Kodak 405 mm Portrait lens Apterure ?

[johnschlicher]

I just acquired a Kodak 405 mm lens but as luck would have it the iris has been removed.

I would like to make a set of stops for it, the front ring unscrews and it has that lip underneath it. My thoughts are to get the aperture sizes f/4.5 --22 -then I could just lay it in there and screw the front back on to hold it in place.

Any thoughts, or suggestions would be appreciated

Thanks John

[Jay Decker]

I just acquired a Kodak 405 mm lens but as luck would have it the iris has been removed.

I would like to make a set of stops for it, the front ring unscrews and it has that lip underneath it. My thoughts are to get the aperture sizes f/4.5 --22 -then I could just lay it in there and screw the front back on to hold it in place.

Any thoughts, or suggestions would be appreciated

Thanks John

John - the 16" Kodak Portrait lens is a lot of fun and I would encourage you to get it working again. I'm working with a local trophy shop who has a x-y laser cutter to see if they can cut waterhouse stops for some of my old brass lenses.

Do you have any images of what the lens looks like without the aperture?

[johnschlicher]

John - the 16" Kodak Portrait lens is a lot of fun and I would encourage you to get it working again. I'm working with a local trophy shop who has a x-y laser cutter to see if they can cut waterhouse stops for some of my old brass lenses.

Do you have any images of what the lens looks like without the aperture?

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That is just a test fit of cardboard, so I'm pretty sure this will work. Isn't there a mathematical formula to determine the correct stops of a lens?

Thanks John

[Jason Greenberg Motamedi]

The Kodak Portrait is a very simple achromat, so you can probably use the simple formula aperture size=focal length/fstop, so 405mm/f8=50.6mm, so a f8 stop would have an opening of 50.6mm. That said, it may not be so easy, since the halation/flare may contribute to some over-exposure. I think the best way would be to find someone else with the same lens and ask them to measure.

[Steven Tribe]

So this is the lens from the lensboard of the Century 10a you have just sold! It reminded me of my plasticca! Are you certain it was supposed to have stops? My Plasticca certainly didn't have them. This "lip" may been for a yellow filter. I think you were very generous in your asking price by the way (10A)!

[johnschlicher]

It has the aperture ring on it the goes from f/ 4.5 - f/ 22, so I'm pretty sure this was made originally with a iris in it. --Yes this was the lens from the 10A, and he will probably be going up next.

I was going to try to make a set stops for it first?

[Jay Decker]

John - thanks for posting the photos. I am going to tell you what I would do in your situation in hopes that you it might help you develop some ideas of your own...

1) Purchase a decent paper circle cutter, the one that I happen to have is called "Circle Scissors", here's how it works: Circle Scissors Video (http://www.youtube.com/watch?v=vyT7z3WH_eQ&feature=PlayList&p=B0A75C1C3629C728&playnext_from=PL&playnext=1&index=7). There are many variations that probably work as well or better. If I were to purchase a new one today, I'd probably buy the Circle Scissors Pro.

2) Cut waterhouse stops using the circle cutter to cut concentric rings that fit on the face of the iris ring. Regarding stop material, look for black, heavy weight construction paper, art paper, poster board, or thin plastic (thin phenolic paper is nice) to cut the stops from. You want something that does not transmit light, is thin, has some stiffness, and that the circle cutter can cut.

3) You can hold the stops in place with tape, e.g., black gaffer tape. But, if you think you are going to want to change the apperture with any regularity, you probably want to consider holding them in place by other mechanical means, e.g., magnets, Velcro, etc. (I seem to be on kick of using small magnets to hold stuff in place. If this appeals to you, you might want to take a look at the small neodymium disc magnets at kjmagnetics.com. )

4) You also might want to consider putting a tab on the stop to hold-on to the stop when placing or removing the stop in the lens. Again, you could use a tab made of tape, or fashion something and fix it onto the stop, e.g., a plastic pull tab glued onto the stop.

Good luck and I hope to be seeing you post some photos taken with your new lens!

[Tracy Storer]

If you can disassemble the lens and remove what remains of the old aperture mechanism, you will find a slot in the barrel. This is the slot through which the outer adjusting ring coupled with the internal mechanism.....it's in just about the perfect spot for WH stops, which can be cut on a Laser cutter from black Delrin plastic.
It's a wonderful lens.

[Tracy Storer]

Jason is right about calculating f/stops for this lens, I just measured f/8 on mine, and it looks like 50mm and change.