Bessa R2a Shutter Speeds & Auto Exposure

[paxship]

If the R2a shutter has a range from 8 to 1/2000 seconds, and the meter has a range of EV 1 to EV 19, under what conditions (EV and ISO) would it select 8 seconds? As you know, an R (and probably any Bessa's) meter will "freeze" if you set the shutter speed at anything more than 1/(ISO/100)... that is with ISO 400, the meter work if the shutter is set for 1/4, but will "freeze" at the minus sign if you set the shutter to 1/2.

 

[pvdhaar]

0EV is 1sec @ f1 with ISO 100 film. Going from there: 1EV (which is the lower limit of the meter) is 1sec @ f1.4

From 1sec to 8sec is 3 stops, corresponding to f1.4->f2.0->f2.8->f4.0

So, with ISO 100 film, at f4 (not quite coincidentally corresponding to the slowest CV lenses like the 25/4) and at the limit of the meter's sensitivity, the exposure will get to 8 seconds.

 

[paxship]

Pvdhaar --

Thanks for the prompt response. The meter range is the controling factor. Can I conclude that that means that the extended times are of no use if the ISO is greater than 100 or if my lens is wider than 4.0?

 

[pvdhaar]

Pvdhaar --

Thanks for the prompt response. The meter range is the controling factor. Can I conclude that that means that the extended times are of no use if the ISO is greater than 100 or if my lens is wider than 4.0?

No, that's not quite the case. The Bessas have a TTL meter, and no electronics that communicate the aperture from the lens to the camera. It doesn't know what lens and aperture you have. And it also doesn't know the actual light value outside. So if you have a lens that's a stop faster than f4, and the light is lower by 50%, the meter doesn't see a difference, because the same amount of light hits the meter. It'll still go to 8 seconds..

But if you load ISO 400 instead (assuming still an aperture of f4), the meter doesn't get more light, and also doesn't gain sensitivity. The exposure will now presumably max out at 2seconds.