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From: ransley on 6 Aug 2010 08:02
I use the T1i, dpreview gives a higher rating to Jpeg over Raw. I
believe its because Jpegs settings are optimised by Canon very well.
For my jpegs they come out very good. Is Raw recomended because jpeg
looses quality every time you open and close it? Is the difference
noticable by opening and closing it say for example 5 times printed at
5x7 or 8x11? Does the loss on jpeg only occur if you completely close
the photo? What are other benefits of Raw to make it worth the extra
hassle of complete editing. I am happy shooting jpeg, I am working
with 5 shot Photomatrix hdr and have done both Raw and jpeg [I think
Photomatrix loaded the jpeg] I am fully happy with the results but
jpeg is so much easier. I think for special photos made and composed
Raw may be optimal , but its time very consuming.
From: Martin Brown on 6 Aug 2010 08:21
On 06/08/2010 13:02, ransley wrote:
> I use the T1i, dpreview gives a higher rating to Jpeg over Raw. I
> believe its because Jpegs settings are optimised by Canon very well.
> For my jpegs they come out very good. Is Raw recomended because jpeg
> looses quality every time you open and close it? Is the difference
> noticable by opening and closing it say for example 5 times printed at
> 5x7 or 8x11? Does the loss on jpeg only occur if you completely close
> the photo?

This is a FAQ and dealt with in the JPEG FAQ. See Q10 of

http://www.faqs.org/faqs/jpeg-faq/part1/

Opening and closing a JPEG file doesn't alter it at all unless you Save
the file again as a JPEG *and* overwrite the original file. If you treat
your original JPEGs are readonly then there is no problem at all.

The level of degradation with successive saves is not huge provided that
you work at a fixed quality level. But it is ever present. This means
that in a workflow you want to keep work in progress saved in a lossless
format (typically one native to the application you are using that will
preserve layers and masks).

> What are other benefits of Raw to make it worth the extra
> hassle of complete editing. I am happy shooting jpeg, I am working
> with 5 shot Photomatrix hdr and have done both Raw and jpeg [I think
> Photomatrix loaded the jpeg] I am fully happy with the results but
> jpeg is so much easier. I think for special photos made and composed
> Raw may be optimal , but its time very consuming.

Raw gives you more freedom afterwards to rescue dynamic range and adjust
colour balance. This can be important if you know that the image will
contain black velvet in shadow and a white bridal dress in sunlight. And
there is little chance of retaning it if the exposure is even slightly
off. It is hard for the in camera auto adjust and save as JPEG to get
both exactly right simultaneously and a risk if you let it.

Most of the time in camera JPEG encoding is fine - ie good enough.
(some makers high quality JPEG encoding is better than others)

Regards,
Martin Brown

From: ransley on 6 Aug 2010 08:27
On Aug 6, 7:21 am, Martin Brown <|||newspam...(a)nezumi.demon.co.uk>
wrote:
> On 06/08/2010 13:02, ransley wrote:
>
> > I use the T1i, dpreview gives a higher rating to Jpeg over Raw. I
> > believe its because Jpegs settings are optimised by Canon very well.
> > For my jpegs they come out very good. Is Raw recomended  because jpeg
> > looses quality every time you open and close it? Is the difference
> > noticable by opening and closing it say for example 5 times printed at
> > 5x7 or 8x11? Does the loss on jpeg only occur if you completely close
> > the photo?
>
> This is a FAQ and dealt with in the JPEG FAQ. See Q10 of
>
> http://www.faqs.org/faqs/jpeg-faq/part1/
>
> Opening and closing a JPEG file doesn't alter it at all unless you Save
> the file again as a JPEG *and* overwrite the original file. If you treat
> your original JPEGs are readonly then there is no problem at all.
>
> The level of degradation with successive saves is not huge provided that
> you work at a fixed quality level. But it is ever present. This means
> that in a workflow you want to keep work in progress saved in a lossless
> format (typically one native to the application you are using that will
> preserve layers and masks).
>
> > What are other benefits of Raw to make it worth the extra
> > hassle of complete editing. I am happy shooting jpeg, I am working
> > with 5 shot Photomatrix hdr and have done both Raw and jpeg [I think
> > Photomatrix loaded the jpeg]  I am fully happy with the results but
> > jpeg is so much easier. I think for special photos made and composed
> > Raw may be optimal , but its time very consuming.
>
> Raw gives you more freedom afterwards to rescue dynamic range and adjust
> colour balance. This can be important if you know that the image will
> contain black velvet in shadow and a white bridal dress in sunlight. And
> there is little chance of retaning it if the exposure is even slightly
> off. It is hard for the in camera auto adjust and save as JPEG to get
> both exactly right simultaneously and a risk if you let it.
>
> Most of the time in camera JPEG encoding is fine - ie good enough.
> (some makers high quality JPEG encoding is better than others)
>
> Regards,
> Martin Brown

I use Adobe and just save as it prompts me, is that the proper way? I
wonder since Canons jpeg is optimised if I am not going backwards with
Raw and missing what they have put major effort into perfecting. How
is dynamic range improved? Color balance controls in editing are the
same, how is Raw better?
From: Ofnuts on 6 Aug 2010 08:38
On 06/08/2010 14:02, ransley wrote:
> I use the T1i, dpreview gives a higher rating to Jpeg over Raw. I
> believe its because Jpegs settings are optimised by Canon very well.
> For my jpegs they come out very good. Is Raw recomended because jpeg
> looses quality every time you open and close it?

No... RAW is recommended because JPEG can only code 8 bits per "channel"
(*). In a camera with significantly more than 8 bits per channel (**)
going to JPEG requires to discard some information, which cannot be
recoverdd later. RAW allows these choices to be made later (and pick up
among them the best choice for a specific photo).

> Is the difference
> noticable by opening and closing it say for example 5 times printed at
> 5x7 or 8x11?

JPEG loss only happen when you save the file. If you only open the file
for printing nothing happens to the orginal file.

> Does the loss on jpeg only occur if you completely close
> the photo?

"Close", no. "Save", yes, to some extent. This is why applications that
re-save the picture behind your back should be taken out and shot (this
is what happens with Windows Picture and Fax viewer when you rotate the
photo). But for the "quality" setting of most photos, this is very minor
and you won't notice anything un,les you edit and save the image ober a
dozen times. But you can completely avoid this by saving the
intermediate versions in a lossless format (TIFF, for instance) or the
native format of you picture editor (this will save layers, selections
and whatever) and only export to JPEG the final result.

> What are other benefits of Raw to make it worth the extra
> hassle of complete editing.

Showing off :-)

> I am happy shooting jpeg, I am working
> with 5 shot Photomatrix hdr and have done both Raw and jpeg [I think
> Photomatrix loaded the jpeg] I am fully happy with the results but
> jpeg is so much easier. I think for special photos made and composed
> Raw may be optimal , but its time very consuming.

Agreed. I usually shoot JPEG too. I use RAW only when I know I'm going
to do some extensive work on the picture (difficule shooting conditions,
etc...).

(*) without getting into goory details, JPEG actually encodes luminance
and chrominance separately, and puts less emphasis on chrominance bcause
we are less sensitive to it, so it doesn't really encodes the primmary
colors...

(**) moderns SLRs achieve more than 10 bits most of the time

--
Bertrand
From: David J Taylor on 6 Aug 2010 09:02
"Ofnuts" <o.f.n.u.t.s(a)la.poste.net> wrote in message
news:4c5c0239$0$28746$426a74cc(a)news.free.fr...
[]
> No... RAW is recommended because JPEG can only code 8 bits per "channel"
> (*). In a camera with significantly more than 8 bits per channel (**)
> going to JPEG requires to discard some information, which cannot be
> recoverdd later. RAW allows these choices to be made later (and pick up
> among them the best choice for a specific photo).
[]
> (*) without getting into goory details, JPEG actually encodes luminance
> and chrominance separately, and puts less emphasis on chrominance bcause
> we are less sensitive to it, so it doesn't really encodes the primmary
> colors...
>
> (**) moderns SLRs achieve more than 10 bits most of the time
>
> --
> Bertrand

Bertrand,

Don't forget that the brightness range coding in RAW is linear, but the
coding in JPEG is "gamma-corrected", meaning that JPEG can actually handle
a /greater/ dynamic range than RAW, but at a lower precision for a given
brightness level.

Where JPEG codes colour differently brightness is in the spatial
resolution. The eye cannot perceive colours as finely (spatially) as it
can greyscale differences, so in JPEG the colour component may only be
encoded at half the resolution (for example, you could look at it as 2 x
2.5MP colour difference images with a 10MP greyscale image). It can
encode primary colours as well as RAW - but at a lower resolution.

Appreciate you are trying to simplify, though.

Cheers,
David

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