Like I suggested to Graham elsewhere, I think the upper left is lens flare; the upper right I isolated definitively to leak from the mount of the camera body.
The story's been quietly making the rounds, starting with Imaging Resources, and now Lens Rentals. It all actually started over two months ago when I first reported the problem on the SONY Alpha group on Facebook. Since I do a lot of daytime long exposure photography, this was disturbing, so I suggested people test for it, and came up with a rather crude, quick and dirty method; set ISO to super high, lens cap on, 30s exposure mode, then shine a flashlight around the mount area. With this method, I was able to isolate the location of the worst leak (3 O'clock position), and most importantly, that the leak was happening not between the lens & flange, but from the body itself, the gap between the silver flange that interfaces the lens, and the orange-colored outer ring. By applying some gaffer's tape to cover that, the leak went away.
Now, having several years of doing daytime long exposure photography, I believe I've come to understand where we should and shouldn't expect light to leak.
• If you're using an SLR, you want to cap your OVF, especially when you have the sun behind you, as light will seep into the body via the mirror-up position.
• If you're using a zoom lens, or worse, a tilt-shift lens, you want to cover your lens barrel, as those moving parts have small gaps through which light can find their way inside.
• Doors to access various ports (usb, flash sync, remote, etc.) can leak light if left open. Close them, or if you are using a wired remote, cover that area.
• If you're using Lee, Cokin, Formatt-Hitech, etc., filter holder system, make sure there is no gap between the holder and the ND filter (E.g, Big Stopper), as light will find its way through there as we..
*Never* had I needed to put tape around the mount of any of my cameras to keep light out. I've owned a K200D, K20D, K7, 5D, 5Dmk2, (also GF-1 and NEX-6, but never did LE with those). I've also done daytime LE with film, with various Hasselblads, Rolleiflex SL66, Kiev-friggin-60, Speed Graphic, Chamonix 045N-2; never have I seen light leaking from the mount/flange area.
The only place that consistently caused leaks is the VF. I've many shots ruined because I forgot to cap it, or forgot to fold down the waist level finder. I've had a couple with my filter system, where, using a Lee Big Stopper with a Cokin-Z, the light seal isn't perfect. And I experienced some light leaking through tilt shift lenses a few times, with my Hartblei Super Rotator. But I've never seen light coming in from the mount.
And yet, my A7R is consistent. It doesn't matter which way it's pointed. If shot for more than 60 seconds at ISO50 in daylight, I will always get a leak showing up as the crescent shaped ghost in the upper right of the frame.
I find this very unusual.
And yet, partially because for some reason, this "ISO25,600, 30sec in broad daylight" meme sprung up, and these websites are treating that as some golden standard to mock and laugh at. Rather disheartening.
Here's what I would consider a VERY modest daytime long exposure shot. 76 seconds at ISO50. The second one I agree is a bit more extreme, it's 8.5 minutes at ISO100. I'd still not consider that excessive, though. With my Canon 5Dmk2 I could easily shoot 5-10 minutes without any leakage as long as I remember to cap the OVF. But considering there's all sorts of things happening in that image, I'm OK with accepting that one to be extreme. But 76s @ ISO50?? I just can't accept that.
I would however love to hear your experiences; if you've ever had to deal with light leaks in your long exposure photographs (landscape, seascape, etc.) NOT from the lens or the OVF, but specifically from the flange area, please share your experience. Thanks!
