pixel aspect ratio

DM
Posted By
david_michael_2
Apr 24, 2005
Views
304
Replies
5
Status
Closed
I have received tiff files that someone else scanned in which the pixel aspect ratio was incorrect the visual was extreemly condensed in regards to width. I had to change to square pixel aspect to restore proportions. I need to find out what could have caused this distortion in order to instruct the person sending how to avoid this problem. (the files were black & white tiffs, some of the files were huge – 2.8 meters x 50 centimeters at 400 dpi.
I was unable to open the files on PC, although I know that they were scanned and created on PC, I had to open them on a mac, and then only a few of them opened.

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G
goodidea1950SPAM-SPAM
Apr 24, 2005
Wouldn’t those files be between 1/2 to 1 G?
Photoshop won’t create a file that big and I
was figuring in black and white, not grayscale.
Is that right?

wrote in message
:I have received tiff files that someone else scanned in which the pixel aspect ratio was incorrect the visual was extreemly condensed in regards to width. I had to change to square pixel aspect to restore proportions. I need to find out what could have caused this distortion in order to instruct the person sending how to avoid this problem. (the files were black & white tiffs, some of the files were huge – 2.8 meters x 50 centimeters at 400 dpi. : I was unable to open the files on PC, although I know that they were scanned and created on PC, I had to open them on a mac, and then only a few of them opened.
GH
Gernot_Hoffmann
Apr 24, 2005
David,

the distortion could be a result of a fax compression (CCITT) for monochrome images (only black dots).

Please tell us the purpose of this task. How can somebody scan a 2.8m x 0.5m image ? Was it already rastered (halftoned) ?

Best regards –Gernot Hoffmann
DM
david_michael_2
Apr 25, 2005
Gernot,
Thanks for responding to my question.
The drawings which are huge engineering drawings were scanned on a machine called KIP, but I am not quite sure that I remember the name correctly – as I am on holiday and will check on my return next week. The drawings are line drawings and do not need rasters. I think I should check the facts 100% first and get back.
but in the meantime with this limited info you can think of something – I will be grateful. All the best
David
GH
Gernot_Hoffmann
Apr 25, 2005
David,

thanks for the feedback. Instead of pondering about ‘why is it wrong ?’ I would tell the scanner company ‘save as compressed 1-bit TIF’. This is lossless and the compression ratio is probably high.
Personally I would use 8-bit grayscale because the drawing would look less jagged (400dpi is not very much for monochrome). White areas are cleaned by increased contrast.

Best regards –Gernot Hoffmann
G
goodidea1950SPAM-SPAM
Apr 25, 2005
I am not familiar with your use of the word
raster. To me a raster and bitmap are the
same thing. Do you mean vector?

wrote in message
: Gernot,
: Thanks for responding to my question.
: The drawings which are huge engineering drawings were scanned on a machine called KIP, but I am not quite sure that I remember the name correctly – as I am on holiday and will check on my return next week. The drawings are line drawings and do not need rasters. I think I should check the facts 100% first and get back.
: but in the meantime with this limited info you can think of something – I will be grateful.
: All the best
: David

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