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# Working with High Definition Photographs

Posted on 2011-10-29
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I have recently been working with high resolution scanned photos.  I previously used Microsoft Digital Image Pro software, but it cannot open high resolution photos (more than 52 million pixels or one dimension in excess of 32,000 pixels).  I purchased Adobe Photoshop, which can open many files that Digital Image can't, but even Photoshop shows some of my high quality files as "placeholders" (not displaying or being able to print the image).

I am not a professional graphic artist, and just need a pretty basic photo editing program that will accept my higher resolution photos.  Photoshop is really too sophisticated for me, but I purchased it figuring that I wouldn't have to worry about the size/resolution issue.  Can you help?

Thanks,

Phil Simmons
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Question by:philsimmons

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Phil

Are you saying that some of your images are 32,000 x 16,250 pixels in size?

A new full colour 24-bit (16 million colour) image with nothing but a transparent background is going to need just less than 1GB of memory to open, and an image of that size with a block colour is going to need about 1.5GB.

A 256 colour image of those dimensions is going to need a bit less than half a GB of memory to open, and at 72dpi will have an effective print size of 444 x 225 inches!  That's a printed image of 37 x 18.75 feet if printed at its real size!
At 150 dpi that equates to a print size of 17.75 x 9 feet.

That's a billboard, and I have to wonder what size the scanned item was and what size of scanner you have.  If you have a standard domestic flatbed scanner and scan a standard A4 page, there isn't really much sense in creating an image that will be rendered the size of the side of a greyhound bus.

To quote from the article of one of the leading experts here, Ray Paseur:
"Image size on the printed page is determined by the pixel dimensions divided by the DPI setting."
He refers to "rendered size" rather than my "printed size" expression, but hopefully you will understand when you read the article:
http://www.experts-exchange.com/A_5931-Putting-Your-Photos-Online.html

What you also have to remember for an image editing application is that although you might save out an image with a fair amount of compression to reduce the file size, the application "inflates" the image again when opened and therefore requires as much memory to temporarily store the data as the data will occupy when inflated for display.

For example, I've just took a screenshot of this page, pasted it into an image editor, resized it to 800 x 600 at 72dpi, and saved it as a JPG with no additional compression.  It creates a file of 264 KB.  When opened in an image editor it occupies 1.3 MB of RAM Memory.  The same screenshot reduced to the same dimensions and saved with 50% JPG compression creates a file of 60 KB, but when opened in the image editor again it occupies exactly the same amount of RAM Memory as the one with the larger file size and no compression.

This explains why a massive image won't open in an image editor.  It's down to how much RAM is available for use by the image being opened in the program, and may not necessarily be any specific restriction by the application.

Perhaps we can help.

What exactly is it that you scanned and what is your proposed use for the images?

Do they really need to be scanned to that pixel dimension?

Bill
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Assisted Solution

Good link by Dave.  Adobe have obviously decided that nobody really needs to create nor have an image that is more than a 1/3 million pix x 1/3 million pix.  Yours appear to be one tenth of those maximum dimensions, so I would suspect that it's simply down to how much memory your computer has available at the time.
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Author Closing Comment

Thanks, guys.  I think the bottom line is that if I want to deal with larger files I need to do it in a TIFF format (which is fine).  Bill, to answer your thoughtful and interesting queries ... as I mentioned I'm not a pro, and I always figured that the higher the resolution the better the printed result.  Depending on the photo, I generally try to scan in the 600-1000 dpi range, which (if I understand you correctly) is way more than I need to get the best possible printed result (at least that my eyes can discern).  Is that correct?  As a general rule, at approximately what resolution do we stop being able to notice a difference?
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My biggest reason for 'over-scanning' a pic is when I'm going to crop it or take pieces out of it.  Here http://www.printingforless.com/images.html is a decent explanation.  And here's another http://www.scantips.com/basics3b.html about what happens with printer.
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Thank you Phil.

I found an excellent site by Ken Watson that tries to spell out some of the myths, misconceptions, and realities regarding digital images.  In particular I think you will find these two pages particularly helpful:
http://www.rideau-info.com/photos/mythdpi.html
http://www.rideau-info.com/photos/scanning.html
as well as the links in them to other equally informative pages within his site.

Observe also the mouseover drop-down menu on the "DPI" menu button to related separate pages.  Similarly the "PRINTING" button has a drop-down menu to two separate pages that deal with commercial print shops and home printing:
http://www.rideau-info.com/photos/printshop.html
http://www.rideau-info.com/photos/printing.html

You will note in the "print shop" page that the author draws attention to the manner in which printers ask for images at a certain number of dots per inch (he prefers to use pixels per inch PPI rather than DPI, but they are the same) without specifying the pixel dimensions.

What you need to know are the maximum dots per inch that your scanner is actually capable of, and how many dots per inch your printer can print at.  There s absolutely no sense in exceeding these.  The other thing to consider is whether you want to scan an item and later print it at a larger size than the original.  Ken Watson gives the maths to work out scan settings for a few different scenarios:
http://www.rideau-info.com/photos/scanning.html
http://www.rideau-info.com/photos/math.html

To buy a book containing all the information from the site above would cost a fair amount, especially if it contained example images to illustrate the examples.  There are loads of other resources, but some may not be simplified into laymens' terms as much as the above site.  Just google "optimum dpi for printing" and "optimum dpi for scanning" and you will get some idea how many have written about this elusive science.

The direct answer to your question about what resolution we begin to notice the difference isn't quite cut and dried as you will realise reading through Ken Watson's pages.  It depends on the size of the print, what distance it is to be viewed from, the actual content (eg. straight lines, faces, landscapes, variation of shades, etc) of the print, and so on.  You can only really udge for yourself by using sensible guidelines (maybe even from the scanner/printer manuals or accompanying tutorial CDs), a little bit of maths, and then experimenting within a few different ranges until you get an optimum setting for different types of content.

Our eyes can fool us greatly at times into seeing things that aren't really there at all, and not seeing things that are.

Bill
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Author Comment

Bill,

I really appreciate all your feedback.  This is tremendously helpful ... changed my life.  I wish there was some way to give you more expert points.

Phil
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Don't worry about points Phil.  Some people here volunteer for the T Shirts on reaching certain levels, others do it for the visible ranking and are very competitive, but the vast majority like me just enjoy sharing knowledge and helping others out.  I'm glad we were able to guide you in this instance, and perhaps some day in the future you will be able to guide someone else with the information here or with some other concept that causes common misunderstandings.
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