Digital Noise and Electrical Storms

[CBImages]

A few days ago I took some images of lightening during a prolonged electrical storm, when it returned home and examined my images I noticed lots of noise in the sky and water, I was wondering if the sensor or the DA converter might have been effected by the electricity or static in the atmosphere.
Anyone any thoughts?

I was using a Canon 5D MkIII, shooting 10 second exposures at 100 ISO.

I have done lots of low light photography before using 800, 1600 and even 3200ISO along with 30 second exposures and never had such noisy files before.

[chauncey]

Short answer is no, as to why excess noise we need to see images and settings.

[CBImages]

Short answer is no, as to why excess noise we need to see images and settings.

What other settings do you require?
I will post image later

[Manfred M]

I bit hard to be sure without seeing your images, but...

Generally we see digital noise in underexposed parts of the image, especially the dark areas. Long exposures (10 seceonds certainly counts) obviously are going to make this worse, even at ISO 100.

The issue with electrical storms is the large dynaminc range you are dealing with; the lightening will be very bright (possibly blown out) and the sky and water will consequently be rather underexposed (and dark, when compared to the lightening), which brings out the issue.

[CBImages]

Thanks - I do understand about the reasons behind noise - colour, luminance and pattern noise but 10 seconds is a relatively short exposure time for such an amount of noise in an image taken with a 5D MkIII and at base (100 ISO).
As I mentioned in my initial post I have taken many, many 30 second exposures using up to 1600ISO and never had such noisy files before.
The only difference between the scenarios that I could think of was the electrical storm.

We all know the problems an electrical storm caused to analogue television signals so I was wondering if it might somehow effect the Digital to Analogue signal conversion within the camera circuitry or if anyone else had noticed a similar phenonomen?
Not sure why someone thinks seeing my image would help diagnose the problem as it would need to be compared with a similar image taken under similar conditions and using the same settings and that what only prove what I have already said in my previous posts - that the storm images contain more digital noise!
But I will happily post the image if it would help.

Thanks for replying

[Manfred M]

From a technical standpoint, I can't think of any reason why an electrical storm could have this kind of an effect. The camera should be shielded from electrical fields by design (thinking of performance new power transmission lines, microwave ovens, van de Graaf generators at the local science museum, etc).

Any electric fields generated by an electrical storm should be quite low, unless you are quite close to where the lightening strikes. In that case, you and your camera would probably not survive.

[chauncey]

Taking into consideration that the static electricity generated from a lighting strike could, in theory, affect the capture of an image on the CF card were you in close proximity to the strike, however, in all practical scenarios, as Manfred suggests, it's not likely.

[dem]

Underexposure?