Diatomes

bernhardinho · Post by **bernhardinho** » Tue Apr 22, 2008 2:13 pm

Hi folks

came across some nice diatomes these days.

There you go:

Gyrosigma

Bacillaria

Stauroneis

Obj. Leitz 20x Plan, 40x EF, 100x EF P, Periplan 10/20 , Coolpix 990, flash

So long

Bernhard

Ken Ramos · Post by **Ken Ramos** » Wed Apr 23, 2008 2:50 am

Pretty neat shots here Bernhard.

I have often wanted to see a live Bacillaria but being far inland, the chances are slim I suppose.

bernhardinho · Post by **bernhardinho** » Wed Apr 23, 2008 11:42 am

Ken Ramos wrote:Pretty neat shots here Bernhard. I have often wanted to see a live Bacillaria but being far inland, the chances are slim I suppose.

Hi Ken

well, this one was found in a freshwater pond! So your chances should be less slim than you think.

Cheers

Bernhard

BJ · Post by BJ » Thu Apr 24, 2008 5:01 am

Ola Bernhardinho.

As fotos excelentes. Gosto muito a foto de Stauroneis - e muito netido.

[ Hi Bernhardinho, excellent photos. I really like the photo of Stauroneis - its very clear]

...Ken, for years I looked for freshwater Bacillaria without success, then I started to find it quite commonly but unpredictably in shallow rather weedy ponds. If my life depended on finding it I would certainly always look in seawater. A recent paper (2007) suggests that there are three similar but distinct species, one freshwater/brackish, one marine bottom-dwelling and one marine planktonic - and that they should be put in different genera.

Apparently Bacillaria was one of the first diatoms described - back in 1782

Ciao
BrianO

Mike · Post by **Mike** » Thu Apr 24, 2008 5:19 am

Hello Bernhard,

Very nice shots!

I see you are using a CP990 - do you have any problems with artifacts from the lens?

All the best,
Mike

bernhardinho · Post by **bernhardinho** » Thu Apr 24, 2008 7:22 am

Mike wrote:Hello Bernhard,

Very nice shots!

I see you are using a CP990 - do you have any problems with artifacts from the lens?

Hi Mike,

yes indeed, my CP shows rather strong ringartefacts. And as you probably know they get really prominent in higher magnifications. There are though a couple of things you can do to avoid them:

1. use as little zoom as possible
2. open the iris diaphragm a bit more than Köhler would require.

With the Obj. 100x even these tricks won't work anymore and here I use a nice little tool ( http://www.picolay.com ) to substract a flatfield image. That is to say that after the foto session I take a pic of a spot on the slide wich shows no object but nothing but the rings (same light conditions!). This one is being substracted from the other pics which completely eliminates the artefacts! This technique I used on the third image (apart from cleaning up the background using the copy tool in PS )

Cheers for now

Bernhard

Mike · Post by **Mike** » Thu Apr 24, 2008 9:11 am

Hello Bernhard,

I thought as much - I've used a similar using ImageJ that does a wonderful job of flat field subtraction. I was actually hoping to find a CP that did not have artifacts, as all the version I've tried (995, 4500, 5000) are 'afflicted' to a greater or lesser degree.

All the best,
Mike