Digital Photography ISO

Ysarex

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I'm not going to engage with you on this because you are clearly crazy.

OK -- let's just leave it at everything you said is technically way wrong but you prefer a model of error and ignorance because it helps you understand stuff.;)

Joe
 

smoke665

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Joe is correct and is highly knowledgeable about the technical aspects of photography. He is the unofficial walking, talking encyclopedia of knowledge here on TPF, who has been a valuable source of knowledge for many of us, myself included. ISO, as it relates to a digital camera, has nothing to do with the sensor. The gain is nothing more than an amplification of the signal obtained from the sensor which I believe has already been mentioned several times.
 

Digital Matt

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Once again, your obfuscating the issue. ISO is one of three controls of exposure. The OP has been a film shooter for years and clearly understands how to use ISO with regard to film, but is hitting a stumbling block with digital, by reading overly complex, technical focused stuff. You did nothing to help him understand how to use ISO to make photos. It's clear that you are here to talk technology to the nth degree. I use technology to make images. I gave a simple straightforward answer that was not wrong, not in any way. ISO provides the same function on a digital camera that it does with a film camera. I fully understand that it does not do it in the same way. They are completely different technologies, obviously. Knowing when/where/how the camera amplifies the signal in no way helps you make better images.

I came back to this forum after a decade long hiatus and I see not much has changed. Maybe this will be short lived.
 

vin88

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This is something I have been struggling with, and after reading this article, I'm still struggling. I "grew up" in film and I understand film ISO. I also understand the basics of electronic sensors. So I should see a digital ISO and know what it is telling me, right? Well, I really don't. I just use it like I was using a film camera as best as I can.

"You probably don't know what ISO means – and that's a problem" Published Aug 6, 2018 | Richard Butler
I know what ASA does for film. never knew what ISO did. now in the digital age, its point and shoot, dam the consequences.

ASA? ....dam the consequences? WTF?!

I started in photography when ASA was the film sensitivity standard here in the US. I've followed along and kept up through the transition to digital and continue to enjoy taking photographs as I did 40 years ago.

Whatever it is that you're trying to say or comment on I suspect is predominantly your problem.

Joe
just American English, not a problem for me. vin
 

Ysarex

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Once again, your obfuscating the issue.

I'm clearing up the profound confusion that you're flailing around in and that led you to write down this nonsense: "f/8 @ 1/100 records 3 stops more light at ISO 800 than it does at ISO 100."

ISO is one of three controls of exposure. The OP has been a film shooter for years and clearly understands how to use ISO with regard to film, but is hitting a stumbling block with digital, by reading overly complex, technical focused stuff. You did nothing to help him understand how to use ISO to make photos. It's clear that you are here to talk technology to the nth degree.

I thought you weren't going to engage on this! Yet already it's amazing how much you know about me!! WOW!

I use technology to make images.

You don't say.

I gave a simple straightforward answer that was not wrong, not in any way.

This is wrong: "It's the sensitivity of the sensor."
This is wrong: "How that sensitivity is achieved from a technical standpoint and how it is the same or different from film does not matter."
This is wrong: "It makes your sensor more sensitive to light."
This is major wrong: "f/8 @ 1/100 records 3 stops more light at ISO 800 than it does at ISO 100."

ISO provides the same function on a digital camera that it does with a film camera. I fully understand that it does not do it in the same way. They are completely different technologies, obviously. Knowing when/where/how the camera amplifies the signal

Who said it amplifies the signal? That's one of the things the OP was confused about and I sent him to a website where he can get clear answers instead of nonsense.

in no way helps you make better images.

Understanding how and why things work may not always be necessary but it is not harmful and it can be both helpful and satisfying. The OP was asking about a technical article and I gave him references where he could get additional info.

I came back to this forum after a decade long hiatus and I see not much has changed. Maybe this will be short lived.

Where you came from and where you're going has nothing to do with ISO.

The current ISO standard was revised in 2006 to address digital cameras (ISO 12232:2006) and provides more than one option for establishing ISO values. Most camera manufacturers use the SOS (standard output sensitivity) measure which does not reference the sensor -- it is not the sensitivity of the sensor but is determined by the brightness values in the camera software processed JPEG. reference -- It can be useful to understand that.

Even during the good ol' days of film ISO was never an exposure determinant by the standard definition of photographic exposure: "When a photograph is taken, light from the various areas of the subject falls on corresponding areas of the film for a set time. The effect produced on the emulsion is, within limits, proportional to the product of the illuminance E and the exposure time t. We express this by the equation H = Et Before international standardization of symbols, the equation was E = It (E was exposure, I was illuminance) and this usage is sometimes still found. The SI unit for illuminance is the lux (lx). Hence the exposure is measured in lux seconds (lx s)." (from Ilford's The Manual of Photography, 9th edition p. 218)

This one's a little simpler and easier to understand: "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."

Notice that ISO isn't identified in either definition as a factor that determines exposure which goes a long way to explaining why this: "f/8 @ 1/100 records 3 stops more light at ISO 800 than it does at ISO 100." is so very very wrong.

What the camera records is bottom line a function of exposure. Raising the ISO most certainly does not add more light which would be more exposure. That is, as my old Latin teacher would say, bass ackwards.

Joe
 
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Fujidave

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Just reading through the last couple of posts, and I am lost on what to believe or think.
 

snowbear

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Just reading through the last couple of posts, and I am lost on what to believe or think.
All I know is when I increase the ISO, the meter in the camera swings toward the “lighter” side and I can speed up the shutter and/or use a smaller aperture to center it. When I decrease the ISO, the opposite happens.
 

Digital Matt

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The essential elements of photography like exposure, have not changed in over 100 years. You can pick up a photography book from 70s, read up on shutter speed, aperture, and ISO, go pick up a digital camera, put it in manual, and start shooting successfully, employing that knowledge. You can believe that by trying it out yourself.
 

Fujidave

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The one thing I do know is, to take a photo you need Light. So for me I have to really learn the Exposure Triangle, if I am right that is Shutter speed, Aperture and ISO. That`s if I read it all right that is.
 

Ysarex

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Just reading through the last couple of posts, and I am lost on what to believe or think.

It's not difficult to understand. First understand this: When the transition from film to digital began it was easiest to try and keep things feeling familiar. Lots of film photographers got their first digital cameras and rather than explain what was actually going on the simple answer was, "it's just like film." At the same time the industry was still figuring it out! I got my first digital camera in 2002. There was no ISO standard for digital cameras at that time. It didn't come along until 2006! (ISO 12232:2006). In the meantime a bazillion self-publishing experts got busy creating all those Youtube videos explaining it all. ;)

If you want to actually read the ISO standard you have to pony up some serious $$$ as selling the details is how ISO pays the bills. In this case however there's a free way around it. In 2006 what ISO did was simply adopt the standard from CIPA (Camera & Imaging Products Association) of which all our camera manufacturers are members. CIPA - Camera & Imaging Products Association: CIPA Standards Specifically you're looking for this document: http://www.cipa.jp/std/documents/e/DC-004_EN.pdf

I've read it and if you want to avoid slogging through it you can trust me to tell you that the ISO "sensitivity" values that you find on your camera are arrived at by measuring the brightness produced in a sRGB JPEG generated by your camera's processing software when exposed to a standard target. Who cares right? Well Fujidave might care eventually since he's shooting a Fuji camera. Since ISO is not a measure of the light sensitivity of the camera sensor is it possible that's actually different and could that matter to the photos you take? The answer is yes and yes especially if you're shooting a Fuji camera -- I shoot a Fuji too.

Next: Changing ISO on your camera does not change the sensitivity of anything. ISO on your camera does two things: a) It puts a spin on the metering systems and the camera meter calculates a new exposure. As you raise the ISO value the camera calculates an exposure reduction and as you lower the ISO the camera calculates an exposure increase. Many people confuse this ancillary function and make the spurious jump to thinking ISO therefore determines exposure at least in part. It does not. b) ISO boosts, brightens, gains (description of this process is tricky because old words like amplify have connotations that aren't quite right and multiple technologies are employed) the analog data coming from the sensor prior to and/or during ADC (analog to digital conversion) to normalize brightness in the raw file from which the JPEG is then created.

Joe
 

Ysarex

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The essential elements of photography like exposure, have not changed in over 100 years. You can pick up a photography book from 70s, read up on shutter speed, aperture, and ISO, go pick up a digital camera, put it in manual, and start shooting successfully, employing that knowledge.

That's exactly why I used good old Ilford's The Manual of Photography up above to prove you wrong. First published in 1890 and still the go to reference when you want to get your photography right!

You can believe that by trying it out yourself.
 

Fujidave

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Just reading through the last couple of posts, and I am lost on what to believe or think.

It's not difficult to understand. First understand this: When the transition from film to digital began it was easiest to try and keep things feeling familiar. Lots of film photographers got their first digital cameras and rather than explain what was actually going on the simple answer was, "it's just like film." At the same time the industry was still figuring it out! I got my first digital camera in 2002. There was no ISO standard for digital cameras at that time. It didn't come along until 2006! (ISO 12232:2006). In the meantime a bazillion self-publishing experts got busy creating all those Youtube videos explaining it all. ;)

If you want to actually read the ISO standard you have to pony up some serious $$$ as selling the details is how ISO pays the bills. In this case however there's a free way around it. In 2006 what ISO did was simply adopt the standard from CIPA (Camera & Imaging Products Association) of which all our camera manufacturers are members. CIPA - Camera & Imaging Products Association: CIPA Standards Specifically you're looking for this document: http://www.cipa.jp/std/documents/e/DC-004_EN.pdf

I've read it and if you want to avoid slogging through it you can trust me to tell you that the ISO "sensitivity" values that you find on your camera are arrived at by measuring the brightness produced in a sRGB JPEG generated by your camera's processing software when exposed to a standard target. Who cares right? Well Fujidave might care eventually since he's shooting a Fuji camera. Since ISO is not a measure of the light sensitivity of the camera sensor is it possible that's actually different and could that matter to the photos you take? The answer is yes and yes especially if you're shooting a Fuji camera -- I shoot a Fuji too.

Next: Changing ISO on your camera does not change the sensitivity of anything. ISO on your camera does two things: a) It puts a spin on the metering systems and the camera meter calculates a new exposure. As you raise the ISO value the camera calculates an exposure reduction and as you lower the ISO the camera calculates an exposure increase. Many people confuse this ancillary function and make the spurious jump to thinking ISO therefore determines exposure at least in part. It does not. b) ISO boosts, brightens, gains (description of this process is tricky because old words like amplify have connotations that aren't quite right and multiple technologies are employed) the analog data coming from the sensor prior to and/or during ADC (analog to digital conversion) to normalize brightness in the raw file from which the JPEG is then created.

Joe


Thank you very much for this, as you have helped me in the past I will gladly listen and take it on board.
 

Ysarex

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The one thing I do know is, to take a photo you need Light. So for me I have to really learn the Exposure Triangle, if I am right that is Shutter speed, Aperture and ISO. That`s if I read it all right that is.

The Exposure Triangle can be initially helpful but it does lead to confusion. Typically it's presented like this:

exp_triangle.jpg


Suggesting that each vertice of the triangle is an exposure control (shutter, aperture, ISO) and that each of those variables controls a secondary element of your photo;
shutter = motion blur
aperture = DOF
ISO = noise.

People who learn with that model tend to adopt some misconceptions. For one they assume ISO is an exposure determinant and it is not. More importantly they make the mistake of assuming that ISO causes noise -- that noise is the result of raising the ISO and that's wrong.

SET A
1/250th sec, f/5.6, ISO 200
1/500th sec, f/4, ISO 200
1/125th sec, f/8, ISO 400
~~~~~~~~~~~~~~~~~~~~~~

SET B
1/250th sec, f/5.6, ISO 200
1/500th sec, f/4, ISO 200
1/250th sec, f/8, ISO 400
~~~~~~~~~~~~~~~~~~~~~

Two sets above: all three in each set the same exposure yes, no?

There are weaknesses in the model and even though it may seem at first helpful for beginners it typically results in misunderstanding. I deal with it every semester with a new batch of students. They arrive already "exposure triangle" indoctrinated and they're taking worse photos than they should be because of the misconceptions I've noted above. Once I can get those misconceptions cleared up I can help them take better photos.

You're shooting a Fuji X camera with an APS-C sensor. What kind of results do you get at ISO 12,800? I have the same sensor in my camera. Have a look at this photo I shot at ISO 12,800 socks and tell me what you think about the noise level.

Joe
 

Fujidave

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As you might know Joe, I am still learning with both my Fuji X cameras, the socks image is great as if I am right you have exposed it bang on with no noise at all ?
 

Fujidave

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I will try and dig out a photo, but last week using the X-T2 + XF 35mm f2 in a pub. Lighting was turned right down and it waas dark out side even though I was in side, had to put the iso up to 800 and deleted them all as they were terrible when I got them in LR6 and hit the exposure slider, then I went again but this time same sort of lighting turned down, iso 640 and the shots were not to bad.
 

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