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View Full Version : Making m'own Waterhouse Stops!



Scott --
21-Jul-2010, 05:24
Hi, all -

Alright, so I've got the new-to-me Ross Universal 10" Petzval. It has a Waterhouse slot, but no stops. I 'd like to use this lens for portraits, and maybe stopped down a bit for some landscape shooting. So, I need a few stops.

I do a little reading, do a little thinking, and realize I have a glut of old 5x7 darkslides. No idea where they came from. But about half are aluminum, and half phenolic. Phenolic's easier to cut - starting there.

Measure the slot and find it's exactly two inches as viewed from above. Cut a strip off the first donor darkslide 2" wide. Slides in snugly to the lens. Take a pencil and scribe the inside profile. Take a tin snips and start rounding the bottom corners. Through a bit of trial-and-error, I get a nice fit.

http://i531.photobucket.com/albums/dd359/smpsweeps/IMG_5730.jpg

I measured the existing aperture. Lens is an f/6 as-is. Thought it was a bit faster, but the images I'm getting from it are decent, so I'm happy. Now to figure out what stops I want!

Brian Stein
21-Jul-2010, 05:31
IIRC half the diameter of the aperture is 2 stops down, so this should guide you in the size of the aperture as a reasonable approximation.
How close do you want to be to "modern" stop sizes? If you just use a standard sqrt(2) sequence from your f6 you'll get ~f8.5 f12 f17 f24 .... If you want to move to the more usual 8,11,16 etc the first stop will have to be a bit bigger than calculated, then the others in proportion to this stop.

Scott --
21-Jul-2010, 05:50
Well, I drilled my first - had a 5/16" Forstner bit, and with a 254mm lens, I got an aperture of 7.9375mm - exactly 5/16". Just check it on the ground glass. Beautifu. Think I'm making an f/16, f/8, and maybe an f/11. Should cover me for now.

Scott --
21-Jul-2010, 06:49
There ya go.

http://i531.photobucket.com/albums/dd359/smpsweeps/IMG_5732.jpg

Made f/6, f/8, f/10, f/16, and f/32. Should work well for everything I need right now. And if I need more, they're easy enough to make.

That was fun.

john biskupski
21-Jul-2010, 08:24
Scott

Looks nice work, very rewarding too. Just a question, what do you use for the metal cutting - knife, dremel, machining?

Thks

Scott --
21-Jul-2010, 08:33
Hi, John -

These are phenolic, so I used a knife and a tin snips to shape. Finessed the edges with 220-grit sandpaper. When I make them out of aluminum, as I expect to sometime, I'll likely use tin snips and a bandsaw.

Scott

Steven Tribe
21-Jul-2010, 13:42
Dear Scott - did you have any "real" waterhouse stops to compare them with? I think I can see chamfering (twice x stop thickness) but I am not sure?

Scott --
21-Jul-2010, 14:01
No - just cut and drill. Do you mean "chamfering"? Like, a beveled edge to the holes? Shouldn't be one there - these were drilled with Forstner bits. As to whether there should be one to limit diffraction effects, the stops are on the order of 1/32" thick, and the image on the ground glass looks spectacular, so I'm not too worried.

Proof of the pudding's in the eating, though - trying to talk the boy into sherpa'ing my Ries for me on a couple mile hike to shoot my favorite lil' waterfall tomorrow. Again. :D

Steven Tribe
21-Jul-2010, 14:15
The general modern view (these pages?) is that it doesn't matter if there isn't a bevel, although I always do it. This includes wheel stops as well. The 19th century guys erred on the side of caution. The smallest aperture is always nearest the camera.

The Forstner bit is not a tool I know.

Scott --
21-Jul-2010, 14:59
Well, I'll let you know how they work, Steven. If need be, it'd be easy to chamfer one side.

Forstner bits (http://www.leevalley.com/en/wood/page.aspx?p=45533&cat=1,180,42240) are awesome for this application. Very precise diameter and rapid, smooth cutting.

eddie
21-Jul-2010, 15:47
looking good.

i was just doing some myself....from black 2 ply....wanna do some more for me? har har har

swmcl
21-Jul-2010, 16:15
I have a question ...

Having not seen a lens with a slot and no Waterhouse stops ... yet, can someone tell me why the bottom of the stop is not a semi-circle ? Surely rounded edges from square will allow light in at the edge of the lens ? Is this not an issue ?

Also, what's the deal with the chamfering ? Am I to understand that the camera side of the aperture device should have the full depth chamfer - resulting in as sharp an edge as possible ?

Cheers,

Steve

Steven Tribe
21-Jul-2010, 18:38
Yes, thats the theory. More a thin edge to reduce possible defusion - same type of problem as pin hole people have everyday.

Most waterhouse stops fit between two "washers" fixed to the inside of the barrel. So you only need a small section on the bottom of the stop which touches the internal circumference to fix the horizontal position. The side to side position is fixed by the width of the stop which just fits the slot. The washer system means that you don't have to have a slot the full width of the barrel.

c.d.ewen
21-Jul-2010, 19:35
looking good.

i was just doing some myself....from black 2 ply....wanna do some more for me? har har har

Keep your fingers crossed, eddie, and maybe I'll be making some brass ones next week. I was all set to go, when the CNC-mill went down with an unexplained malady, followed by me doing the same thing. I'm hoping to be back in action next week. I'll let you (and everybody else, I suppose) know.

Charley

swmcl
22-Jul-2010, 03:46
Thanks ST for your reply.

Steven Tribe
22-Jul-2010, 05:34
I enclose a schematic of the waterhouse stop in the barrel - without and with the double edge washer system. This one has a bevel that only goes about 2/3rds of the through the stop width - safety concerns? Note that later waterhouse stops have an edge that sticks out as well as the handle. It looks like they were worried about light leaks.
Labeling is very different! some have F stop, others numbers (1 -5) or nothing at all. Dallmeyer, I think, were so company-minded that every stop had the serial number of the objective with which they were sold stamped on them.

Scott --
23-Jul-2010, 13:22
Ok, here's a little test:

Shot at f/6:
http://i531.photobucket.com/albums/dd359/smpsweeps/0016.jpg

Shot at f/10:
http://i531.photobucket.com/albums/dd359/smpsweeps/0017.jpg

Had I been thinking a little more, I'da shot the second at f/32. Ah, well. Anyhoo, there's a noticeable increase in DoF with the f/10. So, looks like they work. :D