f/5.6 is orange because at this setting the lens should provide
acceptable quality images (given it's depth of field) from about 12 feet
to infinity.
The full power setting for the A-flashes is for fill-in primarily -- the
instruction sheet provides some basic info on calculating the aperture
setting using distance and guide number. It also says to use the
setting (100 or 400) closest to the film you are using, though we
usually say to use 100 for anything 200 or slower, 400 for any film
faster than 200.
In "Flash" mode, the XA sets the aperture at f/4, but limits the shutter
speed for hand-held use. Do not move the aperture off "Flash" for
low-light shots unless you want the shutter to stay open for an extended
period.
The XA's lens is of a unique internal focusing design, prone to
vignette, but with exceptional depth of field, as is typical for wide
angle lenses. How this compares with "normal" lens designs I'm not
sure, though it doesn't seem unusual for there to be a short "throw"
from infinity to (for example) 5m.
Trevor Urlwin wrote:
> Can someone tell me why the F5.6 numbers on my Olympus XA are coloured
> orange and all the rest of the f stops are coloured white? How and
> when should I use the 100, full and 400 switch on the A11 flash? What
> aperture does the camera select when I am using flash? There is very
> little movement required to change the focus from, say, 5 metres to
> infinity. Does this mean that there is a large depth of field, or is
> that relatively fixed for each focal length of lens, and therefore
> this 35 mm lens would have similar depth of field characteristics to
> an OM Zuiko at the same aperture? Is there an manual somewhere on the
> internet tha I can access. Hope someone can help. Thanks and good
> wishes from Jakarta Trevor Urlwin
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