camcorder through car window glass

Will the autofocus work through a car window?

What else should I be asking?

 

If it is IR focus, you may have a problem, but my Sony TRV520
seems happy shooting through the window. DON'T let it touch
the window or you get the vibration "float" it as much as possible
(the less coupling you get to the car/vehicle, the better the image.)
You may find simply setting it on manual works best (things going
by close like a bush next to the road drive the autofocus nuts - and
you).

mikey

 

"Rick Merrill" wrote ...

Depends on what kind of autofocus it is.

Ultrasonic will clearly focus on the inside surface of the
window. Even window/door screens will confuse them.

Infrared may or may not, depending on several conditions.

The kind that analyzes the video image likely has the best
chance of working properly through a window. I believe that
is the most common kind we see in recent products.

Why you should consider using autofocus at all?

 

It will. But might get a little confused when the sun hits the windshield,
and when it sees low-contrast areas. But why would you want to use
autofocus anyway in this situation? You won't have any benefit from it, as
no subjects will get close enough to require a decent focus readjustment.
You're better off working in manual (set to infinity, with a high
aperture).

cheers

-martin-
--

 

It's a bit obvious, but I'll say it anyway... remember to clean the window!

Any dirt on the glass won't help the autofocus...

Gareth

 

The 'subject' may change from 300 ft to 2 ft pretty quickly
plus I' may or may not have a way to support the camcorder
other than with my hands alone.

 

Dang! That's a good idea that had not occurred to me at all!

(i.e. it's not my vehicle)

 

First off, this is WHY manual focus is such an important camera feature.

Second, shooting through glass - a polarizing filter is your friend.

Third, have fun!


For what it's worth.

 

Don't worry too much. If you would have a focal length of 6mm (wide angle),
and an aperture of 5.6, then at 2 ft you are in-focus from 0.9ft -
infinity. If you're shooting during the day, you will have an even smaller
aperture and an even higher depth-of-field (this all assuming you have a
1/3" CCD).
You can work it all out for yourself at
http://www.panavision.co.nz/main/kbase/reference/calcFOVform.asp
And then you can pick your optimal numbers. If you focus on the
hyperfocal-distance, you will be in focus from the minimum calculated till
infinity. So, say in this example the hf is 1.9ft, min is 1.1 ft, max is
infinity.

cheers

-martin-
--

 

Polarizers often give very odd results through tempered glass.
Watch for strange "blotchy" patterns when using one - some
windshields are fine, others .... eeeeeeek !!

mikey

 

Maybe he *wants* the picture of that dead bug??

 

Hooo, a polarizer would be good shooting into the sun.

Anyone produced a Police Video? - tagging along with the constabulary -