Could you be confusing the " which is actually seconds as in 35'36" (35min 35sec) as inches? When the shutter speed can no longer be shown as 1/xxx it will be shown as parts of a second - 0.3" i.e. 3/10sec.
This is because shutter speeds are generally displayed in stops, aka Exposure Values (EV's), where each is a doubling of halving of the light. Using this common unit allows us to accurately translate values of one of the three variables: ISO, S/speed, Aperture between them so we can keep an exposure constant, but change the compositional aspects of the image - such as changing the shutter speed by 1EV up, which means that one of the others will have to go down in exposure value by one EV.
In ISO those are ascending scale 100-200-400 etc., as the number goes up, the gain applied to the sensor (signal amplification, if you will) is doubled.
In apertures each EV is represented by an increase or decrease by the square root of 2 (because it's calculated as focal length/aperture, where the area is a function of Pi x((D/2) squared). So, to get a consistent doubling or halving of light, it must be increased or decreased by 1.4, which is why apertures go up as: 1, 1.4, 2, 2.8, 4...etc. Because the aperture is the denominator, an aperture is correctly expressed as a fraction: f/2, f/5.6, f/8 etc. which explains why, as the number gets larger, the actual aperture hole gets smaller.
With shutter speed, if we start at 1" (1 sec), the next EV value would be 1/2 but if the camera is using smaller values than 1EV (which is common), as it gets between 1 and 1/2sec, it will show the shutter speed in units of decimals of a second, thus 0.3".
cheers, TREVOR
The mark of good photographer is less what they hold in their hand, it's more what they hold in their head;
"All the variety, all the charm, all the beauty of life is made up of light and shadow", Leo Tolstoy;
"Skill in photography is acquired by practice and not by purchase" Percy W. Harris
