The opposite of a close-up lens?

Can you screw the lens mounting to move it towards the film ever so little?

"Roland" wrote in message ...

I have used my Horizon for night photography with good effect. You have to
steady it, of course. I am afraid that getting the distance in focus with
your Noblex is going to be problematic. If you find some way of putting a
correction lens in front then this will be a very weak lens. Not something
that will be common. If it is fixed focussed to 30 feet, say, then its
correction lens will be -1/10th, I think (can anybody confirm this or
otherwise?)

-1/10th diopter is correct for 30 feet. The resulting image
degradation on a Tessar at f/8 or so would be completely negligible.
You're also right that such a weak lens isn't common.

Another solution would be to have the lens somehow further back
in its mounting. But I guess this would be difficult to achieve with
accuracy and would be very expensive.

Assuming the lens is focussed at 30 feet, you would need to move it
back about 0.25mm.

You are going to have to sell it and
"rely" on your Horizon. I say "rely" in quotes because they are not very
robust cameras. Mine shows some banding and now the film counter is broken.

It beggars belief that a group of people will go to all that trouble to
design a swing-lens camera and not get the focussing distance right. Only
the Horizont+Horizon series has a lens fixed-focussed to infinity. You would
have thought that a swing-lens camera was made for the purpose of capturing
wide vistas, obviously at infinity, so why do they have it focussing closer?
People like that need weeding out of the gene pool.

One of the classic uses of swing lens cameras was taking large group
portraits, so perhaps the hyperfocal adjustment is a reasonable
compromise.

Brian
www.caldwellphotographic.com

(Ralf R. Radermacher) wrote in message ...
brian wrote:

I assume that you've got a "normalish" lens such as a Tessar with a
modest field of view.

It is in fact a Tessar type but at a focal length of 50 mm for a
medium-format camera it isn't exactly what one would call "normalish".

Ralf

Since the lens only has to cover the short side of the format it is
optically "normal" even though it produces an ultrawide panorama. The
vertical coverage would be about 54 degrees. If, as is discussed
below, the hyperfocal distance is set to about 30 feet, then you would
only need -1/10 diopter of correction to focus at true infinity. The
resulting astigmatism introduced by such a weak plano-concave negative
lens would be negligible compared to the inherent zonal astigmatism of
a Tessar. Alternatively, you could attempt to move the lens back by
about 0.25mm. Do you know where the focal distance is set?

Brian
www.caldwellphotographic.com

brian wrote:



One of the classic uses of swing lens cameras was taking large group
portraits, so perhaps the hyperfocal adjustment is a reasonable
compromise.


That and many "sweeping landscapes" will have things in the foreground that
would need to be somewhat in focus.

--

Stacey

yes, but at least they have recognized the problem, the noblex 150 E2
version cited at http://www.whistlerinns.com/noblex/150_e2.htm seems to
be fixed focused at 10.4m, so as to get infinity in focus at every stop
from f/4.5 to f/22, as with the Horizon 202s etc. The diopters the table
lists are + diopters for doing closeups, shifting the close focusing
distances closer, at the expense of losing infinity focusing.

So this is NOT the case with the earlier Noblex 150E series evidently.

The easiest solution would be to screw the lens farther back by a
millimeter or so (check with ground glass at focus point and loupe).

hth bobm
--
************************************************** *********************
* Robert Monaghan POB 752182 Southern Methodist Univ. Dallas Tx 75275 *
********************Standard Disclaimers Apply*************************

In article , (Bob
Monaghan) wrote:

The easiest solution would be to screw the lens farther back by a
millimeter or so (check with ground glass at focus point and loupe).

Which reminds me to ask: Just where is Infinity?

Nope, this is not an old stoned hippie asking for directions. I'm looking
for a good rule of thumb. Isn't Infinity something like 200 times the
focal length?

jjs wrote:

In article , (Bob
Monaghan) wrote:

The easiest solution would be to screw the lens farther back by a
millimeter or so (check with ground glass at focus point and loupe).

Which reminds me to ask: Just where is Infinity?

Nope, this is not an old stoned hippie asking for directions. I'm looking
for a good rule of thumb. Isn't Infinity something like 200 times the
focal length?

Maybe we need a new definition: infinity is so far that you can't get a
corrective lens that would improve things. The weakest lens regularly
available seems to be a -0.25D eyeglass. I checked at home the 2003
catalog of Edmund Optics, and their weakest lens is a stunning -8D
(focal length -125mm)!

-- Lassi

P.S. Maybe Noblex could fix that focus, you they could be talked into
providing an infinity focus accessory lens for those that regret buying
the cheapo model...

In article , Lassi
=?iso-8859-1?Q?Hippel=E4inen?= wrote:

jjs wrote:

In article , (Bob
Monaghan) wrote:

The easiest solution would be to screw the lens farther back by a
millimeter or so (check with ground glass at focus point and loupe).

Which reminds me to ask: Just where is Infinity?

Nope, this is not an old stoned hippie asking for directions. I'm looking
for a good rule of thumb. Isn't Infinity something like 200 times the
focal length?

Maybe we need a new definition: infinity is so far that you can't get a
corrective lens that would improve things.

Well, okay, but I was thinking of calculating infinity for any lens
without supplementary lenses.

David J. Littleboy wrote:

Given that the distances involved are quite small, I wonder if the camera
could be adjusted (i.e. lens repositioned a fraction of a mm closer to the
film) to put the focus point enough closer to infinity to make it acceptable
for what you are doing???

Which is exactly what they've offered to do at the factory when I phoned
them today. Should have thought of this a lot earlier.

Thanks to all for their help and suggestions and to jjs for a few
downright silly but rather entertaining remarks. ;-)

Ralf

--
Ralf R. Radermacher - DL9KCG - Köln/Cologne, Germany
private homepage: http://www.fotoralf.de
manual cameras and photo galleries - updated March 30, 2004
Contarex - Kiev 60 - Horizon 202 - P6 mount lenses

"brian" wrote in message
...
(Ralf R. Radermacher) wrote in message
...
brian wrote:

I assume that you've got a "normalish" lens such as a Tessar with a
modest field of view.

It is in fact a Tessar type but at a focal length of 50 mm for a
medium-format camera it isn't exactly what one would call "normalish".

Ralf

Since the lens only has to cover the short side of the format it is
optically "normal" even though it produces an ultrawide panorama. The
vertical coverage would be about 54 degrees. If, as is discussed
below, the hyperfocal distance is set to about 30 feet, then you would
only need -1/10 diopter of correction to focus at true infinity. The
resulting astigmatism introduced by such a weak plano-concave negative
lens would be negligible compared to the inherent zonal astigmatism of
a Tessar. Alternatively, you could attempt to move the lens back by
about 0.25mm. Do you know where the focal distance is set?

1/100 of an inch is about two layers of bond paper. A layer of duct tape on
the pressure plate ought to do it. I think Littleboy suggested that some
fifty posts ago.