Re: Pixel Resolution vs Light Sensitivity

On Nov 6, 9:21 pm, H20S <charleywat...@xxxxxxxxx> wrote:
I'm in the process of purchasing a digital camera for my Olympus CX41.
One option is buying a 3.0 megapixel camera (Moticam 2300) that is
fairly light sensitive. Another option is buying a 5.0 megapixel
camera (Moticam 2500) that is a bit less light sensitive.

The obvious trade-off is that increased resolution probably requires
more light. The rub is that my microscope is outfitted for phase
contrast for the upper objectives. I'm concerned that phase contrast,
slightly less intense than bright field light, might be just dark
enough to make imaging with the 5.0 megapixel camera difficult.

Does anyone have an opinion as to whether phase contrast light will be
too dark to work well with the higher megapixel resolution camera?

Thanks,
CW

Usually, the camera's field of view is adequately sampled by 3
megapixels. The extra 2 megapixels may well be empty magnification.
This is not too difficult to calculate. Lens resolution in microns is
more or less equal to 1.22*0.5/(2*NA), where NA is numerical aperture
of the objective. So figure out how many microns across is the field
of view for one of your lenses, such as by photographing a ruler or
stage micrometer. Divide that by the resolution and you get the
number of pixels in one direction needed to resolve an image. Then
repeat for the other axis and the product is the number of pixels
total. You would need three times as many for color.

The wider the field of view for the camera, the more pixels needed.
That is controlled by the adapter and the size of the sensor in the
camera. Usually, 1 megapixel is plenty for black and white.

How fast the camera needs to be is controlled in part by the
brightness of your light source. A 100-watt halogen bulb would have
plenty of light. A 20-watt might not. All else being equal, faster
is better.
.

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