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did anyone try this: cheap point-n-shoot on the back of a large format beast?

 
 
jjs
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      08-04-2004
"chibitul" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) ...
> In article <Q2YPc.18274$Oi.4714@fed1read04>,
> "Mark M" <(E-Mail Removed)> wrote:
>
>
> >
> > How will the "image act as an object" without the glass?

>
> just to clarify, the image is there regardless if you have the glass or
> not. The rays will keep propagating toward the digicam, and they
> "emerge" from the real image, no glass needed. as I said, optics.


Magical thinking.


 
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Mark M
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      08-04-2004

"IRO" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> In article
> <(E-Mail Removed) >,
> chibitul <(E-Mail Removed)> wrote:
>
> > just to clarify, the image is there regardless if you have the glass or
> > not. The rays will keep propagating toward the digicam, and they
> > "emerge" from the real image, no glass needed. as I said, optics.

>
> The problem at this point is that the light rays from the big camera's
> lens are radiating outward in a cone, focused on the glass screen (or
> film). The P&S can only ever see a tiny fraction of that cone where-ever
> you put it, except perhaps very close in behind the camera lens where
> its tiny lens can intercept the complete cone. Unfortunately the image
> would be wildly out of focus there, plus it would negate all the
> features of the large format camera you are hoping to utilise.


A couple of years ago, there was a similarly confused poster here, who swore
endlessly that one could copy slides using a slide project WITHOUT a screen.


--He stubbornly clung to the idea that by pointing a camera directly at the
slide projector from accross the room...and focusing the camera on the same
PLANE where the screen would have been (where the projector was also
focussed)...that one could photograph the entire picture--as though this
created (I guess) some sort of new magical light-radiation point (or some
such thing) in the air at that unreflected point fo focus.

-No amount of explaining would persuade him otherwise.
I finally suggested that he try it.
....I didn't see any posts from him after that.


It's easy to forget, I guess, that some of these basic directional concepts
are not necessarily intuitively understood by everyone. Perhaps it's a case
of too many Star Trek episodes where they have the magically impossible
capability to...from and single point...project an image, and have it show
up with no point or field of reflected light in the middle of the room's
air.


 
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Gregory Blank
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      08-04-2004
In article <pan.2004.08.04.04.01.37.448000@NO_SP_A_Myahoo.com >,
PGG <papagordygrapes@NO_SP_A_Myahoo.com> wrote:

> They make digital scanning backs for large-format cameras. $20,000 I
> think.


Lower, down to 5.5k.

--
LF Website @ http://members.verizon.net/~gregoryblank

"To announce that there must be no criticism of the President,
or that we are to stand by the President, right or wrong,
is not only unpatriotic and servile, but is morally treasonable
to the American public."--Theodore Roosevelt, May 7, 1918
 
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Leonard Evens
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      08-04-2004
chibitul wrote:
> In article <(E-Mail Removed)>,
> Leonard Evens <(E-Mail Removed)> wrote:
>
>
>>chibitul wrote:
>>
>>>Did anyone try to use a large format camera to get an image (with all
>>>the advantages of large format cameras: tilt, shift, etc) and then use a
>>>small digicam instead of film to snap the picture? I imagine if you make
>>>some sort of fixture to attach the digicam to the back of the large
>>>format camera, and focus on the glass plate, you should be able to snap
>>>*that* image. I never used a large format camera and I do not intend to
>>>venture into this field unless I can do it digitally. I am not into high
>>>resolution stuff, I read some of Ansel Adams books and I am impressed
>>>with what you can do with large format when you can tilt/shift the lens
>>>and the negative as you want. Just wondering if I can "piggy-back" a
>>>cheap point-n-shoot on the back of a large format beast?

>>
>>If you mean to use the point and shoot camera to photograph the image on
>>the ground glass, it won't work. The image is much too dim to record
>>with such a camera. Also, you couldn't focus close enough unless the
>>camera had a macro mode, which most likely it wouldn't.
>>

>
>
> yes, that is what I mean. Most cameras have a macro mode, but you can
> also put the camera about 0.5 meters away from the ground glass.


I've bought several point and shoot cameras as presents for children and
grandchildren, and not all of them could focus that close up, but there
certainly are such cameras which can.

>
> Ok, the image is dim, but this is large format camera here, not sports
> or action. we're talking landscapes, biuldings, etc, right? what's wrong
> with a slow shutter speed?


Well in principle you could do something like that, but there are a
whole host of problems.

For one, I hate to disillusion you, but things move in landscapes, e.g.
foliage blowing in the wind. For architecture, a car may drive past or
someone may walk across your field of view. You can't usually assume
that very long exposures are acceptable. Also, the gg, depending on
what type it is, may have signficantly more drop off in illumination
towards the sides and corners than you would see in a film image.

>
> And do you really need the ground glass? what if you *remove* the ground
> glass, the image will act as an object for the digicam. it should work.


Some view cameras don't allow you to remove the ground glass that
easily. But if you have one that does, what you suggest might be
possible if you can focus accurately enough to isolate the image plane.
You certainly couldn't do it by automatic focusing. That requires
some physical object to focus on. I suppose you could focus on the
physical back of the camera, hold that focus and then remove the ground
glass, but I doubt if you could get it to focus precisely enough not to
end up with a very blurred image. I would have to think about the
optics or try it to see if there are any other problems.

As someone else pointed out, the problem of using a digital camera with
a view camera to record the image has already been solved by Cambo. The
package together with the digital camera cost about $11,000 the last
time I looked, but maybe it has come down in price since. I've looked
at it at Calumet Photo in Chicago, and it is a really neat contraption.
Were I a billionaire, I would buy one just to play with it. But I
wouldn't throw out my 4 x 5 view camera yet.

I think the upshot is that you might in fact be able to do what you
suggest with some point and shoot digital cameras, but you would end up
with a pretty low quality image.

If the object is moderately low cost digital capture, you would be
better off making a film exposure and scanning it with a scanner such as
the Epson 4870.


 
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Leonard Evens
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      08-04-2004
Mark M wrote:
> "chibitul" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed) ...
>
>
>>yes, that is what I mean. Most cameras have a macro mode, but you can
>>also put the camera about 0.5 meters away from the ground glass.
>>
>>Ok, the image is dim, but this is large format camera here, not sports
>>or action. we're talking landscapes, biuldings, etc, right? what's wrong
>>with a slow shutter speed?
>>
>>And do you really need the ground glass? what if you *remove* the ground
>>glass, the image will act as an object for the digicam. it should work.

>
>
> How will the "image act as an object" without the glass?


It won't, but there is an aerial image there even without the gg. Take
off your gg if you can and use a magnifier or loupe to look at where it
was. You will see an image. But you have to point the magnifier in
the right direction. If you don't do that, I'm not sure what you get;
probably extremely diminished intensity.

>
>


 
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Dave Martindale
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      08-04-2004
chibitul <(E-Mail Removed)> writes:
>In article <Q2YPc.18274$Oi.4714@fed1read04>,
> "Mark M" <(E-Mail Removed)> wrote:


>> > And do you really need the ground glass? what if you *remove* the ground
>> > glass, the image will act as an object for the digicam. it should work.


>> How will the "image act as an object" without the glass?


>optics 101.


Sorry, you failed the course.

The large format lens will form a real image in the plane of the
focusing screen. The digital camera can focus on that real image. But
you'll get an almost entirely dark frame, with a tiny bit of the image
illuminated in the very centre.

The problem is that, except right on the optical axis, the light that
leaves the exit pupil of the large format lens reaches the image plane
at an angle. Without a focusing screen, the light continues in the same
direction and *none* of it reaches the P&S camera lens. No light, no
image. Just try looking into the back of a large-format camera with
your eye when the focusing screen is removed.

The focusing screen takes the incoming light from the first lens and
scatters it in all directions, which gives a dim image of the entire
scene no matter where you place your eye. Sometimes a Fresnel lens just
in front of the focusing screen is used to redirect more of the light
towards some assumed eye position.

In order to photograph an aerial real image like what is suggested here,
it's not sufficient to have the second optical system focus on the real
image formed by the first optical system. You also need to
*simultaneously* form an image of the exit pupil of the first lens onto
the entrance pupil of the second lens, in order to get the light where
it will do some good. And that requires additional optics in between
the first and second lens.

Dave
 
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Leonard Evens
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      08-04-2004
chibitul wrote:
> In article <Q2YPc.18274$Oi.4714@fed1read04>,
> "Mark M" <(E-Mail Removed)> wrote:
>
>
>
>>How will the "image act as an object" without the glass?

>
>
> just to clarify, the image is there regardless if you have the glass or
> not. The rays will keep propagating toward the digicam, and they
> "emerge" from the real image, no glass needed. as I said, optics.


Okay, I knew there was something wrong with this cockamamie idea, but I
temporaily thought there might be something to it. You should go try
it, as I just did. There is an aerial image there, but when you look at
it with another lens, including the lens in my digital camera, you see
the iris diaphragm opening with a clear image of a small portion of the
scene. If you move the viewing lens (or digital camera) around, you
can see the rest of the scene a very small section at a time. This, I
believe, is exactly what geometric optics says you would see. The point
is that if you have something there, such as a gg or film, the
converging rays produce a physical effect in the physical medium.
Otherwise they just continue off into space and it gets much more
complicated as to what you see with a lens placed at the right distance
from the aerial image.


 
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Leonard Evens
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      08-04-2004
Mark M wrote:
> "chibitul" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed) ...
>
>>In article <Q2YPc.18274$Oi.4714@fed1read04>,
>> "Mark M" <(E-Mail Removed)> wrote:
>>
>>
>>
>>>How will the "image act as an object" without the glass?

>>
>>just to clarify, the image is there regardless if you have the glass or
>>not. The rays will keep propagating toward the digicam, and they
>>"emerge" from the real image, no glass needed. as I said, optics.

>
>
> Cameras collect lens-projected light, but they can't reach out and bend
> projected light at some imaginary plane and change it's direction so that it
> is bent toward a tiny sensor which is too small to collect the light as it
> is projected by the lens. Draw a picture to see why this doesn't work.
>
> The light must be bent toward the tiny confines of the sensor, or you'll get
> nothing but a tiny piece of the image...which would basically appear big
> blurry light.


You are basically right, but the tiny image isn't blurry. Try it.

>
>


 
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Brian C. Baird
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      08-04-2004
In article <chibitul-8CD38A.21263503082004
@newsclstr01.news.prodigy.com>, http://www.velocityreviews.com/forums/(E-Mail Removed) says...
> do you have any idea what a large format camera can do??? you can move
> the lens and the focal plane independently, achieving effects never
> possible with a point-n-shoot (or even a dSLR).


Canon makes Tilt/Shift perspective control lenses for their EF mount.
--
http://www.pbase.com/bcbaird/
 
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Paul Atreides
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      08-04-2004
In article <(E-Mail Removed)>,
Leonard Evens <(E-Mail Removed)> wrote:


> Otherwise they just continue off into space and it gets much more
> complicated as to what you see with a lens placed at the right distance
> from the aerial image.


So in theory although they may be very very dim, there are images
all around us, some are probably quite old and from galaxies far far
away.

Maybe even stuff that hasn't happened yet
--
To win one hundred victories in one hundred battles is not the
measure of skill. To subdue the enemy without fighting is the
measure of skill. Sun Tzu
 
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