From: diamond@jit533.jit.dec.com (Norman Diamond)
Subject: Re: Canon 10s Vs Nikon N90, Which one?
Reply-To: diamond@jit.dec.com (Norman Diamond)
Organization: Digital Equipment Corporation Japan , Tokyo
Date: Mon, 28 Dec 1992 09:11:39 GMT

In article <1992Dec28.031152.9205@jarvis.csri.toronto.edu> acs@csri.toronto.edu (Alvin Chia-Hua Shih) writes:
>In <BzyIHq.KoC@jrd.dec.com> diamond@jit533.jit.dec.com (Norman Diamond) writes:
>>In article <1992Dec25.032603.25071@jarvis.csri.toronto.edu> acs@csri.toronto.edu (Alvin Chia-Hua Shih) writes:
>>>In <BzszB1.ICv@jrd.dec.com> diamond@jit533.jit.dec.com (Norman Diamond) writes:
>>>>In article <1992Dec24.205338.11007@jarvis.csri.toronto.edu> acs@csri.toronto.edu (Alvin Chia-Hua Shih) writes:
>>>With those "Monitor Preflashes" it should be possible to calculate all
>>>of the exposure information at that time and set the flash's power output

>>To repeat, do you want to quench the flash when only part of the film has
>>been exposed?

>From my understanding, the F90 lifts its mirror and the preflashes *with
>the shutter closed*.  The shutter supposedly has the tone of film emulsion.

Yup.  That's why it works better than ordinary TTL, while the shutter is
fully open.

>So, with the preflashes, one could calculate how bright the
>actual flash has to be, pick the power output in advance,

If you pick too dim a power output, the flash doesn't fire.  If you pick
too bright a power output, you fry it.  All you can pick is duration.

>>>(Canon had "Flash Exposure Lock" with the T-90 that did something like this
>>>for spotmetering.

>>For shutter speeds faster than the fully-open speed?

>The 300TL did not support FP sync.

Bingo.

>The SB-25 accomplishes FP-sync (I believe), by simply keeping the flash
>tube illuminated for the full duration of the shutter being open.

Bingo.

>The trick is to change the brightness of the flash, rather than the duration.

Hmm.  Return to incandescent flash bulbs, anyone?

>But calculating exposures for fill flash is kind of a pain.  I'd rather
>have all that gee-whiz computing power do it for me.

Ordinarily it does.  If you want high-speed fill flash, I'm surprised to
learn (from your previous post) that you even have two possible choices.

>>>>>"Practical Photography" finds the SB-25 performance "disappointing"
>>>>>because of "noticable darkening of the image at the edges" [...]

>>>>Are they sure that's because of the flash rather than the lens?

>>>Nikon F-90 with an AF 35-70/2.8 (can't see whether it's "D"-series or not,
>>>I suppose it's possible for a cheap lens like that to have bad
>>>vignetting problems...  :-)

>>Well, I have a cheap[*] but famous fixed Nikkor lens with vignetting visible
>>through my F801s viewfinder, so I wouldn't be surprised if the zooms can
>>have it too.
>>[* 105 F2.5, cost 24,000 yen from a used camera store, about C$250.

>I was being facetious about the 35-70/2.8 being a cheap lens.

Me too.  The fixed MF 105 F2.5 isn't one of their most expensive lenses, but
neither is it one of their most despised.  [Try to beat THAT understatement.]
--
Norman Diamond                diamond@jit.dec.com
If this were the company's opinion, I wouldn't be allowed to post it.
Pardon me?  Or do I have to commit a crime first?