Dumb flash questions from a total newbie

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david_c

Canon EOS-7D

Canon EF 17-40mm f/4.0L USM

09/25/2008 09:24:21 AM · #1

1. Flash sync. What does that mean? My camera manual says I can "sync" at 1/200. OK, I think I get this part....if I'm at 1/30 shutter speed with the flash set to 2nd curtain, the flash will fire for the last 1/200 of the 1/30, right? If it's set to 1st curtain, it will fire on the front end of that 1/30. What happens if my shutter speed is, say, 1/500?

2. Is that the same for an external stobe? Let's say I want to drown out the sun, and light my subject with the external flash...the ambient light means I need a fast shutter at 1/2000 to do so. Will I need to go "manual" on the strobe to make it fire?

3. Let's say I have a Canon Camera and a Canon Speedlite, which I'm using off-camera. Is it possible to use another manufacturer's brand of strobe in the chain as the backlight or rimlight via remote control?

4. What happens if I splurged on a radio transmitter/receiver for the gear....I dunno, like, Pocket Wizards or something. I have my camera, main strobe and a slave unit, but I want to trip the shutter from 20 ft. away with my little hand-held wireless remote control. Will it fire?

Thanks, in advance.

rlewis

Canon EOS-40D

Canon EF 24-70mm f/2.8L USM

09/25/2008 09:56:35 AM · #2

bump

Spork99

OM System OM-1

Canon EF 100mm f/2.8 USM Macro

09/25/2008 10:09:34 AM · #3

Originally posted by david_c:

1a. Flash sync is the highest shutter speed where the shutter will be fully open long enough for the flash to light the whole frame.

1b. Yes, you're right about front/rear curtain sync.

1c. If you set your camera to a shutter speed higher than the sync speed, the rear curtain will begin to close before your flash fires. This can lead to only partial illumination of the scene by your flash.

2. Strobes typically have a longer duration light pulse and require a slower sync speed. So, to overpower the sun, you will need to shoot at a small enough aperture to get the shutter speed to the sync speed (or slower) and then set the strobe power accordingly.

3. Yes, but be careful, because unless the 3rd party strobe is compatible with Canon's built in IR slave controls you'll need to use some sort sync to fire it. If you use a cable, that will work fine, but optical syncs can get triiped up by the E-TTL pulse that Canon flash units use for E-TTL exposure determination. There are optical sync units that can be set to ignore that first pulse and fire at the correct time.

4. Yes, when you use the remote and the camera fires, the transmitter in the hotshoe will tell the flashes to fire.

OdysseyF22

Panasonic DC-G9

Olympus 12-45mm f/4.0 Pro

09/25/2008 10:11:46 AM · #4

1. Sync is the speed at which the flash and the shutter "play well" together. If you start to go over the max sync speed, the shutter moves faster than the flash fires, and you get black bars over part or all of the frame, where the flash wasn't able to have an effect before the sensor recorded. 1/250 is usually the most you can get away with, unless your flash has a High Speed Sync Mode, in which case you can go much faster (1/500, etc). In this mode, the flash pulses very quickly to "catch up" to the shutter speed.

2. To drown the sun with an external, you will need a fast shutter speed. Always remember: shutter speed controls ambient light and aperture controls flash! Using the strobe on Manual is easiest, since you just tell it what you want and go for it, without having to try and override/out-think the computer. However, most off-camera setups will not allow you to use high speed sync, so you have to work within the limits of the equipment (which is doable.) Very open aperture plus low ISO plus fastest shutter speed you can get plus flash at full power is probably a good place to start.

3. Sure. You can use any combination of strobes from any manufacturer. So long as you can get them to talk to each other. Radio slaves (Pocket Wizards, eBay Cactus, etc) are the easiest way to do this. Set all the strobes to manual mode, dial in your settings, and when you fire the camera, the transmitter will tell them all to go off. However, if you want to use the TTL settings and Auto modes, all the strobes will have to be the same brand as your camera. (I use three Nikon speedlights with my Canon camera via the eBay Cactus radio transmitter system.)

4. Already touched on this a bit, but let me elaborate. Get transmitters! If you're serious about using flashes, you want them off-camera for the best results. (See Strobist for full explanation.) Transmitters are the only good way to do this (otherwise you end up with LOTS of cables to store/trip over/cuss at). Pocket Wizards are the standard, but I think they are grossly overpriced for what they do. The Elinchrome Skyport system is new, as are Radio Poppers - each has pros and cons. Like I said, I used the Cactus 16 channel slaves from Gadget Infinity, an eBay store out of Hong Kong. They're really cheap and a bit flaky with certain flashes. Most people buy the V2 series - I bought the 16 channel ones meant for studio strobes because I heard they worked better. I had to cut off the strobe plugs and splice on PC connectors. I also did a mod to the transmitter that attaches an antenna for MUCH better range. In the end, my whole radio slave kit cost me about $60 and I can use it anywhere - I just got done using it in a college gym the other day - worked perfectly.

Photography is all about the light. Flashes let you bring the light with you - learn to use them well :-) The Strobist site I linked to is the Holy Land of off-camera flash information. Start with the first of the Lighting 101 lessons and read through them to fully understand techniques, equipment, etc.

dwterry

Canon EOS-1D Mark III

Canon EF 24-70mm f/2.8L USM

09/25/2008 11:06:47 AM · #5

Originally posted by david_c:

if I'm at 1/30 shutter speed with the flash set to 2nd curtain, the flash will fire for the last 1/200 of the 1/30, right?

You already have other good answers, I wanted to touch on a different aspect.

The duration of your flash is probably measured in 1/10,000ths of a second. That is why shutter speed makes no difference in determining "exposure" for flash output, because the flash duration is much shorter than the shutter. So you typically set your aperture to control flash exposure, and your shutter to control ambient light exposure.

Anyway, I point this out mainly because you mentioned thinking that the flash was firing for 1/200th of a second and that would actually be a very long exposure for a flash. However, as has already been stated, when you put your flash into High Speed Sync mode (to shoot at shutter speeds faster than sync speed), then that's exactly what the flash does. It rapidly strobes the flash over a 1/200th of a second in order to keep the output going while both shutter curtains travel across the sensor.

david_c

Canon EOS-7D

Canon EF 17-40mm f/4.0L USM

09/25/2008 12:43:55 PM · #6

Great replies, thanks very much.

Nullix

Canon EOS-5D Mark III

Canon EF 17-40mm f/4.0L USM

09/25/2008 05:47:07 PM · #7

Before you buy flashes and pocket wizards.

Check //strobist.blogspot.com/. It'll give you more ideas about buying pocket wizards and flashes.

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