Dimensions of Omega D2 lens cones

AmysDarkroom · Jul 7, 2020

Hello there,

I was wondering if anyone had the exact measurements or even better some kind of technical drawing of the various lens cones for the Omega D2.

I've come into ownership of an Omega D2 which I have lovingly restored over lockdown. However I am missing a few bits and seeing as I live across the pond in England, parts are very difficult to come by and aren't in my budget.

My father has the equipment and machinery to be able to make our own lens cones so we thought we'd have a go. I'm more specifically interested in the 4 1/2 inch cone as I will be using a 150mm lens.

Thank you.

MattKing · Jul 7, 2020

KHB may be willing to share the information: http://www.khbphotografix.com/omega/Enlargers/D2.htm

ic-racer · Jul 7, 2020

Does the enlarger have a cone? Other than the length (stated on the cone), the are all pretty much the same.

Donald Qualls · Jul 7, 2020

Even a flat lens board would give you the critical measurements -- screw pattern for mounting and relative centering of the mounting hole. Hole will need to match the thread on your lens, naturally, either M39 (same as a Leica thread lens) or M42 (same as a Pentax Spotmatic). Likely the larger for a 150mm. Or, if you have a lens with a ring, just a clearance hole for the threads and install the ring on the inside.

mgb74 · Jul 7, 2020

You might search around this site. http://www.classic-enlargers.com/
It's no longer maintained, but you might find the info you need in the forums.

In the meantime, I think I have a flat lensboard here. I'll trace it and scan the trace. I'll also measure key dimensions in case the scan is not perfectly to scale.

jimjm · Jul 7, 2020

Here's a few pics of my 2 3/4" cone, which will give you an idea of some of the dimensions.
Most important would be the "base" or mating surface of the cone to the bottom of the bellows. Then the dimensions where the lens plate mounts to the bottom end of the cone.
The lensplate shown attached in the last photo is a 39mm threaded plate.
Obviously, the length of the cone itself is 2 3/4". For ease of construction, I don't see any reason why it couldn't be a tube, rather than cone-shaped.

mgb74 · Jul 7, 2020

My feeble attempt is attached. I traced a flat board. But because it has pins, it doesn't lay flat. But you get a sense of shape. The dimensions are taken directly from the lensboard, so should be correct within the precision of my ruler and eyes.

jvo · Jul 8, 2020

here's what i know...
a 2 3/4 cone for 135 lens
a 4 3/4 inch cone for 150 lens

John Koehrer · Jul 8, 2020

From KHB, with a link:http://www.khbphotografix.com/omega/Enlargers/D2.htm#Mounts

AmysDarkroom · Jul 8, 2020

mgb74 said:
My feeble attempt is attached. I traced a flat board. But because it has pins, it doesn't lay flat. But you get a sense of shape. The dimensions are taken directly from the lensboard, so should be correct within the precision of my ruler and eyes.

Much more than a feeble attempt! this will be very useful thank you! it's these measurements I was after

AmysDarkroom · Jul 8, 2020

Donald Qualls said:
Even a flat lens board would give you the critical measurements -- screw pattern for mounting and relative centering of the mounting hole. Hole will need to match the thread on your lens, naturally, either M39 (same as a Leica thread lens) or M42 (same as a Pentax Spotmatic). Likely the larger for a 150mm. Or, if you have a lens with a ring, just a clearance hole for the threads and install the ring on the inside.

unfortunately, I don't have anything to compare to, my enlarger didn't come with any lens boards at all

MattKing · Jul 8, 2020

For clarity, you need both a lens mount and a lens disc.

mmerig · Jul 8, 2020

AmysDarkroom said:
Hello there,

I was wondering if anyone had the exact measurements or even better some kind of technical drawing of the various lens cones for the Omega D2.

I've come into ownership of an Omega D2 which I have lovingly restored over lockdown. However I am missing a few bits and seeing as I live across the pond in England, parts are very difficult to come by and aren't in my budget.

My father has the equipment and machinery to be able to make our own lens cones so we thought we'd have a go. I'm more specifically interested in the 4 1/2 inch cone as I will be using a 150mm lens.

Thank you.

I have the 4 1/2 inch cone, and will send a detailed drawing. I wonder if the lens extender (i.e., cone) needs to be in fact a cone, rather than a cylinder which would be easier to make.

MattKing · Jul 8, 2020

Isn't it a cone because the lens discs are smaller than the part of the enlarger that the cone mounts to?

Donald Qualls · Jul 8, 2020

Most likely it's a cone because it was die cast, and the cone shape gives the draft for separating the die to release the finished part.

jimjm · Jul 8, 2020

Functionally, I don't see any reason it couldn't be a tube rather than a cone. A tube would not interfere with the focus or any other function of the enlarger. The diameter at the narrow end of the cone is only a half-inch smaller than the wide end (not counting the flattened flange).
As Donald mentioned, it was probably due to ease of manufacture and maybe for aesthetics also.

Ian C · Jul 9, 2020

You could certainly make a lens-mount cone for an Omega DII, or D2 (same cones for both machines) with a cylindrical extension. I think that the taper of the original is to make it easier to shape in a forming die. The conical angle makes it easier to extract the part from the forming die in manufacture.

The outside diameter of the flange is, I think, designed to be 6.5”, although the sample I have measures 6.489”. The flats cut out of the flange leave it 5.75” wide for insertion/removal from the retainer. The OD of the wide base of the cone close to where it flares to become the flange is about 5.56”. So, if you make a cylindrical extension, it should be no larger in outside diameter than that to clear the spring plates of the retainer.

The thickness of the flange of the lens cone measures 0.098” thickness on my sample. Bear in mind that some of the thickness is that of the paint. The mounting holes, two for the lens disk and two for the filter-holder bracket are threaded for 6-32 Phillips-head cap screws 3/8” long.

The lens-disk mounting screws are 3.25” apart on a diameter line A. The filter-holder bracket screws lie on a line parallel to and 2.00” from line A. These two screws are 1.063” (1 and 1/16 inch) apart and are equidistant from the perpendicular bisector of line A. The flats cut into the flange are also parallel to line A.

If you want to layout the holes for the filter-holder bracket with a divider, they lie on a bolt-hole circle of 4.139” diameter or about 2.069” from the center (radial distance from the center of the mounting cone/plate to the centers of the screw holes for the filter hanger).

Although it’s possible to make your own, it usually easiest to keep checking eBay for the cone you want. I’d use a search string like “Omega D2 lens cone” or “Omega D2 lens mount.”

KHB Photographix has a good reference source for the components.

http://www.khbphotografix.com/omega/Enlargers/D2.htm

Be careful in buying used cones. The Automega D3 and D4 machines used similar-looking cones that are not compatible with Omega DII and D2 enlargers. Often, the sellers are not knowledgeable about what they have. I sometimes see “D2” cones for sale that are actually D3/D4 cones that won’t fit the DII and D2.

For example, here is an advertisement for a “D2” lens cone. Note the flat flange adjacent to the clearance flats and the short flat at the front and rear (obscured). This is a D3/D4 Automega cone.

https://www.ebay.com/itm/Omega-D2-L...820133?hash=item41e0f1d825:g:qBAAAOSwYtla5-Ot

The following shows the proper flange for the DII/D2 cone (best shown in the second photo).

https://www.ebay.com/i/143575709227...MI-rqO5f2_6gIVDNvACh0seQxYEAQYASABEgJIU_D_BwE

outwest · Jul 9, 2020

Also, there is nothing said that it has to be a cone. For a longer lens it may have to be 4 sided (2 sides parallel to the width of the springs for insertion and 2 sides as far apart as possible on the long dimension). Being rectangular keeps the corners of the negative from being partially obscured.

Donald Qualls · Jul 9, 2020

outwest said:
Being rectangular keeps the corners of the negative from being partially obscured.

Mostly, the (square) bellows does that. All the cones do is the same thing an extended lens board does on a view camera -- lets you focus with a longer lens without needing so much bellows you can't focus with a shorter lens.

AmysDarkroom · Jul 9, 2020

Ian C said:
You could certainly make a lens-mount cone for an Omega DII, or D2 (same cones for both machines) with a cylindrical extension. I think that the taper of the original is to make it easier to shape in a forming die. The conical angle makes it easier to extract the part from the forming die in manufacture.

The outside diameter of the flange is, I think, designed to be 6.5”, although the sample I have measures 6.489”. The flats cut out of the flange leave it 5.75” wide for insertion/removal from the retainer. The OD of the wide base of the cone close to where it flares to become the flange is about 5.56”. So, if you make a cylindrical extension, it should be no larger in outside diameter than that to clear the spring plates of the retainer.

The thickness of the flange of the lens cone measures 0.098” thickness on my sample. Bear in mind that some of the thickness is that of the paint. The mounting holes, two for the lens disk and two for the filter-holder bracket are threaded for 6-32 Phillips-head cap screws 3/8” long.

The lens-disk mounting screws are 3.25” apart on a diameter line A. The filter-holder bracket screws lie on a line parallel to and 2.00” from line A. These two screws are 1.063” (1 and 1/16 inch) apart and are equidistant from the perpendicular bisector of line A. The flats cut into the flange are also parallel to line A.

If you want to layout the holes for the filter-holder bracket with a divider, they lie on a bolt-hole circle of 4.139” diameter or about 2.069” from the center (radial distance from the center of the mounting cone/plate to the centers of the screw holes for the filter hanger).

Although it’s possible to make your own, it usually easiest to keep checking eBay for the cone you want. I’d use a search string like “Omega D2 lens cone” or “Omega D2 lens mount.”

KHB Photographix has a good reference source for the components.

http://www.khbphotografix.com/omega/Enlargers/D2.htm

Be careful in buying used cones. The Automega D3 and D4 machines used similar-looking cones that are not compatible with Omega DII and D2 enlargers. Often, the sellers are not knowledgeable about what they have. I sometimes see “D2” cones for sale that are actually D3/D4 cones that won’t fit the DII and D2.

For example, here is an advertisement for a “D2” lens cone. Note the flat flange adjacent to the clearance flats and the short flat at the front and rear (obscured). This is a D3/D4 Automega cone.

https://www.ebay.com/itm/Omega-D2-L...820133?hash=item41e0f1d825:g:qBAAAOSwYtla5-Ot

The following shows the proper flange for the DII/D2 cone (best shown in the second photo).

https://www.ebay.com/i/143575709227...MI-rqO5f2_6gIVDNvACh0seQxYEAQYASABEgJIU_D_BwE

Thank you for this, especially the part about accidentally buying d3 or 4 cones, I actually had the one you linked in my watch list! saved me there.

outwest · Jul 11, 2020

Yes, that is why bellows are square - to prevent obscuring the corners of the image. If for a longer than usual lens you are using an unusually long cone on an enlarger or an unusually long extension board on a camera you have to take care to not cut the corners of the image out. Simple geometry will show what has to be done to allow the full image to reach/clear the full rear element of the lens. I faced this putting a 210mm lens on my Omega E. You are limited in the width of the cone (or an least the mounting board) by the width of the spring mounts. The cone can be larger than this by having an extension to clear the mounts but the round hole in the board must be cut out to a rectangular shape to prevent obscuring the corners.

eli griggs · Jul 11, 2020

If you are handy with a welder, or have a friend that is, a mild 4, 6 or 8 sided, steel box construction with the lens hole on one end and the correct flange connection on the other, should be easy enough to knock together, with a reasonable amount of care.

Matt Carbon Black acrylic paint for the finished product and make sure it fits parallel to the enlarger, with the narrow end of whatever cone, able to fit in the lower square or hex shaped space, for enough clearance.

In a 'emergency' a soup can, with a proper lens 'hole' and hot glue, might do the job, until you get what you want to replace it.

Heck, with a wood box or thick cardboard tube tube and good flat, parallel mounts on both ends, will work for that matter.

Just because we are so dependent on metal or plastic products, being provided complete or nearly so, for our every need, does no mean it is breaking a Law of Man nor Nature to seize upon an opportunity to think and act on our own behalf, and to build what it is we need at any given moment, out of any material we may have to hand

IMO..

ic-racer · Jul 12, 2020

Some of the Omega "D" cones were made with deep draw stamping and there is no manufacturing need for a tapered shape. Some were tapered and others were not. The "E" series 'cones' were polygons. You can deep draw stamp a polygon but the "E" series 'cones' were constructed from multiple pieces.

There is a "D" cone on ebay now, you could use the pictures as a reference.

Kilgallb · Jul 12, 2020

Here is a picture of my home made system. See the link. I made it with two lens boards and a pice of sewer pipe

eli griggs · Jul 14, 2020

Kilgallb said:
Here is a picture of my home made system. See the link. I made it with two lens boards and a pice of sewer pipe

View attachment 250261 View attachment 250262 View attachment 250263

Nicely done, and I'm thinking that the resulting images are as good as if they had been made with the correct lens spacer.

Independence from the Tyranny of Industry and 'The Market', is something we should all aspire to, IMO.

Dimensions of Omega D2 lens cones

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