Flashbulbs in the Darkroom; Using a Graflex Synchronizer Tester

Part 1

By Les Newcomer

Synchronization, simply put, is getting the shutter to open and close when the flash bulb is at its brightest. The difficulty is that the duration of the light output of a typical flashbulb is 50-60 milliseconds1 and needs about 20 milliseconds to get to half-peak, or 50% light output.

(solenoid and shutter)

Until mid way through WWII, flash synchronization was achieved by tripping the shutter through a solenoid. The photographer pushed the button on the flash battery case that closed two circuits: one to the flashbulb and one to the solenoid. Linkage in the solenoid delayed tripping of the shutter for about 20 milliseconds, enough to get the flash to peak brightness.

But this linkage was, pardon the phrase, a weak link in the design. Too tight and it wouldn’t have enough inertia to trip the shutter, too loose and the shutter would open too late. Links stretched and solenoids shifted during the hard
knocks a press camera took. It didn’t take much to cause a weak flash. Photographers are inveterate tinkers and it didn’t take long for several companies to come up with synchronizing testers, including Graflex.

(case)

The Graflex Synchronizer Tester2 is unique among testers in that it is the only one to use gravity as a standard. The testing was done in two phases, the first a visual to get close and the second using flashbulbs and photo paper to get it right on.
(tester from back with flashlight and holder)

The apparatus consists of a two-piece L-frame, an angled flashlight and special film holder that’s been modified and weighted.

(not sure closeup)

In operation, the lens board is mounted to the tester. The micro-switch on the right is wired to the trip circuit (behind the red button, on the flash) and the solenoid is wired to the battery case normally. A lever on the tester is set to the center, which opens two small holes behind the lens.

(closeup of corner of holder)

The film holder has an oval hole milled through it and the dark slide has three holes in it. Two are covered with red and blue filters, the center one is left white.

The test is made by turning on the flashlight and dropping the film holder down the back of the upright while looking at the lens. As the film holder falls it closes the micro-switch that closes the solenoid circuit and trips the shutter. Light from behind the tester illuminates the holes. Graflex instructions say, “If all is well, you’ll see a blue light at the top, white in the center and red at the bottom. A red light at the top or center means the shutter opened early, a blue light at the center or bottom means the shutter opened late.” In operation, the colors don’t mean a whole lot. If its not in sync, you won’t get three lights. Top, or top and center means it’s early. Bottom or bottom and center means it’s late.

Before getting too deep in the testing, make sure the solenoid and the battery case are compatible. Graflex originally stated that a No. 2 solenoid was used with 2-cell battery cases, and the No. 3 was used with 3-cell cases. While you can use a No. 2 solenoid with a 3-cell flash (over voltage), using a No. 3 solenoid, with a 2-cell flash (under voltage) is asking for misfires. To complicate matters (it is Graflex after all) by the 1950s, solenoids were used mainly for tripping internally synchronized shutters and Graflex moved to referencing the solenoids (2, 3 and even a No. 0) to the size and trip-strength of specific shutters. For this article, I’m sticking to the earlier designation, a No. 3 solenoid with a 3-cell flash, and a No. 2 for a 2-cell flash.

With the solenoid cap screwed on about half way, start by slightly loosening the solenoid mount, and pushing the solenoid up slightly. Now cock the shutter and set it to 1/400. Press the button on the flash unit to trip the shutter, then carefully and slowly pull the solenoid down until it just trips the shutter. This is the base synchronization. Test using the visual method. Further adjustment can be made by pulling it down to decrease the time-lag, or up to increase it.

(Insert photo of lens on tester, shutter open with three lights visible)

Phase two requires photo paper and flash bulbs. Back in the day this was the cost of maintaining your equipment. Today with the smallest bulbs reaching over a dollar each, this part could get expensive.

Take the equipment into a darkroom with a safe light. Graflex says to set the shutter to the highest setting. Graph No. 2 suggests 1/200 might be a more accurate setting as the starting times for 1/200 and 1/50 are the same. Move the lever to it’s up position. This closes the top and bottom holes behind the shutter leaving only the center hole. It also uncovers a hole outside of the lens board. Place the Graflex flash in the hole and aim the flash (with a bulb) at the shutter. Go dark. Load the paper in the open side of the holder. Close your eyes, drop the holder.

(Insert Graph No. 1 Synchronicity and? Graph No. 2 shutter speed)

After developing the paper, the left side of the paper will have a long black trace that is tapered on both ends. This is the flash trace. The right should have a relatively short black spot. That’s the shutter trace. Comparing my trials with that from the Signal Corps instruction book, it seems photo paper has gotten a lot faster in 70 years; what they show as a line with a slight bulge in the center has become something like a line drawn with leaky fountain pen.

Graflex says, “If the shutter trace is centered in relation to the bulb trace, it’s “in sync.” If the shutter trace is low, it went off too soon. If the shutter trace is high it was too late.” If you like to shoot flash at 1/200 or above, then follow their advice. If you like to shoot flash at 1/200 or above, then follow their advice. However, Graph No. 2 shows the trace straight from passing the Visual Test. Buy Graflex standards, it looks early at 1/400, it certainly isn’t centered to the brightest part of the flash. But at 1/50, the shutter is in sync. Mark the solenoid cap with a reference line. Adjust the sync by either tightening (decreasing time lag) or loosening (increasing time lag) the cap. Before you test with a bulb, make sure the solenoid trips. Extreme adjustments at either end can cause a misfire (flash but no exposure) In which case you’ll need to move the solenoid within its mount. In either case you’re gonna need more flashbulbs and paper.

While this tester was designed for solenoid synchronization, it will work equally well on internally synchronized shutters. However, adjusting those shutters are more of a dark art left to somebody that’s experienced with such things.

Finding a Graflex Synchronizer Tester is difficult. Finding one complete is even harder. The angled flashlight is a TL-122-A issued by the government to just about every GI that wore a uniform. These were later improved (less brass, more plastic) to the TL-122-B and C. A mint condition TL-122-A (which is what should be found in a Graflex Synchronizer Tester) is coveted by WWII re-enactors almost as much as Graflex flash units are to fans of Star Wars. Consequently, they are often missing. That said, any bright light source behind the shutter area will work, but don’t pay a high price for an incomplete tester.

Part 2 Life outside of Graflex (Yes, William, it does exist); The Kalart Synchroscope, the Wilcox Flash-o-Graph and adjusting non-Graflex solenoids.

_________________
1 Synchro–Press No. 5, 50ms, Wabash Superflash Press 40, 60ms. Photo Lab Index, 8th ed. Henry
Lester 1946.

2 The Signal Corps called the tester a Timer, PH-191-A, and the War Department prepared a technical manual TM 11-2378, dated 4 October 1944. The U.S. Navy didn’t bother giving this one a name, they just rubber-stamped an anchor on the instructions in the box.

The tester was first shown in a Graflex civilian catalog dated November 15, 1945, with the following “new products” description: “Developed for military use, it is compact but a very serviceable unit…. At present, designed for use with lenses mounted on 4” square lensboard, but can be adapted by the user for operation with smaller lensboards.”