Fine Tuning SX-70 Exposures with a Variable Neutral Density Filter

Note: There is a video version of Using the Zone System with Polaroid SX-70 Film, Part 1 at the bottom of this post.

It would be nice to adjust exposures in ½ EV increments with my MiNT SLR670-S camera. Unfortunately, the camera can only make full shutter speed adjustments, one EV at a time; there is no ability to select in-between speeds. While most manually-controlled cameras allow f-stops to be set in half or third stop increments, the original SX-70 cameras that MiNT refurbishes have a ‘fixed’ f/8 aperture. 

All too often, I will take a meter reading only to find that the best exposure lies between two shutter speeds, for example between 1/125s and 1/250s at f/8. Because I can’t change the aperture, I’m forced to choose the lower shutter speed, which will result in a slight over-exposure, or the higher shutter speed, which might be darker than I wanted.

Because I’m shooting Polaroid SX-70 integral film, which has a very limited latitude, especially in the highlights, these seemingly minor compromises in exposure can have a major impact on the quality of the final photograph.

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