shooting .95 darkened image

[stump4545]

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any noct .95 shooters find themselves boosting exposure to compensate for shooting at .95 as the image tends to darken overall not just vignette?

[01af]

Due to the so-called r-stop error (mostly caused by vignetting), the widest aperture of any lens, in terms of exposure, is not the same as it is in terms of entry pupil geometry. Exposure at full aperture is always a little less than the numbers suggest. The wider the aperture, the more pronounced the effect is; that's why it's more obvious in the Noctilux but it's present in any lens.

 

So when using a lens' widest aperture, add one third or one half of a stop worth of exposure by using a slightly slower shutter speed (or crank up the ISO setting by one notch, or dial in a small positive exposure bias when using auto exposure mode).

 

By the way, the only camera and lens manufacturer who took the r-stop error of his lenses into account and provided his cameras with an r-stop error compensation used to be Minolta. The MC Rokkor, MD Rokkor, and MD lenses gave perfect exposure at all apertures including the widest when used with in-camera TTL metering. But people were too dumb to appreciate it and kept complaining, so Minolta gave it up when they switched from the SR to the AF system.