> Ah but was the Artworks-derived Xara for the PC really comparable to 
> Artworks on the Acorn or is it just another Blender to Paint comparison?

Well the GUI was pretty much identical, and I assume the backend rendering 
code was following similar algorithms, maybe even sharing a lot of the 
code - I don't know.

Post a reply to this message

>> 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

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

Post a reply to this message

> My point is still that you can't reover what isn't there any more.

Of course, but there is still plenty of information there in that photo, 
even in the blue channel.  Attached is the histogram plot for the colour 
channels (R top, B bottom), looks like plenty of mid-level blue still there 
to me, in fact all pixels have a fair amount of blue in them.

If I just shift the blues a bit brighter, and the reds a bit darker, I get a 
pretty good output, but of course as Sabrina said you can do much more funky 
transforms to get near perfect looking results.  If you know how the colours 
shift during ageing, you simply tell the software one colour that you know 
should be white, and it will fix the rest.  Actually Paint Shop Pro has a 
"fade correction" option, and it works very well on this photo.

Post a reply to this message

Attachments:
Download 'image4.png' (15 KB)

Preview of image 'image4.png'

scott wrote:
>> My point is still that you can't reover what isn't there any more.
> 
> Of course, but there is still plenty of information there in that photo, 
> even in the blue channel.  Attached is the histogram plot for the colour 
> channels (R top, B bottom), looks like plenty of mid-level blue still 
> there to me, in fact all pixels have a fair amount of blue in them.
> 
> If I just shift the blues a bit brighter, and the reds a bit darker, I 
> get a pretty good output.

All I know is that when I take a dark image and try to make it brighter, 
it comes out hopelessly noisy.

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

Post a reply to this message

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] removethiszbxtnetinvalid

Post a reply to this message

> 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.

Post a reply to this message

>> 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*

Post a reply to this message

> 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.

Post a reply to this message

>> 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*

Post a reply to this message

> 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.

Post a reply to this message