Sorry I didn't get back to you earlier Dom.. I wanted to be thorough so hope you have a read and take in my experiences
Well, here is my take on remote flashes.. just a disclaimer that this is how I use them, by no means may it be the correct or best way, this is just how I roll. It has taken many a day and night at the track to figure out how to use flashes effectively, and by all means I am still learning each time I go out !! it is an ongoing process.
Another thing to throw out there, is that I am driven by laziness. I do not like to have to do a lot of post processing / editing
at all. I try to do my best to make the photo count at the time it was shot and not have to screw with it afterwards... That's also a personal challenge to try and capture a great pic, and not have something look cool because I spent an hour with photoshop on it. If I spend 30 seconds on a picture in post, that's a lot for me. Rarely I'll have a really cool shot that I'll want to tweak up and make nice but that's maybe 1 out of 1000. Usually it's just a crop and then a preset in lightroom to screw with sharpening a little. I could get some much nicer looking pics if I worked harder with lightroom, that I am still trying to develop
That being said,
Equipment, I did on the super cheap. Why? Because it works and I have better things to spend money on.
I opted not to use Canon's built in wireless flash technology, because it needs line of sight and you have to be rather close. There is always someone standing in front of my flash blocking the IR port, or harsh sunlight, or me being down track to ofar, keeping this from working. If you were the only person around, than yeah, use canon's wireless, as you get high speed sync and that is nice.
Transmitters and receivers: are ebay specials, you can find them if you search ebay for "RD616." I did
this modification on the transmitter to have an external antenna, and it actually gets very good range. For sync cables, I get them from
www.flashzebra.com . I use mini plugs on everything in case I move to pocket wizards at some point. Speaking of pocket wizards, yes, they are great, but if you compare how much they cost, I think I did all right. Also, at big races (like Shakedown for example) there are a ton of photogs fighting for pocket wizard channels -- I don't have that problem. This transmitter and receiver combo works great IMO - they fire 99% of the time. The only goofy thing I have is when the receivers are near a 430EX flash.
Flashes: I am using Vivitar 285HV's for slaves. Why? Very cheap and effective. Stands/tripods get knocked over, it does happen.. I'd much rather have a $90 flash go over than a $390 flash. On full power, yes, you have to wait for recycle time, but you will for any flash. To hook them up to the receivers I use the hotshoe from flashzebra.com that has a mini plug on it. As for batteries for the flash, I made some battery packs out of 6volt 6mah batteries, and to connect them to the flash I got quantum battery cables from ebay, cut off the ends, and put some custom ones on. Bought 6 volt battery tenders, they sit on the chargers unless I am at the track. I can, on the safe side, estimate I can get at least 500-700 full power flash pops without having to change them out. Beats the hell out of double A's! I spent $160 and made 4 battery packs, which was the cost of
one of these battery packs .. or compare to a quantum battery pack that is at least $300 PER pack.
Flash placement -- the side flash is normally around the door of the car, or at the back at an angle. Whatever you do, just make sure the rear flash is not at a 45 degree angle to where you are standing or you will get funny glare. Front flash placement depends if I am taking a shot very close to the starting line, or down a little ways.. I'll move the flashes to get what I want. Sometimes I am lazy and will put the 3rd and 4th flash out on the wall too, further down, so I don't have to keep moving stuff around. This is useful when there are random huge wheelstands 30 feet out like at that SGMP race
My hotshoe flash on the camera is a Canon 580EXII, I took out the PC port from the foot and put in a mini port. I hate PC ports. This flash is great, during the day, I usually leave it on Auto as it will do the trick for fill. At night, usually it is on manual as it will try to brighten things up a little too much, as it is not aware of remote slaves.
Ok.. on to the hard part, actually using them.
You have to take a few things into consideration before you go using these. First, sync speed. When I first started out, I shot with a high shutter speed as I was not very good at all with panning or following the subject. (disclaimer, I am referring to canon here - a lot of people with Nikon have the luxury of 1/500 sync speeds, at least) With my slaves and bodies, the max sync speed is 1/250 (you don't have this problem on a camera like a 1D for example, because it does not have a leaf type shutter. If you have a 1D though, you are not reading this, because you have lots of money and will get the expensive stuff
). Anything past this, and the shutter is already closing while the flash is still going off. You can cheat the max sync speed, however, because on canon bodies the shutter closes from bottom to top. So, for example, I can shoot at 1/320, and I won't get the benefit of the flash at the very bottom of the frame, but that does not matter to me because I'll frame the shot so that is wasted space on the track / below the car. To find out max sync speeds, put a slave flash in a dark room, aim right at it, and take a picture. Keep shooting faster and you'll see the black bars on the picture.. when there are no black bars, that's your max sync speed.
Next thing you'll have to get used to is making the shot count on one / not many tries. If you like to sit there and hold the shutter down and take 20 pics of each launch, you're going to be disappointed here. During the day, if I am just taking starting line launch pics, I almost always use the flashes on full power as a fill flash. You only get one shot here, so you either have to make it count, or be satisfied with having to brighten up things in post processing every now and then. Of course, this does not apply if you are doing some sort of panning, with these slower shutter speeds, you can turn down the flash power and get a few pops out of them before they have to recycle.
Here's an example of what I am talking about, look at the underside of this car.. in the first pic, flash fired.. in the second, it was recycling, so no nice view of the exhaust and suspension, had to (try to) brighten it up in post. Again, I am lazy, I'd rather I don't have to edit stuff, I'd rather the picture counts the first time.
If I have some sort of gradient filter on the lens during the day to try and tone down the bright sky, and underexpose it a little for it to show up nice, the fill flash helps bring back the light to the front of the car.
Not a great example, but in this case, the sky was really bright, casting funny shadows on the car. tried to fix that here
A lot of why I like the flashes is it brings out the little details on the car... like the grills, carbs inside a scoop, blades on a turbo, etc...
At night, I do crank the flash power down as you can get good lighting with 1/4 or 1/2 power, compared to needing full power as a fill flash during the day. If there is a cool skyline or something, I try and expose for the sky and then flash the cars as needed.. At a track with no lighting like Atco or Cecil.. generally the side flashes are on 1/4 or 1/2, hotshoe on 1/4, and I am in the neighborhood of 1/250 f/4.0 iso 400.
examples of exposing for the sky, flashing the car
hope that helps