Fitting the Lens

This is a good time to point out that this particular project is dealing ONLY with a 127mm lens. Which is 13mm longer than the stock lens of the 250. When choosing which of the 2 halves of the lensboard to attach your lens to, take this distance from stock into consideration.

Less than stock places the lens further back, towards the film plane. More than stock places the lens further out.

To figure out which will work best, I attached the lens to the bellows without the lensboard. Using a makeshift ground glass, like I did here, I tested for infinity focus. Hold the lens, attached to the bellows, in one hand and with the shutter open watch the ground glass until infinity is in focus.

I made a measurement of the distance from the film plane to where I found infinity. Re-assembling the lensboard pieces and focus arms, use this measurement to see where this focus point lies.

With my 127mm I found that if you put it onto the front lensboard, it is almost exactly 13mm out from the original focal point. What a nice fit!

Since this is no longer a Model 250 I removed the front label and replaced it with some plastic covering from another packfilm camera back. The rough edge will be covered by the lens.

After grinding out the lensboard to fit the lens I test fit it with the retaining ring. I was thankful I did not need to cut any part of the top of the board to make room.

If you were to put the lensboard back together you will notice that without the inner circuitry there are no less than 4 openings that need to be closed off, to prevent any light leaks. When test focusing with ground glass I did not really notice any problems but I felt it was best to reduce the possibility.

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