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Controlling compression with (Nikon) digital cameras.



 
 
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  #1  
Old December 31st 04, 09:28 PM
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Default Controlling compression with (Nikon) digital cameras.

Dear experts,

I'm very familiar with 35mm photography, but new to digital.

One thing I do know about photo editing is how you can
control the compression on the the jpeg. The more
compression, the more loss, and vice versa.

Yesterday, I bought a Nikon 3200 and a one gig memory card.
The manual says that the compression is set indirectly in
the image mode. When I set it to the highest 3 megapixel
setting, it uses about a 1:4 compression ratio. The next
3M setting uses a 1:8 compression ratio.

I set it to the highest quality image and took a few pictures
with the camera and uploaded them. They all seemed to have
their jpeg compression set to 50%.

In Windows, the 773 kb jpeg file, when saved again as
..jpg at 100%: 1305 kb
..bmp 9217 kb.


Are there point and shoot cameras where you can control
the amount of jpg compression? Which cameras allow you to
do this? How about on the D70?

I've also heard of Raw. Nikon stores these as .NEF.
Is this the same as a .BMP file on Windows?


Thanks

  #2  
Old December 31st 04, 10:02 PM
All Things Mopar
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Default

commented courteously ...

Yesterday, I bought a Nikon 3200 and a one gig memory

card.
The manual says that the compression is set indirectly

in
the image mode. When I set it to the highest 3

megapixel
setting, it uses about a 1:4 compression ratio. The

next
3M setting uses a 1:8 compression ratio.


I have a 5700, which was $700 retail. To give me an idea
what you have, is your 3200 a $400 camera or a $100
camera? If it is like my wife's $150 Kodak, she can only
change resolution, and cannot control JPEG compression
(which Kodak has set way too high, so the pictures have
artifacts despite their 3 mega pixel size!)

I set it to the highest quality image and took a few

pictures
with the camera and uploaded them. They all seemed to

have
their jpeg compression set to 50%.


JPEG compression is not a percentage. Rather, it is an
arbitrary 1-100 scale. Are you saying that your images
look like a JPEG 50? If so, the quality must suck on quite
a few of them. I see lots of artifacts on my wife's
Kodak's and I'd judge the compression at around 25-30.

Are there point and shoot cameras where you can control
the amount of jpg compression? Which cameras allow you

to
do this? How about on the D70?


Little P & S cameras do not have any JPEG controls
generally, ala my wife's Kodak. I'm not sure where the
price point is where you see "basic", "normal", and
"fine" (none have an actual compression number that I know
of) but I'd imagine its around $300-400.

Nikon's "better" cameras have all sorts of controls over
the image. The D70 is a fairly high-priced camera and may
well be overkill for you. If you like Nikon, look around
the web for a 5700. They've been out-of-production for six
months but stores still have them, and Nikon pops for a
$150 mail rebate. It's a very fine camera, I can
personally attest to that (except for flash).

I've also heard of Raw. Nikon stores these as .NEF.
Is this the same as a .BMP file on Windows?


NEF is Nikon's proprietary RAW. It is in *no* way a
Windoze BMP, which is nothing more than an uncompressed
bitmap file (hence its name)! RAW/NEF give you total
control over the picture parameters even after you've
taken the shot. I don't use NEF with my 5700 because I
don't think I need it, but lots of people think that
NEF/RAW is essential to their work.

There's plenty of folks on this NG that are much
knowledgeable than I am about this stuff, so you'd help
everyone lock onto what you need to do if you give some
details on price and purpose.

Good luck, and Happy New Year!

--
ATM, aka Jerry Rivers
  #4  
Old January 1st 05, 04:11 AM
RonFrank
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There is only one camera that I'm aware of (Canon 1ds MII $8000) where you
can specify the actual compression ratio of a jpg image. In camera, rather,
you set the image size, and then the type (JPG, TIFF, RAW). This is how even
most high end cameras (like my D1x) works. The jpg image is saved at a
preset compression based on the output size specified. If you want to LOWER
that, then use software.

The ratio that you are attempting to determine is NOT something you can
mathmatically figure with a simple calculation as jpg size is based largely
on WHAT is in an image. A lot of Blue sky = smaller image. A lot of varied
colored detail = bigger image. One can NOT assume a compression ratio based
on the image size alone.

Shooting RAW has advantages over most other formats. RAW is a 16 bit format
(actually 12 for most) vs. the 8 bit jpg and TIFF formats. Some of the newer
DLSR's have a 16bit TIFF option.

The bottom line is that if your biggest concern in shooting a PnS is the
compression ratio of jpg, than you are likely not going to have to worry
much. There are MANY things that can impact the ability to shoot high
quality images with a PnS digital (as good as they are). So to worry about
jpg compression is rather pointless.

Shoot with the highest res possible, and if you are unhappy with your
images, then you will want a better tool.
Ron



  #5  
Old January 1st 05, 04:11 AM
RonFrank
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Posts: n/a
Default


There is only one camera that I'm aware of (Canon 1ds MII $8000) where you
can specify the actual compression ratio of a jpg image. In camera, rather,
you set the image size, and then the type (JPG, TIFF, RAW). This is how even
most high end cameras (like my D1x) works. The jpg image is saved at a
preset compression based on the output size specified. If you want to LOWER
that, then use software.

The ratio that you are attempting to determine is NOT something you can
mathmatically figure with a simple calculation as jpg size is based largely
on WHAT is in an image. A lot of Blue sky = smaller image. A lot of varied
colored detail = bigger image. One can NOT assume a compression ratio based
on the image size alone.

Shooting RAW has advantages over most other formats. RAW is a 16 bit format
(actually 12 for most) vs. the 8 bit jpg and TIFF formats. Some of the newer
DLSR's have a 16bit TIFF option.

The bottom line is that if your biggest concern in shooting a PnS is the
compression ratio of jpg, than you are likely not going to have to worry
much. There are MANY things that can impact the ability to shoot high
quality images with a PnS digital (as good as they are). So to worry about
jpg compression is rather pointless.

Shoot with the highest res possible, and if you are unhappy with your
images, then you will want a better tool.
Ron



 




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