- My brain is super fried from working on all this ISO stuff, to then have to do another
video for Fast Friday, so consider this video a double video. (upbeat music) Hi everyone, welcome to pal2tech. Today, we are talking
about ISO performance and ISO invariance. Everything I'm gonna discuss today pertains to shooting raw
photos on your Fujifilm camera, and then processing later on in an editor like
Lightroom or Capture One. Unlike aperture and shutter speed, ISO has absolutely no effect whatsoever on how much light is hitting the sensor. It would help if you thought of ISO as post-exposure lighting. And you can apply it either
using the ISO dial on the camera or in post production
using the exposure sliders. Now, when you turn up the ISO dial you are amplifying the
electrical charge that is created as a result of light photons
hitting your camera's sensor. I made a whole video about this process that you should definitely check out, and I will have a link to that video in the description of this video. Now, there's a few other things going on when you turn up the ISO dial. Obviously, increasing ISO will increase the
brightness of your image. That's probably why you're
doing it in the first place. However, it will also decrease the total dynamic range of your image. The higher the ISO, the less dynamic range
you have to work with. Second, higher ISO values
will also affect skin tones. Skin tones are one of the
first things to suffer at high ISOs. Third, higher ISOs can cause
you to clip your highlights. Obviously, if your
scene gets bright enough because of you increasing your ISO, you will start to see highlight clipping. And forth, lastly, is the issue of noise. ISO does not actually create noise. It merely amplifies the noise that's already added as your analog signal travels from your camera's sensor to the analog to digital converter. Test, test, test. Think of ISO as turning up the
gain knob on your amplifier. The louder you get, the more
noise also gets amplified. (frequency roar) The louder you get, the more
noise also gets amplified. You see that? So what is ISO invariance? Well, I have a little
explanation chart right here that I drew up for you. This is your camera's sensor. Now, the minute you take a photo, the signal travels from
your sensor, right? And as it's traveling through
your camera from your sensor to your analog to digital converter, it is picking up noise. There's noise in the camera, there's noise in the circuitry, there's photon noise. It's collecting all this noise as it's traveling from
your camera's sensor to the analog to digital converter. Now, before it gets to the
analog to digital converter, your ISO kicks in and your camera actually has
two different analog amplifiers to amplify the signal. Remember, I said ISO is nothing more than amplification of the signal. So what happens is the signal comes here, it gets a little bit of noise then it hits the amplifiers. Now, here's the interesting thing, and we gotta go back to the chart now. Look at how there's a drop right here. You see that? When you get to ISO 636, it drops down to here. There's less noise. And then the noise continues back up. What is happening here? Why does it drop like that? That is where a different
amplifier kicks in. Your Fujifilm camera has
two different amplifiers. I'm being really simplistic here, but just stay with me. It has two different amplifiers. One of them from ISO 640 and below, the other one above ISO 640. And that other one that kicks in, there's a little bit of drop. It actually gets better quality
at first before it goes up. If you're shooting an ISO less than 640, it's going through this amplifier. If you're shooting an ISO
greater than or equal to 640, you're going through this amplifier. So the signal gets amplified
and made even brighter. Then it goes to your analog
to digital converter. And that point it gets converted. Once it gets converted, it continues to travel,
picking up more noise, and then there's another
amplifier on the other end, a digital amplifier that
amplifies it even more. If you set those crazy high ISO values, you know what I'm talking about, like 25,000 ISO, it'll crank it out and
amplify it digitally, and then spit it out
and onto your SD card. So to recap: Camera takes the picture, signal travels to the amplifier, it chooses which amplifier
based on your ISO setting, and then that continues to your
analog to digital converter, and then that continues. And if necessary, it gets
amplified even more digitally and then it gets stored on your SD card. So I had to explain all this to you because cameras that are ISO invariant have very little noise, usually around this step and
this step in the process. And because they have such little noise, it doesn't matter whether you decide to have
the camera amplify it here or if you decide to amplify it
in Lightroom or Capture One. Let me show you what I mean. Here are two photos I shot with the exact same camera settings, same lens, same scene, same everything, the only difference was the ISO that I set on the dial on the camera. The photo on the left was
shot at the correct ISO, the one that would have
correctly exposed the image that I could see on the
back on the viewfinder, and that was shot at ISO 6400. The photo on the right, I decided to force the camera on the dial to shoot it at ISO 200. That's five stops below what it showed the correct
exposure should be. Then I brought them into Lightroom. So now if I go in and I edit this photo, I decide to crank up the exposure. Have a look at this right here. Right there. Right there. If I crank it up five stops. I've now just added
five stops of exposure. That is the exact same thing as turning the ISO dial up five stops. Have a look at this. Photo on the left was the original, correctly exposed ISO 6400. Photo on the right is the ISO 200. I'm zoomed in one-to-one. And as you can see, they are really close. That's ISO invariance. Basically, you could either
set the ISO on the dial or you could do it afterwards
in post-production. That's an oversimplification of it, but that's what it is in
case you weren't aware of what ISO invariance on a camera is. So here's the question. Why would you care about ISO
invariance in the first place? Meaning, if you're shooting
in a low light situation, why not simply use the
dial to turn up the ISO instead of having to do it
later on in the software? Or likewise, why not just
shoot it 200 all the time and then deal with the ISO
later on in post-production? Okay, remember the noise chart and these two amplifiers right here? Because your read noise
drops at 800 ISO here, this does have implications, for if you wanna decide when and how to bump
up a certain ISO value, either in the camera
or in post production. Let's say that in order to maintain a certain shutter speed and aperture, you need to set your ISO dial to 6400. But you know that by raising your ISO, you are going to be
reducing your dynamic range. All things considered, it might be better to
shoot at a lower ISO, such as 800 or even 200, and then increase the exposure slider in Lightroom or Capture One. But what's the better option? Is it better to shoot at 800 ISO and then increase the exposure slider in Lightroom three
stops to match ISO 6400, or should you shoot at ISO 200 and increase the exposure
slider five stops in Lightroom to match that ISO of 6400? Let's take a look. Okay, here is the original
image shot at ISO 6400. Additionally, I shot this image at ISO 800 and I shot this image at ISO 200. So I'm gonna increase
the ISO 200 five stops to match the ISO 6400. Now, I'm going to increase
the ISO 800 three stops to match the ISO 6400. So all three of these
photos should be the same, but which is the better choice? Photo on the left is ISO 800, photo on the right is ISO 200. From a noise perspective, the photo at ISO 200 is noisier. You can see that right here. Here they are in Capture One, same thing. The ISO 200 has more
noise and grain in it. But although the photo with
ISO 200 has more noise, there's better detail
recovered in the highlights. Have a look at the difference
between here and here. Look at right here versus right here. Again, look at right
here versus right here. You see that? But pretty much at 100%, it's very difficult to tell them apart. Which would be better? To shoot at 3200 ISO and push one stop, or to shoot at 800 ISO
and push three stops? Let's see. Now, in Capture One, I have the 800 image on the
left and the 3200 on the right. And as you can see, it looks like there is just
a bit more noise on the 800, but it's pretty negligible. So we can draw a few
conclusions from this. First off, don't be afraid to shoot between ISO 800 and 6400. In fact, you may sometimes
get better results in low light conditions
if you shoot at ISO 800 than you would if you shot at ISO 500. And that's because of the
dual gain ISO amplifier that I told you about
that's inside the camera. For more information on this, make sure you go and check out the read noise measurement chart on photonstophotos.net. Number two, if you're hovering
around the ISO 6400 range, things get a little more complicated. Because the Fujifilm X-T2,
X-T3 and X-T4 cameras are pretty much ISO invariant, you have a lot of flexibility here. So for example, have a look
at this in Capture One. The ISO 200 image gives
you more highlight detail than the ISO 800 image, but it does give you a
little bit more noise as you can see right there. So if you're worrying
about blowing highlights, you may wanna go for shooting at ISO 200 and then bumping that up in post. This could save your highlights. However, you will have a bit more noise at ISO 200 bumped five stops than you would by just
setting the dial to 6400. Number three, if you need to shoot between ISO 6400 and ISO 12,800, you might wanna consider
shooting at ISO 6400 and then selectively bump
certain parts of your image in post-production to
bring the exposures up to the levels that you want. This is one of the main benefits
of ISO invariant cameras. Number four, if you're needing those special Fujifilm extended ISO ranges in the 25,600 to 51,200 range, I would recommend not
ever using those settings. And this is because to
achieve those ISO values, the Fujifilm camera is
digitally amplifying the signal after all of the
processing here is complete and the camera noise has been added. This is the part of the process at which those high ISO
values are amplified. You see that right there? So it's amplifying all the noise, and so better off to use Lightroom because then you have much more control over what areas of the image for you to selectively push your image those few extra stops. Lastly, keep in mind the
magic ISO 640 number. That's when the second amplifier kicks in. Because of this, if you're needing a high
ISO value to get your shot, and you're planning on
using ISO invariance and setting your ISO in
Lightroom or Capture One via the exposure slider, then I recommend setting your
camera to at least ISO 640 when you take your shot. You may get better results from that instead of trying to bump up more than a stop or two in post-production a camera ISO setting of 200, 400 or 500. In the end, only you know the type of shooting
situations you come up with. And you will need to find
the best in-camera ISO versus post-processing exposure workflow that suits you best. However, I hope today's video
has helped shed some light without the extra noise on this incredibly fascinating topic. Well, I hope you found this video helpful. If you did, be sure to give
it the like and subscribe. And of course I will see you all again in another video next week. Take care.
