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Re: [OM] TTL FUNCTION

Subject: Re: [OM] TTL FUNCTION
From: "Giles" <cnocbui@xxxxxxxxxxxxx>
Date: Sat, 9 Jan 1999 22:10:13 +0000

The OM2, 2n, 2Sp, 4, 4Ti and 3Ti - there may be others (PC?) - all 
have TTL flash control, and except for the 3Ti, OTF metering.  The 
3Ti and 4Ti also have Super FP capability.

Off The Film (OTF) metering is operational in auto mode in the above 
cameras.  It works thusly:  There is a silicon sensor in the bottom 
of the mirror box - behind and beneath the mirror.  This points 
towards the back of the camera and measures light reflected off the 
film during the actual exposure ie. while the shutter is open and the 
mirror is up.  It only functions in this way when the exposure is 
1/60th sec or longer.  For shutter speeds faster than 1/60th the 
exposure is calculated by meaasuring the reflection from a black and 
white pattern printed on the front of the shutter curtain before the 
shutter opens.

TTL is a sort of variation on OTF.  When the shutter is open and the 
flash fires, the silicon cell measures the light being reflected off 
the film.  When it is determined that enough light for a correct 
exposure has reached the film the flash is turned off before it 
delivers its full potential and the shutter is closed.

TTL and OTF work very well, especial for macro photography.

With TTL, the fastest shutter speed a flash can be used with is 
1/60th.  With Super FP faster shutter speeds can be used but 
Super FP only works with the 4Ti and 3Ti.  The IS series cameras can 
also use Super FP with the G40 flash.

Super FP is apparently not as wonderful as it may sound at first as 
the F280 is considered by most to be a bit weak so it is limmited in 
practical use to short ranges.

>From your previous posts I get the impression you are mainly 
interested in macro use.  If this is the case, all of the above 
cameras are very suitable for this purpose as they have TTL 
capability.  There are specialist OM TTL flashes designed 
specificly for macro use - T28, T10 and T8. 

If you want to see more clearly the how the OM sytem cameras and 
flashes can be combined, Tomoko Yamamoto has JPG scans of the OM 
system charts available at her site.

http://www.charm.net/~tomokoy/

Giles

LF wrote:

> Noone answered me so I try again...
> I read in the "Olympus Book" that OM3 and Om4
> have the TTL function towards flash
> I mean, in this way it is possible to stop the flash as soon as the
> subject is well ewposed.
> As someone told me that this function was only in the OM3TI and OM4TI
> I'd like to know if it's real???
> So the book is wrong???
> Or maybe the person who told me intended the SUPER FP FUNCTION???
> Any Idea???
> By the way what is OTF function????
> Thanks
> 
> Luca Felici

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