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Off camera flash query.
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PostPosted: Sat Feb 10, 2018 10:20 pm    Post subject: Off camera flash query. Reply with quote

Hi guys. I know this is the wrong thread for this subject but I am hoping the mods can move or delete it.

So, I am completely new to flash (other than the auto stuff from point and shoot). I am going to Australia and Fiji in a few weeks to do some diving. I have purchased a full set up for my a7ii. Meikon housing sea and sea ys-d2 and sync cable. It all hooks up ok and flashes but I can't get the exposure right. I have the camera set to Auto, flash mode to auto. The sea and sea ys -d2 has a selector for M preflash, M, and DS-TTL. It also has a power selector that goes from 1 to 32. In TTL mode the power range is from -2 to plus 2 with 10 increments available. In ttl mode it blows out the image, nearly a paper white screen at all settings, though it gets even brighter at higher power. On the other 2 options (M and M preflash) I get OK images only on darker subjects at the lowest setting. Any advice or help is greatly appreciated.


PostPosted: Sat Feb 10, 2018 11:15 pm    Post subject: Reply with quote

I think being underwater makes a huge difference, are you testing in a pool or the sea?


PostPosted: Sat Feb 10, 2018 11:56 pm    Post subject: Reply with quote

Pool


PostPosted: Sun Feb 11, 2018 3:24 am    Post subject: Reply with quote

Set your camera to M mode if there is problem with Auto/P mode.


PostPosted: Sun Feb 11, 2018 6:01 am    Post subject: Reply with quote

Yeah, based on my experience with more-or-less modern flashes and my digital cameras (EOS DSLR and NEX 7), I've always had the most accurate results when I select a partial power setting on the flash and set the camera to flash sync, but not anything else. A couple of experimental shots to dial in the correct level on the flash is typically all it takes. Just because you'll be using your gear underwater, it doesn't change things. You need to figure out the amount of light you're gonna need to properly illuminate a scene. Don't worry about all those other settings. Just use the variable output on the flash to dial in the correct exposure. Now obviously this can change when you're underwater and selecting different subjects. But again, it shouldn't take more than a couple test flashes to figure out where your settings need to be.

Calvin makes a good point, that is to set your camera on M mode and then the shutter speed to flash sync. But here's where it can get tricky. With my cameras -- and I'm sure yours too -- if I'm examining a dimly lit scene, if I have the camera set to an auto mode, like Aperture Priority, for example, the camera will boost the low light sensitivity so that I can view the scene on its screen. But if I shoot in A mode, my camera ignores the flash and times out a long exposure. The result is usually bad. Lots of blurriness and one point at which movement is frozen, which is when the flash went off. It can make for some interesting modern looking stuff, but that isn't what I was after. But here's the problem. When you set your camera to "M" so you can have the shutter speed set to flash sync, your screen goes black because the camera isn't adding any exposure to the screen, because I have it set to manual mode. I don't really have a work-around for this. I do my image composition in "A" mode, then quickly switch to "M" mode for the shot. Eh, it works, even if it is a bit cumbersome. But it is something you have to endure when shooting in manual mode with a flash in this type of situation.


PostPosted: Sun Feb 11, 2018 10:40 am    Post subject: Reply with quote

For underwater use, your flash will be your key light. Set the minimum shutter you need and set the aperture in M mode. Set the ISO to Auto or something best for your scene. The flash will try to add the exact amount of light for correct exposure if you use TTL mode. Correct me if I am wrong.