re: Polaroid B&W: what is the ability of the human eye to differentiate between image Exposure Values i.e. 1/2 stop? 1/3 stop? 1/10 stop? 1/50 stop?

And likewise, what is the ability of most film types to differentiate between f stops?

From the practical standpoint, how small an Exposure Value CHANGE is usually considered to be recognizable (by either the eye or the film), and in an attempt to get that 'perfect' exposure, how small an EV change is a waste of film?

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On 2003-12-18 16:22, Perry Arnett wrote: re: Polaroid B&W: what is the ability of the human eye to differentiate between image Exposure Values i.e. 1/2 stop? 1/3 stop? 1/10 stop? 1/50 stop? From the practical standpoint, how small an Exposure Value CHANGE is usually considered to be recognizable (by either the eye or the film), and in an attempt to get that 'perfect' exposure, how small an EV change is a waste of film?

When you say by the eye do you mean look around and use your eye to meter? If so the problem is your brain processes everything you see. If you mean on a print then you've got the whole printing process in the way. If you're using slide film then you can't try and correct during printing.


I don't know of any meter that handles 1/50th of a stop. My digital meter handles 1/10th of a stop but the error might be bigger then that. If you're using slide film then you want to be close to perfect. It can be worthwhile to bracket if possible. If you're using print film then I'd say just go with it. I can get away with sunny 16 outdoors. My mental reading is usually well within 1/2 stop of what the meter reads.

One final monkey wrench. Your shutter. Your aperture. Your meter. All those and more can be off. Those errors all add up. I guess that's the main reason for testing your system out before hand.

SK Grimes said any old shutter- be it a Graphex or Supermatic or even Rapid Compur, when well adjusted is accurate to a 1/2 stop. Copals can get you to 1/3 of a stop for shutter speed.

Beyond that, you'll have to go beyond the practical pictorirical shutter and get into the a more scientific shutter, ususally electonically controlled.

Now most of the older apertures are accurate, but not precise. That is, when is says f16, it really is f16, but the distance between f16 and f22 is in many cases less than 1/4".
How are you going to precisely locate in a repeatable fashion even f16 1/3 and f16 2/3? To parse that space more finely will difficult