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What's wrong with my digital camera?

 
 
John H.
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      07-08-2003
On Tue, 08 Jul 2003 07:19:37 +1000, Lionel <(E-Mail Removed)> wrote:

> On Mon, 07 Jul 2003 17:09:56 GMT, in
> <(E-Mail Removed)>, John H. <(E-Mail Removed)>
> said:
>
> >On second thought I'm not sure any digital camera can take a good picture
> >of a TV that has a shadow mask or aperture grill.

>
> Au contraire!


> I just made a quick demo for you:
> http://lo.ve.ly/test/
> The first image is a drastically reduced EOS 10D shot of one of the
> screens (at 1280x1024 resolution) on my workstation (a CRT - my main
> screen is an LCD). The second image is a 1:1 crop of the full resolution
> image. Yes, the moire from the shadow mask is very visible, but I wanted
> to show a worst case example. The image would've been much smoother if
> I'd zoomed out somewhat.


On third thought I think I was a *little* off with my 2nd thought.
Can't beat actually trying it and seeing the results.

Maybe this makes more sense:

An 'even match' between camera and display would be 4 camera "pixels" (2G,
1R, 1B) for each display pixel (1R, 1G, 1B sub-pixel). For a 640x480 (TV)
display that would be a 1280x960 camera (about 1.3 megapixels). For a
1280x1024 display it would be a 2560x2048 camera (5.2 megapixels).

But anything at or near an even match would probably cause the worst
artifacts because of the complex way the camera's pixel grid lines up with
the display's pixel grid (for example many red camera pixels could be
looking at green or blue display pixels). Much better would be a 2x or
better pixel advantage (with 4 camera pixels counted as 1) for either the
camera OR display.

Using for example a 1 MP camera to photograph a 1280x1024 display should
produce an image (nearly) as good as the CAMERA is capable of because each
camera pixel would see multiple display pixels.

Using a 6.3 MP camera to photograph a 640x480 TV screen should produce an
image (nearly) as good as the DISPLAY is capable of because each display
pixel would be seen by multiple 4-pixel groups in the camera. That's
over-sampling. A film camera would have the best over-sampling of all.


 
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Jack White
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      07-08-2003
Lucas Tam <(E-Mail Removed)> wrote in message news:<Xns93B2602EC46Dnntprogerscom@140.99.99.130>. ..
> http://www.velocityreviews.com/forums/(E-Mail Removed) (Jack White) wrote in
> news:(E-Mail Removed) om:
>
> > Actually I did take all the pics with the digital camera that were
> > posted from more than 4 feet away, well over 4 feet away in some
> > cases.

>
> In that case, did you use the digital zoom?


I didn't use the digital zoom on any of the pics posted in this
thread, the only pic I used a zoom on in this thread was the capture
from the camcorder and that was with an optical zoom.
 
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Dave Martindale
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      07-08-2003
(E-Mail Removed) (Jack White) writes:

>I didn't use the digital zoom on any of the pics posted in this
>thread, the only pic I used a zoom on in this thread was the capture
>from the camcorder and that was with an optical zoom.


However, it seems that this is a fixed-focus camera. Fixed-focus
cameras have small-aperture lenses that are focused at some compromise
distance that's designed to make everything from some near distance out to
infinity "acceptably sharp". But almost nothing in the photos will
actually be in good focus, so there's little incentive for the lens to
provide really sharp images even for objects that *are* in the plane of
best focus. So the lens in these cameras is basically junk.

You should get a camera with a focusing lens, at the very least. You
should be able to get a 2-3 megapixel camera with non-zoom focusing lens
and close focusing ability for about $200.

However, I expect you'll still have some problems. You're shooting a
very difficult subject. A B&W CRT displaying a resolution test pattern
has fine black & white lines on it, and you're likely to see some moire
effects unless the camera has *several times as much* resolution as the
test pattern, to fully resolve the pattern. Colour CRTs are worse yet,
since there's fine detail in the test pattern *and* fine detail in the
shadow mask-produced pattern of RGB phosphors on the screen. Resolving
all that without artifacts across the whole screen may take higher
resolution than any of the consumer cameras available.

Dave
 
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Jack White
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      07-09-2003
(E-Mail Removed) (Dave Martindale) wrote in message news:<befb27$ggh$(E-Mail Removed)>...
> (E-Mail Removed) (Jack White) writes:
>
> >I didn't use the digital zoom on any of the pics posted in this
> >thread, the only pic I used a zoom on in this thread was the capture
> >from the camcorder and that was with an optical zoom.

>
> However, it seems that this is a fixed-focus camera. Fixed-focus
> cameras have small-aperture lenses that are focused at some compromise
> distance that's designed to make everything from some near distance out to
> infinity "acceptably sharp". But almost nothing in the photos will
> actually be in good focus, so there's little incentive for the lens to
> provide really sharp images even for objects that *are* in the plane of
> best focus. So the lens in these cameras is basically junk.
>
> You should get a camera with a focusing lens, at the very least. You
> should be able to get a 2-3 megapixel camera with non-zoom focusing lens
> and close focusing ability for about $200.
>
> However, I expect you'll still have some problems. You're shooting a
> very difficult subject. A B&W CRT displaying a resolution test pattern
> has fine black & white lines on it, and you're likely to see some moire
> effects unless the camera has *several times as much* resolution as the
> test pattern, to fully resolve the pattern. Colour CRTs are worse yet,
> since there's fine detail in the test pattern *and* fine detail in the
> shadow mask-produced pattern of RGB phosphors on the screen. Resolving
> all that without artifacts across the whole screen may take higher
> resolution than any of the consumer cameras available.
>
> Dave


Actually they're not B&W tubes, it's just the test pattern that's B%W.
It's a good thing that they look black and white though, because that
means that there's no moire pattern present when either S-video or
component connections are used.
I didn't think they even made black and white tvs anymore, although I
did see an add for a new black and white tv a few years ago for like
$12.
 
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Jack White
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      07-10-2003
Larry Caldwell <(E-Mail Removed)> wrote in message news:<(E-Mail Removed) nk.net>...
> (E-Mail Removed) (Jay) writes:
>
> > At any rate, try turning up contrast
> > on the tv and see if that helps any. If you have a need to photograph higher
> > resolution stuff off of some kind of monitor, you may want to look into
> > doing so on a computer monitor (the higher the resolution and the bigger the
> > monitor, the better).

>
> Or just using a video capture card in a computer. I have an ATI Rage Pro
> (sort of obsolete now) that has both composite and S-video inputs. It
> will record whatever detail is in the signal to record. No camera
> required.


A capture card is not a replacement for a camera.
A capture card would be TOTALLY useless for use in this situation at
the link below for example.
A camera is used to show the difference between these 2 HDTVs which a
capture card would never show without a camera or camcorder.
http://www.keohi.com/keohihdtv/brand...jul02_pg1.html
 
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Lionel
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      07-10-2003
On 10 Jul 2003 11:45:39 -0700, in
<(E-Mail Removed) >, (E-Mail Removed)
(Jack White) said:

>A camera is used to show the difference between these 2 HDTVs which a
>capture card would never show without a camera or camcorder.


Ah. In that case, it sounds like you're going to need to buy or hire a
reasonably good camera, & learn how to take clear photos of a screen. On
the bright side, I notice that on that page they're only showing a small
area of the screen. If you can live with doing the same, you can
probably get by with a cheaper camera.
Take a look at this: http://lo.ve.ly/test/CRW_7465.jpg
That's a reduced size image, zoomed in on about a 1/4 of the screen with
a Canon Powershot S30. If that's high enough quality, you should be able
to find a Powershot S or G digital at a reasonable price.

--
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. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
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Jack White
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      07-11-2003
Lionel <(E-Mail Removed)> wrote in message news:<bekdpu$q2f$(E-Mail Removed)>...
> On 10 Jul 2003 11:45:39 -0700, in
> <(E-Mail Removed) >, (E-Mail Removed)
> (Jack White) said:
>
> >A camera is used to show the difference between these 2 HDTVs which a
> >capture card would never show without a camera or camcorder.

>
> Ah. In that case, it sounds like you're going to need to buy or hire a
> reasonably good camera, & learn how to take clear photos of a screen. On
> the bright side, I notice that on that page they're only showing a small
> area of the screen. If you can live with doing the same, you can
> probably get by with a cheaper camera.
> Take a look at this: http://lo.ve.ly/test/CRW_7465.jpg
> That's a reduced size image, zoomed in on about a 1/4 of the screen with
> a Canon Powershot S30. If that's high enough quality, you should be able
> to find a Powershot S or G digital at a reasonable price.



Thanks for the info, my old camera was so bad that it couldn't even do
what you just suggested.
It was an HP Photosmart 120 and it had absolutely NO macro capability
whatsoever. It's minimum focusing distance was about 4 feet.
My new camera has more than twice the resolution and a nice macro mode
so I won't have that same problem again.
I also like the backlit TFT active matrix lcd screen on my new camera,
it's way better than my old camera's screen, it reminds me of the
difference between the Sega Game Gear's screen and the Turbo Express'
screen(although the Game Gear's screen was never as crappy as the
Photosmart 120's).
These young whippersnappers today probably don't even know what a
Turbo Express or a Gamegear is and as far as they're concerned if it
ain't a Gameboy Advance SP, then it sucks.
 
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John MCS
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      07-11-2003
Hi Jack,

you can use the free tools at go-here.net to create short links.

regards,
-
John

> BTW, the links may break up because of the long url so if you want to
> see them, you may have to copy and paste the 2 broken pieces of the
> link together in your url bar and then hit enter to see the pic.

 
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Kulvinder Singh Matharu
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      07-12-2003
On 11 Jul 2003 12:13:11 -0700, (E-Mail Removed) (John MCS)
wrote:

>you can use the free tools at go-here.net to create short links.


Or even use "<" and ">" around the url...most newsreaders support it.
The advantages are that you can see the URL and not worry
(security/privacy) where you might get sent to.

--
Kulvinder Singh Matharu
E-mail : ksmatharu # ieee . org [without the spaces and where #=@]
Website: http://www.metalvortex.com/

"It ain't Coca Cola, it's rice" - The Clash
 
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