The classic folding SX-70’s use the “electric eye” popularized in the 60’s with the Automatic Land Camera. Like the Land Camera, it can also be lightened or darkened, based on interpretation of the metered scene, or as a compensation technique, for effect. Unlike the controls on the Land Camera, however, operation is very counterintuitive and cryptic, unless you really do read the manual. You may very well do the opposite. As the industrial design of SX-70 really did try to keep thinks as automated and non-traditional as possible, this really comes as no surprise. Polaroid really leaves nothing to chance in their documentation- it was always outstanding. But, here is a simple way to learn the system.
It is very important to realize that if you make changes in the default setting, that when you close, and then reopen the camera, it resets your override back to the middle. For most exposures, you’ll likely keep it here.
OK, this is where it gets confusing. Don’t try to like up the horizon with a line, arrow, etc. If you move the wheel, and see MORE dark, well, the above shows one stop of exposure compensation. What this equates to in f/stop or exposure value, who knows. But if you look online, and a photographer refers to “one notch towards Darken”, this was the adjustment made.
The other way, the above shows two notches towards Lighten. Most of what I have seen online calls for a one notch towards Lighten setting in cold weather. As each SX-70 has its own personality, and these are, after all, 40-year-old cameras, I don’t think this is gospel, more of a starting point.
These tips may prove helpful, especially if you are coming from use of the Automatic Land Cameras, or the OneSteps, both of which have much more intuitive exposure controls.