Camera ISO and How it Affects Exposure


(relaxing music) – Most people understand
aperture and shutter speed in how it relates to the
exposure triangle, right? Aperture is simply the
photographer controlling how small or wide the aperture blades are, which then, in turn, lets in
a certain amount of light. He has control over that. And shutter speed, for the
most part, is kinda similar. How long to expose the sensor to light? Those are two key decisions. Aperture and shutter speed. What is ISO? And how does it pertain
to the exposure triangle? Actually, ISO is not
part of exposure at all. More on that in a second. It’s a big fat ISO sandwich out there and sooner or later, we
all have to take a bite. (upbeat rock music) Roll intro. (laughing) (upbeat music) Hi everyone, welcome to Pal2tech. Today, we are talking about I-S-O, or ISO. Everything about ISO is confusing. Even the frigging name is confusing. ISO is a rating scale that’s managed by the International
Association of Standardization, which is the main governing body that standardizes sensitivity
ratings for camera sensors. Now, while many people think
ISO should be called I-S-O, you know, because it stands for International Organization
Of Standardization, it is actually technically not an acronym. According to the organization,
the name and pronunciation comes from the Greek root
word, ioos, which means equal, and in this video I will
mostly use the term ISO because I come from a film
background where we had ASA. Today we’re gonna focus
on two key IOS topics. What exactly is it? And how does it relate to exposure? For many years,
photographers simply referred to the exposure triangle
as the application of shutter speed, aperture, and ISO in controlling the overall
exposure of the image. Exposure, at its most
basic level, is all about how much light reaches
your camera’s sensor. Your camera’s sensor is
like an ice tray filled with little cavities in
it called photosites. These photosites have an assortment of red, green, and blue
color filters over them. Light photons come pouring in
from the front of the camera into these cavities on
your camera’s sensor. As soon as this happens,
all these little photosites right here generate an electrical charge. It’s not digital yet. It’s analog voltage electrical charge. This water represents light. Light is now hitting the sensor. It is now hitting the sensor. Okay. Now, the higher the ISO, the more your camera amplifies
the electrical charge. So let’s say you have it on
ISO 400, it’s amplifying it, amplifying the electrical charge, right? Now, the more the electrical
charge is amplified, in other words, as you turn the ISO up, the brighter the image is. Here it is at 800. And here it is at 1600. Okay? (laughing) Got that? And you control this through the ISO dial. Now, here’s the most
important point of all. ISO is applied after
the sensor is finished being exposed to light. It has absolutely no effect, whatsoever on how much light is hitting the sensor. Only shutter speed and aperture
affect exposure in that way. ISO does not. You gettin’ this? Are you gettin’ this? It has nothing to do with increasing how much light hits your sensor. (siren blaring) Now (laughing) because ISO is nothing more than your camera amplifying
things after you have taken the photo and already finished
exposing the sensor to light, you do not get better exposure
by increasing the ISO. You only ever get better
exposure by slowing down the shutter speed or
opening up the aperture. And exposure, if it’s taken at ISO 200, is exactly the same amount of exposure as one that was taken at ISO 3200. The sensor is exposed to
exactly the same amount of light and this is hugely important to remember. Okay, once the camera has
applied your requested ISO by amplifying the electrical charge. I’m not going to do that again. By amplifying the electrical charges and the sensor’s photosites,
it’s all finished. It’s done. And each individual
photosite’s electrical charge is now sent from the sensor, (hissing) from the sensor, into the camera’s analog
to digital converter, which then turns the voltage
into a digital value, which is a binary number. Think of little ones and zeros. This red pen is going to
be the electrical charge coming from the sensor. I am the analog to digital converter. Here it comes. (buzzing) (sizzling) Okay, that was a very nice beach scene with some really nice highlight
details and shadow areas and really just an overall beautiful image with a nice blue sky. 110011011. we’re gonna put this into a jpeg and, go. (dinging) (inhaling and exhaling) I bought that bullhorn
just for this segment. Just saying. (laughing) Now, let’s talk about ISO and noise. ISO does not actually create noise. ISO is amplifying the noise that’s already there to begin with. Now, the Fuji film XT3
camera has a native ISO range from 160 to 12,800. This is the camera’s hardware analog ISO amplification range. And of that range, 160 is
considered the lowest native ISO. That means that at ISO 160,
the camera doesn’t need to amplify the voltage at the sensor before the electrical charges are sent off to the camera’s analog
to digital converter. You got that? Now on the XT2, that ISO number is 200. And all things considered, this is generally your happy place. It’s where you want to, you know, set it as much as you possibly can. Now the camera also has
little L and H markings on this dial right here. And this allows you to use
what’s called extended ISO range. On that XT3, if you put the dial in L, the camera will allow you to use lower ISO than even the native base ISO of 160. On the H setting is the
opposite end of the spectrum. You can extend the ISO, so to speak, all the way up to 25,000 or 51,200. Now what you need to know about the low and high ISO extended
settings on this dial is that they are not
performing any native camera analog amplification to
the electrical charges in your camera’s photosites. Think of it this way, using L and using H on this camera is just like using that crappy digital zoom
focus feature that you see in smart phones instead
of using a real zoom. And as you turn up the ISO on the dial, you amplify the electrical
charges more and more. This amplifies the noise and
you get worse image quality. It’s a trade off. Based on what I told you today,
here are some key takeaways. Number one, whenever possible
always add more light to your scene instead of relying on simply increasing the ISO. ISO is not exposure and
does not increase the amount of light that hits your sensor. Avoid using it as a
crutch, whenever possible. A good way to think of ISO
is that ISO is basically a simulation of what your
photo would’ve looked like if it had been properly
exposed in the first place. Number two, ISO is very
dependent on the camera. How ISO is handled,
strategies for setting ISO, and even ISO noise differences
between different models of the same camera brand can vary. Number three, ISO absolutely
affects your RAW photos. And if you use a value high enough, if you crank up the ISO high enough, even with RAW you will
blow out your highlights. More on this in my future
ISO invariance video. Generally, ISO 6400 is about the max you’d ever wanna go for good results. I pretty much never, ever go beyond that. Most of the time I tend to
hover between ISO 800 and 1600, if I’m needing that extra amplification. Lemme put it to you this way. If I was at ISO 6400, you know, with the slowest shutter speed I could use and the widest aperture I could use and Home Depot was all out of light bulbs and I simply could not make
the scene any brighter. Well, then screw it. I would shoot in ISO 6400. And then I would use
adaptive ISO post-production in Lightroom or CaptureOne to selectively, the word is selectively,
bring up the dark portions of the image I wanted to better
expose without amplifying and multiplying the noise
in the entire image. But I’m lying here. I think having ISO in the
exposure triangle is helpful. Very helpful. To conceptualize how the various controls of the camera work together
to create the image. However, you should remember
that ISO is not exposure. And it’s definitely not
a substitute for getting as much light into your scene, as you possibly can in the first place. In future videos we will
explore this concept further. Here’s the thing about these videos. Listen. I’ve missed seeing you guys. I can’t make these videos
so packed with information that each one is like an
Encyclopedia Britannica. You know, here’s the thing. What I’d like to do is to
see you guys more often, but we’ll go on shorter dates. Okay, (laughing) does that work? All right. Until then, it’s been great to be back and you will have another video from me coming this Friday for sure. If you’ve enjoyed this
video, please give it the like and subscribe. (laughing) I mean, a like and subscribe. (stuttering) You know what, no, I’m
gonna go with the other, I like the other one better. The like and subscribe. If (laughing) you’ve enjoyed this video, please give it the like and subscribe and I will see you again real soon. So long. (upbeat music) It’s hard work as you can see. Okay. You all know your basic exposure triangle. (laughing) More chalk! I need an assistant. (laughing) You know what’s funny,
that could be the outtake at the end of the video. More chalk, more chalk! Thank you, sir.

100 Replies to “Camera ISO and How it Affects Exposure”

  1. I am not into photgraphy, I don't know anything about it, but this video was really interesting. Now I know about ISO! I love the "More intro" bit. Thanks for sharing on the NSC Facebook page.

  2. I have seen Fuji sensors described as ISO-less. I thought that meant that brightening the photo in post has the same result as boosting the ISO while shooting. Is that true?

    Reference e.g. https://fujilove.com/isoless-photography-with-the-fujifilm-x-series/

    I'd also be interested in an explanation of the "dynamic range" setting

  3. Starting 2020 with 10k subscribers….congrats!! Well-balanced video humor/technical explanation. Suggestion for another ISO video: when and why to use the low extended ISO ranges? Great to see you back!

  4. Nice to see you back. Will have to catch this video later today. Now, however, I have 3 inches of snow to shovel and more on the way. 😉

  5. Great tutorial on explaining ISO and exposure. I’m new to photography and this was a fantastic learning video for me! 👍👍

  6. excellent video!
    unrelated…
    …but on the x-t3, how exactly do you get the audio level meters showing in the view finder? (I only see them when I go into adjust audio levels)

  7. Try to go into detail about ISO when using a handheld light meter, in particular differences between the standards of ASA (film/light meter), SOS (standard output sensitivity, used by Fujifilm) and REI (recommended exposure index, used by Nikon, Canon etc.). Maybe research Doug Kerr on this.

  8. Dear pal2tech,

    Really good to see you back and with a really interesting & well thought out topic. It stopped me and made me think, so thank you.

    Looking forward to more of your vlogs in 2020

  9. GREAT to have you back . Excellent explanation. Hugely looking forward to your ISO invariance video . I understand the XT3 sensor to be the most invariant there is . I have the thought that it means that it is ok to be underexposed because of that but don’t understand ISO invariance .

    You mention noise reduction in LR or C1. I suggest that you give Topaz Denoise Ai a trial …I find it to be excellent . It incorporates Denoise Ai and Ai Clear . It is very rare to see anything on Youtube mentioning Topaz .

    I cannot fathom out why Fuji bother to have the ISO dial go above 6400 …noise is awful above that and not easy to get rid of without a soft result.

    Would you please explain more about the benefits and shortcomings of ISO L setting .

    Many thanks

  10. I found this particular low light setting for the XT3 very useful when shooting video: 4K,25p,50shutter,eterna,DR100(very important),100mb is ok and Iso 1600. From all my tests it seems Dr100 prioritize shadows and Dr400 highlights. For some reason when using all these settings together, there is almost no noise. I would never ever be able to shoot in these low light conditions with my GH5s.

  11. FYI, according to Kasson and a handfull others the Sony made sensors (read also Fuji) has ISOless sensors, in fact the newer models have dual ISO ISOLESS capability. This means that you have two native ISOs (160 and 640 on X-T3), everything between 160 and 640 is 160 pushed. Everything after 640 is 640 pushed. This have been tested and confirmed several times. When shooting nightshots I use 640 and underexpose just to push things back again – because I can do it better than the camera while retaining details in the highlights. I aim for 160 If 640 isn't needed when shooting landscapes etc, just to keep MAX dynamic range. If I do weddings etc then I use ISO as everyone else just to see the compositions and to have a decent preview.

    Have a look at this site, the compare with X-T3's graph in link below.

    https://www.dpreview.com/news/4302149407/sony-a7r-iii-dynamic-range-improved-nearly-matches-chart-topping-nikon-d850

    Choose X-T3 in link

    http://photonstophotos.net/Charts/PDR.htm

    Also have a look at these two videos. Lots of good information.
    https://www.youtube.com/watch?v=g8hHFt3ChZ8
    https://www.youtube.com/watch?v=2sshGdMgJxQ

  12. Hi buddy… super topic. In the vid you say that native ISO on the fuji xt3 is 160 and that setting will have zero amplification of signal… hence no noticable noise. If that's the case then how can you set ISO to as low as 80?? What does that mean…. a minus factor of signal amplification. Hmmm leaves scratching my head and wondering if 80 is zero amplification and 160 is amplified but so little no noise is detectable. I know you'll have the exact answer ready for me… 😄🤞 I just thought… I wonder if it's in the xt3 manual?
    Best wishes buddy
    Always enjoy your vids
    Regards… Steve

  13. An excellent video as always. The wait for your return was worth it! Made a very dry subject amusing. Your humour is greatly appreciated. Your children must enjoy you explaining things to them with practical demonstrations like the ice tray! Love it!

  14. Good information, Chris, thanks! I would request follow-up on two points:
    1. Fuji says its dynamic range changes with ISO. On my X-T20, the best ISO, 200, has the lowest dynamic range, then ISO 400 has a higher dynamic range, and then ISO 800 and above have the maximum dynamic range. Why is that, and how do we decide what's the best choice on that trade-off?
    2. I still don't understand what is going on in the lower ISO extensions below the native minimum. What exactly are they doing?
    Thank you!

  15. 👍Spot on, but way too subtle and understated — put some oomph into it 😂. Exposure triangle is convenient but flawed metaphor that is, sadly, perpetuated. I also remember ASA — film “speed” that, indeed, had to do with the sensitivity of the material being “bombarded” by photons; granularity of film emulsion. Interestingly, film speed could be “pushed” or “pulled” in “post” via chemical processes. Remember? I like to think of ISO adjustment like the volume control on a radio — both broadcast “signal” and electronic “static” background “noise” (literally) are increased as we turn up the volume. Good analogy of ice tray, but I don’t get the shake part. Bull horn for sale on eBay.

  16. What about when you are using flash? Watched a video of a guy explaining about exposure with a flash and at certain point he says, and so what can we do? Increase ISO. Can dig the movie if you like. But he is thai guy professor of photography.

  17. I had no idea that ISO was simply post exposure electrical amplification. The analogy to digital zoom is a great shorthand way to understand the concept. Thank you.

  18. Best explanation of Base ISO that I've heard. Great job! The transition from film ISO to digital never really clicked for me. FWIW, I find Fuji's ISO implementation up to 3200 very usable. In fact, with Acros I tend to find the noise and grain very pleasing.

  19. Glad you are back. Very good explanation of ISO. I learned a little more. Thanks for this! I am looking forward to tour next video my friend!

  20. 👍 Back in the saddle I see😉 Hope you enjoyed your respite. Best explanation of ISO…….ever.
    My lazy butt, yeah…it’s fake light. Fugazi.

  21. I been shooting for over 17 years and I never quite understood ISO in the digital world as it feels it was always a carry over from the film days. I knew how it related to the overall final image but I never quite understood. This is a great explanation.

  22. Hi there , excellent video. I now an xt30 and I have a problem seeing the real exposure when I am on shutter priority mode. Do you notice the same wiht the xt3?

  23. After using Fuji and experienced its ISO cheat nonsense I've come to understand that digital cameras do not have any meaningful ISO ratings, exposures are up to interpretations.

  24. UnLearned more about iso than I thought I understood. I had many misconceptions until your brilliant demonstration. So do these principles transpose to film and an “exposure triangle” in film?

  25. Yeah A to D signal amplification and conversion but how does this translate to celluloid film with ISO 100 / 200 / 400 etc ? You need to explain that correlation.

  26. I like the water in the ice cube container explaining the intensity of ISO.. 😛 . As usual very good video! Keep coming 🙂

  27. Nice one !
    Hope you can take on the middle gray aspect of things and dynamic range répartition depending on ISO in a future video.

  28. ISO glad you shared.

    Also, can you explain why there are hard jumps in exposure when I am taking a video with my X-T3? This happens when using auto ISO or auto shutter. It's really annoying. Thanks!

  29. It's like a guitar amplifier. The amp receives a certain signal from the guitar and amplifies the volume after the fact. The volume setting on the amp has nothing to do with the initial signal it receives. Upping the volume on the guitar itself would be the equivalent to adding more light to the scene of the photograph prior to taking it the shot. ISO should be replaced with intensity of light in the exposure triangle (how that can happen is beyond me).

  30. ISO as used in digital cameras has nothing to do with the sensitivity of the sensor and in fact is meaningless as far as a sensor is concerned. The term that accurately defines the sensitivity of a sensor is called QE, Quantum Efficiency. Quantum efficiency of a sensor is also wavelength dependent . This means that a camera sensor has higher QE for Green portion of the spectrum than for the Red for example. Also and most importantly the QE is fixed and can not be altered. The electrical charge generated by the photosites goes through a process of amplification and the measure of this amplification is commonly called Digital ISO which has nothing to do with term that unified the US ASA and the European DIN back in the good old film days. This digital ISO is a marketing hark back to gone era of the film and it was chosen to maintain familiarity for the migration from analogue film to digital. The rest of the explanation given in the video is spot on and thank god someone is trying to clear this mess of confusion. Great video and presentation BTW.

  31. Well done. Can you go over the point you made in take away #2. I can’t tell you how many times I have seen Sony fanboys making the claim that Fujifilm cheats when it comes to ISO. None of them ever explain their claims. It just seems to be some myth repeated on online forums and is never challenged.

    This video seems to dispense the claims and like the word Inconceivable in the Princess Bride ISO seems to not be what people think it is. Again, great job and looking for more on this subject.

    One last thing – you may want to talk about how ISO was set on film stock originally and how the term is carried forward to digital but has a new meaning.

  32. Brilliant thanks a lot for this video which explain and demystify the ISO on digital camera. Did you plan to make a video to explain the relation between sensor size and pixel count Vs low light performance?

  33. I try to avoid higher ISO as much as I can but there are situations where there is no way around (action photography indoor in bad light conditions). Luckily the X-T3 handles higher ISO pretty well. Much better than my old X-H1 did. Great explanation there and nice to have you back!

  34. Excellent explanation. Do you think it would be technically accurate to go back to calling it “ASA” – Applied Signal Amplification? Thanks

  35. In a nut shell, ISO is applied gain and there are going to be times when you will push your ISO past 6400 and those times will be when flash can’t be used like in a concert or in a dark church, but in general I agree with keeping iso as low as you can, but it isn’t always possible, sometimes in sports photography in a poorly lighted gym you will find yourself depending on the lens, and the lens is quite important, but covered by aperture you will find yourself in that 5000 iso range.

    Great information here that should be mentioned more often, but like you said they try and keep it simple by using the exposure triangle to maintain a concept. In the film days you picked the type of film for the light that you were shooting in so it was a constant that couldn’t be changed and you just worried about shutter speed and aperture.

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