PPI???

J

joshgrace_photo

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joshua
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hi there guys i have a canon 1100d and i need images that are 300ppi yet mine all come out as 72ppi. Does anybody know how i can change this? Thanks in advance.
 
you can change it in photoshop, or probably irfanview (batch conversion), its largely irrelivant on digital files tho
 
in trying to my images as stock and they request images of 300ppi so i need it, i was just wondering if there's an in camera way to do it?
 
hi shoot in RAW,jpegs are always 72ppi on your camera (not an expert,just letting you know what i done when i had same problem)
 
ahh okay thank you, do raw files let you review them on camera after taking a picture?
 
You have to change it if required as you save the file after processing.

Btw if you're not processing RAWs and optimising your files, then the PPI is the least of your problems for having them accepted for stock.
 
Why do JPGs even have a PPI data field? - they're not even relevant to a digital file. Is it a holdover from an earlier system requirement?
 
Alastair said:
Why do JPGs even have a PPI data field? - they're not even relevant to a digital file. Is it a holdover from an earlier system requirement?
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I wish I knew the answer to this.

Considering how it's irrelevant to most people and how some customers or suppliers put such an importance on it.
 
Alastair said:
Why do JPGs even have a PPI data field? - they're not even relevant to a digital file. Is it a holdover from an earlier system requirement?
Click to expand...

The exif standard includes a field for ppi as it is a useful bit of information when printing, or when an image is used in a page setup program. As you say, most of the time the ppi value is meaningless, but there must be some value set in that field. Zero would probably be a good candidate, but software will divide the pixel dimensions of an image by the ppi value (to get the image dimensions in inches). Stupid software will do this without error checking and will throw a wobbly when it tries to divide by zero.

So, the people that developed the exif standard decided that the default value for ppi neede to be some non-zero value. They decided that where the ppi value was unknown, or inapplicable, the default value should be 72.

Why 72 dpi? Well, that was because these people, in the main, came from places that used Macintosh computers (in those days Macs went by their full name). Macintosh were the favourite computers of people involved in graphics design and the people who designed the early Macs decided that it would be good if the text size on the Mac screen was related to printed text. And printed text uses points, with 12 point text being commonly used. 12 points was 1/6 of an inch tall, so 1 inch high text was 72 points. Apple (for it was they) decided that the Macintosh monitor should display 1 pixel per point, or 72 pixels per inch. And that's why your camera puts 72 in the ppi field.
 
PPI has got to be one of the most needlessly confusing things in all digital technology.

Basically, what they want is a digital image with sufficient pixel dimensions to print with a resolution of 300 ppi at whatever their maximum potential print size is. It doesn't matter if you have "10" or "1,000,000" in the ppi box. It's meaningless. It's the pixel dimensions that matter.

If you must change the number in the ppi field make sure you uncheck the "resample image" box first, or you will ruin your photo.
 
Would a reputable stock agency not understand all this and not be asking for a specific PPI, and be asking for pixel dimensions instead?

I've had this problem before with the local paper and images for a community group - and it usually indicates you're speaking to the wrong person.


.. Oh, it's Josh.. is this a continuation of your get-rich-quick-with-photography plan? :D
 
hollis_f said:
The exif standard includes a field for ppi as it is a useful bit of information when printing, or when an image is used in a page setup program. As you say, most of the time the ppi value is meaningless, but there must be some value set in that field. Zero would probably be a good candidate, but software will divide the pixel dimensions of an image by the ppi value (to get the image dimensions in inches). Stupid software will do this without error checking and will throw a wobbly when it tries to divide by zero.

So, the people that developed the exif standard decided that the default value for ppi neede to be some non-zero value. They decided that where the ppi value was unknown, or inapplicable, the default value should be 72.

Why 72 dpi? Well, that was because these people, in the main, came from places that used Macintosh computers (in those days Macs went by their full name). Macintosh were the favourite computers of people involved in graphics design and the people who designed the early Macs decided that it would be good if the text size on the Mac screen was related to printed text. And printed text uses points, with 12 point text being commonly used. 12 points was 1/6 of an inch tall, so 1 inch high text was 72 points. Apple (for it was they) decided that the Macintosh monitor should display 1 pixel per point, or 72 pixels per inch. And that's why your camera puts 72 in the ppi field.
Click to expand...
This sounds kinda plausible, Frank, but .... you seem to be suggesting that the people who designed the JPEG standard didn't know the difference between print resolution and monitor resolution. Monitor resolutions were typically 72 ppi back then, but printer resolutuions weren't ... were they?
 
i know i wont get rich quick id just like some money to invest in what is a very expensive hobby for a student haha :D
 
StewartR said:
This sounds kinda plausible, Frank, but .... you seem to be suggesting that the people who designed the JPEG standard didn't know the difference between print resolution and monitor resolution. Monitor resolutions were typically 72 ppi back then, but printer resolutuions weren't ... were they?
Click to expand...

The exif people (don't think it was the same as jpeg people, but I may be wrong) chose 72dpi just because it was the standard resolution for a Mac monitor. I guess they did that because they were doing a standard for digital images and were more concerned with on-screen display rather than printed display.
 
hollis_f said:
The exif people (don't think it was the same as jpeg people, but I may be wrong) chose 72dpi just because it was the standard resolution for a Mac monitor. I guess they did that because they were doing a standard for digital images and were more concerned with on-screen display rather than printed display.
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Yes, but...
hollis_f said:
The exif standard includes a field for ppi as it is a useful bit of information when printing, or when an image is used in a page setup program.
Click to expand...
 
A lot of publications still spout on about the 'minimum 300 dpi'. I'm currently working with somebody to publish a paper in a scientific journal, and nearly every journal we've looked at and considered submitting to has had that stupid phrase when it comes to guidelines for figures etc. It makes no justifiable sense as to what size they actually want, and I wish that they would update their guidelines to make some sense! (We're submitting the figures as EPS files anyway so it doesn't really matter as their vectors and as so can be resized to anything).
 
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