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Invisible wrote:
>>> My point is still that you can't reover what isn't there any more.
>>>
>>
>> Right, but the information is still there, and so it is recoverable.
>
> Heh. Next thing you'll be telling me that you can take a photograph that
> has faded to a plain yellow sheet of paper and somehow "recover" the
> image that used to be on it. :-P
>
I have seen a originally black&white photograph (from somewhere of 20th
century beginning, 1920 oslt), which got just scanned and printed with
color printer - and it actually did got some colors. You could see the
color on persons face as well as she was wearing a blue dress. That was
something that really amazed me.
--
Eero "Aero" Ahonen
http://www.zbxt.net
aer### [at] removethis zbxtnetinvalid
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> All I know is that when I take a dark image and try to make it brighter,
> it comes out hopelessly noisy.
That is probably because you took it with a camera that is already
hopelessly noisy, of course brightening it digitally is just going to
amplify the noise too.
Try playing about with a better photo, (googling "photo" is a start!),
darken it by a factor of 4, then lighten it back to its original. Hardly
any noise visible.
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>> All I know is that when I take a dark image and try to make it
>> brighter, it comes out hopelessly noisy.
>
> That is probably because you took it with a camera that is already
> hopelessly noisy, of course brightening it digitally is just going to
> amplify the noise too.
Well, my camera *is* quite noisy. (More precisely: my camera takes very
dark pictures unless used in insanely bright lighting conditions, or on
a very long exposure.) I quickly learned that there is really no point
attempting to take the beer-like shots it takes and make then viewable.
All you get is signal noise.
But then, isn't film inherantly noisy too? And especially a scanned
image, complete with dust and a rough surface...
> Try playing about with a better photo, (googling "photo" is a start!),
> darken it by a factor of 4, then lighten it back to its original.
> Hardly any noise visible.
Heh, not even DCT artifacts? :-P
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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> But then, isn't film inherantly noisy too?
Not really, not in the way digital image sensors are.
> Heh, not even DCT artifacts? :-P
No, just some banding in the sky due to you effectively losing the last 2
least significant bits of data.
BTW, on a lot of digital cameras now you can save your images in "raw"
format, which is usually 12-bit per channel. That way you can make your
colour/contrast/brightness adjustments and still have the full 8-bit output
possible without any loss of a bit or two.
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>> But then, isn't film inherantly noisy too?
>
> Not really, not in the way digital image sensors are.
Really? I thought film was well-known for being grainy at low light
levels...
>> Heh, not even DCT artifacts? :-P
>
> No, just some banding in the sky due to you effectively losing the last
> 2 least significant bits of data.
I'll have to try it at some point I guess.
> BTW, on a lot of digital cameras now you can save your images in "raw"
> format, which is usually 12-bit per channel.
My camera isn't that expensive.
(Kinda amusing how not denying access to data is a "feature", eh?)
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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> Really? I thought film was well-known for being grainy at low light
> levels...
Yes, but a cheap film camera with ISO100 loaded will display orders of
magnitude less noise compared to even a moderately priced digital camera.
> (Kinda amusing how not denying access to data is a "feature", eh?)
But the data never exists as a whole in the first place in cheap cameras.
The demosaic/compression chip will work on groups of lines at a time and
spurt them out to the file-write buffer. If you tried to simply pass the
raw data through you'd need a much bigger buffer and possibly faster
file-writing electronics (unless you're happy to wait 3x-6x longer for each
write).
Also they would need to include some RAW conversion software with the
camera, which needs writing.
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48884e9a$1@news.povray.org...
>
> But the data never exists as a whole in the first place in cheap cameras.
Actually it does exist, at least in Canon cameras. There's even a hack to
get the RAW data instead of the JPEG.
http://www.oyonale.com/blog/2008/03/hacking-cheap-canon-camera.html
>Also they would need to include some RAW conversion software with the
>camera, which needs writing.
I guess that Canon wrote RAW converters for its SLR models. Also, they
bundle a mountainload of crappy, useless "utilities" with the camera anyway,
so it's not like they're lacking developers. Really, this is a case study of
hardware being deliberately crippled through software for marketing reasons.
G.
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And lo on Thu, 24 Jul 2008 10:21:19 +0100, Invisible <voi### [at] devnull> did
spake, saying:
>>> But then, isn't film inherantly noisy too?
>> Not really, not in the way digital image sensors are.
>
> Really? I thought film was well-known for being grainy at low light
> levels...
Depends on the film, if I take a good photo using ISO200 film at 1/60th of
a second I can can get the same exposure with the less grainy ISO100 by
shooting at 1/30th or even ISO50 for 1/15th. Of course leaving the shutter
open that long may not be what I want so I could switch to ISO400 for
1/120th.
The larger the ISO the larger the grains in the film that react to light
so the grainier it gets. Digital cameras don't have grains though, they
have fixed-sized sensors. So to emulate the sensitivity they just up the
gain and well you know what happens when you do that for tiny sensors.
--
Phil Cook
--
I once tried to be apathetic, but I just couldn't be bothered
http://flipc.blogspot.com
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On Thu, 24 Jul 2008 08:57:40 +0100, Invisible wrote:
>>> My point is still that you can't reover what isn't there any more.
>>>
>>>
>> Right, but the information is still there, and so it is recoverable.
>
> Heh. Next thing you'll be telling me that you can take a photograph that
> has faded to a plain yellow sheet of paper and somehow "recover" the
> image that used to be on it. :-P
Even more impressively, they've been able to colour films that were
originally shot in B&W.
http://en.wikipedia.org/wiki/Film_colorization
Jim
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On Thu, 24 Jul 2008 10:21:19 +0100, Invisible wrote:
>>> But then, isn't film inherantly noisy too?
>>
>> Not really, not in the way digital image sensors are.
>
> Really? I thought film was well-known for being grainy at low light
> levels...
Depends on the film speed and camera characteristics.
>>> Heh, not even DCT artifacts? :-P
>>
>> No, just some banding in the sky due to you effectively losing the last
>> 2 least significant bits of data.
>
> I'll have to try it at some point I guess.
>
>> BTW, on a lot of digital cameras now you can save your images in "raw"
>> format, which is usually 12-bit per channel.
>
> My camera isn't that expensive.
>
> (Kinda amusing how not denying access to data is a "feature", eh?)
You're not the first to make this observation. For some cameras, there's
actually alternate firmware you get get that enables this on low-end
cameras that don't expose RAW data to the end user.
Jim
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