Re: Exposure

[Jim Thyer <jimth@xxxxxxxxxxxxxxx>]

From memory, as my reference book is 500 miles away & 48 hours.

A good reference is Horder, The Ilford Manual or any old basic photography book.

My old Contaflex had a leaf shutter and 
I recollect the fastest shutter speed was 1/500 sec. This means 1/1000 sec to open fully and the same to close.

Thus the fact that the shutter was not fully open for the first 1/1000 sec or the last did not really matter on an exposure of (say) 1/100 sec.

Even for an exposure of 1/250 sec the variation between having the lens aperture fully open or closed would be less than 1/2 stop.

Hoping this helps. If any more comments are needed ask me in 2 days when I am home with reference books and a keyboard to type on rather than a tablet & stylus.

Jim Thyer

Sent from my tablet

On 2 Apr 2014 14:53, Andrew Davidhazy <andpph@xxxxxxx> wrote:

Randy,

The blades uncover the whole (set) aperture faster when the diaphragm is set to a small aperture so

effectively the shutter delivers a longer exposure time (vs. the one it is assumed it is delivering). Because

the blades reach fully open position faster from the "midpoint" to the peak one would expect a bit of 

underexposure when the lens is set to a large aperture. 

Another way of saying this: if the diaphragm is set to f/22 the amount of light that f/22 allows to pass 

is available for a longer time than that which is allowed to pass when the diaphragm is set to f/4 for example.

And the full amount that f/2 for example passes is available for a shorter time than that which f/4 passes.

But the discrepancy at the high end tends to be a bit less "problematic" than at the low end where an error 

of maybe 1/2 stop or more can be experienced.

Anyone care to elucidate us further?

Andy

On Apr 1, 2014, at 11:40 PM, Randy Little wrote:

Andy dont they over expose equally though because of the relation of the cone and the aperture?

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