Strange background in the photos

Hello!

Recently I've bought a D200 and in some photos I have found a strange background.

The lens I used was a Nikon 60mm with a flat port specially desing for it by a Spanish manufacturer SAGA http://www.sagadive.com/tienda.php?cat=3#Anch2_68

This problem only appear when there is sand or sandy areas, and it is clearer as the focus is closer.

This is the photo where the background is strange. f11 v1/125

And here, a cropping.

f25 v1/125

f11 v1/125

In this 2 images, It can see the same problem but no so obvious.

Do I have to avoid sandy areas when using this lens?

Have any of you experienced the same problem? Do you know why it happens?

Sorry for my English

Thanks!

BTW, I am really happy with my new camera

Regards from Spain,

Mikel www.photo.net/photos/Mikel

I'm not certain what is causing your strange background, but were you perhaps photographing near a thermocline (or halocline)? Here is a portion of an image of a flamboyant cuttlefish that I took right at the edge of a thermocline and you can see the tendrils of cold water. The effect is called a shadowgraph and is the same phenomena that causes the air above a hot road to shimmer.

It may also be bad bokeh - what lens?

Cheers

James

It may also be bad bokeh - what lens?

 

Cheers

James

ha, good guess, but he mentions that it's the nikon 60mm lens in his post, and I don't thnk the bokeh of that lens is not as bad as what's in his photo

scott

Please, circle exactly what you see as strange background in your images.

It could be just plain old backscatter since it occurs in sandy areas (lots of particles in the water) and goes away when focusing closer (limits the water between the lens and subject; also limits the total depth of field).

Take Care,

ChrisS

(note: if you shot a point-and-shoot housed camera before getting the d200, the point-and-shoot's sensor is tiny which makes the depth of field very large in comparison to your d200's dx sensor at the same f/stop.)

Thanks for your replies

Chris, what annoys me is that:

And the lens I used was a Nikon 60mm. I am new with SLRs and this is my second week with one of them but I consider Nikon 60mm as a good lens, it is really fast and the quality of the images is quite high.

Now I am start thinking it might have been a thermocline issue, as drsteve has said. Although I have seen other photos with the same problem, look at the 2nd photo of the link

http://www.forobuceo.com/phpBB2/viewtopic.php?t=36291

Another photo more:

And the cropping:

Thanks a lot.

Am I being blind .. I don't see anything but out of focusness which to me looks like depth of field constraints.

Oooh ok just saw that last image .. it's just the bottom right corner .. it's not condensation is it ?

It doesnt seem to have any set spot ...

Is it an acrylic port?

Could the pressure cause it to flex and get stress marks at depth?