Round images on negatives.

[JRCriton]

When I first started researching photography years ago I came across a few images that were a round image on the negative vs square . Over the years I've learned they were taken with 8x10 cameras. So I started doing light research into how it was done, but I've ran into a roadblock. Here's what I'm hoping to do. I have a 4x5 Calumet rail camera that takes 4x4 inch lens boards. I'm hoping to get a lens small enough that the image on the negative is round. I was wondering if I bought an old pocket film camera that takes 120 or 620 film and then buy a lens board and cut a hole for the smaller lens like an old Anastigmat Volgtar, would that lens work for what I'm trying to do? If not what do you recommend? Or what's another method to mimic a full image circle on the negative so the sweet spot is in the center of the image then it's soft around the edge and causes a circle image on the negative? Also what potential issues would I experience when it comes to the camera movements?

Here are a few examples of what I mean. Thought they are not exactly what I'm aiming for. Just visual guidelines.
http://media2.onsugar.com/files/2012...er.preview.jpg

Imagine this with black around the image
http://3.bp.blogspot.com/-BjOAQyimGu...ingCircle1.jpg


Thanks for your time and I appreciate the help.
Sincerely,
JRC

[Peter Gomena]

I did exactly what you want to do. I used a 130mm lens off an old Agfa/Ansco folder. The image circle was about 6.5 inches in diameter. I've been trying ever since to find a similar lens (I no longer have the other) that will project a circular image on my whole plate camera. The only issue I ran into was that when the 8x10 bellows was compressed that much, there was no movement possible on my old camera. It wasn't a big deal, I just treated it like it was a big box camera. The bellows on my whole plate camera won't compress enough to allow a short enough lens to be used - it's an antique and the bellows is pretty stiff. A bag bellows would be ideal.

[JRCriton]

So that's one of the draw backs. If I get a smaller lens, I wouldn't have much camera movements to work with. Okay I'm forgetting what I've been taught in school. Why is it that a smaller lens make it so the bellows has to be compressed more?

[lenser]

One rather mechanical means could be to place a round vignetter in front of the lens you already have. That would eliminate the bellows compression problems. To make the edge as sharp as possible, place the the vignette out a bit from the front of the lens and use the f stops at minimum stops to maximize the depth of field and bring the circle edge into a sharp a plane as possible.. Relate this to using a Waterhouse stop in front of the lens instead of at the nodal point inside the lens.

Think of this in terms of how often you've seen cutouts used in motion pictures such as the shape of binoculars or the final frames shrinking down to a pin point.

[JRCriton]

One rather mechanical means could be to place a round vignetter in front of the lens you already have. That would eliminate the bellows compression problems. To make the edge as sharp as possible, place the the vignette out a bit from the front of the lens and use the f stops at minimum stops to maximize the depth of field and bring the circle edge into a sharp a plane as possible.. Relate this to using a Waterhouse stop in front of the lens instead of at the nodal point inside the lens.

Think of this in terms of how often you've seen cutouts used in motion pictures such as the shape of binoculars or the final frames shrinking down to a pin point.

So if I'm understanding what you are saying correctly, if I put the vignette causing material behind the lens it would soften the edge of the image. But if I put it in front, the distance of the material from the lens in combination with the f stop, would adjust the edge softness of the vignette?

[jnantz]

hi there

any lens that won't cover the format will make a circular image on your film
you could probably pick up a longer focal length, meant for 4x5 that doesn't cover and will darken your film ..
http://www.largeformatphotography.in...s/LF4x5in.html
just look for a coverage circle less than 200mm and don't stop down very far ..
maybe a cheap enlarger lens will work ( and a paper negative ) ?

have fun!
john

[lenser]

If you put it behind the lens, I believe it will act as a secondary f stop and effect exposure unless it is right up against the film plane, which is certainly possible to do. Calumet used to sell a 4x5 inside the camera masking frame which could be used to double expose layers of shapes within the frame in camera. I've got one if you wish to see the instruction sheet. I'll be happy to scan and post it. If the vigetter used in front of the lens, the clear core remains at the exposure reading you began with for the subject. I really don't know what it would do to sharpness if placed immediately behind the lens as I've never tried that.

If you can access a Cokin filter catalog, they have a vignette shape kit that is used in their normal holders just in front of the lens. The kit includes several shapes. As I recall, there is a keyhole, a heart, circle, binoculars and a few others.

I've never heard of this being done behind the lens (except as a film plane mask), but I could certainly be ignorant of that technique. From what I've read about motion picture film work, it was done in front of the lens, probably for the simplicity of access if not for any optical or exposure needs.

[lenser]

Back in my wedding shooter days, I often used a matte box that extended about four inches in front of the lens. The mattes fit in slots so that you could layer them if desired and the box had a lid to keep them in the dark to prevent any reflections even though they were made of black matte board. One was an oval with a sharp edge. If I used it close to the lens, it was quite soft, but using it out near the front and stopping down would make the edge much sharper. It would probably been sharper yet if it had been make from a thinner material such as something about the thickness of a dark slide. You might check out the availability of motion picture matte boxes.

[JRCriton]

If you put it behind the lens, I believe it will act as a secondary f stop and effect exposure unless it is right up against the film plane, which is certainly possible to do. Calumet used to sell a 4x5 inside the camera masking frame which could be used to double expose layers of shapes within the frame in camera. I've got one if you wish to see the instruction sheet. I'll be happy to scan and post it. If the vigetter used in front of the lens, the clear core remains at the exposure reading you began with for the subject. I really don't know what it would do to sharpness if placed immediately behind the lens as I've never tried that.

If you can access a Cokin filter catalog, they have a vignette shape kit that is used in their normal holders just in front of the lens. The kit includes several shapes. As I recall, there is a keyhole, a heart, circle, binoculars and a few others.

I've never heard of this being done behind the lens (except as a film plane mask), but I could certainly be ignorant of that technique. From what I've read about motion picture film work, it was done in front of the lens, probably for the simplicity of access if not for any optical or exposure needs.

That's right it would act as an f/stop. What I was thinking about was how some people put their filters behind the lens. I should have thought of that. So my question is now if the mask is close to the negative it would have a sharp edge but if there is a distance the edge of the mask would soften but the mask would have to stay near the film plane? Yes, I'm interested in reading more about it if you don't mind.

[JRCriton]

Back in my wedding shooter days, I often used a matte box that extended about four inches in front of the lens. The mattes fit in slots so that you could layer them if desired and the box had a lid to keep them in the dark to prevent any reflections even though they were made of black matte board. One was an oval with a sharp edge. If I used it close to the lens, it was quite soft, but using it out near the front and stopping down would make the edge much sharper. It would probably been sharper yet if it had been make from a thinner material such as something about the thickness of a dark slide. You might check out the availability of motion picture matte boxes.

Great idea!