# Image resolution



## Gene_mtl (Dec 28, 2012)

I shoot with a Canon EOS-5D that has a full frame sensor that takes images that are 4368 x 2912 pixels. (3:2 aspect ratio)

Not sure why, but I've always exported images (TIFFs or Jpegs) at a resolution of 364 pixels. (basically 12 x 8 inches based on ppi)

I vaguely remember Lightroom defaulting to a resolution of 240 ppi. 

Am I setting my export resolution too high at 364? Is there an ideal image resolution?  FWIW, my output is intended to be printed.

TIA.


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## clee01l (Dec 28, 2012)

The number that you put in the EXIF field has no relationship to the pixels in the data section.  Resolution occurs when the digital data is translated onto media, either paper at a specified number of dots per inch or as transmitted light on a display screen The resolution of the monitor is fixed at the time of manufacture.  HiDPI screens like my retina MBP display at 227 ppi where as your standard density monitor is ~120ppi.  Printers commonly spit out ink droplets at densities of 300, 600 or 1200 dpi.  Now, your 4368 x 2912 image will get translated to another size to display and fit in your 1920X1080 monitor or printed on a home printer at 300dpi.  Neither the graphics software driving your video or the printer driver reads the value that you enter in the EXIF field for DPI.  The EXIF standards set the default for that field at 72 (if not value is supplied) .  You can use 72 too or you can even leave it empty and your images with look everywhere the same as the ones where you set the value to 364 or 240.


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## Tony Jay (Dec 28, 2012)

Hi Gene.

I looked at your post with some interest.
Essentially there is no resolution that can be too high when it comes to printing.
It seems that you may be using a photolab for printing given the fact that you are exporting images prior to the apparent printing session and also that you do not list a printer in your vital statistics, so to speak.

Is the photolab colour-managed and do they provide profiles for their clients to soft-proof images prior to submission. Also what software are they using to guide the printing process, and what printers are they using.
I ask this because ideal resolutions vary between printers and also vary depending what the native resolution, based on print size, is in the first place. If you are able to soft-proof and then give instructions regarding print size and the resolution you want for that print size (usually requires up-rezzing files - never down-rezzing) that would be ideal.
Perhaps ultimate print quality is not crucial for you especially considering much larger prints than 8 by 12 inches are possible from native 5D files.

It is an interesting question because in fact there is no one correct answer for your question apart from the warning never to willingly discard potential resolution for the purposes of printing.

I will be interested to hear from you.

Tony Jay


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## Gene_mtl (Dec 28, 2012)

clee01l said:


> The number that you put in the EXIF field has no relationship to the pixels in the data section.  [. . . snip . . .]You can use 72 too or you can even leave it empty and your images with look everywhere the same as the ones where you set the value to 364 or 240.


Since the inputted value doesn't effect display or print, does that Export File Resolution field serve any purpose?




Tony Jay said:


> I looked at your post with some interest. Essentially there is no resolution that can be too high when it comes to printing. It seems that you may be using a photolab for printing given the fact that you are exporting images prior to the apparent printing session and also that you do not list a printer in your vital statistics, so to speak.
> 
> Is the photolab colour-managed and do they provide profiles for their clients to soft-proof images prior to submission. Also what software are they using to guide the printing process, and what printers are they using.
> I ask this because ideal resolutions vary between printers and also vary depending what the native resolution, based on print size, is in the first place. If you are able to soft-proof and then give instructions regarding print size and the resolution you want for that print size (usually requires up-rezzing files - never down-rezzing) that would be ideal.
> ...



Hi Tony.  I seldom print locally any photos except for a few family snaphots that my wife insists she must have copies. <Smile> My local printer is an old HP Deskjet 5550. (two cartridge).  It works splendidly producing 4.5x5.5 inch notecards of digital paintings I do for that purpose.  I do not do colour management. What little personal printing I do of my photography is done via SmugMug using sRGB colour space.  Have never had an issue with the results. I also use RedBubble, mostly for cards personally, though I have also sold a number of photographic and mounted images on RedBubble to buyers.  Again RB uses sRGB and seem to impose an arbitrary 300 ppi in determining size availability.  I always save the largest pixel size possible to ensure  I am not throwing away 'potential resolution'.  And I do not up-size, not ever having had the need to do so.   If I did, I would rely on SmugMug to do so as they brag that they can produce great images at as low as 80 ppi, and back up that claim with a money back guaranty. <Smile>  Hope I answered most of your questions.

Appreciate the feedback, guys. Thanks


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## erro (Dec 28, 2012)

I've written something on the topic of image size, resolution, PPI and all that:

http://erro.se/artiklar/Bildstorlek/#english


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## clee01l (Dec 28, 2012)

Gene_mtl said:


> Since the inputted value doesn't effect display or print, does that Export File Resolution field serve any purpose?


A very long time ago, commercial printers had all of the logic built into the device.  There was not computer to prepare and send the image through a printer driver to a printing device.  These printers used the information embedded in the image header as instructions to produce a final print. This is no  longer the case, and AFAIK no printer uses this field. So, yes it is a legacy field to accommodate now obsolete equipment.


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## Jim Wilde (Dec 28, 2012)

It's not entirely a legacy field, Cletus. It is used by Lightroom to calculate the correct pixel dimensions when you "resize to fit" and choose inches or centimetres for the dimensions....for example using a 5760x3840 file (3:2 ratio) and selecting a 12x8 inch export size, 300ppi yields a file with 3600x2400 pixels, whereas at 72ppi the export yields only a 864x576 pixel file. So absolutely one needs to pay attention to the ppi setting if attempting to output a file with a specific physical size selected.


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## Gene_mtl (Dec 28, 2012)

clee01l said:


> A very long time ago, commercial printers had all of the logic built into the device.  There was not computer to prepare and send the image through a printer driver to a printing device.  These printers used the information embedded in the image header as instructions to produce a final print. This is no  longer the case, and AFAIK no printer uses this field. So, yes it is a legacy field to accommodate now obsolete equipment.



Thanks Cletus.  Jim Wilde's comments aside, you answered my question. 



TNG said:


> It's not entirely a legacy field, Cletus. It is used by Lightroom to calculate the correct pixel dimensions when you "resize to fit" and choose inches or centimetres for the dimensions....for example using a 5760x3840 file (3:2 ratio) and selecting a 12x8 inch export size, 300ppi yields a file with 3600x2400 pixels, whereas at 72ppi the export yields only a 864x576 pixel file. So absolutely one needs to pay attention to the ppi setting if attempting to output a file with a specific physical size selected.



Thanks, Jim. So if I want to resize on export, File resolution is an important element. But if I am just passing a file between Lightroom and PSE11, without adjusting size, any value in that field is irrelevant. 



erro said:


> I've written something on the topic of image size, resolution, PPI and all that:
> 
> http://erro.se/artiklar/Bildstorlek/#english



Robert: Excellent article, well written. Thanks.

Again, thanks everyone for the feedback. Much appreciated.


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