Hello. I am using a Canon EOS 30D with an Elinchrome 500C studio lighting and have sincronization problems. After setting the exposure to what my handheld meter say, I found that only the upper half of the picture is taken. The bottom half remains black. I tried using different manual exposure settings obtaining of course under or over exposure but never the right exposure. Is like a syncro problem between the camera and the flash. I use a Canon EOS Film Camera, a Canon EOS Rebel XT camera and a Hasselblad 500CM with the very same light and I found no problems using the same parameters that I read in the handheld. I tried to sincronize at 1/250 or 1/125 and I found the same problem. I contacted Canon and they told that they don't give support to non-Canon products and recommend me to buy Canon accessories (?!), so, I am in the air and don't know if is a problem with the camera and the PC Sync feature or what the problem is. Certainly, it's not the flash that is working perfectly for over a year with other cameras including Canon's. The only difference in setting is that in the other cameras I use a universal shoe adapter for connecting the flash and with the EOS 30D I use the PC port that comes with the camera. Will appreciate any support other than a response like Canon's. Thanks in advance.
You might try a lower shutter speed, which does not effect exposure. What you are reporting sounds like shutter curtain cutoff of some of the flash exposure,
Like David suggested, try shooting at a slower shutter speed. Like 1/30 second for example. The other thing you can try is to use the same universal adapter in the hot shoe to see if it makes a difference.
Like most technology related problems, it's more expedient to ask for help after you exhaust all the variable options.