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Nicolas Alvarez wrote:
> In digital cameras, the sensor is receiving light all the time. What does
> "exposure" mean there?
First, it's not. At least in DSLRs. :-)
I suspect in things like the little cameras where you aim thru the LCD,
there's either a non-mechanical shutter, or there's a wire that clears the
sensor, you let it accumulate for some number of miliseconds, and then you
read the sensor.
Second, if you're talking about the ISO setting rather than the exposure,
that's about how much you pre-bias the electrons in the sensor. Basically,
you load up each pixel of the sensor with some electrons, and if light kicks
out an electron, you add one to the intensity of the light there. Adding
more electrons makes it easier to get kicked out.
--
Darren New, San Diego CA, USA (PST)
Linux: Now bringing the quality and usability of
open source desktop apps to your personal electronics.
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Nicolas Alvarez wrote:
> "Fredrik Eriksson" <fe79}--at--{yahoo}--dot--{com> wrote:
>> On Wed, 05 May 2010 20:21:15 +0200, Darren New <dne### [at] san rrcom> wrote:
>>> I just got PSP X2 working again.
>>>
>>> What is with these companies? PSP8 had a perfectly good mechanism for
>>> browsing pictures.
>> Very different companies. Jasc good; Corel bad.
>
> I remember using Jasc Paint Shop Pro 5... Now that had no bloat :)
I can still use 8. The only reason I even bought the new one is that when
working on vacation photos, I tend to open up a bunch from the same scene
(so to speak), do the adjustments, pick which ones I want to keep, then exit
out and tell the paint program to save everything. This fails on PSP8 under
Vista for some reason. Otherwise I was perfectly happy with the program.
--
Darren New, San Diego CA, USA (PST)
Linux: Now bringing the quality and usability of
open source desktop apps to your personal electronics.
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On Wed, 05 May 2010 21:09:57 +0100, Orchid XP v8 wrote:
> Just FYI, the camera doesn't have any option to save anything but JPEG
> format. You can adjust the colour balance (but not very much), and
> exposure and IIRC you can manually set the shutter speed in case you're
> insane.
>
> I still want a new camera. It's a PITA that I can't leave the batteries
> in this one...
What kind of camera have you got? (I suppose I could look at the EXIF
tags.....Fujifilm FinePix S304 it looks like.
Changing the shutter speed, though, that's not insane, that's sensible
when you can tell how it will affect the image.
Jim
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On Wed, 05 May 2010 21:04:31 +0100, Orchid XP v8 wrote:
> Jim Henderson wrote:
>> On Wed, 05 May 2010 12:35:02 +0200, scott wrote:
>>
>>> And typically pros will not let the camera do *any* processing, and
>>> import the raw sensor data to their computer for manual colour,
>>> sharpness and exposure control.
>>
>> Exactly - the adjustments I made were pretty basic with GIMP (similar
>> to the ones you made), but if RAW format images were available, there'd
>> be a lot more room to adjust things like exposure.
>
> ...but once the image has been taken, the exposure has already happened.
> How can you change it after the fact?
I've actually wondered this myself - raw editing software gives you the
option to adjust the exposure; obviously, you can't pull details out
doing this that are completely washed out or completely underexposed, but
it is possible to bring additional detail out by making changes to the
exposure setting (ev) after the photo has been taken.
I've done it, so clearly it's possible, I just don't understand the math
behind it.
Jim
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On 5/5/2010 8:28 AM, Darren New wrote:
> Phil Cook v2 wrote:
>> you can get the latest Paint Shop Pro
>
> Yeah, would be great if it f'ing worked. :-)
>
Snort.. Got X and X2. I use X, I won't touch X2, due to the mangling of
the damn photo browser in it (why the @#$@#$@ does a photo editor need
to scan videos, and not just the first frame, but the entire damn video,
before it can catalog it in the browser, for example?). Oh, yes. And
then there is the lovely fact that they never did have a "good"
integration between the animation editor (which only supported gif
anyway), and PSP, but at least they **had one**, for a while, then
removed that support too. Now you can't even extract, never mind create,
images in one. :p
--
void main () {
If Schrödingers_cat is alive or version > 98 {
if version = "Vista" {
call slow_by_half();
call DRM_everything();
}
call functional_code();
}
else
call crash_windows();
}
<A HREF='http://www.daz3d.com/index.php?refid=16130551'>Get 3D Models,
3D Content, and 3D Software at DAZ3D!</A>
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On 6/05/2010 0:56, Jim Henderson wrote:
> I've done it, so clearly it's possible, I just don't understand the math
> behind it.
there's not really any math involved, the sensor just captures a lot
more than a JPEG-file can store, but a RAW-file stores the unaltered
sensor-data (although in some cases that's not entirely true, but a good
camera will)
cu!
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On Thu, 06 May 2010 07:56:18 +0200, Zeger Knaepen wrote:
> On 6/05/2010 0:56, Jim Henderson wrote:
>> I've done it, so clearly it's possible, I just don't understand the
>> math behind it.
>
> there's not really any math involved, the sensor just captures a lot
> more than a JPEG-file can store, but a RAW-file stores the unaltered
> sensor-data (although in some cases that's not entirely true, but a good
> camera will)
>
> cu!
That makes sense, one of these days I may research it a bit more. :-)
Jim
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> I bet a £7,000 lense is really, really heavy...
Usually you mount the tripod to the *lens* and the camera body hangs off the
back:
http://www.kiroastro.com/images/cannon/8640.jpg
You don't want to be holding that by yourself for very long...
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> ...but once the image has been taken, the exposure has already happened.
> How can you change it after the fact?
Think about how the camera works (in a very simple way). It counts photons
for a certain length of time, applies a scale factor, then gamma correction
and writes the byte values to a JPEG file.
If you start with the JPEG file, you can undo the gamma, scale the data
using some exposure-adjustment factor, then reapply the gamma. You then
have a new file that will look similar to if the camera had used a different
exposure. Obviously the further your scale factor is from 1.0, the more
artifacts will be introduced to the image.
However pros use the raw sensor data from the camera and not a JPEG. This
allows them some margin to adjust the exposure later without adding any
artifacts to the final JPEG image they create. Because of this it is
extremely important not to saturate the sensor (ie 100% white) in any areas,
it is impossible to get back detail in areas that are at 100%. If you
under-expose it you can scale up the brightness without introducing
artifacts (because usually the raw sensor data is higher bit depth than
JPEG).
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> I can still use 8. The only reason I even bought the new one is that when
> working on vacation photos, I tend to open up a bunch from the same scene
> (so to speak), do the adjustments, pick which ones I want to keep, then
> exit out and tell the paint program to save everything. This fails on PSP8
> under Vista for some reason. Otherwise I was perfectly happy with the
> program.
Same story here, except 8 used to crash about 50% of the time when I tried
to crop an image. Got X2 now and TBH I don't remember it trying to index
all the images on my HD (maybe I turned it off somehow, I don't remember).
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