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Aspect ratio - why not exactly 3:2

 
 
David J Taylor
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      01-31-2004
It seems that the Nikon D100 and D70 produce 3,008 x 2,000-pixel images.
Why not a more precise 3:2? I am guessing that pixel count has to be a
multiple of 16 for processing into JPEG, so that the horizontal count must
be a multiple of 48 and the vertical a multiple of 32. 2976 * 1984
doesn't sound as good, does it? I guess the CCD doesn't support Canon's
3072 x 2048.

So is the 3008 just to avoid a figure like 29xx? Marketing in other
words?
Does the lack of precise 3:2 ever matter?

Just some random thoughts....

David


 
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Mark Herring
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      01-31-2004
On Sat, 31 Jan 2004 09:20:11 GMT, "David J Taylor"
<(E-Mail Removed)-this-bit> wrote:

>It seems that the Nikon D100 and D70 produce 3,008 x 2,000-pixel images.
>Why not a more precise 3:2? I am guessing that pixel count has to be a
>multiple of 16 for processing into JPEG, so that the horizontal count must
>be a multiple of 48 and the vertical a multiple of 32.

Why???? I can make an image in PS any size I want and still save as a
JPEG

> 2976 * 1984
>doesn't sound as good, does it? I guess the CCD doesn't support Canon's
>3072 x 2048.
>
>So is the 3008 just to avoid a figure like 29xx? Marketing in other
>words?

Maybe

>Does the lack of precise 3:2 ever matter?

No
>
>Just some random thoughts....
>
>David
>

I suspect that one factor is the number of pixels dedicated to
calibration---ie pixels that exist in the CCD (or CMOS sensor), but do
not appear in the image files.
**************************
Mark Herring, Pasadena, Calif.
Private e-mail: Just say no to "No".

 
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David J Taylor
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      01-31-2004
> Why???? I can make an image in PS any size I want and still save as a
> JPEG


Because the JPEG blocks are 8 x 8, or 16 x 16, or whatever, and therefore
might produce fewer artefacts if the images are multiples of these sizes.

[]
> I suspect that one factor is the number of pixels dedicated to
> calibration---ie pixels that exist in the CCD (or CMOS sensor), but do
> not appear in the image files.


Yes, of course, Mark. It just struck me as a slightly "odd" number and I
had wondered why.

Cheers,
David


 
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Ron Hunter
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      01-31-2004
David J Taylor wrote:

> It seems that the Nikon D100 and D70 produce 3,008 x 2,000-pixel images.
> Why not a more precise 3:2? I am guessing that pixel count has to be a
> multiple of 16 for processing into JPEG, so that the horizontal count must
> be a multiple of 48 and the vertical a multiple of 32. 2976 * 1984
> doesn't sound as good, does it? I guess the CCD doesn't support Canon's
> 3072 x 2048.
>
> So is the 3008 just to avoid a figure like 29xx? Marketing in other
> words?
> Does the lack of precise 3:2 ever matter?
>
> Just some random thoughts....
>
> David
>
>

I guess if 8 pixels trimmed of the side will mess up your composition,
it might. I don't really think I would ever lose any sleep over it...
Grin.
 
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Mark Herring
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      01-31-2004
On Sat, 31 Jan 2004 10:03:09 GMT, "David J Taylor"
<(E-Mail Removed)-this-bit> wrote:

>> Why???? I can make an image in PS any size I want and still save as a
>> JPEG

>
>Because the JPEG blocks are 8 x 8, or 16 x 16, or whatever, and therefore
>might produce fewer artefacts if the images are multiples of these sizes.
>

I don't think so. Any compression algorithm has provisions for what
to do at the edges of the scene. If it is working in blocks, and gets
an "incomplete block", then MAYBE there will be some different
artifact in that area only.
>[]
>> I suspect that one factor is the number of pixels dedicated to
>> calibration---ie pixels that exist in the CCD (or CMOS sensor), but do
>> not appear in the image files.

>
>Yes, of course, Mark. It just struck me as a slightly "odd" number and I
>had wondered why.

there are many things in electronic design that make no sense when you
look at the finished product. (Sometimes they don't even make sense
when you unravel it---there may be just the engineer's whims)
>
>Cheers,
>David
>


**************************
Mark Herring, Pasadena, Calif.
Private e-mail: Just say no to "No".

 
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Don Stauffer
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      01-31-2004
I print a lot of 8 x 10. I'd prefer a precise 5:4 ratio.

David J Taylor wrote:
>
> It seems that the Nikon D100 and D70 produce 3,008 x 2,000-pixel images.
> Why not a more precise 3:2? I am guessing that pixel count has to be a
> multiple of 16 for processing into JPEG, so that the horizontal count must
> be a multiple of 48 and the vertical a multiple of 32. 2976 * 1984
> doesn't sound as good, does it? I guess the CCD doesn't support Canon's
> 3072 x 2048.
>
> So is the 3008 just to avoid a figure like 29xx? Marketing in other
> words?
> Does the lack of precise 3:2 ever matter?
>
> Just some random thoughts....
>
> David


--
Don Stauffer in Minnesota
http://www.velocityreviews.com/forums/(E-Mail Removed)
webpage- http://www.usfamily.net/web/stauffer
 
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David J Taylor
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      01-31-2004
"Don Stauffer" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> I print a lot of 8 x 10. I'd prefer a precise 5:4 ratio.


There are times when I think a square aspect ratio would make things a lot
easier!

Perhaps not for the landscape enthusiast, though!

What I have found is that the combination of 4:3 and 3:2 is actually quite
handy, combines general purpose with landscape. Perhaps even 1:1 and 2:1
would be an even better pairing?

Cheers,
David


 
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JPS@no.komm
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      01-31-2004
In message <x3LSb.2270$(E-Mail Removed)>,
"David J Taylor" <(E-Mail Removed)-this-bit> wrote:

>Because the JPEG blocks are 8 x 8, or 16 x 16, or whatever, and therefore
>might produce fewer artefacts if the images are multiples of these sizes.


Might make the firmware smaller and faster, too, if it doesn't have to
deal with special cases.
--

<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
John P Sheehy <(E-Mail Removed)>
><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><

 
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Michael Geary
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      01-31-2004
David J Taylor wrote:
> It seems that the Nikon D100 and D70 produce 3,008 x 2,000-pixel
> images. Why not a more precise 3:2? I am guessing that pixel count
> has to be a multiple of 16 for processing into JPEG, so that the
> horizontal count must be a multiple of 48 and the vertical a multiple
> of 32. 2976 * 1984 doesn't sound as good, does it? I guess the CCD
> doesn't support Canon's 3072 x 2048.


JPEG compresses 8x8 blocks--it doesn't require multiples of 32 or 48.

3008 does happen to be divisible by 16, while 3000 wouldn't be. This is a
major convenience for Windows XP users, because XP's built-in lossless
rotation requires both dimensions to be a multiple of 16 pixels.

For example, my Canon A80's highest resolution is 2272 x 1704. 1704 is not
divisible by 16, so XP will not do a lossless rotation on these photos. (I
solved this problem by using exifiron which rotates automatically based on
the orientation sensor, and does a lossless rotation at this resolution.)

I don't know if the XP rotation issue is why Nikon chose that size, but it
certainly works to the benefit of XP users.

-Mike


 
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David J Taylor
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      01-31-2004
"Michael Geary" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...

> JPEG compresses 8x8 blocks--it doesn't require multiples of 32 or 48.


If you factor in the 3:2 aspect ratio requirement, then the picture block
size becomes 24 x 16 (or 48 x 32 if you need a 16 x 16 jpeg block size).
That's where those numbers come from.

> 3008 does happen to be divisible by 16, while 3000 wouldn't be. This is

a
> major convenience for Windows XP users, because XP's built-in lossless
> rotation requires both dimensions to be a multiple of 16 pixels.
>
> For example, my Canon A80's highest resolution is 2272 x 1704. 1704 is

not
> divisible by 16, so XP will not do a lossless rotation on these photos.

(I
> solved this problem by using exifiron which rotates automatically based

on
> the orientation sensor, and does a lossless rotation at this

resolution.)
>
> I don't know if the XP rotation issue is why Nikon chose that size, but

it
> certainly works to the benefit of XP users.


Thanks, Mike. I actually use PIE Studio to lossless rotation rather than
XP, so I've not compared XP and PIE Studio as to their JPEG size
requirements. I had a sneaky feeling choosing a number just greater than
3000 might have been marketing! I expect Nikon engineering have some
choice in exactly how many of the available sensor pixels they choose to
use for active pixels.

Cheers,
David


 
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