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Can someone explain how ISO/Base ISO functions these days? (alien.top)
submitted 1 year ago by Spirit-Subject@alien.top to c/photography@viewfinder.pro
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So generally, I’ve always understood that the lowest ISO is best to shoot at. Though with newer cameras, they usually have a higher base ISO and in some cases Dual ISO.

I usually work with the R5C, even for photography. It feels odd to take portraits at 800 ISO because I’ve always been told it should be as low as possible.

So does the Base ISO system, negate the need to shoot at lowest ISO for the clearest and least grainy image?

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[–] TinfoilCamera@alien.top 1 points 1 year ago (5 children)

So generally, I’ve always understood that the lowest ISO is best to shoot at.

This is a myth that hammers way too many new shooters.

The correct ISO is the best to shoot at, regardless of what that ISO might be.

Though with newer cameras, they usually have a higher base ISO and in some cases Dual ISO.

Dual ISO is not so much about noise as it is about dynamic range. It's important, but it's about maximizing details in your shadows when taking poorly/dimly lit photos.

Base ISO is an arbitrary number. If it's 200 or 100 it means the same thing: "I have all the light I need, boss!"

It feels odd to take portraits at 800 ISO because I’ve always been told it should be as low as possible.

It should be as low as possible, but not for the reasons you're thinking.

In and of itself ISO has no adverse effect on your shot. (Heads are exploding everywhere right now)

ISO does not cause noise. The noise is because you did not have enough light and had to raise the ISO... but the noise was already there because you were not capturing enough light. Raising the ISO just lets you see that noise.

Assuming ISO 100 is the correct ISO for a shot the reason it is better is because your sensor is being completely saturated with light - more than enough light to hide the noise that's there - and you therefor do not need more ISO.

ISO is the alarm bell that tells you that you are not saturating your sensor with enough light, and so you will have visible noise in your shot. ISO 800 is telling you that you're missing 3 stops worth of light.

tl;dr -- If you do not have enough light you will have noise. It is just that simple. If you have to raise the ISO, do it, because you're not hurting anything by doing so. A better option when doing portraiture however is to gather enough light that you do not need to do that in the first place. A longer shutter speed, a wider aperture, or add light via flash/reflector (or some combination of these) is what is needed... but if all else fails, raise that ISO without fear - and deal with the noise you're going to have in post.

[–] JeremyAndrewErwin@alien.top 1 points 1 year ago

ISO is the alarm bell that tells you that you are not saturating your sensor with enough light, and so you will have visible noise in your shot. ISO 800 is telling you that you're missing 3 stops worth of light.

By my count, ISO 800 is a sign that you're missing 9 stops of light.

https://filmphotographystore.com/products/35mm-color-kodak-super-low-speed-1-roll

[–] RedHuey@alien.top 1 points 1 year ago (1 children)

This.

Even camera manuals have this fact wrong. Not to mention photo sites and conventional wisdom on the Internet.

Noise comes from light. At least the biggest part of it does. It does not come from the sensor, or amplifying sensor noise, for the most part. As equipment gets better and better, equipment noise has gone way down. Almost all of the noise you see is from light itself and there is nothing than can be done about it.

Seeing more noise at higher ISOs is because light noise is related to the square root of the number of photons. A lower number has a relatively higher square root. Less light has relatively higher noise. In lower light conditions, no matter what you do, you are working with less light, and thus more noise.

The base ISO is the one where the sensor system is designed to have the highest signal to noise ratio at the “correct” exposure.

[–] oldlurker114@alien.top 1 points 1 year ago

Pretty much right, though I'll clarify a bit if I may:

Seeing more noise at higher ISOs is because light noise is related to the square root of the number of photons

Noise is related to the number of photons. What the square root gives is the standard deviation (due to the Poisson distribution that light particles follow) and "noise" is the signal to noise ratio, SNR, the ratio of the number of photons to the standard deviation. And this is of course funnily also the square root of the number of photons.

A lower number has a relatively higher square root. Less light has relatively higher noise

I do understand what you mean, but this is IMHO rather confusingly put and especially for beginners impossible to comprehend what you mean.

Simply, more light means larger SNR. The standard deviation of the signal goes up, but the signal itself goes up much more. What an observer sees as "noise" is simply a product of low SNR.

The base ISO is the one where the sensor system is designed to have the highest signal to noise ratio at the “correct” exposure.

The image sensor has no ISO at all. It can be run at different parameters and typically changing the camera's ISO setting changes there operational parameters.

The concept of "base ISO" isn't officially defined (by ISO, the organization) and can interpreted in many ways. If we go by your definition above, then it would be typically the lowest extended ISO setting as the exposures are typically larger than the ones with the lowest "regular ISO" settings. Many people on the other hand seem to consider the lowest "regular ISO" to be the "base ISO". FWIW, usually the image sensor is driven with the same parameters in both cases.

ISO value itself is really a property of output formats, like JPG.

IMHO the concept of base ISO should be abolished for above reasons. It's likely more harmful than useful for beginners.

[–] X4dow@alien.top 1 points 1 year ago (2 children)

Iso causes noise. Stop spewing the Bs northrup Invents.

Ultra bright outdoors, shoot at 1/4000 f22 iso 26000 it will be noisy. And don't give me the "1/4000 f22 makes little light hit the sensor, it's lack of light"

Lack of light makes you use high iso to expose correctly, therefore noise. Of course.

[–] Raveen396@alien.top 1 points 1 year ago

From an electrical engineering perspective, you’re both right.

ISO in digital sensors is an amplification of the analog signal output by the photovoltaic sensor before it is converted to digital. Amplifiers indiscriminately amplify both noise and your signal of interest. In that sense, he’s right that a high quality sensor with little inherent noise will produce a less noisy image at high ISO than a low quality sensor with a lot of inherent noise. A high ISO (amplification) will serve to amplify noise existing in your signal.

However, amplifiers also have a quality known as “noise figure”, in that all non-ideal amplifiers will add some noise to a signal. So you are also right in that there is some amplifier added noise that is possibly more visible when you increase your ISO, because amplification tends to reduce your maximum theoretical dynamic range through the additive noise, not increase it.

All that being said, this is all semantics and in practice I think the comment you’re replying to is correct, but is a bit loose with some technical concepts that don’t really matter in practice.

[–] TinfoilCamera@alien.top 1 points 1 year ago (1 children)

Iso causes noise.

Oh for crying out loud.

Stop spewing the Bs northrup Invents.

Difficulty: He didn't invent that, he literally parroted it.

Ultra bright outdoors, shoot at 1/4000 f22 iso 26000 it will be noisy. And don't give me the "1/4000 f22 makes little light hit the sensor, it's lack of light"

OK - I won't.

Little green men from Mars caused the noise!

OR... it could just be Signal vs Noise and if you do not have enough signal you will have noise... and all the signal you will ever have is gathered before ISO is applied.

Thus it is proved - all the noise is also gathered before ISO is applied.

Lack of light makes you use high iso to expose correctly, therefore noise. Of course

You realize you just reversed your position, right? Lack of light does indeed force you to use high ISO, and that lets you see the noise that was already there.

[–] X4dow@alien.top 1 points 1 year ago (1 children)

Use that same low light scenario. Shoot at iso 100. And you get a perfectly clean black exposure.

See, low light, no noise. So low light doesn't equal noise.

Boosting iso to get the exposure right when there is a lack of light. Does, as you expose the noise too

[–] Sneezart@alien.top 1 points 1 year ago

I wasn't going to get involved in this one as well but here we go.

In this scenario, if you kept the ISO at 100 but instead of increasing ISO, you kept the shutter open for longer, you will also get a perfectly exposed image with minimal noise. If noise was inherent to low light scenarios, you would be capturing more of it because your sensor would be exposed to that noise for longer, but that's not the case.

And yes, you would still get a small amount of noise (and hot pixels), but that's thermal noise from keeping the photovoltaic sensors exited for a longer period of time.

[–] BigRobCommunistDog@alien.top 1 points 1 year ago

My keeper rate is noticeably up after switching from manual ISO to auto ISO and focusing more on shutter speed.

[–] 2deep4u@alien.top 1 points 1 year ago (1 children)

So is it better to have iso at auto

[–] TinfoilCamera@alien.top 1 points 1 year ago

If Auto will do it for you - sure. Remember that you're not hurting anything by shooting at the ISO the shot needs, and on older, variant sensors you don't hurt yourself in post by shooting at too low of an ISO, which can end up giving you even more noise when you correct those shots in post.

There are times when pushing in a bit of Exposure Compensation is needed, some amount of -Ev to defend against blowing out your highlights or the opposite, dealing with backlit scenes where you need more ISO and +Ev than auto wants to give you.

[–] RealTimeflies@alien.top 1 points 1 year ago

Cameras with duo iso have 2 different analogues to digital circuits. One is much better at converting higher ISOs to digital signals with lesser noise.

https://www.youtube.com/watch?v=FrkkdhihUEU&t=10s

[–] Affectionate_Ear_778@alien.top 1 points 1 year ago

Read what TinFoilCamera said.

[–] FrontFocused@alien.top 1 points 1 year ago

Wait until you look into cameras that have ISO invariance.

[–] teemosillin@alien.top 1 points 1 year ago

Check out the sensor and camera ratings at DxO Mark website to see the dynamic range and other image characteristics at different ISOs.

https://www.dxomark.com/camera-sensors/

[–] ptq@alien.top 1 points 1 year ago

Afaik R5 for photo has 100 and 400, and for video it's 800 and 3200. Probably R5C should be the same.

[–] _dav3nator@alien.top 1 points 1 year ago

Perhaps this will help.

Pal2Tec YouTube Channel Video: What is ISO.

https://youtu.be/ubv-Es_Enio?si=FMHpjyjQ1DRKcNBc

[–] DarkColdFusion@alien.top 1 points 1 year ago

So does the Base ISO system, negate the need to shoot at lowest ISO for the clearest and least grainy image?

If you don't need to under expose, then shooting at the lowest ISO will give you the least noise.

Noise in photos is mostly from the light itself. But some of it is from the Camera Electronics, and when you bring up the exposure in post, you are bringing up that noise too.

A perfect camera could be shot at base ISO, under exposed any amount, and adjusted in post with no harm. Many cameras are pretty close to that over a limited range but not the entire range.

So for your example, if you have to choose to Expose at ISO 100 and under expose by 3 stops, or shoot at ISO 800, you will have less noise in the ISO 800 shot.

If you do not need to under expose the ISO 100 shot, you will have less noise in the ISO 100 shot then the ISO 800 shot.

[–] TiMouton@alien.top 1 points 1 year ago (1 children)

The dual ISO is for low light situation and produces less noise than a regular single ISO.

The ISO nowadays is the sensitivity of the sensor towards light input. With more advancements in sensor technology, higher ISO ranges become less noisy.

A lot of that avancement recently is thanks to software and noise reduction like dual base ISO.

[–] Spirit-Subject@alien.top 1 points 1 year ago (1 children)

With that in mind, if I shoot in a studio setting, is keeping the ISO low still preferable?

[–] VivaLaDio@alien.top 1 points 1 year ago (1 children)

If you’re shooting in a studio setting i don’t see how you would need higher than 100 iso , since sub 200th of a second is the normal flash sync, you’d have to go to like f22 to start overpowering your lights.

[–] Spirit-Subject@alien.top 1 points 1 year ago (2 children)

I understand that very well. My question is that, does Base ISO on your camera signify the cleanest image in all settings?

[–] Sneezart@alien.top 1 points 1 year ago

Yes, base or native ISO will produce the least noise in a correctly exposed image.

[–] TiMouton@alien.top 1 points 1 year ago (1 children)

While u/sneezeart answer is correct, I would like to add some details:

Native ISO is the natural ISO range that your sensor can handle without extra digital manipulation. So for example that would be like ISO100-6400 as a native range and the low setting (ISO50) and high setting (iso12800) would be extended ISO as they are digitally manipulated.

Base ISO is the lowest ISO in the cameras native range. Base ISO yields best image quality as it’s the sensors base sensitivity without amplification (gain) through increased voltage.

If base ISO is 100, that means at ISO 200 the signal of the sensor is amplified with twice the voltage. The more amplification, the more noise.

[–] oldlurker114@alien.top 1 points 1 year ago

Native ISO is the natural ISO range that your sensor can handle without extra digital manipulation

The image sensor has no ISO range, or ISO setting at all.

Typically different ISO settings on the camera cause the sensor to be operated with different parameters (leading to different noise performance curve). May sound like nitpicking, but I think it's important to understand the difference.

So for example that would be like ISO100-6400 as a native range and the low setting (ISO50) and high setting (iso12800) would be extended ISO as they are digitally manipulated.

This is wrong.

Typically the image sensor operates at the same setting at "extended low ISOs" and with the "lowest normal ISO" (though some extended settings may use the same parameters of ISO 125 or ISO 160 for example). What is different is metering - with the extended settings the camera exposure program simply causes a larger exposure to be used by default, thus there will be less headroom (in the JPGs, thus no longer ISO standard compliant). That's it.

The "extended high" settings on the other hand typically add (digital) multiplication to the data. All it does for raw is that it cuts the headroom. For JPG shooters it's not relevant if it's "extended high" or not.

[–] KidElder@alien.top 1 points 1 year ago

If you can't get the shot without high ISO, then use high ISO. Programs are getting better every day to deal with the noise as well as the cameras.

Would you rather have that shot of a lifetime with some noise or miss it because your ISO is too?

[–] KidElder@alien.top 1 points 1 year ago

If you can't get the shot without high ISO, then use high ISO. Programs are getting better every day to deal with the noise as well as the cameras.

Would you rather have that shot of a lifetime with some noise or miss it because your ISO is too?

[–] codenamecueball@alien.top 1 points 1 year ago (2 children)

The dual ISO is for video in order to capture maximum dynamic range when using LOG profiles. It’s got little to no relevance for stills photography, unless you’re shooting stills in log. Max DR for stills is usually at 100, with the R5 sensor it’s 50 according to our friends at DxO.

https://www.dxomark.com/canon-eos-r5-sensor-review-a-high-water-mark/

[–] Spirit-Subject@alien.top 1 points 1 year ago

Great! Thanks for your answer my man!

[–] spider-mario@alien.top 1 points 1 year ago (1 children)

Maximum DR ≠ minimum noise. The DR is higher at low ISO because the highlight headroom is higher, but the noise floor also is, and if you are light-limited, the latter may be more relevant.

[–] codenamecueball@alien.top 1 points 1 year ago (1 children)

Look at the other graphs. Best noise performance and colour depth is also at lower ISOs

[–] spider-mario@alien.top 1 points 1 year ago

“SNR 18%” is higher at lower ISO, but is also 18% of a higher saturation point, so it’s the SNR for a higher amount of light – no wonder it’s higher. For a fixed amount of light, as in low-light situations where you might be limited to, say, f/2 and 1/100s, the highest ISO setting that doesn’t clip anything you care about will lead to less noise. (More or less depending on the camera.)

See figure 6 of: https://www.mdpi.com/2079-9292/8/11/1284/htm

Or: https://www.dpreview.com/reviews/image-comparison/fullscreen?attr134_0=canon_eosr5&attr134_1=canon_eosr5&attr134_2=canon_eosr5&attr134_3=canon_eosr5&attr136_0=1&attr136_1=2&attr136_2=3&attr136_3=4&attr176_0=efc&attr176_1=efc&attr176_2=efc&attr176_3=efc&normalization=full&widget=487&x=0.06014373975539024&y=1.0840726817042607

(The effect is more extreme with the EOS RP.)

[–] Mr_Will@alien.top 1 points 1 year ago

ISO is the least important part of the exposure triangle. Always has been. It's much better to get a sharp image with a little bit of grain than one that is smooth but blurry. If your images aren't visibly noisy at 800 ISO then stop worrying about it.

[–] wobblydee@alien.top 1 points 1 year ago

Shoot at the lowest iso possible to get a good image.

You might have an f2.8 lens but for depth of field purposes youre shootimg at f4. But its getting dark out. Lucky for you you have a modern camera so when you move up a couple stops of iso you maintain your other settings and get an image that comes out just fine.

I dont touch iso until i need to. I shoot moving subjects so setting the shutter speed is my priority. However i can only go so slow on shutter speed before i cant track the subject well enough. Lucky for me auto iso will take me up a bit and come out with a good image.

Dont just randomly set 1/1000 shutter f22 iso:auto but its not the end of the world if iso is above 100. If your other settijgs are maxed out either physically or by the restrictrions needed to still get a good photo dont be afraid to let iso do its thing

[–] Spirit-Subject@alien.top 1 points 1 year ago

Thanks everyone for your comments! Learned a lot .. to be honest, I thought it was a simpler question than it seemed, but I guess theres a lot that goes into it.

[–] oldlurker114@alien.top 1 points 1 year ago
  1. Normally, as you raise the ISO the maximum amount of light the image sensor can collect goes down.
  2. The more light you collect the better the image quality because light itself is noisy - the more you capture, the less noisy things appear to you.
  3. Raising ISO makes the JPG brighter, reducing it darker.
  4. Raising ISO normally reduces the camera added noise slightly - this is mainly relevant if you shoot raw.
[–] Separate_Wave1318@alien.top 1 points 1 year ago

These days, because of modern technology, (more from recent lightroom update than sensor) I don't even worry until ISO 3200. It's more important to have right shutter and aperture for the subject than have lower ISO... unless we are talking about ISO25600 unholy noise slush.