There is some light loss with the B-300 on a lens such as the 135/2.8. The
B-300 is 'optimized' for use with the IS-3/3000 lens assembly... so it
gathers enough extra light to make up for its installation on that lens
(almost, I think it is slightly slower). The B-300 has a fairly large front
element, which gathers more light than the existing front element of the
IS-3 lens... if that also works with other lenses it would only be
coincidence. The B-300 magnification factor works, and since it -is-
gathering some quantity more of light it probably is less light-loss than a
2X or 1.4X converter -behind- the lens, which can only work with the
light-gathering ability in the existing front element. So I think there is
some light loss, but less than the expected 1.7 factor. I've not done any
real experiments to confirm this speculation, however. In any case, the TTL
meter will adjust the exposure as required without any intervention other
than using it as usual. I've found the B-300 works well on the IS-3, and
gives good images when combined with the 135/2.8, on par with a four-element
2X converter.
--
Jim Brokaw
OM-'s of all sorts, and no OM-oney...
on 3/31/03 12:56 AM, Piers Hemy at piers@xxxxxxxx wrote:
> Assuming that the convertor has perfect light transmission capabilities, if
> you double the focal length without doubling the physical aperture, my
> arithmetic says that the maximum relative aperture must be halved (ie f/2.8
> becomes f/4).
>
> I don't know the B-300, but let's assume that it does have perfect
> transmission - I doubt that it doubles the physical aperture!
>
> Piers
>
> -----Original Message-----
> From: owner-olympus@xxxxxxxxxxxxxxx [mailto:owner-olympus@xxxxxxxxxxxxxxx]
> On Behalf Of Clemente Colayco
> Sent: Monday, March 31, 2003 8:25 AM
> To: olympus@xxxxxxxxxxxxxxx
> Subject: Re: [OM] My hunt for long, fast glass
>
>
> Wait, as I recall list members discussed that the B 300 does lead to light
> loss somehow.
>
> ----- Original Message -----
> From: <petertje@xxxxxxxxxxxxx>
> To: <olympus@xxxxxxxxxxxxxxx>
> Sent: Monday, March 31, 2003 4:14 PM
> Subject: [OM] My hunt for long, fast glass
>
>
>>
>> Hi,
>>
>> In the end I settled for an Olympus IS B-300 front convertor. I won a
>> bid
> for one at 142 Euro on eBay last week. Even though I've never used anything
> like it, I liked the reviews it gets all over Internet. And a 150/f2.x
> sounds cooooool :-)
< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
|