Introduction
The three Simmon brothers began producing enlargers in the mid-30s and are still in business today (as
OmegaSatter). The original company was
Simmon Brothers, and the greek Ω symbol was the logo; but over the years the symbol became
the name of the product. Enlargers by Simmon Brothers are almost always referred to as "Omega"
enlargers.
Omega enlargers typically follow a reliable name scheme: the letter designates the format size of the enlarger (i.e. the largest negative the enlarger can accept); the following number indiciates the model generation. A B size enlarger is larger than an A, a D is larger than both, etc. Typically the higher the number, the more recent the model. E.g. a B-22 is more recent than a B-3.
The letter formats are: "A" (35mm), "B" (2-¼-square), "C" (3-¼-square), "D" (4x5), "E" (5x7) and "F" (8x10).
There are some exceptions, as noted. Marketing departments love to depart from a standard naming scheme, and in some cases, a very popular model enlarger (such as the D5) remained in production after more recent machines were discontinued.
To the best of my knowledge, the XL designation refers to an extended-length column.
I have a few of Instruction Manuals and brochures available for download. 
Quick Comparison
| Model | Mfg | Col. Type | Col. Height | Lens Focus | Focus Method | Baseboard | Notes |
|---|---|---|---|---|---|---|---|
| A | 1938-1940s | Single Tube | Unknown | Bellows | Manual | Unknown | Very similar to the B, but for 35mm and similar (e.g. 828) formats |
| A2 | 1955-1962 | U-tube | Unknown | Cone | Manual | Unknown | Two different column lengths available, a standard "portable" and a longer "professional" |
| A3 | 1967-1970 | Single column | 28" | Rack & Pinion (with cone) | Manual | Unknown | Unusual design doesn't mimic the other Omegas. Modern Photography Test March 1968 |
| A6 | 1966-1972 | Dual-Rail | Unknown | Unknown | Manual | Unknown | Intended for professional use |
Series Comments
Omega's A series handled 35mm and equivalent (e.g. 828, 126, and half-frame). There aren't very many models here--most manufacturers had far better sales in medium-format (in modern times, images shot on size 120 roll-film). Since an enlarger can print any negative up to its largest size, many photographers preferred to buy medium-format enlargers even if the bulk of their work was in 35mm, just in case. 35mm enlargers' main attraction was their compact size and light weight, which made them better candidates for temporary darkrooms and small spaces.
Model Comments
Complete (Model A)
Please see my comments in the Other Omega section.Model A
This is actually Omega's second 35mm enlarger (the first being the Complete Model A). This was a traditional enlarger with a single tube column and a double condenser system.Model A-2
The 15 or so years between A models made this a huge updating, like its U-shaped column that's raked forward in the Omega fashion. Unfortunately, according to KHB Photographix, it has very few parts in common with other Omega models, so finding parts for it is tough.
Model A-3
The following is an unsigned review that appeared in the March 1968 issue of Modern Photography.
Specifications: Simmon-Omega A3 enlarger. Construction: Metal cantilevered girder and high-impact plastic and metal lamp housing. Negative Size: 35mm and 126. Lens: 30mm f/4.5 Rodenstock Omegar. Focusing: manual rack and pinion with focusing tube. Light Source: No. 111A 75-watt opal lamp. Optical System: Double condenser. Other Features: Plastic negative carrier, 12 x 21". baseboard, red safelight filter, rotating base, cooling fins, and troughs for negatives in rolls. Price: $89.95.
An Omega enlarger for $89.95? Unlikely. But here it is. The Omega A3 is way under the price of the up-to-now least expensive Simmon machine. But it bears a strong resemblance to the other machines produced by Simmon and it can do a man-sized job. The A3 has the same aluminum cantilevered single girder construction and the lamp housing looks for all the world like a miniature, simplified version of its bigger brothers. From baseboard to top of the girder it measures a scant 28" compared to the bigger Omega enlargers. But the A3 can turn out a full 11 x 14" print at the baseboard. For anything bigger you simply undo the screws holding the girder and swivel it around for floor projection.
The lamp house design is unusual. Light passes from the 75-watt Iamp through a condenser, and thence to a mirror at a 45° angle. The light then goes through the second condenser to the lens. Slots in the lamp housing permit adding heat-absorbing glass and color correction filters for color enlarging. Cooling fins and a type of heat sink effect takes care of overheating nicely. We discovered just how well it works almost by accident. The enlarger was inadvertently left on for several hours. When we finally got back to MODERN'S testing lab the machine was hot--but not as hot as one might expect. We could discern not a bit heat damage either. The heat sink effect (a system used widely for dissipating heat in transistorized high fidelity equipment) works because of the proximity of the lamp house to the aluminum girder. Under normal conditions the housing never got hot enough to be uncomfortable to the touch.
The negative goes between the two halves of the hinged plastic negative carrier (the 126 carrier is optional). Studs on the carrier surface align the negative quickly and accurately. The carrier goes into the spring-load negative stage, which holds it firmly in place. You raise the lamp house to the desired enlargement size by pushing gently. The lamp house rides the girder on a smoothly operating flat platform. Once in position, a generous-sized knob locks the housing in place. The fine focusing control knob works smoothly and with little effort. During extensive enlarging sessions we saw no signs of drift or backlash. The focus stays where you set it and can even withstand moderate jarring.
Illumination tests on the A3 and the 50mm f/4.5 Omegar lens indicatate some light fall-off at f/4.5. At f/5.6 fall-off was barely discernible in test-results and nonexistent at f/8.
Our tests also indicated at f/8 enlargements were more than adequately sharp. At larger apertures enlargements were somewhat less sharp.
The A3 has the added virtue of assembling or disassembling quickly, making it a likely candidate for the kitchen darkroom or the photographer on the move who needs an enlarger that he can tote along. You could pack the Omega in a suitcase and have room for a suit and two pairs of trousers.
The A3 lacks many of the more advanced features of other more expensive Omegas. But if you can do without a variable condenser, auto focusing and other refinements, it's a machine to think about.
Custom-Lab A-6
[Note: if there's an A-4 or an A-5, I am unaware of them.] The last of the A series, and almost the opposite (in terms of design) from the A-3. It offered the dual-rail column, rack-and-pinion height and focusing, and a diffusion head. It was aimed at professionals and labs, rather than hobbyists.