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File size for poster

 
 
Martin Brown
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      01-07-2013
On 04/01/2013 18:32, nospam wrote:
> In article <(E-Mail Removed)>, David Dyer-Bennet
> <(E-Mail Removed)> wrote:
>
>>>> What would be the lowest file size of mp for conversion to a poster without
>>>> too much noise? And what would such a poster cost in a roughly 24" x 36"
>>>> format?
>>>
>>> the file size isn't what's important, it's the number of pixels and
>>> that depends on how far away the typical viewer will be and the level
>>> of quality you want.

>>
>> Yes but -- the file size is directly dependent on the number of pixels.

>
> only if it's uncompressed.
>
> once you compress it, all bets are off.


Not really if you restrict yourself to compression levels that will be
acceptable for making a high quality print. It has to be something
really exceptional like white cat in a snowstorm before unusually high
levels of compression become possible. A good rule of thumb for JPEG is
that on average about 8 bits or 1 byte per pixel will preserve most of
the detail and lose comparatively little information. You will find that
a lot of in camera JPEG codecs use "high quality" around this size. This
is for a Bayer sampled image at 2x1 chroma subsampling.

Obviously if the source image is compromised or mostly out of focus or
motion blurred then it will contain far less high frequency content and
compress much more but images that are *worth* printing at large sizes
tend to contain detail at all scales and spatial frequencies.

A quick directory listing sorted by size will give you a feel for what
image content generates the most incompressible files. Typically strong
contrast foliage in bright sunlight with deep shadows and highlights.
Sky is highly compressible, grass a bit less so and sea depends on the
amount of white horses and spray.

--
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Martin Brown
 
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nospam
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      01-07-2013
In article <p1vGs.28389$(E-Mail Removed)>, Martin Brown
<|||newspam|||@nezumi.demon.co.uk> wrote:

> >>>> What would be the lowest file size of mp for conversion to a poster without
> >>>> too much noise? And what would such a poster cost in a roughly 24" x 36"
> >>>> format?
> >>>
> >>> the file size isn't what's important, it's the number of pixels and
> >>> that depends on how far away the typical viewer will be and the level
> >>> of quality you want.
> >>
> >> Yes but -- the file size is directly dependent on the number of pixels.

> >
> > only if it's uncompressed.
> >
> > once you compress it, all bets are off.

>
> Not really if you restrict yourself to compression levels that will be
> acceptable for making a high quality print. It has to be something
> really exceptional like white cat in a snowstorm before unusually high
> levels of compression become possible. A good rule of thumb for JPEG is
> that on average about 8 bits or 1 byte per pixel will preserve most of
> the detail and lose comparatively little information. You will find that
> a lot of in camera JPEG codecs use "high quality" around this size. This
> is for a Bayer sampled image at 2x1 chroma subsampling.
>
> Obviously if the source image is compromised or mostly out of focus or
> motion blurred then it will contain far less high frequency content and
> compress much more but images that are *worth* printing at large sizes
> tend to contain detail at all scales and spatial frequencies.
>
> A quick directory listing sorted by size will give you a feel for what
> image content generates the most incompressible files. Typically strong
> contrast foliage in bright sunlight with deep shadows and highlights.
> Sky is highly compressible, grass a bit less so and sea depends on the
> amount of white horses and spray.


none of that matters

an uncompressed 6mp raw file will be bigger than a compressed 12 mp
raw, possibly even a compressed 18 mp raw, yet it won't produce the
best quality result.

file size is *not* what matters.

number of pixels is what matters.
 
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Wolfgang Weisselberg
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      01-10-2013
me <(E-Mail Removed)> wrote:
> On Fri, 04 Jan 2013 12:19:23 -0600, David Dyer-Bennet <(E-Mail Removed)>


>>Yes but -- the file size is directly dependent on the number of pixels.


> Directly? Maybe only for an uncompressed raw file. For any type of
> file using compression a more loose function thereof, no?


Nikons JPEG-engines compress to a certain approximate file size,
or so I hear-tell. Which means a highly compressable image
eats space and a high detail one is overcompressed, but you
can judge free space on the card much easier. In this case,
pixel size and file size (with a given compression preset)
*will* be directly dependent.

-Wolfgang
 
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Wolfgang Weisselberg
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      01-10-2013
DanP <(E-Mail Removed)> wrote:
> On Friday, January 4, 2013 4:09:46 AM UTC, Rob wrote:
>> On 4/01/2013 3:02 PM, Steve B wrote:


>> > What would be the lowest file size of mp for conversion to a poster without
>> > too much noise? And what would such a poster cost in a roughly 24" x 36"
>> > format?


>> I print at a 200dpi resolution - you can print at 100dpi but thats
>> pushing it.


> Suppose I want to print really big, a billboard to put on the side of the road.
> 160 inch by 80 inch I have in mind.


> What dpi should I use?


Not less dpi than what you want viewers to see at the closest
distance they're getting to. If they start touching it with
the nose and use magnifying glasses to see details you need
somewhat more dpi than if you're putting an ad on the Goodyear
Blimp to be viewed in flight.

-Wolfgang
 
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David Dyer-Bennet
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      01-12-2013
Wolfgang Weisselberg <(E-Mail Removed)> writes:

> me <(E-Mail Removed)> wrote:
>> On Fri, 04 Jan 2013 12:19:23 -0600, David Dyer-Bennet <(E-Mail Removed)>

>
>>>Yes but -- the file size is directly dependent on the number of pixels.

>
>> Directly? Maybe only for an uncompressed raw file. For any type of
>> file using compression a more loose function thereof, no?

>
> Nikons JPEG-engines compress to a certain approximate file size,
> or so I hear-tell.


You can select a couple of modes, at least on the D700. One favors
image quality.

I was very pleased when I first put my 32GB card in my D700 and saw it
could display "1.5k" as the number of pictures remaining!
--
Googleproofaddress(account:dd-b provider:dd-b domain:net)
Snapshots: http://dd-b.net/dd-b/SnapshotAlbum/data/
Photos: http://dd-b.net/photography/gallery/
Dragaera: http://dragaera.info
 
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me
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      01-12-2013
On Fri, 11 Jan 2013 23:12:56 -0600, David Dyer-Bennet <(E-Mail Removed)>
wrote:

>You can select a couple of modes, at least on the D700. One favors
>image quality.
>
>I was very pleased when I first put my 32GB card in my D700 and saw it
>could display "1.5k" as the number of pictures remaining!


On my D70, D200 and D300 the estimation algorithm is quite
conservative. You might expect a significant fraction more.
 
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David Dyer-Bennet
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      01-13-2013
me <(E-Mail Removed)> writes:

> On Fri, 11 Jan 2013 23:12:56 -0600, David Dyer-Bennet <(E-Mail Removed)>
> wrote:
>
>>You can select a couple of modes, at least on the D700. One favors
>>image quality.
>>
>>I was very pleased when I first put my 32GB card in my D700 and saw it
>>could display "1.5k" as the number of pictures remaining!

>
> On my D70, D200 and D300 the estimation algorithm is quite
> conservative. You might expect a significant fraction more.


Somewhere under 100 I start to sort-of care a bit. Up over 1000 I
really don't, much .
--
Googleproofaddress(account:dd-b provider:dd-b domain:net)
Snapshots: http://dd-b.net/dd-b/SnapshotAlbum/data/
Photos: http://dd-b.net/photography/gallery/
Dragaera: http://dragaera.info
 
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