Distortion on image?

[Seagull Shooter]

Hi All,

I recently posted an image I took in twilight with some point light sources in it. See below.

2026.07.18 London selects.2 by Stephen Pook, on Flickr

If you look closely at the red light on the crane (on the left side of the image), you see some distortion which looks a bit like pixelation or similar.

The shot was taken with a Sony A7iii and a Sigma 24-70 f/1.8 Art lens. It was taken at 39mm f/22, 30 second exposure.

Does anyone have any ideas what may cause this and how to avoid it, as the rest of the image looks pretty sharp to me?

Thanks,

Steve.

 

[GreenNinja67]

Looks like over processing noise to me around the brightest lights. The cyan one bottom left is the same.

I'd be more concerned about the filthy sensor.

Cracking shot by the way.

 

[Seagull Shooter]

Looks like over processing noise to me around the brightest lights. The cyan one bottom left is the same.

I'd be more concerned about the filthy sensor.

Cracking shot by the way.

Thanks GreenNinja. That’s very helpful.
I’ve addressed the sensor but the image needs another edit to clear the specs. Bloody dust!

 

[wornish]

It's a diffraction spike (starburst) effect caused when you are using a very small aperture. Simply use a wider aperture to avoid it.

 

[Seagull Shooter]

It's a diffraction spike (starburst) effect caused when you are using a very small aperture. Simply use a wider aperture to avoid it.

Thanks Wornish. I thought there would be an exolanation...

Every day's a school day!

 

[wornish]

More info here. The effect can be used to be creative.

https://heathercline.zenfolio.com/blog/2016/7/the-sun-burst-effect

 

[GreenNinja67]

It's a diffraction spike (starburst) effect caused when you are using a very small aperture. Simply use a wider aperture to avoid it.

Not sure he means that. In the starburst it's a little pixellated, I think that's what he means.

 

[GreenNinja67]

In all honesty the image is far too small to make any meaningful judgement. Perhaps posting a 100% crop of the light might help.

Try clicking on it to open in Flickr and enlarge from there.

It's easy to see then.

 

[Seagull Shooter]

I was referring to the lines/distortions within the starburst. Is that a product of the ‘starburst’ effect or is it something else going on?

 

[woof woof]

In all honesty the image is far too small to make any meaningful judgement. Perhaps posting a 100% crop of the light might help.

Yes, but the main thing that I see is that it looks overprocessed. I may be wrong but that's how it looks to me on my screen. Maybe the sliders need reducing a bit.

 

[GreenNinja67]

The maximum image is 1024 pixels.

You can still zoom in, try it.

 

[RyanB]

Did you apply ai sharpening in your processing? Slightly overbaked I'm thinking, if I jack up the ai sharpening to the max(or near to it) light sources go a bit odd like this on occasion.

 

[Seagull Shooter]

Did you apply ai sharpening in your processing? Slightly overbaked I'm thinking, if I jack up the ai sharpening to the max(or near to it) light sources go a bit odd like this on occasion.

In the AI sharpening edit window I had 'amount' at 35 and 'detail' at 21 where neutral was 75. I had effectively reduced those options. Strangely (in my eyes), increasing 'luminance' seemed to reduce the effect also. A bit puzzling really. I did adjust the contrast curve but not by a huge amount. I wonder if the 30s exposure caused some burn out on that particulat spot light source?

 

[woof woof]

Stephen. I think what you should do is revisit the file and dial everything back then post the picture again together with your thoughts.