Sure.
But my point is that a full-frame ‘equivalent’ is not a useful point of reference to a someone who has never used a full frame camera.
It is a point of
reference.
Yes. I am well aware. Nonetheless, everything I've said thus far has been my own opinion only. Some people think crop factors are an indispensable tool and I respect that view. Obviously the concept is well embedded in the industry's marketing materials. I just think it creates more confusion than clarity as evidenced by the never ending questions about it in this forum.
I disagree.
The confusion is caused by using terminology based on hitting a predetermined target exposure. This is critical when shooting film.
If you want to avoid confusion, we should be talking about angle of view, not focal length. If we want to avoid confusion we should be talking about aperture diameter, not the ratio of the focal length to the diameter.
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Unfortunately, that change isn't going to happen anytime soon. We are stuck with a system where people use settings where the results differ with sensor size.
Equivalence is an attempt to reduce confusion by helping beginners understand that the results from f/8 or from 50mm can vary from camera to camera.
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Personally, I think things would be clearer if we did use angle of view and aperture diameter. At the same shutter speed, aperture diameter, and angle of view, you get the same results from all cameras. That's far simpler than explaining that f/5.6 on your APS-C camera gives the same result as f/8 on a full frame, or f/4 on M43.
Photographers have been using f/ numbers for over 250 years, you're going to have some difficulty changing things now.
Yes. Film required an exposure centric workflow. The first step was to determine the desired exposure. You then load film designed for that exposure. The workflow is then built around hitting that target. Film photographers had it drilled into them that if they had to keep aperture and shutter balanced. Change one, and you had to make a corresponding change to the other.
Now we shoot digital, and we are no longer required to work that way. Under the hood, digital does not work the same as film. Unlike film, digital sensors have a wide range of exposures where they will produce good results. The concept of digital ISO-speed is a fabrication intended to ease the transition from film to digital (that's according to the spec itself).
With digital you can alter the aperture and leave the shutter unchanged. Auto-ISO handles maintaining constant image lightness.
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But old habits are hard to change. The industry standardized on relative f/stops and focal lengths. Even though many current photographers never shot film, they are still dealing with choices designed around film.
The industry has been trying to address this. That's where crop factors come from. With the introduction of the digital SLR consumers could use the same lens on full frame DSLRs and small sensors DSLRs. Crop factors are an attempt to explain how the results differ with smaller sensors.
While crop factors are normally applied only to focal length, they also apply to f/stop.
Thus we are left with using equivalent focal length as a proxy for angle of view, and equivalent f/stop as a proxy for aperture diameter.
Yes, this isn't ideal, but it's the way it is.
This idea of using proxy values is not limited to photography. In the USA one can buy 15 Watt light bulbs that are marketed as 100W equivalent. Wattage is a measure of how much power the bulb uses, not how much light it uses. A 15W bulb only uses 15W. However, it produces the same amount of light as a traditional 100W incandescent bulb.
It's hard to find incandescent bulbs in my local store, but bulbs are still marketed with "equivalent wattage".
"Equivalent wattage" is not a measure of light output. "Equivalent focal length" is not a measure of focal length. We are probably stuck with both.
