Originally Posted by
Noah A
The lens focal length is what determines how far from the film your lens will be, not the image circle. As Jon said, the bellows extension when focused at infinity is very close to the lens focal length in MM. I don't know how much extension your camera offers, but you should have around 180mm of extension when focused at infinity.
If the distance is much longer than that, do you have a front and rear cell, one in front of the shutter and one behind the shutter and lens board? Some lenses will effectively give a longer focal length without the rear lens cell.
The image circle does not affect how much extension you need. The image circle is the size of the image that the lens projects onto the film plane. A larger image circle will allow you to use more camera or lens movements (rise and fall, etc.).
Not to confuse the issue, but lens extension does affect image circle. As you focus closer, the lens will be further from the film plane. This means the lens will project a larger circle onto the film plane. That's why image circle specifications are usually quoted for infinity focus.
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