Why 'Stops' for exposure?

Started Nov 12, 2012 | Discussions thread
Peter Jonas Veteran Member • Posts: 3,274
Re: How it would work for me in practice

Let's assume we have a camera with an accurate EVF and a good light meter.

I would want to control 4 variables:

Shutter Speed, Aperture, ISO Sensitivity and Exposure Compensation.

I would rarely work in full manual mode, I would mostly be say in Aperture priority.

In this case the camera would control Shutter Speed, so, on my ideal camera I would have 3 control wheels: Aperture, ISO and Exp comp.

Whatever I would want to preselect manually would have to be in the conventional "stops". Because it is simple that way. I take an aperture of 8.0, and ISO value of 100 and initially an Exp Comp of 0 EV.

For all these preselected parameters I would want to use the conventional "stop" values. The camera could be set to have 1, 2 or 3 steps between stops. To me, for preselection it would not make a lot of practical sense to have a continuous control.

However, whatever parameter is determined by the camera could be any value, regardless of the "stops" values.

Now then, I now have preselected my ISO and Aperture. I am looking through the EVF. The camera has chosen a shutter speed and that is giving me an image of a certain look in the EVF. If I don't like it because it is too bright or too dark I will use my Exp Comp dial to adjust. Now, this dial might as well have a fully stepless adjustment, but being a step wheel, the adjustment would have to be made in some steps. I would allow the user to define this between say 1 and 0.1 stop per click.

Then I could just judge exposure by the eye based on the look of the image in the EVF. When I am happy I shoot.

The same thing could work in Shutter Priority as well as in Program modes. For full manual, one would need 4 dials.

So, this would allow the best of both worlds. Automatically determined parameters would not be tied and any "stop" value. But for manual preselection the conventional "stop values" would still make a lot of practical sense. Using stepless odd values here would not have any advantage, but could cause confusion.

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Peter Jonas

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