Please explain sync speed using EOS3

Im using an EOS 3 with a 550EX flash either on shoe or off shoe. I

also have a Novatron 500w monolight in use. For now I am using the

550ex to fire the monolight( soon I will get a pocket wizard so I can

move 550ex anywhere I want.

 

My question is this sync speed business. I have read on some

website .."A sync speed of about 1/60th is generally a safe choice

for nearly all applications" (Im set in manual mode)

 

In the canon EOS3 manual, on page 101...it says.."with large studio

flash, the sync speed is 1/125 sec. or slower. Be sure to test the

flash to see if it synchronizes properly with camera. (ok...that is

my first question: How? You mean...if it seems to flash the moment

you press shutter release its working and in sync?)

 

Also, is setting the sutter speed (manually) the same thing as

setting the flash sync? I have taken some pictures that turned out

O.K. I guess I just need to know if I have this sync speed business

down. Also, I have been told that the sync cord/PC plug for Novatron

does not work(or may not work) on canon EOS3. any comments??

Jim , setting the flash synch speed is the same as setting the shutter speed. it's referring to how fast the shutter speed can be and work with the flash. If the shutter speed is set above the speed at which the flash will synch, the photo will not be evenly illuminated. if your photos are not coming out dark on only part of the frame, you don't have a synch speed problem.The EOS 3 will synch at 1/200 of asecond with a EOS 550EX, and will synch faster than that in high speed synch mode (but with the price of only partial flash output.)

 

with studio lights, high synch speeds should rarely be necessary. Using studio lights, they are going to be your primary source of illumination, and the strobe is going to freeze motion as opposed to the shutter speed. Thus in most studio set ups the shutter speed as long as it is below the maximum synch speed is basically irrelevent. thus if you just set the shutter speed at 1/60th for studio flash work you should be fine.

The maximum sync speed is listed in your manual. Not familiar with that camera but I'll bet it's at least 1/125 sec. That's what they are alluding to on page 101 with that nonsense. Maximum sync speed is simply the fastest shutter speed where the shutter remains fully open for the duration of the flash and it varies from camera to camera. Faster than that it becomes a moving slot across the frame. <p>

Obviously then, if you use a faster shutter speed than the sync speed the flash won't expose the entire frame. When this happens you will see a part of the frame exposed properly with the rest not with a dividing line between the two.<p>

Probably when you mount your flash the camera defaults to 1/60, most do. Yes, in manual you obviously can set the shutter speed, just make sure it's the maximum sync speed or less if you are using a flash of any kind. Usually in a studio shutter speed is pretty much irrelevant anyway unless you are using continuous lighting or relying on ambient so go ahead and use anything you want- 1/60 is a good choice.<p>

 

You didn't ask, but I have to comment on the fact that you are using the on camera flash to trigger your Novatron. This is usually a problem because the flash pre-flashes for metering purposes. These flashes occur before the actual exposure and will trigger your Novatron before the shutter opens leaving you with only the on camera flash at exposure time. You say you aren't having any problems so maybe your camera disables the pre flashes in manual mode.

Just thought I'd add a couple of tidbits of info. If you are using a Canon shoe mount flash on your camera it will override your shutter speed if you have set it above the sync speed of your camera. Other brands of flash compatible with Canon EOS cameras will probably have this feature also. This is a nice fool-proof feature.

 

If you set your 550EX to manual mode (rather than E-TTL) it will not fire a preflash.

 

If you use studio flash with your camera via the pc connector, it's a good idea to get a voltage regulator to reduce the voltage to 6 volts which is the trigger voltage for Canon Speedlites. These devices are available from Wein or you can order custom pc cords with this feature from Paramount cords. High sync voltages can damage the sync contacts in your camera over time. You can check the trigger voltage of your Novatron unit with a volt meter or check the specs for it.

Bill is correct about being aware of the sync voltage. Probably the best way around this as well as a polarity problem is to use a slave transmitter. This also gives you complete mobility around the subject without getting tangled in or tripping over cords. See my reply to your later post above.

I found out the hard way that the EOS3 syncs with studio flash at lower speeds when my shots came back with a (small) black line at the bottom of each frame.

 

So use 1/125 with the Novatron.

I anwered this to a later post, so this may be a bit repetitive...

 

The EOS-3 manual which says 1/200 with on-camera flash and 1/125 with studio flash. My experience with at least 2 brands of studio strobes (3 different Normans and one other--a loaner-don't recall the brand) is that 1/200 works fine. I'm not sure why Canon makes the distinction--makes no logical sense to me. FWIW, I once set 1/250 by mistake and lost very little of the frame. I'm not sure why John Kantor had trouble with his Novatrons.

 

Also, (defying logic), sync speed does make a difference in studio photograpy. I do dance photography (see www.matthaber.com for examples), and had been using Olympus OM until 2002. Those sync at 1/60. I would get blurry feet with my dancers; now with my Canon EOS-3 (identical strobes), I get sharp feet. This is in a pretty dark studio, so ambient light was not the issue.

 

-matt