ISO on the R5

FingerPainter wrote:

BobKnDP wrote:

gossamer88 wrote:

FYI

Is this related to the person who posted some weeks back under the handle "vegetable"?

I presume that this is a trolling post.

Neither the post nor the video in it are trolling. Tony is perfectly correct.

The noisiness of an image depends on its Signal to Noise Ratio (SNR). The SNR depends primarily on how much light you captured in the photo. How much light you captured in the photo depends on the exposure, the surface area of the sensor, and the quantum efficiency of the camera. The latter two tend to be constants for a given camera. The exposure depends on:

1. the amount of light in the scene reaching the lens (scene luminance)
2. the T-stop of the lens (approximated by f-stop), and
3. the length of time the sensor is exposed to light (shutter speed)

The widely held view that the noisiness of an image depends on the ISO setting is an error caused by mistaking correlation for causation, and perpetuated by the omnipresent but fundamentally flawed conceptual model called the "Exposure Triangle".

I admit that I didn't watch the whole video at first. Comparing a greatly underexposed image with its brightness boosted to match a higher ISO shot really put me off. I presume that the quantization noise in the underexposed image was mostly responsible for the poorer SNR.

Nothing in the video is false, but it's playing with semantics. If you set the camera to a high ISO, and take a normal exposure with it, it will be noisier than a normal exposure taken at a lower ISO. The lower ISO exposure will be longer (by the ratio of the ISOs). It makes little sense to compare identical exposures with different ISOs.