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pinhole question

 
 
G.T.
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      06-13-2004
I have a Digital Rebel and am basically just using foil with a pinhole
at the moment. I took a photo of a black & white album cover with a 30
second exposure and when I view it there are quite a few red and blue
pixels and a couple of green pixels. I don't see this when I just shoot
the album cover without the pinhole. What could be causing this? Is it
just noise because of the long exposure and 800 iso?

Greg
--
Destroy your safe and happy lives
Before it is too late
The battles we fought were long and hard
Just not to be consumed by rock'n'roll
 
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Joseph Meehan
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      06-13-2004
G.T. wrote:
> I have a Digital Rebel and am basically just using foil with a pinhole
> at the moment. I took a photo of a black & white album cover with a
> 30 second exposure and when I view it there are quite a few red and
> blue pixels and a couple of green pixels. I don't see this when I
> just shoot the album cover without the pinhole. What could be
> causing this? Is it just noise because of the long exposure and 800
> iso?
>
> Greg


Thirty seconds is a very long time for a digital exposure. In film
photography you often get color shift and reduced sensitivity when you start
using such long exposures. In digital you get "noise." What you describe
sounds like noise. Some cameras have more of a problem than others, but I
am guessing yours is just that due to the long exposure.
--
Joseph E. Meehan

26 + 6 = 1 It's Irish Math



 
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G.T.
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      06-13-2004
Joseph Meehan wrote:

> G.T. wrote:
>
>>I have a Digital Rebel and am basically just using foil with a pinhole
>>at the moment. I took a photo of a black & white album cover with a
>>30 second exposure and when I view it there are quite a few red and
>>blue pixels and a couple of green pixels. I don't see this when I
>>just shoot the album cover without the pinhole. What could be
>>causing this? Is it just noise because of the long exposure and 800
>>iso?
>>
>>Greg

>
>
> Thirty seconds is a very long time for a digital exposure. In film
> photography you often get color shift and reduced sensitivity when you start
> using such long exposures. In digital you get "noise." What you describe
> sounds like noise. Some cameras have more of a problem than others, but I
> am guessing yours is just that due to the long exposure.


Yeah, that's what I figured. I'll try some out where I don't need such
a long exposure.

Greg

--
Destroy your safe and happy lives
Before it is too late
The battles we fought were long and hard
Just not to be consumed by rock'n'roll
 
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Alan D-W
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      06-13-2004

"G.T." <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> I have a Digital Rebel and am basically just using foil with a pinhole
> at the moment. I took a photo of a black & white album cover with a 30
> second exposure and when I view it there are quite a few red and blue
> pixels and a couple of green pixels. I don't see this when I just shoot
> the album cover without the pinhole. What could be causing this? Is it
> just noise because of the long exposure and 800 iso?
>


You expect perfection from turkey foil?


 
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Zol.
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      06-13-2004
It`s probably the ISO but difficult to say exactly - I`d be interesed in seeing your results
from a digital pinhole camera.

regards, Zol.

"G.T." <(E-Mail Removed)> wrote in message news:(E-Mail Removed)...
> I have a Digital Rebel and am basically just using foil with a pinhole
> at the moment. I took a photo of a black & white album cover with a 30
> second exposure and when I view it there are quite a few red and blue
> pixels and a couple of green pixels. I don't see this when I just shoot
> the album cover without the pinhole. What could be causing this? Is it
> just noise because of the long exposure and 800 iso?
>
> Greg
> --
> Destroy your safe and happy lives
> Before it is too late
> The battles we fought were long and hard
> Just not to be consumed by rock'n'roll



 
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G.T.
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      06-13-2004
Alan D-W wrote:

> "G.T." <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed)...
>
>>I have a Digital Rebel and am basically just using foil with a pinhole
>>at the moment. I took a photo of a black & white album cover with a 30
>>second exposure and when I view it there are quite a few red and blue
>>pixels and a couple of green pixels. I don't see this when I just shoot
>>the album cover without the pinhole. What could be causing this? Is it
>>just noise because of the long exposure and 800 iso?
>>

>
>
> You expect perfection from turkey foil?
>
>


Actually I didn't expect anything. And it hardly matters what the
material is as long it's opaque and the hole is smooth.

Greg
--
Destroy your safe and happy lives
Before it is too late
The battles we fought were long and hard
Just not to be consumed by rock'n'roll
 
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Gener
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      06-14-2004
I think anything smaller than 4x5 cut film will be too grainy, and
impossible with digital. I made a 35mm panoramic pinhole camera
and the results were very disappointing. Look for "Pinhole" at
http://www.photoprojects.net/index9.html
and the sample image upper right.
Gene



"G.T." wrote:

> I have a Digital Rebel and am basically just using foil with a pinhole
> at the moment. I took a photo of a black & white album cover with a 30
> second exposure and when I view it there are quite a few red and blue
> pixels and a couple of green pixels. I don't see this when I just shoot
> the album cover without the pinhole. What could be causing this? Is it
> just noise because of the long exposure and 800 iso?
>
> Greg
> --
> Destroy your safe and happy lives
> Before it is too late
> The battles we fought were long and hard
> Just not to be consumed by rock'n'roll

 
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Chris Brown
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      06-14-2004
In article <(E-Mail Removed)>,
G.T. <(E-Mail Removed)> wrote:

>What could be causing this? Is it
>just noise because of the long exposure and 800 iso?


Probably. Long exposures and high ISO don't mix. I do all my long exposure
stuff at 100 ISO, which is much cleaner.
 
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Martin Brown
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      06-14-2004
In message <(E-Mail Removed)>, G.T.
<(E-Mail Removed)> writes
>I have a Digital Rebel and am basically just using foil with a pinhole
>at the moment. I took a photo of a black & white album cover with a 30
>second exposure and when I view it there are quite a few red and blue
>pixels and a couple of green pixels. I don't see this when I just
>shoot the album cover without the pinhole. What could be causing this?
>Is it just noise because of the long exposure and 800 iso?


Yes. Traditionally called hot pixels with higher than average leakage
current. They become a nuisance on long time exposures.

You can hide most of their effect by taking a matching exposure of the
inside of your lens cap under identical conditions and then doing a dark
frame subtraction in the post processing to eliminate instrumental
artefacts. Some CCDs also have a warm corner where the readout
electronics sit which also shows up brighter on long exposures.

Regards,
--
Martin Brown
 
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