I have shot in natural lighting before this. I am just getting started with studio lighting. I just got my Alien Bees Lighting hooked up to my Canon Rebel T3 with Cactus V6 II radios. It was a process with the radios, but it finally got figured out.

BUT NOW my camera is acting weird.

(I have 3 lights set up. So, the chair is evenly lit)

It has a strip of brightness along each image. It didn't do it on the first image, but on the rest it stays in the same spot when I tilt my camera different angles. So, it is not on my screen; it makes me think it is my lens, but I took pictures around my studio and it didn't do the same thing. I don't even know where to begin to fix this. I know it's not that the lighting is uneven, because the first image is even.

If it is still confusing: I'll have my camera normal/horizontal, and the brightness will be at the top. Camera shot vertical/profile to the right, the brightness will be on the right edge of the image. Camera shot vertical/profile to the left, the brightness will be on the left edge of the image. If I completely flip my camera over for a horizontal shot, the brightness will be at the top of the image, but the image is flipped. But if I leave the lighting and it is fine.

This is just one example.

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    \$\begingroup\$ Hi Kally and welcome to Photo.SE! Feel free to take the tour. Currently your question is missing a few details and some prior research. Could you edit your question to include what camera settings you've used? What previous questions have you looked at already? Did any of the suggestions given there help? If not, what was not working for you? These details will help people here to answer your question. \$\endgroup\$ Commented Apr 1, 2021 at 20:51
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    \$\begingroup\$ How long is the exposure? Dark noise from a long exposure is a possibility. \$\endgroup\$ Commented Apr 1, 2021 at 21:10

2 Answers 2


You haven't told us exactly which Paul Buff Alien Bees flashes you're using, but many studio flashes take longer to release their energy than most speedlights do. For the most part, camera's flash sync (X-sync) ratings are based on using the camera with that brand of camera's in-house speedlight selection sitting directly on the hot shoe or using the camera's built-in popup flash. This is particularly the case with cameras that do not have a PC port¹ used to send a "fire" signal to external flashes without using the hot shoe connection.

In many cases, this means you must shoot with an exposure time longer ("slower shutter speed") than your camera's flash sync setting (X-sync speed). If you use an exposure time shorter than the time it takes the flash to fully fire, the second shutter curtain of your camera will begin closing before the flashes have produced all of its light. The parts of the sensor covered by the second shutter curtain as it is closing will be dimmer than the parts of the frame not covered by the second curtain until after the flash has released most or all of its energy.

Your Canon EOS Rebel T3/1100D has a flash sync setting of 1/200 seconds. That is equal to 5 milliseconds. The Alien Bees B1600, for example, has a T.1 flash duration at full power of 1/300 second, or 3.333 milliseconds. So far so good. The flash can release 90% of its burst of light in a shorter time than the camera's X-sync speed. But then you have to factor in the delay between the time your camera signals the Cactus transmitter to "fire" the flash and the time the Cactus receiver(s) tells the flash(es) to "fire". If there is any appreciable delay, then at 1/200 seconds your second shutter curtain will begin closing before the flash has released all of its light.

One thing I would check is to be sure you haven't accidentally dialed in some delay in your Cactus V6 II transmitter's settings. Anything greater than a delay of 1.67 milliseconds (5ms minus 3.33ms) will mean the flash begins firing too late to complete its burst of light before your second shutter curtain is closing. In practice any delay dialed in would need to be shorter than that, because it takes time for the radio trigger's microprocessors to react to the camera's "fire" signal, to then send the radio pulse to "fire", which is an encoded radio signal that has a more than instantaneous length to it, and then for the receiver(s) microprocessors to decode that signal and send the "fire" command to the flash(es) to which it is connected.

As a proof of concept that the shutter curtain beginning to close before the flash reaches T.1 is the root cause of your issue, take a few test shots with increasingly longer exposure times - 1/200, 1/160, 1/125, 1/100, 1/60, 1/30, etc. - and see if the bright area on one side of the frame gets increasing wider towards the "far" side from where you are currently getting the bright strip.

¹ PC in the context of flash photography has nothing to do with a personal computer. It is an abbreviation of Prontor/Compur. Prontor has its origins in the Italian word pronto (quick) and was a brand of shutter produced by Alfred Gauthier in the 1950s. Compur, derived from the word compound, was the shutter brand of the Deckel Company. Both companies were based in Germany and both counted Zeiss as an influential stockholder when they introduced the standard 1/8"-inch coaxial connector for shutter/flash synchronization.

  • \$\begingroup\$ I cannot thank you enough for your detailed answer. It has given me a WAY better understanding of what I need to look at to fix the problem. I have B800 Alien Bees. Would that be compatible? \$\endgroup\$ Commented Apr 2, 2021 at 3:04
  • \$\begingroup\$ Another common cause is if one of the speedlites is using TTL metering or optical flash control and the pre-flash pulses set off optical triggers on dumb strobes early. OP is using radios, so that shouldn't be an issue, but if things aren't configured correctly it might not be listening to the radios. \$\endgroup\$
    – J...
    Commented Apr 2, 2021 at 18:35
  • \$\begingroup\$ @J... There are no speedlights involved in this situation. Studio monolights only. No TTL capable flashes involved. \$\endgroup\$
    – Michael C
    Commented Apr 3, 2021 at 9:12
  • \$\begingroup\$ @KallyJones What happens when you lengthen the exposure time? Does the band of brighter light get progressively wider until it reaches completely across the frame? Have you checked your cactus triggers to be sure you haven't added any 'delay' manually? The instruction manual for the Cactus triggers should outline the procedure. \$\endgroup\$
    – Michael C
    Commented Apr 3, 2021 at 9:15
  • \$\begingroup\$ The Paul Buff B800 Alien Bees should be compatible if everything is set up correctly. How have you got the cactus receiver(s) connected to the AB800s? \$\endgroup\$
    – Michael C
    Commented Apr 3, 2021 at 9:16

Sounds like a syncing problem, your shutter speed might be too fast to fully catch the frame. Try decreasing the shutter speed. It looks like the rear curtain is starting to close before the flash has finished its pulse


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