I finally 'get' equivalence

Started May 22, 2012 | Discussions thread
gollywop Veteran Member • Posts: 8,284
Re: 'Total Exposure'?

Great Bustard wrote:

gollywop wrote:

The f-stop is only one part of the exposure; you're forgetting shutter speed and ISO.

ISO is not a part of exposure. The exposure is the density of light falling on the sensor, and is determined by three, and only three, factors:

  1. Scene Luminance

  2. t-stop (usually closely approximated by f-stop)

  3. Shutter Speed

I'm willing to go along with this, but only so far. Do you think the entire argument would make any sense whatsoever if the two shots were taken using entirely different ISOs? Clearly ISO makes a difference. That's the reason I equalized them in my post.

Of course, the FF sensors tend also to have deeper wells than the FTs, so this objection is mainly theoretical. But it's more than just relative sensor size.

It's not the sensor size, per se, but the diameter of the aperture of the lens, and the efficiency of the sensor (QE, Read Noise, and saturation).

I believe I just said above your statement that "it's more than just relative sensor size." I appreciate your addition as to what that "more" might entail.

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