I have a Workprinter on order and have a question regarding distance of camera.
Why is it better to have the camera a few feet away and zoom in rather than have the camera as close to the workprinter as possible?
Just curious. Many thanks,
Barry.
Workprinter Question
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MovieStuff
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Hi, Barry!
There are several reasons for the distance that the camera sits. The easiest way to illustrate it is by using a postcard or other small target image. If you put your camera on telephoto and position it about three feet from the postcard, you will be able to zoom in and get a nice, flat field image with no distortion. That is to say the horizontal lines of the image will be nice and straight with no bowing or bending. If you move your camera up close, you will be forced to put your camera on wide angle (or possibly macro) to fill the screen with the same image and still be able to focus. The resulting use of the shorter focal length lenses will create distortions in the horizontal lines of the image, leaving a sort of "pin cushion" effect.
The same applies to the super 8 frame being copied via the WorkPrinter. The condenser lens magnifies the gate so that it appears about 3 inches wide. By placing the camera about 2.5-3 feet from the condenser lens (and, in effect, the super 8 frame) then you are able to take advantage of the flat field characteristics of the longer focal length lens on your zoom.
Now, in my illustrious career building optical printers and other high end optical bench equipment, there have been times where a client asked me to create a set up where the camera sits up close to the condenser lens for the sake of convenience. I can do this but I need to know what the specific characteristics are of the camera lens being used and, once built, a different camera might not work on the same set up. The tolerances for close proximity work are in fractions of an inch, whereas putting the camera a good distance means the tolerances are in feets and inches, which is much more manageable for the average person to set up using a simple tripod. Close proximity work generally calls for small worm gear beds to move the camera into the right position. In addition, the condenser lens array for close proximity work is MUCH more expensive as it has to correct for the distortion inherent in shorter focal length (wide angle) lenses on the camera.
And, finally, close proximity work is best achieved with prime lenses and not zoom lenses. The multiple elements in a zoom lens are a haven for dual images and chromatic aberrations and are quite bothersome to get rid of. Longer focal length lenses (even on a zoom) naturally have less chromatic distortions than shorter lenses; or rather, the chance of visible chromatic distortions is lessened dramatically with longer lenses.
The WorkPrinter has no screen and, as a result, one can not choose where the camera lines up in the "sweet spot" that allows for proper alignment with the aerial image. On some cameras it's about 2.5 feet. On others it's as far away as 4 feet. Obviously, I have to make my units work with a wide variety of cameras which is another reason for the distance.
So, it's a balancing act in making the unit distortion free, work with as many cameras as possible and keeping the price at a level that everyone can afford. A different condenser lens would allow some cameras to sit closer but some cameras would be left out of the winner's circle. As it stands, you need a 12x or better optical zoom to work with the WorkPrinter or CineMate. There are a few cameras with a 10x zoom that will work but not many. The ones that do usually have a maximum zoom that is equal to the maximum zoom on the 12x camera. So, while it's not really the zoom ratio that is the issue, I use the 12x as a starting point knowing that it will generally encompass a long enough lens to do the trick from the require distance. Otherwise, a 10x zoom will fall short when cropping into a R8mm frame.
Hope this helps!
Roger Evans
There are several reasons for the distance that the camera sits. The easiest way to illustrate it is by using a postcard or other small target image. If you put your camera on telephoto and position it about three feet from the postcard, you will be able to zoom in and get a nice, flat field image with no distortion. That is to say the horizontal lines of the image will be nice and straight with no bowing or bending. If you move your camera up close, you will be forced to put your camera on wide angle (or possibly macro) to fill the screen with the same image and still be able to focus. The resulting use of the shorter focal length lenses will create distortions in the horizontal lines of the image, leaving a sort of "pin cushion" effect.
The same applies to the super 8 frame being copied via the WorkPrinter. The condenser lens magnifies the gate so that it appears about 3 inches wide. By placing the camera about 2.5-3 feet from the condenser lens (and, in effect, the super 8 frame) then you are able to take advantage of the flat field characteristics of the longer focal length lens on your zoom.
Now, in my illustrious career building optical printers and other high end optical bench equipment, there have been times where a client asked me to create a set up where the camera sits up close to the condenser lens for the sake of convenience. I can do this but I need to know what the specific characteristics are of the camera lens being used and, once built, a different camera might not work on the same set up. The tolerances for close proximity work are in fractions of an inch, whereas putting the camera a good distance means the tolerances are in feets and inches, which is much more manageable for the average person to set up using a simple tripod. Close proximity work generally calls for small worm gear beds to move the camera into the right position. In addition, the condenser lens array for close proximity work is MUCH more expensive as it has to correct for the distortion inherent in shorter focal length (wide angle) lenses on the camera.
And, finally, close proximity work is best achieved with prime lenses and not zoom lenses. The multiple elements in a zoom lens are a haven for dual images and chromatic aberrations and are quite bothersome to get rid of. Longer focal length lenses (even on a zoom) naturally have less chromatic distortions than shorter lenses; or rather, the chance of visible chromatic distortions is lessened dramatically with longer lenses.
The WorkPrinter has no screen and, as a result, one can not choose where the camera lines up in the "sweet spot" that allows for proper alignment with the aerial image. On some cameras it's about 2.5 feet. On others it's as far away as 4 feet. Obviously, I have to make my units work with a wide variety of cameras which is another reason for the distance.
So, it's a balancing act in making the unit distortion free, work with as many cameras as possible and keeping the price at a level that everyone can afford. A different condenser lens would allow some cameras to sit closer but some cameras would be left out of the winner's circle. As it stands, you need a 12x or better optical zoom to work with the WorkPrinter or CineMate. There are a few cameras with a 10x zoom that will work but not many. The ones that do usually have a maximum zoom that is equal to the maximum zoom on the 12x camera. So, while it's not really the zoom ratio that is the issue, I use the 12x as a starting point knowing that it will generally encompass a long enough lens to do the trick from the require distance. Otherwise, a 10x zoom will fall short when cropping into a R8mm frame.
Hope this helps!
Roger Evans
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Barry
Thanks Roger!
Thanks for your time and effort -- I understood a fair bit of it. My camera has a 15x zoom so I should be OK.
If you're still there, you mention 'ariel image' which I've seen mentioned before, but am not quite sure about this either. Does this mean you focus somewhere between the lens of the Workprinter and the camera and not at the lens? Hope you don't mind me asking these questions I'm trying to find out all I can before the unit arrives so I can get transfering as soon as possible. (Can't wait actually!).
Thanks for your time and effort -- I understood a fair bit of it. My camera has a 15x zoom so I should be OK.
If you're still there, you mention 'ariel image' which I've seen mentioned before, but am not quite sure about this either. Does this mean you focus somewhere between the lens of the Workprinter and the camera and not at the lens? Hope you don't mind me asking these questions I'm trying to find out all I can before the unit arrives so I can get transfering as soon as possible. (Can't wait actually!).
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MovieStuff
- Posts: 6135
- Joined: Wed May 01, 2002 1:07 am
- Real name: Roger Evans
- Location: Kerrville, Texas
- Contact:
Regarding an "aerial image":
The thing to do is not think of the projector as "projecting" anything but, rather, it is a passive mechanism that simply holds the film in place with a nice even back light for viewing purposes (much as a light box is used to view slides).
So, then, the trick is "How can I view the 8mm frame since it's so damned small?"
Well, how does one view a 35mm slide that's laying on a light box? You use a magnifier, that's how!
In the same way, the condenser lens magnifies the 8mm frame and makes it big enough for the camera to focus on. In effect, the lens of the projector, the condenser lens and the lens of the camera all work together to constitute one gigantic lens that provides a microscopic view of the surface of the film. With this method, you are actually shooting right off the film frame with no screen in between your camera or the projector.
However, IF you were to remove the condenser lens and replace it with a rear projection screen in the exact same place, you would actually see a collected image, since the projector is still focusing on the same point in space. Remove the screen and the image is still focused in space (hence the name "aerial image").
Now, it should be noted that because you are focusing at that point in space, anything else that shares that space is going to be in focus along with the target image. On Oxberry stands, they often use a HUGE condenser lens (like around 15 inches across) so that artwork or mattes can be focused on along with the film image being copied.
The same holds true for the WorkPrinter's condenser lens. If you focus on the image being presented, you will find that anything on the glass will also be in focus (like dust, finger prints, etc, yikes!). Keeping the glass clean is the best solution but there are other tricks one can do, as well. If you were to hold a piece of paper about three inches in front of the condenser lens and focus your camera on that, the condenser lens and the image it contains will naturally go out of focus. However, you can then readjust the focus on the projector to make things sharp again. The end result, though, is that the surface of the condenser lens is now out of focus (along with any dust or fingerprints!) even though the image floating several inches in front of the lens is IN focus.
Keeping a plastic bag over the condenser lens is the best way to deal with the problem but my point is simply that an "aerial image" can be at any point in space; even a few inches in FRONT of the condenser lens that provides that image.
Roger
The thing to do is not think of the projector as "projecting" anything but, rather, it is a passive mechanism that simply holds the film in place with a nice even back light for viewing purposes (much as a light box is used to view slides).
So, then, the trick is "How can I view the 8mm frame since it's so damned small?"
Well, how does one view a 35mm slide that's laying on a light box? You use a magnifier, that's how!
In the same way, the condenser lens magnifies the 8mm frame and makes it big enough for the camera to focus on. In effect, the lens of the projector, the condenser lens and the lens of the camera all work together to constitute one gigantic lens that provides a microscopic view of the surface of the film. With this method, you are actually shooting right off the film frame with no screen in between your camera or the projector.
However, IF you were to remove the condenser lens and replace it with a rear projection screen in the exact same place, you would actually see a collected image, since the projector is still focusing on the same point in space. Remove the screen and the image is still focused in space (hence the name "aerial image").
Now, it should be noted that because you are focusing at that point in space, anything else that shares that space is going to be in focus along with the target image. On Oxberry stands, they often use a HUGE condenser lens (like around 15 inches across) so that artwork or mattes can be focused on along with the film image being copied.
The same holds true for the WorkPrinter's condenser lens. If you focus on the image being presented, you will find that anything on the glass will also be in focus (like dust, finger prints, etc, yikes!). Keeping the glass clean is the best solution but there are other tricks one can do, as well. If you were to hold a piece of paper about three inches in front of the condenser lens and focus your camera on that, the condenser lens and the image it contains will naturally go out of focus. However, you can then readjust the focus on the projector to make things sharp again. The end result, though, is that the surface of the condenser lens is now out of focus (along with any dust or fingerprints!) even though the image floating several inches in front of the lens is IN focus.
Keeping a plastic bag over the condenser lens is the best way to deal with the problem but my point is simply that an "aerial image" can be at any point in space; even a few inches in FRONT of the condenser lens that provides that image.
Roger