Re: Webcam vs DSLR Target Field of View


Here is a photo I shot with the 1000mm telephoto with webcam.

http://www.pbase.com/image/111769165/original

original picture is located 3.8 meters from telephoto/webcam (scanned)

http://www.pbase.com/image/111769109/original

here is scanned image with zoomed portion of image

http://www.pbase.com/image/111769128/original

Measurement of actual picture is 7 inches horizontal,
5 inches vertical. Telephoto/Webcam located 3.8 meters
away shows an area of only 0.4 inches horizontal
(or only 5.7% of entire picture).

The webcam picture shows 0.15 degrees of picture
which is located at a distance of 3.8 meters.

Calculations:

Specs

4" aperture Telephoto 1000mm focal length f/10
webcam 1/4 inch CMOS 640 X 480 Sensor

picture area taken with telephoto/webcam is 10mm horizontal
at a distance of 3.8 meters hence

degrees of telephoto/webcam coverage = 2 x artcan (0.5 (10mm)/3800)
= 0.15 degrees or 540 arcseconds

resolving power of telephoto = 116 / 100mm = 1.16 arcsecond

pixel scale = 206265 (0.0057/1000)
= 1.185 arcsecond / pixel

Inquiries:

1. In the picture there is rectangular pattern taken with telephoto/
webcam,
what is it? Printing artifact of the brochure?

2. How come I can see vertical lines moving upward in the webcam
preview in the monitor? Noise or because image is dim??

3. Using micro photography, what specs so you can see the same
rectangular printing pattern in the picture of color brochure taken?

4. Using a DSLR, what would be the improvement in resolution and
colors provided dslr and webcam has same pixel pitch?

5. To be noise resistance, does the pixel (or sensel) have to be
at least 4.7 micron? How about 2 micron pixel pitch like in digicam.
Is there no possibility to construct 2 micron pixel pitch in the
future with
the same noisefree performance as present 6 micron DSLR? What
optical principles make it impossible? Something above wavelength
of light inpringing on the neighboring pixel or senses? Or what??

Thanks in advance for those who can answer so I can decide
whether to buy a canon 1000d or not. I need sufficient data
for complete analysis to make a decision to buy or not to buy
canon 1000d or not. Thanks.

Hughes

.

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