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Kim 09-08-2003 11:13 AM

Canon A20 infrared pictures and focus
 
I got a Hoya R72 infrared filter for my aging Canon A20 and have been
experimenting with some infrared shots. They come out pretty well when
there's plenty of sunlight, but everything is always out of focus.
I've only tried shooting landscapes which would be focused on the distance,
so I didn't think focusing would be a problem.

The A20 does not have a manual focus option and sharpening in Photoshop
doesn't help much.

Is there anything I can do about this or am I just going to have to get a
camera with manual focus?

Juan R. Pollo 09-08-2003 02:34 PM

Re: Canon A20 infrared pictures and focus
 
This may be a bit tricky, but how about setting the focus before putting on
the filter? That is, depress shutter halfway, put on filter & shoot.

Juan

"Kim" <kimwatson@nospam.blueyonder.co.uk> wrote in message
news:Xns93F07C610164Bkimwatsonblueyonderc@216.65.9 8.9...
> I got a Hoya R72 infrared filter for my aging Canon A20 and have been
> experimenting with some infrared shots. They come out pretty well when
> there's plenty of sunlight, but everything is always out of focus.
> I've only tried shooting landscapes which would be focused on the

distance,
> so I didn't think focusing would be a problem.
>
> The A20 does not have a manual focus option and sharpening in Photoshop
> doesn't help much.
>
> Is there anything I can do about this or am I just going to have to get a
> camera with manual focus?




Matt Arnold 09-08-2003 03:39 PM

Re: Canon A20 infrared pictures and focus
 

"Juan R. Pollo" <jrpollo@worldnet.att.net> wrote in message
news:Xr07b.130962$0v4.9555880@bgtnsc04-news.ops.worldnet.att.net...
> This may be a bit tricky, but how about setting the focus before putting

on
> the filter? That is, depress shutter halfway, put on filter & shoot.
>


This wouldn't work. This is because when you focus, you're using visible
light wavelengths. When you put the IR filter on, the IR wavelengths are
longer and will not focus on the CCD with your pre-set focus. There may not
be much in it, but that method won't produce a fine focus if you're after
that.

The only way is to put the filter on and use the manual focus to get it pin
sharp. But because you've not got a manual focus, you're going to have a
problem and I'm not sure it's possible.

Matt Arnold
Go further with your Fuji cam: http://www.camerashed.co.uk



Jeff Zawrotny 09-08-2003 07:26 PM

Re: Canon A20 infrared pictures and focus
 

"Matt Arnold" <support@directadvertiser.com> wrote in message
news:bji7ru$rnr$1@newsfeed.th.ifl.net...
>
> "Juan R. Pollo" <jrpollo@worldnet.att.net> wrote in message
> news:Xr07b.130962$0v4.9555880@bgtnsc04-news.ops.worldnet.att.net...
> > This may be a bit tricky, but how about setting the focus before putting

> on
> > the filter? That is, depress shutter halfway, put on filter & shoot.
> >

>
> This wouldn't work. This is because when you focus, you're using visible
> light wavelengths. When you put the IR filter on, the IR wavelengths are
> longer and will not focus on the CCD with your pre-set focus. There may

not
> be much in it, but that method won't produce a fine focus if you're after
> that.
>
> The only way is to put the filter on and use the manual focus to get it

pin
> sharp. But because you've not got a manual focus, you're going to have a
> problem and I'm not sure it's possible.
>
> Matt Arnold
> Go further with your Fuji cam: http://www.camerashed.co.uk
>


Try stopping the lens down as much as possible... won't cure the problem
entirely, but will help, in any event.

- jz



Buster 09-09-2003 02:45 AM

Re: Canon A20 infrared pictures and focus
 
If any of you have older still camera lenses, you will notice that
there is a red mark on the depth of field scale in front of the
aperture ring. This is the IR offset mark for focus. This is because
IR does not focus at the same plane as visible light and since you
can't see it, you can't tell where to focus. On your camera, it is
using a CCD (not film) designed to see IR and the LCD allows you to
preview the IR image. I remember shooting IR with film and an 87
filter. The 87 filter totally blocks visible light. You had to focus
without the filter, then shift the focus to the red IR mark and
install the filter. It didn't allow much spontaneous shooting.
Buster


On Mon, 08 Sep 2003 22:25:44 GMT, "Juan R. Pollo"
<jrpollo@worldnet.att.net> wrote:

>Hmmm...all this talk about different focusing lengths doesn't make a lot of
>sense. My Sony vidcam focuses just great when in Nightshot mode, I don't
>think it uses any special separate IR focusing apparatus. It's the same
>focus under IR as it is under regular mode.




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