On Thu, 06 May 2010 18:00:07 +0200, Fredrik Eriksson wrote:

> Also, the raw data has a higher bit-depth than a JPEG, typically 12 or
> 14 versus lossy compressed 8. This gives you more leeway for making
> adjustments without getting posterization.

That makes sense to me - thanks!

Jim

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On Thu, 06 May 2010 08:16:58 -0500, Mike Raiford wrote:

> On 5/5/2010 5:35 AM, scott wrote:
> Wedding photogs are another group of pro's that some will do jpeg rather
> than raw, simply because they want a ton of images.

That's not strictly true - I know a couple guys who do wedding photos and 
do their captures in raw format.  They just bring several large memory 
cards with them so they can capture lots of images.

Though I suppose it depends on what they're photographing at the wedding; 
if it's the lucky couple, then raw is probably  more commonly used than, 
say, photos of guests at the reception.

> Though most that don't have high volumes of images prefer raw. I prefer
> raw simply because I'm a control freak.

Same here.

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On Thu, 06 May 2010 09:09:05 +0100, Invisible wrote:

> Jim Henderson wrote:
>> 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.
> 
> Yeah, that sounds right.
> 
>> Changing the shutter speed, though, that's not insane, that's sensible
>> when you can tell how it will affect the image.
> 
> No, I mean... When you adjust the exposure, you turn it up or down
> *relative* to what the camera thinks it should be. But with the shutter
> speed, you can have it automatic, or completely manual (i.e., you have
> to somehow *guess* what the number should be without any assistence).
> It's not relative to what the camera chose.

Well, yeah, but "somehow guess" is something that comes with taking some 
trial photos (which I tend to do) until you get a feel for what the light 
levels should be like for a particular setting.

My camera (a Canon PowerShot S50) lets me see what the exposure will be 
without taking a picture - so I can adjust it before even shooting.   I 
typically set the value to -1/3 because I can use raw tools to lighten it 
up (that idea of not overexposing the image that someone else mentioned).

Then when I process it, I typically will increase the colour saturation 
to some degree, as well as adjusting the white balance (my camera's auto-
balance isn't that good; I usually manually adjust the white balance in 
the camera so it's "close" and then do a final adjustment on the image 
when I'm reviewing the image).

Jim

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Sabrina Kilian wrote:
> Now, they mention
> YouTube, and I suppose since currently YouTube does both encode from any
> video type to h.264 and then display through a decoder that they are
> distrubting, their flash player, that they might be liable to pay a
> license as well.

Youtube doesn't distribute a video decoder. Flash has it built-in, so it's 
Adobe who is distributing the decoder.

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"Fredrik Eriksson" <fe79}--at--{yahoo}--dot--{com> wrote:
> On Thu, 06 May 2010 00:24:07 +0200, Darren New <dne### [at] sanrrcom> wrote:
>>
>> 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.
> 
> No, there is no pre-bias; that is not how the sensors work. The ISO
> setting only affects amplification of the analogue sensor output.

There you go. So if you have the raw sensor output, you can change the ISO 
setting after the fact?

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Fredrik Eriksson wrote:
> On Thu, 06 May 2010 00:56:35 +0200, Jim Henderson <nos### [at] nospamcom>
> wrote:
>>
>> 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.
> 
> When the camera creates a JPEG file, part of the raw data is discarded and
> the rest is then adjusted to fit in the 0-255 range. The camera picks a
> black-point somewhere near the low end of the (raw) range, and all values
> below that are made black (i.e. 0) in the JPEG. Similarly, a white-point
> is selected, and all values above that are made white (i.e. 255). When you
> edit a RAW file, you have access to the parts that would otherwise have
> been cut off. If the exposure was somewhat less than perfect, there can be
> useful data in those parts.

In other words, the RAW format gets you High Dynamic Range.

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Invisible wrote:
> scott wrote:
>> 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).
> 
> ...in other words, you're not changing the exposure (i.e., the number of
> seconds that the shutter opens) at all, you're simulating it.

In consumer cameras that show the image on the LCD screen all the time, 
there is no "shutter opening for N milliseconds". The sensor is getting 
light all the time.

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On Thu, 06 May 2010 23:09:18 +0200, Nicolas Alvarez  
<nic### [at] gmailcom> wrote:
> "Fredrik Eriksson" <fe79}--at--{yahoo}--dot--{com> wrote:
>> No, there is no pre-bias; that is not how the sensors work. The ISO
>> setting only affects amplification of the analogue sensor output.
>
> There you go. So if you have the raw sensor output, you can change the  
> ISO setting after the fact?

Not quite. The amplification controlled by the ISO setting occurs before  
A/D conversion. By applying amplification to the raw data (i.e. after A/D  
conversion), you also amplify any noise introduced by the A/D process. The  
result is similar, but slightly worse.



-- 
FE

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On Thu, 06 May 2010 23:10:25 +0200, Nicolas Alvarez  
<nic### [at] gmailcom> wrote:
>
> In other words, the RAW format gets you High Dynamic Range.

Sort of. Higher than what you get from a JPEG anyway. Not what is usually  
referred to as HDR though.



-- 
FE

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>> ...in other words, you're not changing the exposure (i.e., the number of
>> seconds that the shutter opens) at all, you're simulating it.
> 
> In consumer cameras that show the image on the LCD screen all the time, 
> there is no "shutter opening for N milliseconds". The sensor is getting 
> light all the time.

Sure. But when you take an image, it integrates the sensor output for 
the duration of X seconds. You can't unintegrate it, or reintegrate over 
a different time period, for example. (Unless you got it to shoot a few 
trillion RAW images and save them all...)

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