Here is a link to the file from the Olympus camera.

Dropbox - 2018-04-02-190527-OlympusHomePhotos_DxO.jpg

 

[Ysarex]

Ok, thanks for the reply. Here is a link to the file from the Olympus camera.

Dropbox - 2018-04-02-190527-OlympusHomePhotos_DxO.jpg

That's the camera JPEG. Any chance you have a raw file. It would have an .orf extension.

Joe

 

[eja]

Whoops. My mistake. Here is a link to the original .orf file.

Dropbox - 2018-04-02-190527-OlympusHomePhotos.ORF