How Do I Know What Bits per Pixel my Panasonic Lumix DMC-FZ8 Has

The manual does not state; not even the 'specifications' page at the end. I
have seen one reference on the web to it being 8 bits per channel: 24 bits
per pixel. This seems to be quite low; is it normal for a modern camera?
I use SilkyPix to read the raw files but it does not tell me the bit depth
of the images.

thanks, Davy

"Davy" <david@REMOVEallTHISchobham.org.uk> wrote in message
news:Ho2dnY-C2KSvP5_anZ2dnUVZ8vudnZ2d@brightview.com...
> The manual does not state; not even the 'specifications' page at the end.
> I
> have seen one reference on the web to it being 8 bits per channel: 24 bits
> per pixel. This seems to be quite low; is it normal for a modern camera?
> I use SilkyPix to read the raw files but it does not tell me the bit depth
> of the images.
>
> thanks, Davy
>
>

Most all digital cameras do 24 bit images. That is a standard RGB image.

Somebody!

On Tue, 02 Oct 2007 20:57:08 +0100, Davy wrote:

> The manual does not state; not even the 'specifications' page at the end. I
> have seen one reference on the web to it being 8 bits per channel: 24 bits
> per pixel. This seems to be quite low; is it normal for a modern camera?
> I use SilkyPix to read the raw files but it does not tell me the bit depth
> of the images.
>
> thanks, Davy

When saved to a jpeg file, you get 8 bits per channel. AFAIK - most raw
capable cameras do raw files at 12 bits per channel - don't know, but some
may be capable of more. Have you tried looking at the exif data in your
raw file? It may be in there somewhere.

"Davy" <david@REMOVEallTHISchobham.org.uk> wrote:
>The manual does not state; not even the 'specifications' page at the end. I
>have seen one reference on the web to it being 8 bits per channel: 24 bits
>per pixel. This seems to be quite low; is it normal for a modern camera?
>I use SilkyPix to read the raw files but it does not tell me the bit depth
>of the images.
>
>thanks, Davy

I couldn't find anything sufficiently authoritative to
be postive; but almost certainly the raw data file
produced by the FZ8 is in a 12 bit _linear_ format.

A "RAW converter", such as SilkyPix, generally outputs a
JPEG format image (though others are usually possible),
which is an 8 bit _gamma_ _corrected_ format. The
difference between "linear" and "gamma corrected" is
significant when comparing bit depth.

For example, in the brightest fstop (zone) of an image a
12 bit linear file can save as many 2048 different
values. Your eyes of course cannot see a variation of
1/2000 of an fstop! So JPEG compresses that down to
saving only 69 different levels (which is still finer
than our eyes can detect). In the second brightest
zone, a linear raw file saves half as many, or 1024
values. In a gamma corrected JPEG file there are 50
levels.

The effect is that *if* the JPEG format has the correct
white balance and correct exposure, it will *look* exactly
the same as an image with twice as many bits per channel!
The problem is that if anything is not exactly right, any
attempt at adjusting brightness/contrast to get it right
is almost certainly going to visibly degrade the image.

You camera can produce either JPEG files or RAW files.
Which you choose depends on what you want to do. At the
extremes, most people who shoot snapshots of family,
pets, and neighbors couldn't care less (and can't tell)
when a snapshot is plus or minus 1 fstop of correct
exposure. The last thing they want to do is try fussing
with a photo editor to get every single picture just
perfect.

They definitely want to shoot JPEG. It's faster, it's
easier, they get more pictures, and it's perfect for
them.

At the other end of the spectrum are people who want to
produce art with a camera, and just simply *must* have
control of ever possible detail in every image. They can
do far more adjusting and fussing with a RAW file than
with a JPEG image. RAW is perfect for them.

In between those extremes are where most people live.
The tilt is probably decidedly towards shooting JPEG
only for most people who purchase a Panasonic FZ8, and
that is what it is "tuned" for. But it does provide the
tools and you *can* do RAW processing any time you
choose!

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

"Davy" <david@REMOVEallTHISchobham.org.uk> wrote in message
news:Ho2dnY-C2KSvP5_anZ2dnUVZ8vudnZ2d@brightview.com...
> The manual does not state; not even the 'specifications' page at the end.
I
> have seen one reference on the web to it being 8 bits per channel: 24 bits
> per pixel. This seems to be quite low; is it normal for a modern camera?
> I use SilkyPix to read the raw files but it does not tell me the bit depth
> of the images.
>
Another thought on my question above. It is a 7M pixel camera. If the
camera produces 8 bits per channel, there are three channels and there are 8
bits in a byte - so it would require 3 bytes to record one pixel. So a 7M
pixel camera should produce raw files 21 Mbytes in size. In fact the raw
files are half this - only 11M bytes.

What's wrong with my arithmetic?

Davy

Davy wrote:
> "Davy" <david@REMOVEallTHISchobham.org.uk> wrote in message
> news:Ho2dnY-C2KSvP5_anZ2dnUVZ8vudnZ2d@brightview.com...
>> The manual does not state; not even the 'specifications' page at the
>> end. I have seen one reference on the web to it being 8 bits per
>> channel: 24 bits per pixel. This seems to be quite low; is it
>> normal for a modern camera? I use SilkyPix to read the raw files but
>> it does not tell me the bit depth of the images.
>>
> Another thought on my question above. It is a 7M pixel camera. If
> the camera produces 8 bits per channel, there are three channels and
> there are 8 bits in a byte - so it would require 3 bytes to record
> one pixel. So a 7M pixel camera should produce raw files 21 Mbytes
> in size. In fact the raw files are half this - only 11M bytes.
>
> What's wrong with my arithmetic?
>
> Davy

- the channels are (most likely) recorded at 12-bit quantisation

- at each pixel, only /one/ colour is recorded

- there may be lossless compression in the raw file

With no compression, expect 7M x 1.5bytes => 10.5MB

David

"Davy" <david@REMOVEallTHISchobham.org.uk> wrote:
>"Davy" <david@REMOVEallTHISchobham.org.uk> wrote in message
>news:Ho2dnY-C2KSvP5_anZ2dnUVZ8vudnZ2d@brightview.com...
>> The manual does not state; not even the 'specifications' page at the end.
>I
>> have seen one reference on the web to it being 8 bits per channel: 24 bits
>> per pixel. This seems to be quite low; is it normal for a modern camera?
>> I use SilkyPix to read the raw files but it does not tell me the bit depth
>> of the images.
>>
>Another thought on my question above. It is a 7M pixel camera. If the
>camera produces 8 bits per channel, there are three channels and there are 8
>bits in a byte - so it would require 3 bytes to record one pixel. So a 7M
>pixel camera should produce raw files 21 Mbytes in size. In fact the raw
>files are half this - only 11M bytes.
>
>What's wrong with my arithmetic?

7Mp per image, times 12 bits per pixel, divided by 8
bits per byte, is about 10.5 Mbytes per image.

In addition to the pixel data there would likely also be
significant data about the camera settings, and perhaps
a small JPEG thumbnail image too.

Note that the raw image data is 12 bits per pixel and
there is only a single channel. The raw data has a
Bayer color pattern. Each pixel is one color only, in a
RGGB pattern. Part of converting from raw data to an
image format is using a group of pixels to determine
what each pixel's color would be.

When it is converted to another format it gets changed
to an RGB format, where there are three channels per
pixel. If you have an 11 Mb raw file... try converting
it to 16 bit TIFF or PPM format! That file will end up
being 42Mb in size!

Something you might or might not be aware of is that
every image has EXIF data included with the pixel data.
There are various programs that let you see that data,
and it can be very interesting. If you have perl on
your machine, try finding /exiftool/, which is a set
of perl scripts that can show/edit the data.

Lacking that, if you can put one raw image file up on
the web someplace where it can be accessed, I and
probably many others would be happy to download it and
dump the EXIF data from it, and then post the data with
a commentary on what it means to you.

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

"Floyd L. Davidson" <floyd@apaflo.com> wrote in message
news:87lkaky0m9.fld@apaflo.com...
if you can put one raw image file up on
> the web someplace where it can be accessed, I and
> probably many others would be happy to download it and
> dump the EXIF data from it, and then post the data with
> a commentary on what it means to you.

Floyd, thanks for the offer, the file is at:

http://www.callnetuk.com/home/davystokes/photos.htm - click on the hyperlink
at the top of the page

Regarding your:

>Note that the raw image data is 12 bits per pixel and
>there is only a single channel. The raw data has a
>Bayer color pattern. Each pixel is one color only, in a
>RGGB pattern. Part of converting from raw data to an
>image format is using a group of pixels to determine
>what each pixel's color would be.

I seem to have bought a really crappy camera; only 12 bpp and doesn't even
record what the colour of the pixels are !! :-)

>When it is converted to another format it gets changed
>to an RGB format, where there are three channels per
>pixel. If you have an 11 Mb raw file... try converting
>it to 16 bit TIFF or PPM format! That file will end up
>being 42Mb in size!
You're predictions are exactly right. TIFF (8) files are 20Mb and TIFF16
files 40Mb.

cheers

Davy

On Wed, 03 Oct 2007 09:10:08 +0100, Davy wrote:

>
> "Davy" <david@REMOVEallTHISchobham.org.uk> wrote in message
> news:Ho2dnY-C2KSvP5_anZ2dnUVZ8vudnZ2d@brightview.com...
>> The manual does not state; not even the 'specifications' page at the end.
> I
>> have seen one reference on the web to it being 8 bits per channel: 24 bits
>> per pixel. This seems to be quite low; is it normal for a modern camera?
>> I use SilkyPix to read the raw files but it does not tell me the bit depth
>> of the images.
>>
> Another thought on my question above. It is a 7M pixel camera. If the
> camera produces 8 bits per channel, there are three channels and there are 8
> bits in a byte - so it would require 3 bytes to record one pixel. So a 7M
> pixel camera should produce raw files 21 Mbytes in size. In fact the raw
> files are half this - only 11M bytes.
>
> What's wrong with my arithmetic?
>
> Davy

Actually, it's raw data is probably 12 bits per channel but, as I
understand it, each physical pixel is one color, so it's acutally 12 bits
or 1.5 bytes per pixel, so 7mp should yield about 10.5 MB - right on
target. The information is 'demosaiced' to create a usable image - i.e.
the data from the r,g,b pixels surrounding each location are combined to
come up with the r,g,b channels for each pixel. I think the widipedia
article on raw digital camer formats does a good job of explaining it.

On Wed, 03 Oct 2007 14:12:30 +0100, Davy wrote:

>
> "Floyd L. Davidson" <floyd@apaflo.com> wrote in message
> news:87lkaky0m9.fld@apaflo.com...
> if you can put one raw image file up on
>> the web someplace where it can be accessed, I and
>> probably many others would be happy to download it and
>> dump the EXIF data from it, and then post the data with
>> a commentary on what it means to you.
>
> Floyd, thanks for the offer, the file is at:
>
> http://www.callnetuk.com/home/davystokes/photos.htm - click on the hyperlink
> at the top of the page
>
> Regarding your:
>
>>Note that the raw image data is 12 bits per pixel and
>>there is only a single channel. The raw data has a
>>Bayer color pattern. Each pixel is one color only, in a
>>RGGB pattern. Part of converting from raw data to an
>>image format is using a group of pixels to determine
>>what each pixel's color would be.
>
> I seem to have bought a really crappy camera; only 12 bpp and doesn't even
> record what the colour of the pixels are !! :-)
>
>>When it is converted to another format it gets changed
>>to an RGB format, where there are three channels per
>>pixel. If you have an 11 Mb raw file... try converting
>>it to 16 bit TIFF or PPM format! That file will end up
>>being 42Mb in size!
> You're predictions are exactly right. TIFF (8) files are 20Mb and TIFF16
> files 40Mb.
>
> cheers
>
> Davy

Here's the exif data I see:

ExifTool Version Number : 6.98
File Name : P1000195.RAW
Directory : /home/ray
File Size : 11 MB
File Modification Date/Time : 2007:10:03 09:42:17
File Type : RAW
MIME Type : image/x-raw
Exif Byte Order : Little-endian (Intel)
Panasonic Raw Version : 0202
Sensor Width : 3130
Sensor Height : 2319
Sensor Top Border : 7
Sensor Left Border : 15
Image Height : 2311
Image Width : 3087
ISO : 100
WB Red Level : 492
WB Green Level : 263
WB Blue Level : 434
Make : Panasonic
Camera Model Name : DMC-FZ8
Strip Offsets : 1536
Orientation : Horizontal (normal)
Rows Per Strip : 2319
Strip Byte Counts : 11613552
Exposure Time : 1/125
F Number : 4.0
Exposure Program : Program AE
Exif Version : 0220
Date/Time Original : 2007:09:20 15:45:33
Create Date : 2007:09:20 15:45:33
Exposure Compensation : 0
Max Aperture Value : 2.8
Metering Mode : Multi-segment
Flash : Off
Focal Length : 72.0mm
File Source : Digital Camera
Aperture : 4.0
Flash : Off
Image Size : 3087x2311
Shutter Speed : 1/125
Blue Balance : 1.65019
Focal Length : 72.0mm
Light Value : 11.0
Red Balance : 1.870722