Wednesday, April 15, 2015

Do you need a new camera?

"Should I upgrade my existing camera body?", "What should I buy next?". These are questions commonly read on the forums and facebook groups. The short answer is that if you need to ask then you probably don't need to upgrade because if you did need to upgrade you would already know why and wouldn't have to ask.
Often the first factor that is quoted is megapixels which reminds me of a camera store I was in 10 years ago. I was browsing the cameras on display when I heard the clerk telling a customer "Your camera is only 5 megapixels, that's only good for printing 6X4's but if you want to print bigger you need to upgrade to this new 8 megapixel version." This was not too long after the days when they were printing billboards taken from 3 megapixel images.
This was taken recently with my 6 meg Nikon D50.

About a year later I heard a clerk in the same store telling a customer "Your camera is only 8 megapixels, that's only good for printing 6X4's but if you want to print bigger you need to upgrade to this new 12 megapixel version." believe it or not I'm still reading comments like that about people "needing" to upgrade from 12 megapixel bodies to 24 megapixel versions.
Are you amazed by some of the images you see from 36 megapixel cameras? Well you're probably viewing them on a screen that is less than 6 megapixels which tells you that the same image could be done with a 6 megapixel camera and it would still amaze you - it's not the camera that is amazing, it is the photographer's skills you are seeing.
Actually sometimes it's just blind luck like this picture I got early one morning while touring New Zealand :) Nikon D40, 18-200mm VR lens.

I'm actually so tired of reading these discussions about why people who don't even know how to use their 12 megapixel camera should 'upgrade' to a 24 megapixel camera that I'm inclined to post more images taken from my 6 megapixel cameras "just because".
Granted, if you are a professional doing a shoot for an advert and know exactly what you want from it then by all means choose a good camera body and lens combination [most likely a prime lens] and do your the job that you know is earning you a living. But if you are still learning then please consider simply learning to use what you have before throwing more money at gear.
My person preference is..... whatever lens is on the body. If I want wide angle I'll grab my D90 with the 12-24mm lens on it. If I want versatility I'll grab the D40 with the 18-200mm lens - I don't care much how many megapixels the body is because I know that 6 meg is enough for a full page picture in a magazine - why do I need more than that?
Of course many will say "You can crop more with more megapixels" [possibly the same people who used to scoff at "digital zoom" on a camera]
I also love the versatility of a "low quality" super-zoom that can get me from 18mm to 200mm for vastly different images in the same scene.
Quite often when I had just bought a 70-200mm F2.8 VR lens I would go for a walk to find something to photograph with this high quality lens only to find that I couldn't zoom back far enough when I needed to. There's no point in obsessing about image quality when you don't have a useful focal length to get the images you want. And if you don't know what you are going to need when you go for a walk then it's best to be prepared. Rather get the shot you want at 90% quality than miss the shot at 99.9% quality.
It's not fancy gear that gets you good shots, unless you are shooting sports or something that needs really fast auto-focus - it's knowledge and sometimes just the luck of being in the right place at the right time - with the right focal length lens at your disposal. That is less likely to happen if you have a prime lens on your camera.
Many of my favourite shots were taken with my 6 meg bodies simply because they had the lens I wanted on them at the time.
This shoot for example involved being in the harbour and the risk of getting everthing wet. I chose the 6 meg D40 and 18-200mm lens rather than my new D90 at the time. This is the shot I was aiming for - at about 200mm.

Then I decided to go wide so I could show people the setting, and zoomed back to 18mm [couldn't do that with a 200mm F2.0 lens :) ] and got this shot. I love the versatility of a super-zoom and realistically for my uses [having fun] I doubt I would see any difference with prime lenses that would simply limit my creativity.

At the last wedding I shot I had my 16 meg D5100 but since I already had the 18-70mm lens on my 10 year old D50 I grabbed it for a shot similar to the one above. You can make a large canvas print from a 6 meg image so it was more than enough for my needs.
I was once driving home and saw this sunset developing in the distance. I 'only' had my D40 and 18-200mm lens on the seat next to me and raced down to the beach. It would have been nice if I could have gone wider but 18mm did an ok job this time.
Then there was the shot from the comparison at the top of this page. The lighting was just right and since I was doing a tour I had my 18-200mm on the D40 once again.

So please think carefully before making your next purchase. For my particular style of shooting the only thing that entices me to upgrade is better low light image quality - clean high iso. With today's technology they could probably make a really good low light 6 meg dx body but instead they are forcing 24 megapixels onto the sensors and trying to get the most out of them. Just think, back to 6 meg and they could do 4x better in low light but infortunately the masses see megapixels as what makes a good camera to buy and nobdy will step back to 'only' 6 meg [besides me] if they make such a camera.
My advice is this: If your camera is really old then wait till the next new release and buy a second-hand body from "last year" for $200 as the masses rush to buy the latest and greatest. If after a year you decide you would still like that body that was new back then you will probably be able to buy it for $200 less than when it was released and you will now have a spare body, plus that camera - for the same price as what it would have cost when they were just released. You will probably also find that your pictures are no different except perhaps in low light.

Thursday, April 9, 2015

Camera settings for beginners.

The settings I am about to describe are what I call "safe mode". If I were to hand my camera to someone and ask them to take some photos for me or simply grab the camera myself to get some quick photos these are the settings I would have my camera on.
For those of you who know what you are doing and what settings you want to use this blog is not for you - it's to help beginners find a safe selection of settings to use before venturing out on an unplanned shoot where they don't really know what they will be photographing and are not entirely sure what settings to use. It's also the settings that my cameras are always at unless I have it on a tripod in manual mode preparing for some 'experiments'.
The photos here are of my D90, taken with my D5200. I don't care which of the two I grab to take pictures with, it depends which lens I am after. The D90 usually has the 18-200mm on it and it's the one I grab for most walkabout shoots. The megapixels mean nothing to me, if I need the 35mm f1.8 lens I grab my 6 meg D40 because I have never needed more than 6 megapixels.
First I will mention the basic setting my camera is on for image quality. I only shoot in jpeg mode. If you want to shoot RAW then I advise setting your camera to RAW+jpeg and comparing the two files after editing them and see if you need to shoot RAW. RAW is superior in every way except the amount of memory space it wastes and the fact that you have to edit it before sharing.  Having said that I shoot in jpeg mode to discipline myself to get as many settings as possible right in-camera when shooting. if I did photography for a living I would shoot RAW.
I set my image quality to "large" and "fine". If you print out two photos, one taken in "fine" and one in "basic" they will look exactly the same - unless you edit them, and almost every photo needs a fine tweak of some sort no matter how well you have your exposure set - there are too many variables to get it right in-camera every time besides the limitations of the sensor itself.
A jpeg fine is like a thick slice of bread, it looks exactly the same as the thin slice [basic] from the top but if you put them both in the toaster [Photoshop] the thin slice will 'warp' while the thicker slice will handle it better. This means that jpeg fine has more information to 'throw away' to achieve the desired result when you edit. RAW is like a quarter loaf of bread in comparison, you can choose where you cut it before putting it in the toaster - within reason of course. :)
I leave my wb on auto as well. Auto settings are by no means perfect but they generally get the images close enough to be able to save them through editing later. If you set white balance manually you need to be fast enough to change it with changing light and have the memory [in your head] to do so. I don't have a good memory so I let the auto modes do some of the thinking for me.

I also have my iso set on auto. I set the actual iso manually to the lowest - iso 200 in this case because "lo-1" is a trick mode that loses quality. I have it set to be able to choose the maximum iso necessary to allow me to use my other settings with a minimum speed of 1/125th. That way it will keep increasing iso to prevent my shutter speed dropping below 1/125th because "you can fix noise but you can't fix motion blur!". What's the point of staying at iso settings for the best image quality if your shutter speed is so slow that the subject is a blur? In any case it's perfectly fine to have some noisy images in a set, many non-photographers will think it's artistic :)

I have my AF area mode set to 'dynamic' so it uses all the focus points for its calculations but I choose the main one myself. This prevents the frustration of it choosing a subject that is closer if it is in fully auto mode. I set the centre focus point to "narrow" because I find that when I have it at "wide" it doesn't focus as well, usually on something behind my subject.
Now most of the time when I am doing 'walkabout' shooting I am in program mode. Shocking isn't it? Not really because I know how it thinks and I have the camera set up to take advantage of this. When you are in program mode the camera will remember what the minimum shutter speed is that you have told auto iso to allow. If the subject is a little dark the camera will do everything it can to prevent increasing the iso, which is good for image quality.
First it will open the aperture to its widest, then it will lower the shutter speed, but not below that 1/125th sec that was set for auto-iso. Once it hits 1/125th sec it now only has one setting left, iso. It will then increase iso to the point where it reaches what it deems to be 'correct' exposure [I have a long chapter on this in my ebook]. So you may end up at let's say f3,5, 1/125th sec and iso 800 - but you couldn't go wider on the aperture, you don't really want to be shooting slower than 1/125th for motion blur so all that is left to save the shot is an increase in iso - or you can't get the shot. If it gets to its maximum iso [iso 3200 for my D90] it will do the only thing it has left to do and use a slower shutter speed which may or may not get you the image you wanted but there isn't much else you can do in a hurry.

Then I put my camera in shutter priority where you tell it what speed to use.
I set this to 1/30th sec. and that's not just some random number, it's for a reason.
During normal shooting in program mode we are trying to avoid motion blur but every now and then a situation presents itself where the motion blur can actually add to the image. For me it's normally around 1/30th sec where the VR on the lens can save me from movement just enough to have a sharp background with a blurred subject - that's when I know that at the flick of the dial over to "S" I know that the camera has memorized the last setting I put it at, 1/30th, to give me the image I want without missing the moment. I was taking pictures of something from the top of my photovan and saw this truck coming past. Knowing that I had shutter priority set to 1/30th and wanting to make the speed look a little more dramatic it simply involved moving the dial to "S" and I got my shot. Then straight back to "P" again to continue shooting.

It's not about letting the camera do the thinking for you, it's about learning 'how' your camera thinks and using it to your advantage when time is limited. When you know why you choose these settings you are generally competent enough to shoot the same way in manual mode when time permits.

What about Aperure priority? I very seldom use it actually. perhaps indoors but most of the time I know that Program mode is going to choose settings very close to what I would choose while taking snapshots. If I'm indoors perhaps I may select the widest aperture my camera can go to but then again I know Program mode will do that anyway.

When I go to manual mode the settings for Aperture priority and Shutter priority are there as a base point to work from before turning off auto-iso if I have the time.
But there is another trick to turning off auto-iso [kinda] without digging into the menus - so you know it is ready to work for you again at the flick of a dial. Switch to Shutter priority and dial the speed slower than 1/125th sec.
If you have your camera on a tripod perhaps and you want to get some motion blur on the sea with a nice sunset you don't want auto-iso taking your speed up to 1/125th again. By having the camera in shutter priority you are telling the camera what speed to use regardless of what you have told auto-iso to do. But auto-iso will still work to get what the camera deems to be correct exposure.
As you dial the shutter speed slower the iso will drop back to 'base iso' [200 for the D90] and once it reaches this and you keep going slower it will start closing down the aperture to get the correct exposure. So basically you can set your camera to take a 1 second exposure at f11 and iso 200 even if auto-iso is turned on - without going into the menus. As soon as you flip back to Aperture priority or Program mode auto-iso will work exactly as before. :)
There is one other mode I use occasionally. Sports mode is handy when something happens in a hurry and you don't have time to change many settings. If I suddenly need to shoot something fast moving I simply flip to sports mode, there's no shame in using an auto mode if you actually know what settings it will choose and why - because it means you could choose the right settings if you had the time.
All of the advice I give here is just a guideline for people who just want to go out and shoot for fun and learn with time. I would suggest using these settings when you want to be in 'safe mode' and when you have the luxury of time to experiment then try manual mode. For me I know that when my wife wants to grab one of my cameras and take some photos they are set up to pretty much get the pictures as close to the settings that I would choose anyway - then she will enjoy it rather than being frustrated by the camera and give up on it.
And just keep in mind that a jpeg could easily be published in a magazine :)

Saturday, April 4, 2015

More dangerous – The Trigatron

In my search for a fast switching method to fire up my experiments someone mentioned a spark-gap-switch on one of the forums. I went into an electronics store to ask if they sold them and was informed that I would need a special license to have one imported for me. When I replied that I would rather make my own I was warned that the FBI might start keeping track of what I do as the Trigatron is known for its use in detonating nuclear weapons. Well if that’s not what I’m going to use it for then I think it’s ok to make one because, after all, they do have other uses. 
Do a search on “Trigatron” for a detailed description of its operation but for now the basic principle of the Trigatron is that you can switch very high voltages and currents without anything making contact. By having two contacts very close to each other, but far enough away to prevent arcing, waiting to switch a high voltage and current; all you have to do is use a third electrode to ionize the gap which enables the electricity to flow across the air-gap. The next image shows my first crude attempt at a basic Trigatron using a modified gear-reduction starter motor to hold the contacts where I wanted them. The spark-generating-coil provides my trigger spark and a 3300uf capacitor charged to 325 volts by an old flash is joined at either end of the contacts with a fuse in line that will blow if it conducts. This attempt failed probably because the gap was too large.

As can be seen from a close-up image my contacts are really large and rough, as is the trigger electrode, making it difficult to get them close enough for a 325 volt supply to jump the gap.

But I did eventually get it to work and the design shown below is what worked. The two red wires coming off the contacts were eventually connected to the large blue capacitor strapped upright to the flash. The blue line drawn in shows where the HT lead from the coil went. 

This is the more complicated design to make for a Trigatron. Instead of adding a third electrode from the side, which ionizes half the gap as it jumps across, almost the entire gap can be ionized by having the third electrode running down the centre of one of the main electrodes. This way when the spark jumps across to the other side it creates a path for the lower voltage supply to rush across as well. The professional way of doing this apparently involves drilling a 1mm hole down the centre of the electrode and having an extremely thin, insulated wire, as the trigger electrode in the centre of that hole. 
My skills do not include finesse. I found a 5mm plastic tube with a metal rod running down the centre, which used to be connected to the central locking system of a car I had worked on. This would have to do. I drilled a 6mm hole and inserted my “trigger electrode”.  

The normal solenoid contacts of the starter motor were then modified to be able to go extremely close together making the gap for the 325 volts to jump as small as possible without too much fireworks and guide-dog training. 

This is how it was all wired up. 

As per the photograph with the sparking-coil and the solenoid contacts, once the capacitor was charged up with 325 volts from the old flash head all that had to be done was to take a photograph with the spark-generating coil connected to the camera. When the flash fired (away from the picture) a spark was generated that jumped the (small) gap thereby ionizing the air and allowing the capacitor to dump its charge across a 7.5 amp fuse, blowing it to bits. The disadvantage of a CCD sensor can be seen by the flare pattern created by the huge flash of light. The advantage is that this picture could actually be taken at 1/1000th of a second with this sensor.

A few seconds later we heard a “plop” in the office as our secretary finally lost her grip on the ceiling fan. It was like a gunshot going off. I will guess at some figures because there’s little chance of measuring the energy released in that small explosion. A 7.5 amp fuse normally takes about 15 amps to blow. I have no idea how this equates to a 325 volt supply because it may behave differently but even at 10 amps that would be 3250 watts, or 3 kilowatts, of energy in less than 1/1000th of a second.
This system proved somewhat unreliable because the next attempt was a misfire and the trigger electrode needed adjusting. It blew a 10 amp and a 30 amp fuse as well. The 30 amp fuse would have been close to 20 000 watts of energy. The fuse on the left is 10 amps and on the right is 30 amps. They looked a lot worse than the average fuse that has blown on a 24 volt truck circuit. 

When we inserted a 40 amp fuse there was a really loud noise and the tip of the electrode was melted off in a fraction of a second. I definitely need to make some progress with this project. The Trigatron and I have some interesting photography to produce yet. 
We have a metal recycler down the road from our workshop and they had a nice thick 25mm (1 inch) thick brass rod that will provide me with a powerful electrode. Once I get around to drilling the correct size hole and making a framework that can (safely) hold the electrodes the right distance from each other we will be back in business but the noise will be pretty loud. I’ve found that in situations like this wearing a high-visibility vest goes a long way because people don’t bother questioning you then. I once took some photos next to a river at a major park. I wrapped a sword in rags dipped in torch-fuel and set it alight while my model in a Samurai outfit held it out at arms length. We needed to be close to the river in case she caught alight if you can see the logic in that. I wore a high-visibility vest which immediately makes people think you are officially allowed to be there and they don't bother you.
I can just imagine it now, these 8 capacitors all wired up in parallel joined to the Trigatron. I wonder what thickness wire will be destroyed and how much noise it will make before the helicopters start circling (again). 

I still believe that besides the pure fun of photographing an explosive event there is perhaps a scientific use for this aspect of superspeed photography. Perhaps by my next book I will have discovered it; then again perhaps I will only have discovered another way to get the attention of the armed-offenders squad, who knows?
Anyway that’s as much as I have to share for now because, as mentioned, there is still a lot of “un-chartered territory” in this area of photography and my latest purchase just arrived and needs my attention. 
How will I approach this project, the SCR and wire/gunpowder, the spark-generating-coil and Calcium Carbide, some other invention? We’ll see ;).

Thursday, April 2, 2015

Dangerous stuff – The SCR

By now it’s possible that people may have worked out that I enjoy moments of destruction. Seriously, what I would probably rate as the best day of my life was when I wrote off my work van in a crash with a bus. The bus pulled out in front of me and I slid into the side of it at 80km/hr. I will admit to feeling the slightest bit of fear in the form of “What will the boss say about me smashing my work van?” but when I realized there was no more I could do to avoid it and it wasn’t my fault I just sat back and enjoyed the ride. A loud bang, smashing glass in all directions [until the windscreen wrapped itself around my head that is], most of the side windows were smashed, all the auto-electrical spares in my van flying all over the place-mainly toward my head. The heavy tool-box at the back ripped out of its holder and the ladder behind my head took most of the force before allowing it to rest up against my shoulder. After the fire department eventually cut me out I looked at the side of the bus and realized that if the bottom part hadn’t been so strong I would have slid into the luggage compartment and possibly left my head at the back of the van somewhere. Two weeks later I was still picking bits of glass out of my head. If I had to choose one day to re-live I know what it would be. 

Due to the dangerous nature of this type of photography I’m not going to mention the part number of the SCR I used because anyone wanting to duplicate this type of photography should be competent enough to look it up and know what they are dealing with. If I remember correctly the one I am using is capable of switching up to 800 volts with an initial surge of 3800 amps. A rough calculation tells me that is 3 million watts of energy, or basically 3000 times more powerful than the average microwave which is why you need to be very careful with this type of photography. 

And this is how I wired it up. If you can work that out there’s a good chance you are capable of using it reasonably safely but there’s no way I will provide a step-by-step guide for total beginners to fry their hearts. 

Now for those who think I’m not capable of being artistic think again! This is what my first box looked like :D .

For my fist experiment I simply switched the capacitor across a thin piece of wire to see the wire explode. I’m using a 3300uf capacitor charged to 325 volts by an old flash. 

The little D40 can do this all the way up to maximum shutter speed. 1/4000th at F8.

The next experiment was to see if a wire would still give a bright flash under water. And it did.

What happened next was both surprising and encouraging. This time I had the wire a little close to the side of the jar, I got my picture but the shock wave of the burst traveled downwards and blew the bottom of the jar out. The video can be seen under the title “SCR in water” on YouTube. 

The resulting destruction of the jar was pretty impressive. I need to get some more jars I think

I have since refined the design of my SCR switching circuit and now perhaps it has a better chance of clearing customs perhaps?

The block of switches cut out all the dangerous wires so I can work with my subject – if I remember to switch them all off that is! With the right tools I think the circuit could be greatly improved and made more compact. The 12 volt battery doesn’t need to be so large, it was just the only one I had.

What else can be done with this system? Well it’s all up to your imagination I suppose. What would happen if we wrapped the exploding wire around a balloon full of propane gas for example? Nothing actually, the mixture is either too rich to ignite or the wire explodes so fast that it is all over before the gas manages to escape. Taken with the D40 with its 1/500th flash sync speed. 

This all happened so fast that all I got was a balloon lit by the flash of the wire without time to burst. 

The solution was a little scary to work with. I needed to put a candle next to the balloon so that when the gas escaped it had something to light it. It’s a little ‘iffy’ when you consider that we are also working with wires that have sharp ends that could burst the balloon while lighting the candle. It also required using 5 fps with the D90 because an explosion actually takes a long time to happen compared to how fast a wire blows up. 

Enough of that, let’s get the gunpowder out. It’s actually not that scary to work with because it will only explode if confined. When you light it in the open it just fizzes. 
In the first sample image it becomes apparent why Nikon don’t still make CCD sensors that can trigger flash at any speed. One of their disadvantages is the fact that they flare with bright light, not that you can’t control it once you know how. You can also see the green flash that the wire causes on the stone on the right. 

If you place a stone on top of the gunpowder, and a bursting wire in the middle of it all, you get a flash, a loud ‘pop’, and the stone jumps up in the air. 

What about water balloons? Well the biggest problem is the bright flash that dominates the scene and the fact that it is al over so quickly that there isn’t much time to see the balloon burst in all that light.
One solution is to use an optic trigger and let your camera’s flash trigger that with its pre-flash. You see, when you take a picture using flash, just before the picture is taken the flash fires very weakly so that the camera can do its measurements and decide what power to fire the flash at. So if you set your flash power to “-3” you won’t even see it in the final image, but the pre-flash that your camera/flash does to measure the final output will trigger the optic sensor of your SCR system and cause the wire to burst a fraction of a second before the picture is taken, that way you won’t see the flash. Of course if you want to use the flash to help freeze the motion that is also an option. Just be sure nobody is taking pictures of you doing this when handling the SCR because that could make it go off in your hands if they are using flash! 
The following image was taken using the pre-flash to trigger the bursting wire just before the picture was taken, so there is no green flash of wire in the image. 

Of course in a situation like this it is better to use the flash to freeze the motion. This is where HSS or high-fp flash (if your camera/flash can do it) is handy. The camera uses a trick mode, explained in my previous book, to fire the flash continuously at any speed. That way you could take a photo at 1/4000th of a second and blow something up just before the shutter fires and not have the bright flash of the wire bursting, but still have the camera’s flash lighting the scene at high speed. Of course with balloons there is always the variable of if and where a piece of rubber may be when you capture the image .

Another possibility, if you have patience, is to freeze the wire in ice and see what happens when it bursts. With my first attempts the rapidly expanding steam simply blew the wire out of the hole surrounding the plastic part.

 If I had more patience I would do it again and tie a knot in the plastic part of each end of the wire so that it can’t be pushed out, perhaps the ice cube will split open for me. I have so many ‘shelved’ experiments waiting for a rainy day still as I continue my quest for a decent explosion. 
Speaking of which, I think it’s time to start discussing the Trigatron, perhaps the answer to…… actually I don’t know what the question is but it sounded pretty cool didn’t it? 

Tuesday, March 31, 2015

The spark generating flash
This is the point where I start mentioning disclaimers. Don’t do anything that I have done here, you could seriously injure yourself (if you actually survive). Capacitors store a lot of energy at high voltages that can kill you! These illustrations are for the interest of those who are fully capable of working with high/dangerous voltages and should not be copied by anyone.
When a flash is turned on and the capacitor is charged up the voltage from the capacitor is always making contact with the flash tube and the wires are always live, even after the flash has been turned off the capacitor holds a charge for a dangerously long time. There is a trigger wire just off-centre of the flash tube that ionizes the gas in the tube to fire the flash at different powers, depending on the time of the trigger voltage.
I will repeat this for emphasis: The capacitor is permanently connected to the flash tube and the wires at either end are always live even when the flash is not firing and for a a long time after it is turned off! 
Now let’s have a look at a flash that has been modified to generate a spark when it fires. 

The basic principle involved here is that if an ignition coil is wired in series with the flash capacitor it will share some of the energy of the capacitor discharging through the flash tube. I’m not sure how much of that energy; all I know is that with most of the reasonably powerful flashes I get a spark equivalent to about 30 000volts. With one design I added a second capacitor in parallel with the main flash capacitor, which is similar to jump-starting a car with another battery.  This gave me a spark that jumped a gap that was probably equivalent to about 50 000volts. Who knows, it’s impossible to actually measure that voltage so it is merely assumed based on a table of distances and gasses etc. In the image below it is jumping a small gap, it jumps a 5cm (2 inch) gap when required.

And when you consider the fact that the flash is firing pretty brightly as well it shows how much more power could be available for a spark if we didn’t have to share it with the flash tube. 
Now for the wiring diagram, to show you what you shouldn’t attempt. If a flash head is opened, the old hammerhead style flashes are easier to get apart; you will find a tube with a wire at either end. These two wires are connected to the capacitor, which usually has around 300volts available - which is enough to blow off your fingertips while frying your heart. Starting to get the picture? Now if one of those wires is cut (either one) and two extension wires are connected up to be joined to either end of an ignition coil, the flash will still fire but some of its energy will be used up, in the coil to generate a spark, while the rest is released as light energy. The HT (high-tension) lead of the coil will need an earth wire and the side that it needs to be connected to will depend on which side of the flash tube you cut into and which way around the coil is connected. Play around with both options and see which gives the best spark.

There are obviously technical ways of working out which way around to connect the wires on the coil and which side of the coil to connect the earth lead to but generally it is much simpler to just try different variations and see which works best. Of course you could spend hours learning about the actual theory of it all and get it right by logically working out which way around it should be connected but there is always the possibility that the coil you decide to use isn’t wired up the way the text books suggest it should be. To me it’s just not worth the bother, decide what you want to do, connect things up, and see what works best – it’s worked pretty well for me so far! 
So what is the purpose of this exercise then? Well for one thing you now have a tool that generates a 30 000 volt spark (approximate of course) each time you take a photo. 
You could put the HT lead next to some water and put the earth lead inside the water. 

If you are using a normal camera with a focal plane shutter you will be limited to the flash sync speed of your camera, usually around 1/200th of a second. I’m not going to go too much into the focal plane shutter, I did that in my first book “Photography Masterclass”, but I will make mention of a rather ‘special’ camera that is good for this type of thing.
In fact there are several models to choose from that have a CCD sensor. The Nikon D70/S, D40, D50 are the main ones I can think of. They are special in that they can sync flash at 1/500th of a second and faster if you trick them. They do not use a focal plane shutter that simply varies the size of the slit for speeds above 1/250th. Instead the whole sensor switches on and off to capture the exposure. This means that when the flash fires the entire sensor is exposed to the light every time, even at maximum shutter speed. They have disadvantages like sensor bloom (bright patches) when shooting into bright lights so they don’t make them like this any more . I love these cameras and do a lot of my work with the D40. If you use a hotshoe adapter and pc cord the camera doesn’t know there is a flash connected so it doesn’t limit your shutter speed to 1/500th when you’re doing ‘different’ photography. 
As an example of what I am talking about I’ll show a range of images of a spark taken at various speeds with the D40 and the spark-generating-flash system. This is what I call “superspeed” photography, the act of photographing an event that you have triggered by pressing the shutter release. Any camera can do this speed. 

Only a camera with 1/500th sync speed can do this. Try it with a camera with a focal plane shutter and you will perhaps see half a spark as the slit of the shutter blocks half the screen. You could frame the image with the spark in the top half and capture it though, just the bottom half will be blacked out. 

Now we go to higher speeds. 

And the fastest shutter speed the D40 can do. 

The way I see it this set-up can be used as a scientific tool. Photographing an event at a set speed that you know is generated when you press the shutter. I think it has a lot of potential. 
Once I got this working I thought I had it made. Now I could start photographing gas explosions! What a disappointment though, it’s not easy making a gas explosion no matter how much the fuel stations get our hopes up. The air-fuel ration has to be pretty good or nothing happens. I had a bag full of petrol with a 30 000 volt spark jumping from above the liquid’s surface right down to the earth wire under the surface and still nothing happened. The mixture was too rich, not enough oxygen. Eventually I got a lame burst of flames from a reasonable mixture of air and gas but nothing to write home about. 

I’ll just emphasize what people say about my photography at this point. The pictures aren’t very artistic but what’s the point of setting up fancy backgrounds before you even know if something will work? I know they are right, I look through my images and they all look pretty ‘mechanical’ but wait till I get the technique right before hurling any more accusations, once I have perfected my methods I start getting artistic, it’s just that I’m still working towards perfecting them but sharing what I have learned so far in the meantime. 
My next idea was to buy some gunpowder, I had never worked with the stuff before and in hindsight perhaps the container shouldn’t have been so close to my experiment area. Why do people keep giving me fire extinguishers??? 

The experiment was a failure; a spark does not ignite gunpowder. Electricity simply looks for the easiest path to the earth connection, which involves pushing the granules of gunpowder out of the way to get there. 

Occasionally I saw a glimmer of hope but knew this wasn’t reliable enough to start getting artistic. 

The next step was to use something that would slowly produce some gas in an existing oxygen rich environment. It’s a good thing my microwave volunteered for the job by not working a few days later when I wanted to use it. I had no hesitation in buying a replacement rather than trying to have it repaired, I had plans for it. 

That was the best image I got from my D90 at 5fps but if you look up “fireball two” on YouTube you can watch a video taken at 400fps with the Nikon J1, another useful high-speed tool. This exercise involved throwing a teaspoon of Calcium Carbide in a can of water, which results in the release of Acetylene gas. The spark-generating-flash ignited the mixture as I took the first photo with the D90. I’m not after a loud noisy destructive explosion, just a nice fireball.  I made some low quality screen captures of the video, which shows a few stages of the fireball.
First the flash fires and generates a spark igniting the mixture.

The flame front starts to spread.

Eventually the fireball reaches out of the microwave oven.

The spark-generating-flash system provided me with some interesting images and may prove useful with exact air-gas mixtures but I needed something more reliable if I wanted to photograph a decent explosion. This led me to do some research and learn about the Silicon Controlled Rectifier (SCR).