David Irisarri Vila wrote:
:Recently, I´ve read something about OTF and Kodachrome films.
:I think OTF word is sometimes confused. Everybody knows OM3Ti and
:OM4Ti both uses OTF light metering and the unique difference between
:them are mechanical and electronic shutter, but I think there´s a
:big difference here. I think, we must talk about OTF direct light metering
and :OTF flash metering. When we use OM4Ti direct light metering, and we
:meter the sun light (talking about kodachrome films) film reflectance
:won´t affect to exposure because shutter curtain with the computer
:calculated dots will measure the light after you´ve pressed the
:shutter release
That's right; OTF available light exposure on an OM-2 or OM-4 really means
"Off The Curtain" (OTC) with shutter speeds faster than 1/60; film
reflectance will have minimal influence. When the shutter speed moves
towards slower values the influence of film reflectance (OTF) gradually
becomes bigger and finally completely takes over. OTF flash exposure is
obviously always measured off the film.
:With all of this we can say that OM3Ti is much better camera than
:OM4Ti with OTF flash, because you have from 1s to 1/2000s OTF flash
:but with OM4Ti only from 1/60 to 1/2000s (normal and superFP).
I wouldn't agree with that. The 3Ti being a better camera due to its
mechanical robustness or battery independency - maybe, but certainly not
thanks to its flash technology which is in no way superiour to the one used
in the 4Ti.
It is true that when the 4Ti is set to Auto and a mounted flash is set to
Normal Auto or TTL Auto, the camera will always use 1/60, unless available
light yields a shorter speed in which case the flash won't fire; with the
F280 in FP mode 1/60 is used as a bottom value when available light yields
longer speeds. But when you set the 4Ti in manual mode, you loose the
availability of TTL Auto flash, but with Manual flash, Normal Auto flash and
Super FP flash all shutter speeds can be selected (of course the first two
flash methods are only sync'ed up to 1/60). The FP mode in Manual is used
exactly like on the 3Ti: GN based, where the GN not only depends on film
speed but also on shutter speed, with available light as an uncertain
additional factor that makes it rather complex and unpredictable. FP flash
mode on the 4Ti in Auto mode is more automated and integrated.
For me OTF flash with shutter speeds longer than 1/60 doesn't really make
much sense. The shutter will remain open after the camera has cut off the
flash, indicating enough light is emitted and received. When available light
is strong enough to have influence in this remaining period you'll get
overexposed pictures. If you do want mixed lighting with longer shutter
speeds, Manual flash or Normal Auto flash are much more appropiate because
you have the options to reduce the flash effect to the benefits of available
light. This is also true for daylight fill flash. It is accomplished by
using a longer distance or smaller aperture than the GN yields (manual mode)
or using a smaller aperture than the flash aperture setting indicates
(Normal Auto mode).
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