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Re: [OM] Zooms at Dawn - the 50mm shootout - Teaser

Subject: Re: [OM] Zooms at Dawn - the 50mm shootout - Teaser
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Date: Wed, 21 Apr 2010 07:52:17 -0400
One can focus with the converter if desired but that's not really the 
way it's intended to be used.  What I was referring to was my difficulty 
focusing anything in manual mode on my Canon 5D.  Old eyes and focusing 
screens sans focusing aids make life difficult.  You are quite welcome 
to be a real photographer.  I'm quite happy to have my autofocus but I 
do still shoot mostly in manual mode.

Chuck Norcutt


richard mcgrath wrote:
> ...you don't have to focus it (the converter) if it's like the Vivitar
> teleconverter I have.  Just stick it between the lens and the camera, forget
> about autofocus, maybe forget about autoaperture and go take pictures like
> real photographers do.
> Richard
> 
> ----- Original Message ----- 
> From: "Chuck Norcutt" <chucknorcutt@xxxxxxxxxxxxxxxx>
> To: "Olympus Camera Discussion" <olympus@xxxxxxxxxxxxxxxxx>
> Sent: Tuesday, April 20, 2010 11:15 AM
> Subject: Re: [OM] Zooms at Dawn - the 50mm shootout - Teaser
> 
> 
>> I have a Vivitar 2X macro converter that I've never used.  I discovered
>> it on the bay about a year or two ago quite by accident and it was going
>> for a low price.  I guess I should give it a try... if I can focus it.
>>
>> Chuck Norcutt
>>
>>
>> Ken Norton wrote:
>>> Moose thus grunted:
>>>
>>>> Undoubtedly someone has gone to the trouble of designing an internal
>>>> focusing prime with close to constant effective focal length, but it's
>>>> got to be tricky and expensive to do. OK, maybe nobody has built one;
> I
>>>> just want to cover my bases.
>>>>
>>>
>>> Please, somebody, tell me who makes that lens!  I'll get one today!
> (well,
>>> maybe not today, but you get the point).
>>>
>>>
>>>
>>> In any case, most of them do change focal length as focused closer. That
>>>> was one factor in my choice of the Tamron 90/2.8 macro, which uses a
>>>> conventional long helix to focus. The Canon 100/2.8 macro is IF. So as
>>>> one focuses closer, the working distance gets even shorter than would
> be
>>>> expected with conventional design.
>>>>
>>>
>>> Exactly. This is one of those reasons why I've been such a fan of my
> lowly
>>> 100/2.8 with extension tubes. I get fantastic macro quality as well as
>>> serious working distance. Extending the 300/4.5 gives me stupidly long
>>> working distances.
>>>
>>>
>>>
>>>> With any lens at 1:1, the the focal plane to subject distance is 4x the
>>>> focal length. The Canon 100 mm, instead of 400 mm, has a close focus of
>>>> 1:1 @ 310mm, for an effective FL of 77 mm.
>>>>
>>>
>>> Moose, I agree with your calculations. However, I am remembering
> something
>>> that might alter that equation. I hope that somebody on this list has
> one to
>>> confirm or deny my allegation.
>>>
>>> Vivitar made a 2X Macro/Teleconverter. This was a brilliant piece of
>>> engineering that included an extending section of the tube which moved
> the
>>> lens farther away from the film-plane which yielded close focusing and
> then
>>> the 2X optics further magnified the image. If you placed a 50mm lens on
> the
>>> Vivitar, you could achieve an effective coverage of a 100mm lens, but
> the
>>> working distance remained about that of a 50mm lens. Also, the bokeh
>>> characterists remained that of a 50mm lens--just blown up bigger.
>>>
>>> It all had to do with the position of the 2X optics themselves. If you
>>> placed a normal 2X teleconverter on the back of a 50mm lens and then
>>> extended the pair from the film plane, it acts like a 100mm lens in
> working
>>> distances, etc., but when you extend the 50mm lens first and then
> multiply,
>>> it acts pretty much like a 50mm lens. Anybody with a 2X and some
> extension
>>> tubes can easily experiment with this and see for themselves.
>>>
>>> The reason why I mention all this is because certain modern
>>> lenses--especially the 14-54 and 12-60 act like shorter lenses with
>>> teleconverters built in. The working distance of the 14-54 in macro is
>>> stunningly close.  Like REALLY close. As in even at the 54mm setting the
>>> lens hood is shading the subject. The 14-54 really does, to MY eye, look
>>> like it is being internally extended (focused closer) giving a bit of
>>> shorter focal length to begin with, and then multiplied by the second
> lens
>>> group at the back of the lens.
>>>
>>> AG (it's all smoke and mirrors) Schnozz
>> -- 
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