[Elphel-support] Reasonable motorized lenses for 50-60 meters zooming for Elphel camera

[Roman Golomidov]

On Wed, Oct 21, 2009 at 9:19 PM, Andrey Filippov <elphel at gmail.com> wrote:
>> My task implies remote zooming at 50-70 meters distance with quality
>> enough to recognize a faces.
>
> Roman, we need to find out the actual required resolution that you need to
> recognize faces -  I do not have any experience with that. There should be
> probably some studies on the matter, you can also look at artificially
> blurred photos to find out what resolution (in mm with a given contrast) you
> need.

My question is not about face recognition. Its another big problem.
My question is about zooming till possibility to recognize face
(recognize by human).

> After that we can calculate the required parameters of the lens, knowing the
> pixel size is 2.2um and the best "5MPix" 1/2" lenses that do publish their
> specs have <=150 lp/mm (in most cases <120 lp/mm)

Experimenting with telelenses and professional photo cameras I come to
conclusion what it would be enough to recognize face if it will be
minimum 150 pixel height. So if face is about 20cm height, lenses must
provide zooming for 150pixels/20cm at 60 meters. Dont know how to
convert it to lenses units :) (x-y, f...)

>>
>> I suggest it would be enough  H10Z1218MS         12-120mm F1.8 10X, 3
>> motors w/ spot  from http://rmassa.com/manu/computar.htm
>> Am I right? May be where is another better solution?
>
> There is no resolution data in the datasheet of that lens, and knowing that
> it does not say "5MPix", "3MPix" or even just "megapixel" it's resolution is
> likely good only for old analog video cameras that have 640x480 at most, so
> you'll be able to get same details with higher resolution lens with 3-4
> times smaller focal length. It can make more sense to have a custom setup
> with 2 sensors and 2 fixed-focus lenses connected to the same camera using
> 10359 multiplexer board (the coming model 373 camera will have two sensor
> front end connectors on the main board)
Hmm, try to wait till this.

Actually, I thought about 2 lenses, but its not nice and general
solution. But its real right now.
So thats why I try to understand better solutions possibilities.


>
> At the same time, if you plan to use zoom - you'll probably need pan/tilt
> platform too. Is that so? Do you have a good platform selected?

I supposed if I have such a wide picture from camera I can zoom into
certain regions (for example with your built in Point of View).
Without rotating or tilting.
I need only about 20-30 degrees of view.


>
> There are some lenses with RS-232 interface (haven't seen with USB but there
Got it. Firstly I must understand about lenses.
>

Roman Golomidov