[daveyuk]

As yesterday was such a nice day I thought I'd get some more practice with my Sigma 170-500mm lens and take a few shots of the aircraft flying over my house.
And I need some more practice

Anyway I took this shot of a DHL aircraft and it's ok but I see rings in the blue sky and I've no idea what I've done to get them.


Camera Canon 350D, Lens Sigma 170-500mm, ISO 200, f5.6, Shutter speed 1/640
Focal length 500mm, Exsposure mode Apeture priority, No flash. Hand held.
All that I have done in PS is to run "Auto Smart Fix" and saved for the web.

Many thanks in advance for all help and advice given

[Dabhand16]

Were the rings there before the processing?

[daveyuk]

Dabhand16 yes I first noticed them when I loaded the image into PS

[Rob Barron]

What qwuality setting were you using on your camera Dave? Might you have selected a lower quality jpeg (higher compression) as that is what this looks like. This would normally be seen when someone has compressed a photo and then shown on here as compressing fairly flat colour can often produce this effect. Just wondering if your camera has done the same thing.

Cheers,
Rob

[Dabhand16]

Good point from Rob, there. Must be worth trying some shots at highest jpeg quality and RAW before anything else. The only thing i could think of to give circular artifacts would be something to do with the lens elements.

Have Sigma got a forum you could have a look at to see if there are any others who have suffered similar effects?

[Sonsey]

It might possibly be caused by a reflection of a filter, if you had one on the lens?

[Les Meehan]

This is a fascinating problem. Can I ask, have you cropped the bottom of the image? There is a very definite central circle but it isn't quite in the middle of the shot.

Maybe, due to the vignetting caused by the lens, in-camera processing has caused the effect. I would recommend trying to replicate the effect. Make images at all different settings the camera has (that is quality settings). Keep all other things the same.

This effect is similar to what can happen when you create a gradient in PS. Take a look at my blue panorama in the galleries to see this in the sky which, of course, is false.

[daveyuk]

Thanks for all your reply's guys

Rob camera is set to large jpeg image quality

Sonsey no filter on this lens

I've had a look at some of the other shots I took yesterday and there are no rings on them.

Think I might get the lens striped and cleaned

[Dabhand16]

If this is the only shot displaying the problem, it might be the 'one-in-a-million' angle/subject/lighting that you may never see again.

Before I had the lens serviced, I'd see if there are any known issues etc.