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Randy Rhine <> wrote in
news:aKeSb.139392$sv6.755735@attbi_s52:

> Does reversing give more magnification than using extension tubes? I
> suppose it depends on the lense combination. probably some formula to
> determine the magnification factor. But, with extension tubes, you
> get AF and aperture control. I have the Kenko ext tubes...and they get
> me as close as I've wanted so far
>
> rr
>
>
>
> PhotoMan wrote:
>> "Paul Dalen" <> wrote in message
>> news:aleSb.10161$Q_4.7172@okepread03...
>>
>>>Is it possible to reverse an EF lens? I mean, to install it
>>>backwards (on purpose)
>>
>>
>> HP Photo in New York has the reversing adapters. Note: you will have
>> no AF or aperture control.
>> Joe Arnold
>>
>>
>

As I understand it, the reason some lenses are used reversed is because
they are designed so the focused plane (the film) at the back of the
lens is closer than objects at the front. After reversing, your subject
is then closer to the lens while the film is farther since you use a
bellows or tubes. However, results will vary depending on the
particular lens you use.
I have tried one that was able to focus reversed but had a lot of field
curvature so the edges looked bad. Another I tried was not able to
focus at all when reversed. The best results I've gotten were from a
regularly mounted 100mm macro lens. The 1:1 ratio I get from it is more
than enough for my uses, but tubes could be used to get closer if
needed.

Jeff

In article <aleSb.10161$Q_4.7172@okepread03>, Paul Dalen wrote:
>Is it possible to reverse an EF lens? I mean, to install it backwards (on
>purpose)?

Forgive my newbie-like question, but why would you want to do this?

- awh

On Fri, 6 Feb 2004 09:25:52 -0500, (Drew Hamilton) wrote:

>In article <aleSb.10161$Q_4.7172@okepread03>, Paul Dalen wrote:
>>Is it possible to reverse an EF lens? I mean, to install it backwards (on
>>purpose)?
>
>Forgive my newbie-like question, but why would you want to do this?
>
> - awh

If you reverse a Wide angle you get a makro. My 24 mm Nikkor, reversed
makes 8 x 12 mm a full frame (24 x 36 mm).

You have to do it manually though.

/Daniel L.

Drew,

the typical photographic lens is optimized for imaging far away objects onto a
near-by sensor (film). 'Optimised' refers to correcting abberations of light
tracing through the lens, mainly diminishing geometric and colour 'errors'.
This correction is sensitive to the distance of the object to the lens.

Obviously 'macro' shots don't fit the bill of this optimisation because in a
macro shot situation the object is positioned near to the lens and the distance
between sensor (film) and lens has to be quite large. When doing macro shots
the geometry of the imaging process is -so to speak- inversed with regard to
the design specifications of the lens. You might either buy a 'macro' lens or
place your lens inverted ('backwards') into the path of the light. The latter
was done routinely in earlier times when people used extension tubes for macro
shots.

When you are interested in these things I would urge you to buy some old
equipment, ideally a wooden camera of ancient times with a focusing screen, or
next to this ideal an old SLR with 'extension rings' for macro photography.
Equipment of this type can be bought very cheaply and it needn't be of high
quality for the purpose of gaining some first hand experience with optics. in
addition, a simple introductory text book on optics would be helpful, as well.

Unfortunately, the modern zoom lens design is incorporating some devilish
tricks that completly mask the very simple underlying physical priciples of
optics. You cant't get meaningful insights into optics from naive observation
anymore from this newfangled stuff.

Guenter



Drew Hamilton wrote:

> In article <aleSb.10161$Q_4.7172@okepread03>, Paul Dalen wrote:
> >Is it possible to reverse an EF lens? I mean, to install it backwards (on
> >purpose)?
>
> Forgive my newbie-like question, but why would you want to do this?
>
> - awh