Lightning strikes twice

Started Aug 7, 2012 | Discussions thread
efg40
Veteran MemberPosts: 6,176Gear list
Like?
Re: A physicist's analysis of reflection
In reply to falconeyes, Aug 8, 2012

falconeyes wrote:

I've browsed thru the thread here and it has quite an entertainment value.

While it is true that lightnings can strike multiple times thru the same ionized channel which additionally can have a drift, this is not what has happened here.

I analyzed the image via overlay:

The 3D-look to the middle channel is the result of the secondary channel being an EXACT copy of the primary channel, offset as marked by the red line. The duplicated secondary channel fill parts of the primary channel giving it this 3D look, meaning it is an exact copy.

The problem with this is that this means that the secondary channel is not reaching earth! It is not a real object, just an optical illusion. The wind speed argument already hinted at that.

Moreover, the optical effect is easily explained: The lightning stroke is so bright that it overblows the sensor by several orders of magnitudes, many EV stops. Therefore, even the faintest reflections within the optical system become visible, as well as even minor chromatic aberration.

And there is at least one unavoidable reflection in any system: Between the sensor's protective glass inner surface and the Bayer-AA filter (or IR cut filter) outer glass surface. The offset should be larger towards the borders of the image which may be a reason why it is more pronounced in the second lightning.

As a rule of thumb, such reflections often occur at the same time as CA becomes overly strong. It is a known phenomenon from night photography with overblown light sources towards the borders of an image.

Kind regards,
Falk

Whoa, where did the third line come from?

But thanks for the analysis Falk!

-- hide signature --

Elizabeth
efg40

 efg40's gear list:efg40's gear list
Olympus PEN E-PL1 Olympus OM-D E-M5 Panasonic Lumix G 14mm F2.5 ASPH Panasonic Leica Summilux DG 25mm F1.4 Olympus M.Zuiko Digital 14-42mm 1:3.5-5.6 II R +1 more
Reply   Reply with quote   Complain
Post (hide subjects)Posted by
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark post MMy threads
Color scheme? Blue / Yellow