ISO invariance - can you do it too?

Discussion in 'Technical threads' started by Ade, Oct 11, 2016.

  1. So, I've been hearing about a thing called ISO invariance. It seems to mean that you can massively under expose (up to 5 stops!) a digital photo and then fix it in post. It just so happens my Fuji XT1 is one of the cameras that is supposed to be able to do this. I watched a video...



    ...and then gave it a try. I took a shot 3 stops under exposed...


    ...and then fixed it in post...


    I know it is difficult to tell the quality in these small images but I was really impressed how I was able to recover the detail. In Lightroom the left of the shot was almost entirely black, I certainly could see no wall or photo frame, just some noise in the darkness.

    Amazeballs!
     
    Chris and billowens like this.
  2. You call it ISO invariance, I call it saving a cocked up raw file that should have been exposed properly lol ;)

    I've been doing this for quite a long time, providing that the camera has a decent sensor it's quite easy. I can do it on my 5dmkiii and the xt-2. I actually had underexposed a lot of food photography recently to get myself better shutter speeds to avoid camera shake, then in post bang the ISO back up.

    If the ISO to noise ratio kicks up a lot of trouble, then the key is to downscale the image when going to print it. When you reduce the physical file size from 5000px down to 1000px at 200dpi then the bits that look bad will fade away. If all that still fails, time to hide it with Photoshop tricks etc


    Sent from my iPhone using Tapatalk
     
  3. My only DSLR - and in fact my only digital camera apart from an iPhone - is a seven-year-old Pentax K-x. Its top ISO Is 12,800 and I think it was made before the concept of ISO invariance was a thing... on the other hand it might be interesting to try this with the iPhone, since I do have an app to allow me to control all of the camera settings. I just need to figure out how to navigate its frustrating UI :(
     
  4. I get that, but I think you're oversimplifying it. The fact that you can make the ISO gain similarly in post production means you don't have to apply it globally. If you think of the invariance as a way to apply selective ISO gain to different image areas then you have something quite powerful.

    And time consuming, and annoying but nonetheless powerful.
     
  5. Bill if you use an app that shoots raw then you could try this really well - if you have a raw converter for your phone. I am trying LR on my phone for this. If you shoot jpegs though you will lose all the data I suspect.
     
  6. I have an iOS app call Custom Cam that lets me select RAW, and Photoshop Express will open those pictures and let me manipulate them. I don't think it's really workable though; pushing the exposure slider does lighten up the picture a little but nothing like what you've done or what was shown in the video. I'm concluding that the sensor isn't actually ISO invariant, and that doesn't surprise me given how little it must cost compared with the chip in a Fuji camera...
     
  7. I don't have that app, and you need a fairly recent iPhone for RAW shooting as well. I'm finding with my iPhone 6S and LR mobile though that I can recover quite a lot of detail if I need to.

    Not that I would necessarily call that ISO invariant but it is way better than just getting a jpeg.
     

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