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09-20-2017, 01:23 PM   #1
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Is This a Shutter Problem? Mirror? Something else?

Hi all.

So after my last outing, I noticed that about 5-10% of my shots had weird "lines" in them, ie zones that are less exposed. Here are two examples:





(Yeah, the critter took off before I hit the shutter on that last one.)

As you can see, in the first one there are two lines, a subtle one near the top, and one much darker near the bottom. As the second shot demonstrates, there's not always two lines, and they're not always in the same place in the frame.

I was shooting flash macro at 1/160s, with pretty low flash power (1/32 to 1/4). So for one thing, ambient contributes only very slightly to the exposure. And for another, the flash duration is way less than 1/160, so I don't quite understand how these artifacts could be created. I would think that if a shutter curtain was getting stuck, you'd see a hard edged black zone...?

Anyone know what these are?

09-20-2017, 04:02 PM   #2
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Do you see this when flash is not used? If not, what is your flash setup and how is flash triggered?


Steve

Hint: Those look like shadows
09-20-2017, 04:11 PM   #3
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This is a great puzzler. I'm posting simply to see where this goes. Here are my two cents:
a) I don't see how it could be caused by either the mirror or the shutter. The lines should be horizontal and not slightly skewed. Were these all shot with the OVF or live view? In other words, mechanical or electronic shutter?

b) You said you were shooting "flash macro". What kind of flash? Ring flash? Built-in flash, but macro lens? Was the flash direct or bounced? The darker lower shadow reminds me a cast shadow created by a lens hood using the built-in flash. Your metadata says "flash not fired". Could this be an anomaly with the flash that isn't fully charged/cycled?

Sorry, but more questions than answers to hopefully figure this out.

Of course, the biggest mystery is why in only 5-10% of your shots. What could have been differently in the other 90-95% where you are not seeing this?
09-20-2017, 04:16 PM   #4
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It really does look a lot like a flash sync/shutter lag issue. Have you seen any exposure problems in non-flash images?

09-20-2017, 04:23 PM   #5
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QuoteOriginally posted by Alex645 Quote
The darker lower shadow reminds me a cast shadow created by a lens hood using the built-in flash.
My thoughts too. I am thinking there might have been something in the way of the flash.

QuoteOriginally posted by Alex645 Quote
Your metadata says "flash not fired". Could this be an anomaly with the flash that isn't fully charged/cycled?
It means that the body was not in communication with a compatible flash or that a compatible flash did not confirm firing. The "flash not fired" note is always present with non-dedicated flash.


Steve
09-20-2017, 05:18 PM   #6
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Thanks for the thoughts everyone!

I'll take a rig setup shot soon. But here are a couple of informational updates:
  • On the same outing, I also had several instances of the flash not firing at all, which I'd blamed on my settings, but thinking back now I think it is more likely related.
  • Flash is a freshly charged Godox V850ii with a cheap diffuser, fired via a cable off the camera's PC sync connection.
  • The flash is on a bracket and is in a fixed position with respect to the camera for all shots.
  • Shots are taken from liveview, but this is not an electronic shutter. It's just mirror-up operation of the mechanical shutter.
  • The lens is D-FA 100mm WR (without hood) plus a Raynox DCR-250 attached with a step-down ring.
  • I've been using this flash, diffuser and lens combo constantly all summer without any issues.
  • I've only changed two things in my setup recently:
    1) Very recently, I broke my PC Sync cable while pulling it out of my bag, and switched to a new, in-theory-identical one (I'd ordered two from China). This was in fact my first outing with this cable.
    2) A bit less recently, I moved from using a hotshoe adapter with a PC sync connector (with the cable plugged into that) to running straight from the camera's PC sync socket.
I just took a few test shots indoors, and I was quickly able to reproduce both the dark band and the misfires (though the band looked more hard-edged than before).

However, the interesting thing is that if I reintroduce the hotshoe adapter (this thing) and plug the sync cable into that instead, I am unable (so far) to reproduce the issue. I am thinking it might be either the PC sync port on the camera, the cable itself, or (most likely) a faulty/partial/transient connection/electrical contact between the two. (Since the thread on PC Sync connection on the camera is non-standard, I am unable to screw the cable in place on the camera's PC Sync port.) It's odd that this would lead to these kinds of bands though. I would think you'd only see misfires. But maybe if the tolerances are almost there, sometimes the voltage peak for the flash might get across a little late?

Last edited by Doundounba; 09-20-2017 at 05:24 PM.
09-20-2017, 05:48 PM   #7
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Are the bands always slightly skewed and not horizontal? That part is curious, as are the two transition areas. Are they always in the same place?

Have you tried different shutter speeds? Break out 1/180s and see if it gets worse, try slower and see if it gets better. Also try different power levels. I've only dealt with sync issues via a wireless connection, faster shutter and higher power on the flashes will sometimes make matters worse as the timing with the shutter gets more demanding, so this might help you diagnose the issue.
09-26-2017, 06:51 AM   #8
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Just a quick update. I went camping this weekend, and decided to use my hotshoe adapter with a PC Sync connection rather than plug into the camera's PC Sync port (but with the same cable). Didn't see a single misfire or dark band. I am relieved that it's probably not the shutter or mirror and most likely just something about the electrical contact between the cable and the camera's PC Sync port (or a problem with the port itself). If I have time, I'll run some more tests with the problematic configuration this week...

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