There are several ways around the shadows problems.
First is to elevate your flash over the axis of your lens, both when you are in the horizontal and vertical camera positions.... This is best done with a grip such as the relatively inexpensive (under $20 in most cases) Stroboframe Camera Flip Bracket... This bracket will allow you to switch positions without having to adjust the flash.
https://www.adorama.com …RuXutV9o5fbxoCyHcQAvD_BwE
I like a camera flip bracket better than a flash flip bracket since I don't need to readjust the flash after flipping the camera. Having the flash positioned over the axis of your lens will tend to keep shadows behind and below the subject or subjects. That way the shadows do not seem intrusive...
Second is when shooting in areas without anything to bounce the flash off, using a Joe Demb Flash Diffuser Professional with the Flip It Portion angled at about 45 degrees towards your subjects will, in most cases provide a decent and soft light. I like to use it in conjunction with an over-the-lens flash bracket...
www.dembflashproducts.com
Here is a shot that I did outdoors in the falling light of the evening using the Flash Diffuser Professional in that manner. Obviously, being outdoors, there was nothing off which I could bounce the flash, I still achieved a relatively nice lighting using the single flash...
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This one was done indoors using the Flash Diffuser Pro...
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One thing, using the flash on a bracket, you either need to trigger the flash with an off camera cord or with a radio trigger. I have tried the Canon optical trigger system and it was not fault proof enough to trust at a wedding.
However my Godox radio controlled flashes work great. But, using a battery grip and a Godox trigger, I needed to modify my flash bracket to make it larger than the original Stroboframe Camera Flip Bracket. The camera is equipped with a battery grip and the flash is triggered with a radio trigger.
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This is the result of that modification built around the Camera Flip mechanism allopwing me to flip from horizonytal to vertical configuration...
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On the other hand, using a lens with a tripod collar simplifies everything. Here is a Custom Digital T Bracket that I slightly customized for use when I am shooting with the tripod collared lens...
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