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I'm trying to assess the image quality of several cameras and have been
downloading iso100 full-size sample images from dpreview. Are these
images examples of the highest detail that I would receive from the
cameras or would RAW images show much more detail? So far, I haven't
been impressed with the digital SLRs in my price range but was wondering
if their RAW images would provide higher detail.

Thanks.

I saw some tests of RAW vs. JPG under difficult high contrast conditions and
where the JPGs had blown out the highlights there was still detail in the
RAW files. A wider dynamic range basically.

Tim wrote:
> I'm trying to assess the image quality of several cameras and have been
> downloading iso100 full-size sample images from dpreview. Are these
> images examples of the highest detail that I would receive from the
> cameras or would RAW images show much more detail? So far, I haven't
> been impressed with the digital SLRs in my price range but was wondering
> if their RAW images would provide higher detail.

Raw images preserve more information in the highlights and shadows.
Bringing up the shadows in a raw image will frequently show details
that are missing in a JPEG.

However, a raw image will not be sharper or show details that simply
are not there. If a line looks fuzzy in JPEG, it is because it is fuzzy
in the raw image. If you are not impressed, it is because the images
you are looking at are tiny areas of the whole image blown up large. In
real life, you probably not get anywhere near the detail that the
DPReview pictures have. Still, it is probably more detail than you
would get in 35mm film, which does not have the dynamic range or number
of colors that digital has. Whether 35mm film is sharper or less
grainy, of course, depends on the film and the ISO of the digital
image. In general, digital now produces more detailed pictures than
film, but film still has more 'shoulder,' that is, it continues to
preserve more details in blown highlights and deep shadows than even a
raw image.

That's right. RAW does give more detail in the highlights as that is where
most of the information is stored (ie 2048 levels out of 4096 are in the
brightest section (first stop) of the dynamic range.
Also that is why you should expose to the right in the histogram when
shooting RAW.
Best to read this article for better explanation http://tinyurl.com/2hebo
I've seen some amazing detail come out of what appeared to be an overexposed
RAW image.





"SteveB" <sbrads@nildramDOTcoDOTuk> wrote in message
news:...
>I saw some tests of RAW vs. JPG under difficult high contrast conditions
>and where the JPGs had blown out the highlights there was still detail in
>the RAW files. A wider dynamic range basically.
>

Tim <> wrote:
: I'm trying to assess the image quality of several cameras and have been
: downloading iso100 full-size sample images from dpreview. Are these
: images examples of the highest detail that I would receive from the
: cameras or would RAW images show much more detail? So far, I haven't
: been impressed with the digital SLRs in my price range but was wondering
: if their RAW images would provide higher detail.

: Thanks.

You have already heard about the level of information that is in the
extreems of lighting so I won't go into that. The amount of detail is
largely dependent on the size of the light sensitive elements with
relation to the whole. If an image is made up of only four light sensitive
elements, the smallest discrete element that can be resolved will be 1/4
of the whole. If the same image is made up of 1 million sensors, the
smallest element resolvable will be 1 millionth of the whole. So a 1 mp
raw image will have the same minimum resolvable element as a 1 mp jpg
image. Of course the subsequent jpg compression and or any changes in
color pallet would impact this resolution. If the color pallet of the Raw
file from the camera is 16 bit per pixel and the jpg conversion compresses
this to 8 bit per pixel, the subtle variations within an image may be lost
or muddied.

But to compare this to film the pixel resolution of a digital camera can
directly relate to film grain. But with film the grain size was a function
of the film speed (to an extent). With digital this isn't a direct
relationship. A 3 mp sensor and an 8 mp sensor can both give the same ISO.
Even tho the 8 mp sensor will capture much finer detail (in relation to
the whole image) than the 3.

Randy

==========
Randy Berbaum
Champaign, IL

Tim wrote:
> I'm trying to assess the image quality of several cameras and have been
> downloading iso100 full-size sample images from dpreview. Are these
> images examples of the highest detail that I would receive from the
> cameras or would RAW images show much more detail? So far, I haven't
> been impressed with the digital SLRs in my price range but was wondering
> if their RAW images would provide higher detail.

I never had or used a dSLR but read a lot about it .

dSLR have a large CCD chip (say, 20 mm x 30 mm) as compared to a
point-n-shoot (at most, 6 mm x 8 mm). This means the dSLR can have a
small deapth of field (DOF). This means that you can have
"traditionally-looking" (as in 35 mm film) portraits with blur of
background. (No background blur for small-sized CCD sensors.)

The other advantage of having a large CCD chip is that pixels can be
large. This means they provide less of noise. If you shoot your picture
in the conditions which are less than perfect (e.g. dimly-lit room),
then you will have less noise and thus more of "detail". If you shoot a
small-sensor camera with the same high speed in a dim room, you will
get lots of noise. When the camera process theimage and doe noise
reduction, the details go.

A speedier optics of dSLR provides more light to CCD chip. Thus, less
noise (=more detail) when shooting at high ISO.

If you process your RAW image into a JPEG by your computer (and the
processing is not done by an on-board camera processor), you have more
powerful software at your fingertips. With a certain degree of skill,
you are able to get more detail.

Now, I presume you would like to hear from the people who actually used
dSLR about what levels of detail and noise they see in their real
world-shot pictures, as compared to those made with smaller-sensor
cameras.

\/

Tim wrote:

>I'm trying to assess the image quality of several cameras and have been
>downloading iso100 full-size sample images from dpreview. Are these
>images examples of the highest detail that I would receive from the
>cameras or would RAW images show much more detail?

The samples will give you a guideline and close approximation of what
you can expect, but not always completely accurate.

For instance, my lowly Canon Rebel XT seems to be better at doing
"in-camera" conversion to JPG files than my friend's Nikon D70s.
However, the Nikon seems to be capable of finer detail and resolution on
a pixel to pixel scale (due to pixel size?). The Canon has a sensor with
more pixels, so overall it captures more detail.

If we take identical shots with the Nikon though, and convert the D70s
RAW file in software, it contains substantially more detail and
resolution than the "in-camera" JPG.

The Nikon D70s seems to losing detail in the JPG conversion in an effort
to keep file sizes lower. For 4x6 snapshots, that works great and you
wouldn't notice the difference compared to Nikon or Canon photos of
similar shots. But if you intend to enlarge or show the images on a
computer, the D70s RAW images have a LOT more fine detail and it's the
preferred storage format.

In the end, if you shoot RAW with any camera, you should have the best
it can offer.

> So far, I haven't
>been impressed with the digital SLRs in my price range but was wondering
>if their RAW images would provide higher detail.

You will always get higher detail, highlights, resolution, etc. with a
RAW file because it hasn't been converted to JPG, which is a lossy file
format.

"My View" <no spam > wrote:

> That's right. RAW does give more detail in the highlights as that is
> where most of the information is stored (ie 2048 levels out of 4096
> are in the brightest section (first stop) of the dynamic range.
> Also that is why you should expose to the right in the histogram when
> shooting RAW.
> Best to read this article for better explanation
> http://tinyurl.com/2hebo I've seen some amazing detail come out of
> what appeared to be an overexposed RAW image.

Why not expose correctly to begin with? This is a serious question, not a
snide remark.

>
> Why not expose correctly to begin with? This is a serious question, not a
> snide remark.

Because there is no correct exposure. (This is not a snide remark

With film there was a shoulder when exposing film. This meant that in
places where the film was 'overexposed' there was still some difference
in the exposure.

Digital (CCD's) are far more lineair. So exposure goes to a certain point
and beyond that you get overexposure. In those overexposed area's there
is no difference in the exposure anymore. So for any important parts of the
picture you should not cross that line. (Where with film the line was more
vague).

With digital (CCD's) most information goes in the high end of the exposure.
Allthough varying with different camera's there are a lot of digital value's
for the high end exposure. For a 12 bit system there are over 2000 values
in the highes level (1 stop) for the exposure.

So if you do postprocessing with your digital picture, you should not cross
the line for overexposure, but should use as much of the higher levels as
possible. For high contrast scenes this will often be the correct exposure
as wel. But for low contrast scenes, this can give an overexposed scene,
but with more information to play around. It's (fairly) ease to correct this
exposure digitally in postprocessing.
So with digital camera's there can be a difference in capturing as much
information as possible in a scene and capturing with the correct exposure.

Because correct exposure is not totaly defined, you can choose for
capturing as much information as possible and get the correct exposure
on a pc.
But if you are capable of making the correct exposure for sure, you can
choose to make the correct exposure at the time of making the picture.
If the exposure is correct you have enough information for the picture,
but less information to play around with.

So to capture as much information the advise is expose to the right, but
NOT beyond. For low contrast scenes you probably have to reduce
the exposure in postprocessing, this will give good results.
(Making the mistake of underexposure, you have to postprocess and
increase the exposure. This is not optimal and in some instances will
result in worse pictures).

with kind regards,
ben brugman

Lobby Dosser <> wrote:
>"My View" <no spam > wrote:
>
>> That's right. RAW does give more detail in the highlights as that is
>> where most of the information is stored (ie 2048 levels out of 4096
>> are in the brightest section (first stop) of the dynamic range.
>> Also that is why you should expose to the right in the histogram when
>> shooting RAW.
>> Best to read this article for better explanation
>> http://tinyurl.com/2hebo I've seen some amazing detail come out of
>> what appeared to be an overexposed RAW image.
>
>Why not expose correctly to begin with? This is a serious question, not a
>snide remark.

"What appeared to be an overexposed RAW image", wasn't
over exposed.

It would have been more correctly exposed than the others it is
being compared to!

It's just that if someone shoots off 300 frames that all turn
out looking right, and the exact same raw data to image format
conversion makes the 301st image look over exposed, people will
(incorrectly) tend to say it "appeared to be over exposed".

In fact it wasn't, and the other 300 should be described as
"appearing to be under exposed, and requiring special adjustment
to compensate".

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska)