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

[Andrey Filippov]

>
> 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.
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)

>
> 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)

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?

>
> And second question is about to control this lenses. As Elphel answered -
> thereis no standard on board possibility to control such lenses from camera.
>

That is correct. Unfortunately there is no single standard for the motorized
lenses with C/CS-mount world. Most lenses even come with unterminated wires
so camera manufacturers put custom, camera-specific connector there. It is
OK when you provide the cameras with a single lens, but not so convenient
when you try to make something universal. Additionally, motorized lenses
have generally lower resolution - and this is really a challenge to find
even a good fixed-focus lens for multi-megapixel cameras. To say nothing
that the C/CS-mount motorized lenses are usually much larger/heavier than
the manual ones. That is why we do not provide motorized lenses with Elphel
cameras

But it is possible to connect lenses to camera's USB port through
> controller. Can anybody suggest any model?
>

There are some lenses with RS-232 interface (haven't seen with USB but there
are plenty ~10$ USB-to-serial adapters that are known to work nicely with
the camera), but they are usually rather expensive ones (
http://www.google.com/search?q=c-mount+zoom+rs232 ). Even having 2 cameras
with different focal length lenses would be less expensive. On the other
hand, if you do have some lenses and pan/tilt platform it should be rather
easy to connect them to the camera. Camera has php running inside, so
connecting some such a device and providing basic web interface fro it can
be a one day job. Or - one week if you want really nice interface.

Additionally you can use many microcontroller boards (like
http://www.arduino.cc/ ) that have USB device port and have outputs that can
be used to control motors - directly or with small number of added
components, you definitely can adapt one fro PTZ control of analog platforms
and motorized lenses.

Andrey
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