Re: More on A.pellucida

Rene,

I am beginning to have doubts regarding your competence.
Your recommendation that I should keep it up because I will be
learning a lot is entirely misplaced as the following lines will
clearly show.

From your recent post:
"rene" <renevanwezel@xxxxxxxxxxx> wrote in message >news:1169727731.244566.22640@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Hi NoSpam, can you tell me where exactly this is located on the
Baertierchen site??

The site where you can find the article by Martin Mach showing the
van Heurck A. pellucida picture is under
http://www.baertierchen.de/archiv.html
where there is the telling title: Februar 2004: Feine Strukturen.

From your recent post:
Also, you seem to have been lucky to be able to download Spitta's and
Carpenter/Dallinger's book, I could only get snippets which were
useless. Would you mind sending them to www.yousendit.com, so that
we could download them from there?

The Carpenter/Dallinger book can be found exactly where I
said it can be found. Now you will know that long, that is
several line long links, are not properly handled in newsnet
messages. It is therefore unproductive to just click on the
address as given. What you need to do is copy the entire link
to a text editor, like Notepad. You do this by "copy" the link
in sections, line by line, and reconstructing the address
by "paste" in your text editor. Then you copy the entire address
so obtained into your browser and VOILA, there is the book.
(To be entirely sure I repeated this process just now and it
works, like it always does.) I do not know how else I can make
it easy to find this source. Believe me, I spent a lot more time
finding it and then the page numbers, than it would have taken
you to follow the described process! So go ahead, download
the book, look at the pages I quoted and you will be able to
read the text and see the picture.

You are quoting from a prior text of yours:
The more empty magnification, the lower the contrast. 36mm fim and
3Mp cameras are more then adequate.
Your addition to that text is:
I stand with this conclusion. A 100x 1.4NA lens with 20mm secundary
image (such as seen with a 10x eyepiece with fieldnumber 20) only needs
2000 pixels along the middle line for all detail for all to be resolved
(ie 2 pixels for 0.2 um). If you fix a 36mm frame inside the field of
view, you will need less pixels, but add some to compensate for the
Bayer filter in the digicam, then you will have enough with 3Mp.
I agree with you, increase pixelSIZE (but not total amount of pixels)
and with corresponding extra magnification will reduce noise, but that
is irrelevant in this discussion.

You seem confused by the issue of contrast. I will say it
one more, final time: contrast increases when the target's
image spatial frquencies move to the left on the MTF curve.
The only way for this to happen at a fixed pixel or grain size is
to decrease the spatial frequency, that is to increase the size of
the image.

What may lead you astray is the custom of presenting the MTF
curve for targets with 100 % contrast. The x% which are deemed
sufficient for detection are then at a certain position on the hori-
zontal axis. BUT, when the contrast of the target is less than 100%,
this point moves to the left and for small contrast it moves a lot to
the left.

Your quote from a prior post of mine:
I produced an image of A. pellucida by projecting the
intermediate image of this diatom upon the CCD of my *ist Pentax (n=1)
and was UNable to resolve the striae. I then projected the intermediate
image through a 2.5 projection lens (n=2.5)and could resolve the striae
perfectly well as shown at
http://www.mikroskopie-forum.de/read.php?2,25394,25394#msg-25394 .
Your response to that quote:
I'm not sure exactly where your exp did go wrong. By 'direct
projection' you mean you simply took out the projection lens/eyepiece
and adjusted focus? That would increase the effective tubelength a
couple of cm from the original 160mm it was designed for. This would
create spherical abberation, ie unsharpness. Your CCD should be at the
place where the secundary image is placed (where your eyepiece 'picks
it up'), somewhere a cm or so below the rim of the tube).

You say you are not sure where my experiment went wrong. Well, it
just simply did not go wrong! The image was taken by placing the CCD
of the mentioned camera to exactly where the intermediate image is
located and taking the picture. The picture itself was only 100x (the
magnification of the objective) x 70 micrometers( the length of the diatom),
or 0.7 cm tall. This is smaller than the vertical dimension of the CCD leading
to a loss of contrast and inability to see the striae by the mechanism I have
described above.

It may well be that you did not read my notes well. In these notes it
is stated that I am using an Olympus BX51, a microscope with infinity
optics and a fully corrected intermediate image. This intermediate
image is accessible above the dovetail connection on the trinocular
leading to the camera port.

You quote a prior post of mine:
Finally I wish to point out that my image of A. pellucida (see
the link in my original post) was obtained using a magnification
of 250x (100x from the objective, 2.5x from the projection lens),
while Dr. von Heurck used magnifications of 1800x to 3000x.
Your response to it:
That would make your specimen a very big one ;-)

Please see the arithmetic I have gone through above, showing that
my diatom was of regular dimension and not a "very big one".

From your recent post:
ps, keep it up, you are learning a lot.

Rene, please refer to the first paragraph in my response.

G.R.

Relevant Pages

  • Re: aperture and magnification gain puzzle
    ... >> It is mentioned in Rutten Telescope Optics that as contrast ... >> get lowered in an object, one must increase the magnification ... > best contrast between the background night sky and object by going to ... > or the Andromeda Galaxy through binoculars or a telescope. ...
    (sci.astro.amateur)
  • Re: aperture and magnification gain puzzle
    ... > It is mentioned in Rutten Telescope Optics that as contrast ... > get lowered in an object, one must increase the magnification ... It means that when you observe in the best dark sky, ... or the Andromeda Galaxy through binoculars or a telescope. ...
    (sci.astro.amateur)
  • Re: Jupiters GRS detection at 54x
    ... > Size of image versus the eye's resolving power? ... Those two issues push the required magnification in different directions. ... If the contrast were sufficiently high, ...
    (sci.astro.amateur)
  • Re: Detecting the "ringness" of the Ring Nebula
    ... >>improved by increasing magnification. ... As Roger notes, everything changes brightness equally, so ... > contrast increases with increased magnification. ... notes "apparent contrast" does. ...
    (sci.astro.amateur)
  • Re: Camera modeling & filter selection
    ... a high contrast between apple and bruise as high as ... possible, given a CCD, optics and lighting. ... T1= bandpass filter transmittance ...
    (comp.soft-sys.matlab)