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Details Of The Photo Booth

As promised in a posting about the pseudo-neon sign, here are some details about the physical construction of the photo booth…

Here is the booth in action at a recent luncheon with the neon sign at the top:

photobooth at luncheon

The booth frame is constructed from 1″ electrical conduit. 3/4″ conduit would probably have worked just as well and would have been cheaper, but after buying the 1″ fittings, I was rather committed…

Here are two early photos taken during construction when I was still hanging the monitor on the back wall. (I’ve since moved it because it causes people to be looking up and off into space.) I’m also not using battery powered strobes any more.

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The conduit is joined with car port/canopy fittings I bought from Yuma’s Bargain Warehouse. (I recently discovered there is a relatively local supplier of the same fittings, Shade King, located just north of Austin, TX, so I could have bought these locally and saved the shipping cost.) Below is a diagram of the rough dimensions of the booth. I won’t bother with the specifics of the fittings and lengths because I would construct it slightly differently had I to do it all over again…

photobooth drawing

The shelf was constructed from 1×8 poplar painted black (it was on clearance at Home depot, so I bought it instead of white pine). It’s held to the frame by 1″ single-sided conduit clamps. The camera mounts to the center of the board with a Manfrotto 234RC tilting quick release mount, allowing the camera to tilt up and down for adjustment. It can’t be seen well in the image below because it’s behind the frame that holds the TV with HDMI input.

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The photo booth is skinned with tablecloths I bought from Amazon. These were the cheapest source of good weight material with which to skin the booth AND the edges were already hemmed. All the “real” fabric stores wanted more money for lighter weight material. Along with the tablecloths, I bought a 20 yard roll of hook and loop tape from Amazon for attaching the tablecloth curtains to the booth. More tablecloth was used to fashion a cap to cover the top of the booth. Again, I won’t bore with the details, since I don’t expect anyone to copy me exactly… The tablecloth skin can be seen in the photo at the top of this post.

Inside the booth, white tablecloth hangs as a background (unless the event organizer orders a custom printed background). Behind the camera and monitor, white tablecloth hangs as a bounce diffusion surface. Two 45 Watt-second AC slave strobes are optically triggered by the camera’s flash. The strobes and confined space of the booth allows using an aperture of F11 and pre-focusing the lens so that everything from about 2 feet out to 5 feet are in focus. (The camera I’m using is a Nikon D90 with a 24mm/2.8 prime lens, which has the focus distance markings on it.)

Constant illumination in the booth is provided by a home-made LED stick consisting of 3 meters of 3528 warm white strip LEDs stuck on an aluminum meter stick in a T8 protective tube.

The photo booth software itself is still a work in progress. It’s basically a Python script I wrote. Linux runs on a fanless quad core ARM computer (see below) with a Freescale i.MX6Q, 2GB of RAM, and a 32GB SSD inside. Everything I used is open source, mainly libgphoto2 and piggyphoto, python-pygame, and graphicsmagick. I’m reluctant to release the source code because it is not turn-key software.

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There are two USB flash disks plugged in. For redundancy, I copy each set of image files to multiple drives in case anything goes wrong. The additional advantage of extra flash drives is that at the end of an event, it is fully stocked with all the photos so I can deliver a purchased drive immediately. The USB hub has the wireless keyboard, the camera, and a custom “keyboard” plugged into it.

The custom “keyboard” is a microcontroller board programmed as a USB keyboard. The 50mm lighted arcade buttons (see below) provide the user input.

IMG_3916

The bottom board is a Freescale FRDM-KL25Z with a custom shield board I made on top. There is currently no differentiation in the script between the buttons, but they each generate a different letter. The buttons came from Amazon.

In operation, the Python script waits for a button push to start the sequence. Four photos are taken and displayed in succession, then two versions of composites are generated: one is intended for displaying on screens at the event and the other is a vertical strip much like what the old fashioned photo booths used to spit out. Two of these latter images side by side can be printed on 4×6 paper. All the raw source images are saved along with the composites.

All of the images are shared on the local network via SAMBA. This allows setting up several Android devices around a venue to display the photo booth images in a slide show. Although it’s hard to make out in the photo at the top of this post, there is a TV hanging from the top of the photo booth just to the right of the opening. Having this SAMBA share also allows me to look at the photos with my Android phone to check on things.

The booth is very functional at the moment but not quite ready to hire out. I plan to add near real-time uploading of the images to our SmugMug.com account (where examples of the booth photos can be seen in addition to on Facebook). I am also thinking of adding an option to print the double print strip images.

There are improvements I need to make to the booth physically as well – I need to be able to set it up and break it down in 30-45 minutes. One of the things that can help with this is to build a box to house the camera, computer, monitor and button(s) allowing all the connections to be left intact. All that would need to be done is fasten the box down and plug in the power.

One interesting side note is that the Nikon D90 will drain a battery dead if left plugged into an active USB host. To avoid the hassle of having to use, charge, and switch out batteries, I purchased an AC power supply for the D90.

 

 

Posted by by david

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Light Saber – DIY Saberstrip

Recently, I came across a nifty light modifier for small battery flashes called the Saberstrip. It’s a tube with a mount for the flash at one end, and a mirror at the other end, and a long window covered with diffusion fabric. The long linear light source makes a diffuse shadow in one direction. They can be doubled up and oriented as an “L” to give a look closer to an umbrella or soft. One big advantage of the Saberstrip is that it’s not a big sail that’ll catch the wind out on location. At US$135 plus another 15 for shipping, though, it’s rather expensive for the hobbyist.kat-01

Continue Reading…

Posted by by david

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Moving Vintage Norman 200Bs into the Modern Era…

**** UPDATE *****

UPDATE:  NEW DESIGN COMING SOON THAT REDUCES CURRENT IN THE CAMERA/TRIGGER SWITCH AS ~20mA MAY BE TOO HIGH FOR CAMERA INTERNALS.

*****************

This post needs to be prefaced with a major disclaimer: Open your Norman 200B at your own risk. The 500V inside is potentially lethal. The author was careless once and accidentally discharged the cap with a meter probe which caused a big char streak in the connector and took a hunk out of the meter probe and one of the head plug pins. Proceed/attempt at your own risk. If you die, break your 200B, or both, I am not responsible.

Now that that’s out of the way, on the to the good stuff.

The Norman 200B trigger voltage is on the order of 100V. It was fine for old film cameras with mechanical sync switches. Modern digital cameras don’t care for such high voltages, so some sort of conversion or adaptation needs to be made. Optical slave triggers are one way to go, but the author smoked one accidentally by just letting the 200B sit waiting to flash. Apparently, some modern optical slave triggers do not care for such a high trigger voltage either. They are also going to end up dangling and exposed where they can become disconnected or in the extreme, get broken off.

Slave triggers and the like are not inexpensive, either. Sure, they come encased in a nice little plastic package and all, but at $8-10 or more apiece, they add up quickly, especially after having acquired four complete pack and head sets. Sometimes, it’d be useful and nice to use all that fire power at the same time and not have to carry all those little slave triggers and wires and stuff…

So, what to do? Reverse engineer the trigger circuit and make and a low voltage adapter for it using piece parts… Here’s the photo of the board alongside a mirrored and colorized photo of the traces on the bottom side that was used:

Norman 200B controller board

Here is the partial trigger circuit (please ignore all the extraneous numbers and notations) of the stock 200B blue circuit board:

Norman 200B LowVmod-5

Observant readers of Harold Edgerton’s book, Electronic Flash, Strobe, will notice that this circuit is pretty much the opposite of one within his book. The difference is that the Norman 200B is uses a positive ground, so everything is upside-down in comparison to Edgerton’s circuit. Another thing that should be noted is that when the SYNC connection is grounded, the charged 0.02uF capacitor discharges, turning on the gate of the SCR. Only a small amount of current will flow if the SYNC connection is held grounded, probably as an added safety benefit.

One would think that adding an optoisolator across the SYNC connection and the chassis would be sufficient to adapt the 200B for low voltage operation. That was tried but it did not work because the current that flows is too small to latch the triac within the optoisolator ON, so the capacitor does not discharge quickly enough, and the 200B never triggers. An early attempt to correct this consisted of shorting the diode. When the two resistors dividers are shorted together at their center points, the 200B could be fired with an optoisolator between SYNC and the case. But then additional current flows unnecessarily from the high voltage supply.

The first incarnation of the low voltage adapter was built into a plastic Tic-Tac and hung off a house hold plug that was plugged into the head. A sync cord then plugged into the Tic-Tac trigger. It was too many connections, something extra to carry and/or break. So when the opportunity to use two of the Normans for a photo shoot presented itself, it was time to move the adapter inside the pack and make the outside connections simpler…

In order to hook this into the 200B, three parts on the blue controller board need to be removed: a diode and two resistors. The colored circles indicate where the tap points are for the adapter board. The three parts need to be removed to completely isolate the SYNC connection to the head so that only optoisolated low voltage goes to the head socket. Note that two of the removed devices have a colored circle on one of their leads. The third one is unmarked in this photo but it is to the right of the orange filter capacitor and +12V connection (it can be seen in a later photo).

Norman 200B LowVmod

Here is the schematic for the low voltage adapter:

Norman 200B LowVmod-4

And here is the parts list with Digikey part numbers:


Digikey part number
Description
Note
497-2960-5-ND
IC REG LDO -5V .1A TO-92
negative 5V regulator
160-1378-5-ND
OPTOISO 400VDRM TRIAC OUT 6-DIP
optoisolator, MOC3023
CF18JT180RCT-ND
RES 180 OHM 1/8W 5% CF AXIAL
I limit resistor
399-1249-1-ND
CAP CER 0.1UF 50V 10% X7R 1206
output cap
399-1285-1-ND
CAP CER 0.33UF 25V 10% X7R 1206
input cap

The negative 5V regulator is probably not absolutely necessary, but the most often quoted number for DSLR maximum sync voltage I’ve seen is on the order of 7-9V; 12V would then be too high. A negative regulator is required because of the positive ground design of the 200B. The two capacitors are required by the regulator; surface mount chip caps were used because they take up a whole lot less room. The 180 Ohm resistor limits the current for LED inside the MOC3023 to about 20mA.

The circuit was wired onto a small perforated prototype board as can be seen below on the left. The board is positioned in this photo so the devices can be seen. The bottom of the board is normally up when assembled into the pack.

Norman 200B LowVmod-3

The pack assembled with the “protective” plexiglass cover can be seen in the photo below. The protective plexiglass is often broken on these old units… The cover also does not afford a whole lot of protection anyway since fingers can still get at the high voltage. I typically keep my fingers well clear when the power is applied and for a long while after the power is turned off as a precaution.

Norman 200B LowVmod-2

 

Posted by by david

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Vintage Portable Light: A modern take…

A couple of months back, I saw a Craig’s List listing for a Norman 200B pack, head and charger. The battery was dead and would not charge but the owner reported that it worked the last time he’d used it, it worked. I figured that for 200 Watt-seconds, $65 was not too unreasonable to gamble, so I bought it.

After purchasing, it was very interesting to note the date codes of the parts on the circuit board. They were all circa 1979. What’s more, it has the battery positive connected to the case: it was one of those positive ground devices I’d heard about but had never seen. Very interesting, indeed.

When attempting to power it up with a power supply, I had difficulty finding a power supply that would source enough current to get it to anything other than trip the over current and shut off the power supply. I ended up having to charge a large battery in the lab and using it. The pack draws pretty near 20 Amps while it’s charging up the capacitors, no small amount of current…

Intrigued by the 200B, three more packs, heads, flash tubes and chargers were cheaply acquired from the net and eBay. All the units, including the original had something wrong with them, though… I also picked up a 20 foot extension cord, and an 18 foot cable with no connectors that was turned into an extension cord by re-purposing the connectors from a charger and dual Y charging cable. The total investment in hardware for 4 complete units (pack, head, tube, reflector) and two extension cords, and an extra tube was about $300. That’s about $75 per 200 Watt-second unit…

While there are service centers that will repair old Norman hardware, the $65 starting fee for each unit plus the shipping forced digging into the hardware and reverse engineering the design. All four packs were restored to working order pretty quickly, easily and inexpensively. Two of the units failed because the foam packing inside allowed the torriodal transformer to shaker around too much and break a wire – supremely easy fix. All that remains currently on three of the units is repacking to completely restore them. Along with the repairs was the modification for low voltage triggering by modern DSLRs – the original sync voltage is about 120V…

Replacement batteries run near $100, a very unappealing price point. Gel cells that fit into the battery compartment run about $25 but only have a 2.9 Amp-hour capacity. I found 12V 7 Amp-hour UPS batteries on Amazon, two for $30, so I ordered them. The big disadvantage with the UPS batteries is that they are way too big to fit into the Norman pack.

Thus we arrive at the purpose of this post: Packaging up the Norman 200B pack with the UPS battery so that it can be taken on location.

A carried was built using 1×4 and 1/4″ thick particle board as can be seen below with one of the extension cables connected. The battery is held in place with a tight friction fit. The battery cable passes through a hole filed into the case halves.

The battery connections are brought out to banana connectors as seen below. They are spaced at 3/4 of an inch, the standard spacing for a dual banana plug/socket. The jacks allow for charging or powering something else. I’ve considered adding a cigarette lighter socket above the battery in the left 1×4 but not having one, I’ve shelved that for the time being. What’s missing for safety is a fuse. The pack itself has one internally, but there really should be one up and close to the battery, particularly if a cigarette lighter socket is added.

On the other side, I added D rings for carrying and for strapping the carried to a light stand. The whole assembly doubles as a weight, given all the lead in the battery, so why not put that to use? No need for carrying sand bags as well…

These photos were taken about 3 feet in front of a 70″ octobox with the Norman LH2 head inside. The octodome had an Alien Bees insert in the speed ring, so an adapter needed to be made. Fortunately, 3″ threaded PVC just fit inside the Alien Bees hole in the insert. A bracket for the head was made with PVC cut from a short length of gutter (the mount details will be the subject of a subsequent post…). At the moment, the mount does not swivel up or down since a Manfrotto super clamp holds the PVC fitting atop a light stand. Tilting will hopefully come later…

From behind the octobox with the shroud removed, we see the flash tube:

From the front side, with the inner and outer diffusion moved to the side:

I’ve been giving some thought to adding IGBT triggers to these for variable power control. Given the cost of parts, the possibility of popping the IGBTs, and the time to get it to work reliably, it probably does not make sense to modify or update these further. Used modern Alien Bees strobes with variable power can be picked up for around $250 or less.

But boy do these Normans recycle fast, even at full power, compared to fully charged, AA-batteried modern flashes… Popping at full power in quick succession warms up the black and red cable from the battery to the pack.

Posted by by david

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Sunday morning light tent…

This is was a draft post for the longest time.  Finally getting around to finishing and publishing it…

Jacci made a baby shower invitation for our daughter, Tricia using some stuffed animals and other items. Jacci also tried her hand at stop motion animation while taking the still photo for the invite. Here’s one of the photos she took in the series:

Sunday-morning-light-tent-3

The movie can be seen here: elephant and monkey stop motion-desktop

It was early on a Sunday morning when Jacci started trying to set up the shot. She was having some difficulty in getting some white foam core to stand up and stay where she wanted it. I went out into the garage and rounded up some 1/2″ PVC and fittings from an old project. I cut the PVC pipe into 8 equal lengths.  Then using 8 90-degree elbows, the structure below was assembled.  [I'd recently seen a PVC box design like this somewhere, but owing to the long time sitting as a draft, I no longer remember where so I can't give credit for it.]

Sunday-morning-light-tent-2

A sheet of white foam core makes the white floor.  A piece of white Tyvek hangs from the top back and slopes down to meet the foam core floor makes the continuous white background. Translucent white material hangs down on the left and right sides and over the top. Two SB-600s were placed on the left and right sides and an SB-900 was suspended over the top of the cage.

All told, creating the box and taking the series of photos took no more than about 2.5 hours total.

Posted by by david

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