ISO Invariance

October 26th, 2015

I just read an article on ISO invariance.  This is a concept that applies primarily to Fuji and Nikon shooters.  It apparently doesn’t work on Sony or Canon units.

The concept is that if you shoot night scenes at a low ISO, say 100 or 200, and then bring up the exposure level in Photoshop, the results will be the same as if you had shot the image at, say, 1600 or 3200.  Why is this a benefit?  Because you can be selective about which areas you brighten.  Areas that don’t need much brightening will be much more noise free.  I’m looking forward to trying this out!

Here is a comparison of a Nikon to a Canon shot at high and low ISO:

iso-invariance-test-small

Here is a list of the results of many volunteers testing their own cameras:

Cameras that are ISO Invariant

  • Sony A7RII (Much better highlight detail from shooting at base and brightening later, but lose a a slight amount of shadow detail.  I might even dare say that noise is handled JUST A TINY TINY bit BETTER on the brightened picture than on the high-ISO shot.)
  • Fuji XT1 (This is my personal camera.  I switched from Nikon to Fuji.  It’s probably the most iso-less camera out of all those that I tested.)
  • Fuji X100
  • Fuji XE1
  • Nikon D810 (Relying on data from DPReview.  The Sony A7R uses the same sensor, so I would ASSUME that it is as well.)
  • Nikon D750 (Only did one test with this, but appears to be entirely ISO invariant.  Would like to test more)
  • Nikon D7100 (Tested only at base vs ISO 800, but the noise pattern is identical)
  • Nikon D5500 (I did not personally test this one.  Relying on data from DPReview)
  • Pentax K5 (At ISO 800 vs base ISO, you can’t tell any difference.  Very high ISOs not tested)

Cameras that are Somewhat ISO Invariant

  • Olympus OMD-EM1 (Tough call.  Detail and contrast are definitely lost when brightening in post, but noise appears to be reduced quite a bit on the brightened image.  I’d like to do more testing.)
  • Olympus OMD-EM5 II (Difference is indistinguishable when zoomed out, but when you zoom in, the higher ISO photo is VERY VERY slightly better in terms of noise and contrast.  The 40mp mode brings the contest even closer.)
  • Sony A7S (I was interested to see this one.  The noise pattern on the brightened image is close to the high ISO shot.  However, the brightened image lost a SURPRISING amount of contrast).
  • Sony Nex 7 (This one is really close to being ISO invariant.  The noise is about the same, but contrast is lost on the brightened image.  Very close to being ISO-less.)

Cameras that are NOT ISO Invariant

  • Canon 5D Mark III (Not even CLOSE!  Nick Page tested this one for us and it looks really bad when you shoot low and brighten later.)
  • Canon 6D (Not even close, and the camera did a horrible job of selecting the white balance in the under-exposed shot.)
  • Canon 70D and Canon 60D (Not too bad, but it’s still much better to shoot at the higher ISO.  Horrible white balance in the underexposed shot.)
  • Canon 7D (Not nearly as bad as the 5DIII, and you can’t tell the difference with the naked eye at ISO1600, but when you zoom in it’s obvious that the higher ISO shot is cleaner.  White balance not good in the underexposed photo.)

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