Why not the best of lenses?
Earl Fieldman
chair, and damned if I didn't sit on them. One
of the lenses fell out. It laid around a while, but one
day I picked it up and lazily subjected it to my "port
wine test", that being, hold it up and see how high
it is to focus the ceiling light on my pantleg.
Damned if it didn't focus. Sort of high up, but
I confirmed it, focusing the ceiling light onto the floor.
I taped the fallen reading glass lens onto a lens board,
Copal 0 size was the max. Stuck it onto an 8x10, and
checked out the ground glass. Damn. There's an image,
lookin pretty good all the way to the corners.
Some quick tests with paper yielded the conclusion that
I had about a 400mm f20 lens, with good 8x10 coverage.
(two for $14.99, without shutter). Now for a piece
of TMX.
Now I had hopes that what I would see from the results
was a pleasant softness. At least an interesting distortion.
After all, a single piece lens has been inferior since before
1850. No correction of any kind, you know.
The really disappointing part is that a contact 8x10 print
is sharp as can be imagined. I don't have any doubts
that when enlarged the difference between a 2-fer-$15
lens and a $1000 multi-coated modern lens would be
readily observable. Probably if I just photographed
something which would demonstrate conciseness it
would be readily observable. What I'm saying is that
a portrait style contact print shows no degradation at
all. Truly disappointing. Might as well have used
my 14in Commercial Ektar, not at all what I had hoped
for.
Earl F.
Silicon Valley
John Yeo
John
"Earl Fieldman" <e...@ucf.not.no> wrote in message
news:O9EJ4fVTBHA.2196@cpimsnntpa02...
Robert Wood
YES!!! Please post a scan! Thanks for the great story.
rw
Ryan
Photography, published by The Fountain Press sometime between 1939 and
1945 (little sign stating printed to War Economy Standard).
Found an reference to Spectacle Lens: and here is an extract
Such a lens can be used for landscape and portrait work on fairly
large plates and gives a certain amount of diffusion that is often
pleasant.
To obtain even definition over the field the focal length must be long
in relation to the negative. A spectacle lens that is double the
diagonal of the negative is desired.
In the case of a plano-convex or meniscus lens the image will have
good central sharpness if the convex side faces the subject. Less
central sharpness but eveness of definition will result if the convex
side faces the plate.
Think I will shoot a few spectacle shots this coming weekend.
Now does anyone know how to convert a simple lens prescription like
+1.5 to focal length?
R.
On Thu, 4 Oct 2001 21:42:06 -0700, "Earl Fieldman" <e...@ucf.not.no>
wrote:
Earl Fieldman
"John Yeo" <jon...@thegrid.net> wrote in message
news:BGbv7.807059$ai2.61...@bin2.nnrp.aus1.giganews.com...
> Interesting. I would love to see a scan.
I'll have to get a different picture.
My wife would kill me. I promised her
I was just fooling around, and there was
no chance that what resulted would be
a usable picture. She wasn't participating
in any way, even growling occasionally, but
I do find it a whole lot more informative to take
a picture of a person as compared to, say, a
bookshelf. Even when the
subject is barely cooperative.
A 2nd report.
This lens does not like to be tilted, it
gets so soft that it's not really focussable
at maximum front tilt on my Cambo, but
it does not obviously vignette.
I did a 2nd negative last night with the
lens, with a significant rear tilt, working
on its portrait potential.
For what it's worth, I've found the easiest
way (or at least a way) to use this lens to be at
night, with a low lit room. Remove darkslide, wait
for "the moment", fire SB26 flash at full
intensity. Replace darkslide. The affect
of the dimly lit room duration is little
or none. This has yielded reasonable exposure
with the film and flash at about 10 ft from
the subject and about 6 feet from the subject.
Earl F.
Silicon Valley
koolish
meniscus.
After that, you can try pinhole photography and fresnel zone plates for
interesting
effects.
Martin Jangowski
> Now does anyone know how to convert a simple lens prescription like
> +1.5 to focal length?
Easy. Prescriptions are measured in dioptries, that's 1/f in meter. A
positive value means a convex lens (for farsighted eyes), negativ values
are concave lenses for nearsighted eyes. A +1,5 lens has a focal length
of 666.7 mm.
Martin
Ryan
R.
On 5 Oct 2001 20:52:11 +0200, Martin Jangowski
Jim Hand
news:3bbdc9a6...@news.sf.sbcglobal.net...
>
> Now does anyone know how to convert a simple lens prescription like
> +1.5 to focal length?
Yup. Look here:
http://www.geocities.com/ocular_times/diopter.html
The formula is focal length (in meters) = 1 meter / diopter
So, the focal length of a 1.5 diopter lens is 1 / 1.5 or 667mm
Jim
Jim Hand
> +1.5 to focal length?
>
Robert Monaghan
In one of Feininger's classic books, he has a large 8x10" camera ground
glass view pointing out at New York City skyscrapers IIRC. In one photo,
the edges are quite unusably soft, but the center looks promising. In the
second photo, the overall view is quite sharp and looks good to the edges.
What lens was he using? A cheapy office magnifier lens. In the second
case, he cut a waterhouse stop for the lens. ;-)
I have wanted to retry that experiment, but with a decent two element
achromatic diopter lens (nikon series or ??), with and without stops. I'd
bet the results would be pretty impressive too, on the larger film format.
Might even work on 4x5? hmmm ;-) grins bobm
--
* Robert Monaghan POB752182 Southern Methodist University, Dallas Tx 75275 *
* Third Party 35mm Lenses: http://people.smu.edu/rmonagha/third/index.html *
* Medium Format Cameras: http://people.smu.edu/rmonagha/mf/index.html *
Earl Fieldman
"Robert Monaghan" <rmon...@smu.edu> wrote in message
news:9pt9ac$i2r$1...@post.cis.smu.edu...
>
> In one of Feininger's classic books, he has a large 8x10" camera ground
> glass view pointing out at New York City skyscrapers IIRC. In one photo,
> the edges are quite unusably soft, but the center looks promising. In the
> second photo, the overall view is quite sharp and looks good to the edges.
>
> What lens was he using? A cheapy office magnifier lens. In the second
> case, he cut a waterhouse stop for the lens. ;-)
Thanks for all the reaction. Really great. I think that Feininger
was my kind of photographer. A hacker from the old days.
Here's an update.
I've by now printed an 8x10 which was an enlargement from
a 4x5 piece of a contact print from the reading glass negative.
Indeed, it is not purely sharp; neither is it particularly soft,
it's not exactly what I imagined I was looking for in a
portrait lens, but it's very usable.
It rapidly deteriorates when tilted.
Portraits have an
advantage that they seldom need corners which
are even close to sharp; this lens is plenty sharp enough
in the corners.
I've concluded that the lens which fell out of my reading
glasses is more likely a 500mm f20 or so lens. A +2.
By achromatic, I take it you mean those screw-on close
up "filters"? I have some old Nikon ones. I'll check them
out. I never imagined...
Earl F.
Silicon Valley
Winifred Carbunkle
Now I've gotta try a couple of my Grandagons mounted into spectacle
frames, to wear instead of eyeglasses. Suave!
Ken Myrtle
You may want to try using both of the reading glass lenses
with one lens placed on each side of the aperature stop.
If I recall correctly two symmetrically placed lenses operating
at 1:1 will have no coma or transverse chromatic abberation
and a 8x10 portrait lens would almost be operating at 1:1.
A pair of screw on close up filters would probably work much
better here is a list of achromatic close-up filters
http://www.angelfire.com/ca/erker/closeups.html
to help figure out the focal lengths.
Sort of like reinventing the wheel but fun to try anyway.
Ken Myrtle