ISO Is Not Fake and Tony Northrup Is Wrong

A few days ago, camera industry guru Tony Northrup published a video arguing that in the age of digital photography, ISO is effectively meaningless and that it’s no different from dragging the exposure slider in Lightroom. Photographer Dave McKeegan has offered a response and argues that Northrup’s logic is completely wrong.

Like many others responding to Northrup’s video, McKeegan’s point hinges on the fact that the camera, in processing the signal from the sensor, is multiplying that data before it is converted from analog data into digital data. This is what Fstoppers' own Lee Morris was suggesting might be happening when performing his own tests last week, albeit without knowing the science behind it.

In effect, the exposure slider in Lightroom is dealing with completely different information than a camera’s ISO setting, thus creating a different outcome. As one of the comments on Northrup’s original video observes, sensor signal is to raw as raw is to JPEG. Essentially, exposing incorrectly and relying on editing software is definitely not recommended as a means of exposing your digital images, and adjusting your camera’s ISO setting is a better option.

If you’re interested in the technological aspects, be sure to watch all of McKeegan’s video. Beyond that, if you’re still keen to know more, you might want to deep dive into the comments on both videos. You will almost certainly want to check out the comments made in response to the Fstoppers article, paying particular attention to informed contributions from community members Gary Gray and Paul Gosselin.

Whatever the outcome of this discussion, it’s useful to have an awareness of how cameras and editing software deals with information differently, as well as having an insight into how ISO functions as an industry standard, albeit with various hangovers from the film era.

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Michal Wachfaitl's picture

Garden test where I have apparently skipped ISO 200 :) with ten years old full frame camera; in every case, the results do not look same at all...mainly right curtain area is horrible when shot on lower ISOs pulled up afterwards.
RAWs processed in Lightroom without a touch, composed and exported in PSP, JPG 85%.

Maybe the solution is: Have the sensor and camera manufacturers list the signal to noise ratio of their sensors in the camera specifications. This will give a better description of the quality of the sensor. If the SNR of sensor "a" is exceptionally low, then maybe ISO 100 post processing amplification might be equal to sensor "b" with a higher SNR value and using a higher ISO.

Wow, this ISO subject was taken to a level I never expected. Lots of arguments and angry people...over ISO. It's a nice talking point, but don't understand the emotional responses. At the end of the day, learn to shoot as close to a correct exposure as you can with whatever gear you have. Some cameras look a little different at whatever ISO than another. Learn to go with it.