It is all about exposure, not ISO setting - real world photos

Started 8 months ago | Discussions thread
Magnar W
OP Magnar W Senior Member • Posts: 3,877
Re: It is all about exposure, not ISO setting - real world photos

Hank Radt wrote:

At the risk of showing my ignorance (well, not really much of a risk), help me understand how best to use ISO settings. I had been under the impression that low ISO is good/high ISO is bad, but your photos above are shaking my faith in what I thought I knew - cognitive dissonance is setting in...

My take with newer Sony cameras is:

  • Use as low ISO as possible for cleanest exposure, and do NOT underexpose. My preference is to expose for the highlights, so that they still has some detail. Then shadow detail will follow nicely.
  • If you need to underexpose, go to ISO 640 or above.
  • If there are no blown highlights at high/very high ISO settings, or blown highlights doesn't matter, just go for these high/very high ISO settings!

Then the more tricky part starts:

  • If using high/very high ISO setting will clip highlights that you want to keep, use the same exposure that looks fine at high/very high ISO (shutter speed and aperture), and go for a lower ISO value that doesn't clip the highlights.
  • The viewfinder will turn darker, and the file will look dark when opened with your post processing software.
  • Then brighten the mid-tones and shadows, so that the file looks fine. Noise will be the same as with the higher ISO where the brightness looked fine in-camera, but now you will keep more highlight detail.

This technique, often referred to as ISO-invariance exposure, is excellent for sunsets, cityscapes at nights, polar light scenes, and other scenes where dynamic range is large.

Until now (at least), I've just set my camera to Auto ISO and then adjust EV+/- to make sure I have everything in the histogram, trying to keep ISO as low as possible. Which may make sense for general walkaround use. But, as I (try to) improve my skills, it appears I have something to learn. Feel free to respond or point me to a link - happy to do the work myself, but appreciate any direction or guidance that would help sort through the internet chaff.

I have nothing at all against auto settings. The clue is to understand exposure, what these auto settings are doing, and then keep the control over your camera.

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