Should I buy a Speedlite?

[VitorMachado]

I recently just got asked to shoot pre-prom photos for my high school. I'm a little undecided as to which I should buy, a fast lens (50mm 1.4) or a Speedlite (430 EXII). The shots will probably be taken at around dusk times. My fastest lens as of right now is my 40mm 2.8 or my 60mm macro 2.8 (focal range will not be usable for this occasion). Also, if you guys were wondering the flash will be used on camera. What do you guys suggest?

[neuroanatomist]

I suggest avoiding on-camera flash like the plague, unless there's a white ceiling or wall off which to bounce that flash.  For pics of two people, a fast lens isn't as helpful as you'd think - yes, you can keep ISO down with f/1.4 or f/1.8, but DoF will be thin, and prom couples would prefer to both be in focus, I expect.  Of the two options, I'd get the 430EX II, but get it off-camera with a light stand, umbrella, and 'dumb' wireless triggers.

But I'd recommend neither.  A one-Speedlite portrait isn't going to make many people happy. My advice - rent.  Lensrentals.com has a two-monolight kit (with stands, wireless triggers, one softbox and one umbrella, for $133 + $35 shipping for a 5-day rental. 

[paul13walnut5]

Get the 430ex.

Use it with the 60d and pancake set to f5.6

Use if off camera and through a diffused brolly or off a silver one.

Wex do a decent enough kit.

[Wilmark]

Fast lenses wont help as already point out - unless you shoot for a good distance, I find speedlites are overpriced - pick up a few yougnuo or even cheaper compatible flahses for less than 50$ each like the Neewer TT560 on amazon. A few pairs of inexpensive remote triggers like those from yougnuo and even an umbrella/lightstand will work wonders all for less than you would pay for a single canon speedlite.

[verysimplejason]

Your 6D + 24-105L and 40mm will do nicely with any speedlight.  That said, a Canon 430EX or any third party equivalent (Nissin, Yongnuo... if your budget is tight) will do nicely for your photos.  One would be good, 2 would be better.  If you can buy 2 speedlights + umbrella + lightstand, then it's worlds better even if you go only for third party speedlights.  Put one on camera and the other one off-camera.  If you can't afford a remote for your off-camera, make sure that at least one of your speedlights can be triggered via light.  Have fun taking photos.

[VitorMachado]

I suggest avoiding on-camera flash like the plague, unless there's a white ceiling or wall off which to bounce that flash.  For pics of two people, a fast lens isn't as helpful as you'd think - yes, you can keep ISO down with f/1.4 or f/1.8, but DoF will be thin, and prom couples would prefer to both be in focus, I expect.  Of the two options, I'd get the 430EX II, but get it off-camera with a light stand, umbrella, and 'dumb' wireless triggers.

But I'd recommend neither.  A one-Speedlite portrait isn't going to make many people happy. My advice - rent.  Lensrentals.com has a two-monolight kit (with stands, wireless triggers, one softbox and one umbrella, for $133 + $35 shipping for a 5-day rental.

I decided the mono lights will be better for me. Now, one more question for you sir. As you may know the 6D has no sync port.. so would you suggest a hot shoe adapter with an extra PC sync port so I could use a moonlight with no triggers? Or another better alternative?

[JonB8305]

I suggest avoiding on-camera flash like the plague, unless there's a white ceiling or wall off which to bounce that flash.  For pics of two people, a fast lens isn't as helpful as you'd think - yes, you can keep ISO down with f/1.4 or f/1.8, but DoF will be thin, and prom couples would prefer to both be in focus, I expect.  Of the two options, I'd get the 430EX II, but get it off-camera with a light stand, umbrella, and 'dumb' wireless triggers.

But I'd recommend neither.  A one-Speedlite portrait isn't going to make many people happy. My advice - rent.  Lensrentals.com has a two-monolight kit (with stands, wireless triggers, one softbox and one umbrella, for $133 + $35 shipping for a 5-day rental.

I decided the mono lights will be better for me. Now, one more question for you sir. As you may know the 6D has no sync port.. so would you suggest a hot shoe adapter with an extra PC sync port so I could use a moonlight with no triggers? Or another better alternative?

See if your local shops can rent you a profoto D1 air kit and you wont need the sync port. One local shop has them here for $100/day.

[neuroanatomist]

I decided the mono lights will be better for me. Now, one more question for you sir. As you may know the 6D has no sync port.. so would you suggest a hot shoe adapter with an extra PC sync port so I could use a moonlight with no triggers? Or another better alternative?

You could do that, with some cabling. But I do think radio triggers are a lot easier - no wires for people to trip over.

[cocopop05]

I can only comment on what I have used.  I have a 5D Mark III with 24-104mm f/4 and Speedlight 600ex-rt.  The flash is worth it's weight in gold.  So many precious moments I have captured with that flash.

I have no hesitation in recommending you invest in Speedlight.

[risc32]

at dusk speedlights can certainly get it done, but you'll want it off the camera, and then you'll need to trigger it..  well, since you are going with monolights i hope you have an AC source near, or a battery pack. i don't think monolights are a bad idea at all, it's just something you need to plan for. And you realize you'll be shooting with only manual flash control. again, not bad, just something not everyone knows.

[Mt Spokane Photography]

I suggest avoiding on-camera flash like the plague, unless there's a white ceiling or wall off which to bounce that flash.  For pics of two people, a fast lens isn't as helpful as you'd think - yes, you can keep ISO down with f/1.4 or f/1.8, but DoF will be thin, and prom couples would prefer to both be in focus, I expect.  Of the two options, I'd get the 430EX II, but get it off-camera with a light stand, umbrella, and 'dumb' wireless triggers.

But I'd recommend neither.  A one-Speedlite portrait isn't going to make many people happy. My advice - rent.  Lensrentals.com has a two-monolight kit (with stands, wireless triggers, one softbox and one umbrella, for $133 + $35 shipping for a 5-day rental.

+1
 
You need to be in control of the lighting, or you may not like the results, and may make a few enemies. 
Speedlites can shoot into or thru a umbrella, and they are portable, but having the right lighting for portraits is critical.