Re: affordable camera suggestions

Posted by Gabriel Landini on Feb 12, 2011; 5:06pm
URL: http://imagej.273.s1.nabble.com/affordable-camera-suggestions-tp3685628p3685632.html

On Saturday 12 Feb 2011, you wrote:
>                      You will not find resolution values in the scant
> literature supplied by microscope manufacturers,

Hi Brad,
The Olympus objectives we use came with some blurb where it was stated.
However, I just checked and strangely they do not provide this information in
their co.uk website. The objectives have their specifications listed but not
resolving power.

> So, if we wish to  capture a 20 x 20 mm square area of the intermediate
> image (a reasonably large fraction of what we see in an eyepiece)  we need
> 0.9, 2 and 1.5 megapixels minimum (i.e. to record full detail without any
> empty magnification.
> In practice, microscopists usually choose to work with about
> 3x the linear magnification at the Nyquist minimum,  so this means that the
> preferred number of pixels would be nine times this, unless the camera was
> recording a reduced area of the intermediate image. This means that the
> high pixel numbers of the modern  DSLRs are not overkill.

My point, (maybe I did not articulate it well) is that the data being stored
in such large number of pixels would not be adding anything in terms of image
detail and yet it will require larger storage and more processing.
If this is not taken into consideration one risks processing and reporting
morphological detail which could not be resolved in the first place. This is
of course obvious to experienced microscopists, but not perhaps to those who
did not think of this in the first place.

Let's use the example of fractal objects imaged with such level of empty
magnification. Applying the yardstick method, their perimeters measured with
small yardstick sizes will appear smoother than they really are because the
detail of sizes close to the image pixels cannot be resolved.

I must confess that I wasn't aware of the 3x preference by microscopists. Is
there a reason for this number?
Regards,

Gabriel