# Re: Telephoto Picture & Technical Analysis

Hughes <eugenhughes@xxxxxxxxx> wrote:

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

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

Target (scanned) is located 3.8 meters from telephoto/webcam (note:
photo taken is middle portion of brochure with the girl's neck joining
the boy with yellow shirt)

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

here is scanned image with zoomed portion of image

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

[snip]

Inquiries:

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

It's a standard colour printing method easily googled, easily
investigated with a good magnifying glass.

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

Obviously you need a combination of distance and angular resolving
power which can resolve them. Since you've posted pages of
angular resolution, etc., I can't understand why you can't easily
answer this question for yourself. It's simple optical trigonometry
based on all that stuff about circles of confusion and airy disks
you've posted so much about. And now you have the kit you don't need
to make assumptions, you can make your own measurements of the actual
resolving power you've got and easily calculate how much closer you
need to get it to the object to see what you want.

Did you not understand all those calculations you posted?

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

Could be lots or none. Depends on the details of the DSLR and webcam
sensors and how used. Far too vague a question.

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.

Noise isn't something that's either present or absent, it's a
measurable quantity expressed in various numerical ways. You've
already recommended to us some sites which explain the various kinds
of sensor noise very well.

You now have the lens and camera. Try answering some of your questions
by setting up your own experiments. When the photographs you post have
more bearing on the questions you ask and vice versa you're likely to

--
Chris Malcolm
.

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