----- Original Message -----
From: "Terry and Tracey" <foxcroft@xxxxxxxxxxx>
> How much light was coming in the back of the viewfinder? I just experiemnted
> a similar thing with a just purchased 35-105. Light from the viewfinder
> caused a noticable error.
No I wasn't using an eyecup, and yes, using a makeshift eyecup (a black tape
spool)
creates about a 1/3 to 1/2 stop difference in E.V. (interior lighting).
Wow. I didn't know that!
----- Original Message -----
From: "C.H.Ling" <chling@xxxxxxxxxxxx>
> Just tested the newer 35-105 setting at F8, point to a plain wall. My OM-1n,
> 2n and 4
> all read 1/2s (with the 2n read very little below 1/2s, I think it was less
> than 1/3
> stop). There is no different between 35 to 105mm on my OM4.
The actual difference from f3.5 to f4.5 is log(4.5/3.5)/log(1.4142) = 0.73 f
stops.
You should be getting 3/4 stop difference (unless new model lens is different,
mine is the flat rear element model).
I coupled the lens to my Sekonic meter at the focal plane (using plumbing!).
The Sekonic showed 3/4 stop change as I zoomed the lens. This is exactly
the expected value.
So, now comes the kicker - I had originally installed new silver oxide batteries
in the OM4T (replacing the LiMn battery.) Now I took the (what I thought were
pretty new) siver oxide batteries out of the OM2N, and replaced them with the
(very new) batteries in the OM4T.
Lo and behold! 2 stops increase in absolute E.V. on the OM2n, and the change
due to zoom (with "eyecup T") was now over 1/2 stop (my estimate is 0.6
stops). This is within the measurement error as far as I'm concerned.
I thank everyone in the list for their thougtful responses. I certainly
learned more than I expected from the exercise of a little neurosis about
my new (used) OM4T!
So, what about those "new" AgO2 batteries? I guess I'll have to be neurotic
about those now!
Now I want 2 eyecups. Anyone got some kicking around?
- Parzival
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