Red Golden Gate : Flares+JPEG artifact

[Gregoire]

Hi all,
I like this view of the Golden Gate.
I didn't want any car on it, so I chose long exposure, f8, to have the lights. I forgot to shoot the same with wider aperture, but even though it would have reduced exposition time.

I guess I could reduce the flare with a wider aperture, but is it noise or JPEG artifact "between" the flares.
I posted on zing the original (http://www.zing.com/picture/p45f753cca976a013acb5951c8d8b45c1/fea5380b.jpg.orig.jpg) size one. I used superfine compression.

http://www.zing.com/picture/pceb8684b58bb072f83d86a75b4d32a35/fea53b2f.jpg.orig.jpg

Any comments ?

[Pekka]

(note to all: you have to see the bigger version of Gregoire's photo to notice the problem).

I've seen similar effect, but not so heavy. See e.g. in
http://studio-on-the.net/photography/G1/108-0881_CRW.html
and
http://studio-on-the.net/photography/G1/134-3457_CRW.html

Here are my three "common sense theories" (actually I have no real knowledge what it really is :) ):

Theory 1:
The "rings" of the lens flare are so thin that G1 can't display them (so they become heavily interpolated). It seems that JPEG compression attempted to display the detail and failed (noise instead).

Theory 2:
The dynamic range of G1 is not sufficient in displaying the change on levels from pure white to blue: the in-between levels have to have color steps. I've shot in RAW which has 10-to-8-bit conversion which might make this effect smoother.

Theory 3:
The lamps are not steady but emit constantly slight variations in light density. The camera mixes these small changes in long exposure to a mess. The aperture affects the form (lenght and number of flare 'hands') of the flare, so this effect is not so pronounced in fully open aperture.

I think the truth might be all three theories combined.

[prosurfer]

How long was the exposure? Could it be the CCD?

[Pekka]

It seemed to be an 8 second exposure. It explains the high noise levels but does not explain the odd rippling effect.

Here's the EXIF:

Camera Model Name: Canon PowerShot G1
Shooting Date/Time: 4/9/2001 8:16:09 PM
Shooting Mode: Manual
Tv (Shutter Speed): 8
Av (Aperture Value): 8.0
Metering Mode: Center-weighted averaging
Exposure Compensation: 0
ISO Speed: 50
Lens: 7.0 - 21.0 mm
Focal Length: 7.0 mm
Digital Zoom: None
Image Size: 2048 x 1536
Image Quality: Super Fine
Flash: Off
White Balance: Auto
AF Mode: Single
Parameters: Contrast Normal, Sharpness Normal, Color Saturation Normal
File Size: 1584 KB
Serial Number: 105-0579
Drive Mode: Self-Timer Operation
Macro: Off
Owner's Name: Gregoire Cacheux

[prosurfer]

Heh, I think I got it by just giving the picture a 2nd look (and Pekka's theories guided me to the right direction of course):

The picture is apparently shot in the evening, and it is prolly not extremely warm even in NCal this time of year. So the heat from the lamp warms the air around it, and creates distortions when the light reflects from the layer between cold and warm air. CCD-noise gives it an extra effect, of course.

Buying it? =)

[Pekka]

But heat goes only up, right? ;)

[prosurfer]

In the end, yes, but the lamp emits the same amount of heat to all directions =)

[Gregoire]

This one http://www.zing.com/picture/pdd0df5dd04de204d286badcff77df703/fea49293.jpg.orig.jpg, has a 2.5s shutter speed. I wish I had tried different aperture to reduce the flare.

[John - NJ]

Gregoire:

Was there a strong power source, like a transformer, any where near you? Just a thought.

Has this happened with any other evening photos in a different location?