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RE: [OM] Olympus 1.7X B-300 converter (was: Ken's new IS3)

Subject: RE: [OM] Olympus 1.7X B-300 converter (was: Ken's new IS3)
From: "Per Nordenberg" <per.nordenberg@xxxxxxxxxx>
Date: Tue, 17 Feb 1998 11:56:46 +0100
-----Ursprungligt meddelande-----
Från: Frank van Lindert <lindertv@xxxxxxx>
Till: olympus@xxxxxxxxxxxxxxx <olympus@xxxxxxxxxxxxxxx>
Datum: den 17 februari 1998 09:50
Ämne: Re: [OM] Ken's new IS3


>On Mon, 16 Feb 1998 15:26:39 -0600, Ken Norton <kenorton@xxxxxxxxxx>
>wrote:
>
>snip...
>>
>>Oh, do tell about the B-300.  I want to know every detail about it such as
>>flare, sharpness, contrast, etc.  Paul (yes, that Paul) has one for sale
>>that I almost grabbed along with the rest of the order.  I'm wondering how
>>it would do with some bird photography.
>>
>>Ken Norton
>
>I haven't taken any pictures with it, Ken. It is only 3 days ago that
>I picked it up. 
>I have of course looked through it, and it seems quite sharp.
>A strange thing that showed at once is, that you can only use the
>converter when the zoom is at (almost) full length, but the zoom
>mechanism itself is not switched off... so you keep trying to use the
>zoom with blackening corners showing immediately. I think I will have
>to get used to that.
>
>I have also put the extender on front of my OM-Zuiko 200/4 (changing
>that into a 340/4.5) and I certainly will put this combination to test
>as well. This set also looks promising.
>
>I will try to come back to this once I've got some results.
>
>Frank van LIndert.
>



Frank, I know we´ve been through this before (perhaps you and some other 
listmembers remembers), but I don´t think your 200/4 changes into a 340/4.5. I 
have an IS-3000/B-300 combo myself and I was as surprised as you perhaps will 
be when I learned this.

These front converters or front extenders do not affect the main lens in the 
same way as ordinary converters (which are put between the body and the lens) 
do. In technical terms they are referred to as Galileo telescopes. Ordinary 
converters affect lens speed but not close focus, but these extenders affect 
close focus but not lens speed (quite an astonishing statement, right?). These 
facts are also reflected somewhat in the small instruction leaflet to the 
B-300, although I didn´t understand this at once. It says: "This telephoto 
conversion lens can be easily attached to the lens of the Olympus IS-3/IS-3000. 
WITHOUT CHANGING THE APERTURE SETTING, THE FOCAL LENGTH IS MAGNIFIED 1.7 TIMES 
(300 mm)."

The conclusions of the earlier discussion was as far as I can remember (have it 
archived on another PC but no monitor to use) that there is no easy way to 
confirm that the lens speed remains unchanged and that these extenders did this 
with the help of the human eye. 

My experience with the B-300 is mostly positive. As you say you can only use it 
at the extreme 180 mm tele position on the IS-3. I´ve find it somewhat 
difficult to mount at times since the threads are very fine threaded, but when 
once mounted you can practise handheld shooting almost as with just the IS-3. 
The combo is a bit frontheavy and you must rest it in your left hand though. 
Other drawbacks are you cannot use filters with these extenders and that the 
front element on the B-300 is rather unprotected (the convex surface of the 
element protruds somewhat and there is no lock that keeps the cheap plastic 
lens cap in position and it frequently falls off). I haven´t found any 
significant decline in sharpness when using it, and I sure would want the wide 
converter as well if I could find one. It´s interesting that you can fit it to 
all OM lenses with a 55 mm thread, although I don´t have any myself. Hmm.. a 
65-200F4 / B-300 combination would certainly be interesting. BTW, I paid 1 350 
SKR for mine used but in mint condition. I´ll look forward to hear your results.

Best regards,
Per Nordenberg
Sweden      


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