Questions on resizing raw images to jpg at 72 ppi

I am using Adobe Bridge to process my raw images and need to convert to jpg at 72 ppi.

I normally do a batch conversion to jpg using Tools->Photoshop->Image Processor and then set my Quality to 5 and also perform an action for watermark.

I found that if I open the jpg image in windows photo viewer or photoshop, the property of the image shows that it is 240 ppi, 3840x5760 pixels, 40.64x60.96 cm with a 1.56MB memory size.

I then tried to set the Quality in the Image Processor to values below 5, but then I am still getting the same jpg image properties i.e. 240 ppi, 3840x5760 pixels, 40.64x60.96 cm but the memory size is lower than 1.56MB.

Why isn't the ppi reducing with a lower Quality setting?

Thanks for any inputs and suggestions!

You may benefit from watching THIS video.

Thanks for the video! What I want to do is to publish my photos in Flickr with not too high a quality that will allow others to make high quality prints.

I guess that there are two ways. One is to compressed the original by a certain factor so that it is more "pixelated". In the Image Processor, which Quality setting do you think will be safe?

The other way is to resize the images after conversion to jpg to a certain pixel width and height suitable for Flickr. Can you recommend what would be a safe the pixel width and height?

Many thanks!

For posting to Flickr I use 1024 pixels on the long edge. This will disply nicly on most monitors. I usually use a quality setting of 80 (equiv to PS 10) which gives the best quality/file size ratio. Setting the PPI value to 72 but using the full pixel resolution will no nothing to stop people printing large prints. Limiting the pixel resolution to 1024 will at least reduce the posiblities for printing, but even so there is not a lot you can do to stop people trying printing your images.

Alan

The 'dpi' specification affects only images made on the commercial offset press (printed brochures and catalogs and magazines)...it never affects images made with inkjets or commercial optically imaged (e.g. Fuji Cystal) paper.

Parameters such as '72' vs. '300' are 'dpi' (dots per inch), and not 'ppi' (pixels per inch), which is merely a calculated result of printing a certain pixel count on a certain paper size...

• 4000x6000 pixel image at 4"x6" is 1000 PIXELS per inch, while
  
• 4000x6000 pixel image at 40"x60" print is 100 PIXELS per inch,
  

As already indicated ppi has no bearing on image or file size and is altogether a separate thing to jpeg quality. You can set the ppi to 72 or 1000 and it does not effect file size.

mrmarks wrote in post #16760035
Thanks for the video! What I want to do is to publish my photos in Flickr with not too high a quality that will allow others to make high quality prints.

That video kind of explains that.

mrmarks wrote in post #16760035
I guess that there are two ways. One is to compressed the original by a certain factor so that it is more "pixelated". In the Image Processor, which Quality setting do you think will be safe?

mrmarks wrote in post #16760035
The other way is to resize the images after conversion to jpg to a certain pixel width and height suitable for Flickr. Can you recommend what would be a safe the pixel width and height?

Many thanks!

You can do that but you need to do BOTH. The main thing is to reduce the number of pixels so that people can see the image on the screen (exactly as he did). Making it something like 800 pixels on the long edge will make for a very small image at quality 10.

BigAl007 wrote in post #16760071
For posting to Flickr I use 1024 pixels on the long edge. This will disply nicly on most monitors. I usually use a quality setting of 80 (equiv to PS 10) which gives the best quality/file size ratio. Setting the PPI value to 72 but using the full pixel resolution will no nothing to stop people printing large prints. Limiting the pixel resolution to 1024 will at least reduce the posiblities for printing, but even so there is not a lot you can do to stop people trying printing your images.

Alan

To me 1024 is too big. I could get a fairly decent 10" print at 1024 pixels.

Even an 800px image canbe printed at around 8" - 10"!
More compression will reduce the quality of the print but will also reduce the quality of how you see it on the screen. Using save for web lets you preview how compression looks.

What will also help reduce printing is Watermarking the image.

Wilt wrote in post #16762037
The 'dpi' specification affects only images made on the commercial offset press (printed brochures and catalogs and magazines)...it never affects images made with inkjets or commercial optically imaged (e.g. Fuji Cystal) paper.

Wilt I'm sorry but that is totally inaccurate information. DPI is how many dots of ink any printer lays down on the paper. Your home printer prints in dpi. DPI relates to the resolutrion of the printing device itself - dpi has nothing to do with digital images - no matter where they are printed.

Wilt wrote in post #16762037
Parameters such as '72' vs. '300' are 'dpi' (dots per inch), and not 'ppi' (pixels per inch), which is merely a calculated result of printing a certain pixel count on a certain paper size...

Sorry but again Totally inacurate information Wilt.

Both dpi and ppi are resolution numbers. they are unrelated but do have common attributes. (what has paper size to do with anything)?

72dpi = the printer lays down 72 droplets of ink/toner etc per inch of print. This controls the quality of the final print - In an epson Printer it would be related to the quality settings - Max Quality on my old R2400 was 5760x2880dpi - Best Photo setting related to 2880 x1440dpi.


You NEVER want to print at 72dpi and most labs use printers with around 300dpi.

That however does not stop you sending any value ppi image to be printed. I can send a 72ppi image to be printed at 300dpi. If that 72ppi image is very large it will look perfectly fine.

Wilt wrote in post #16762037
LIST

4000x6000 pixel image at 4"x6" is 1000 PIXELS per inch, while
4000x6000 pixel image at 40"x60" print is 100 PIXELS per inch,

Correct

Wilt wrote in post #16762037
and both can be produced at equal quality regardless if '72 dpi' or '300 dpi' is embedded within the EXIF data of the file!

You want to limit PIXEL COUNT, as changing DPI does NOTHING for limiting print quality ordinarily.

1ppi, 10ppi, 72 ppi, 150ppi, 240ppi or 300ppi (pick any number) - is how closely the pixels in the printed image are actually packed together. The higher you set the number, the closer the pixels will., print - and therefore the smaller the print you will get. PPI affects the size of your prints for any given pixel count.

DPI IS EVERYTHING to do with Print Quality - It has nothing to do with digital Image Quality.

Unfortunately, the terms DPI and PPI have gotten mixed up over the history of digital imaging. Here we have two attempts to accurately explain things but things are getting messy!

In our present day, there is still not a uniform agreement. You can see this when looking at the image size/resolution functions/dialogs in the Canon software Digital Photo Professional, where the output resolution is labeled as "dpi' and then in the Adobe software where it is labeled as ppi. They are being used to describe the same thing!

The history for this confusion goes a ways back, although we as digital image processors tend to settle on the fact that "PPI" is the resolution of an image aimed toward a specific print size. The fact that the jpeg images require a resolution "label" is a bit unfortunate, and the fact that Canon calls that label "DPI" whereas Adobe calls it "PPI" is also unfortunate.

The points that EOS_JD made about DPI relating to printing are interesting, because printing can use a "dots per inch" value in different ways, but that's another discussion, at least I don't want to wade into it!

EOS_JD wrote in post #16771521
Wilt I'm sorry but that is totally inaccurate information. DPI is how many dots of ink any printer lays down on the paper. Your home printer prints in dpi. DPI relates to the resolutrion of the printing device itself - dpi has nothing to do with digital images - no matter where they are printed.

Have you EVER noticed that the actual dpi of any printer has NOTHING TO DO with the EXIF value embedded in the photo?!
In spite of that fact, the inherent printer software DPI is meaningless, because I can take a file from a camera which might have '72 dip' embedded within the EXIF information, and I can make a 4x6" print or an 8x10" print on a Canon printer or a 4x6" print or an 8x10" print on the Epson printer, and I have previously done NOTHING to change the embedded EXIF value from the camera default '72 dpi', and even though the Canon claims a different DPI value from Epson in the print driver software that they provide!
'dpi' does have a meaning in OFFSET PRESS printing (brochure, magazine, etc. printed material) but NOT in 'photographic' printing; 'ppi' is meaningful in photographic printing

Printers have values like 9600 or 4800, their software might assume values like 360. Yet these claimed values can be quite meaningless.
https://photography-on-the.net …hp?p=16015048&p​ostcount=3

EOS_JD wrote in post #16771521
Sorry but again Totally inacurate information Wilt.

Both dpi and ppi are resolution numbers. they are unrelated but do have common attributes. (what has paper size to do with anything)?

72dpi = the printer lays down 72 droplets of ink/toner etc per inch of print. This controls the quality of the final print - In an epson Printer it would be related to the quality settings - Max Quality on my old R2400 was 5760x2880dpi - Best Photo setting related to 2880 x1440dpi.

You NEVER want to print at 72dpi and most labs use printers with around 300dpi.

that however does not stop you sending any value ppi image to be printed. I can send a 72ppi image to be printed at 300dpi. If that 72ppi image is very large it will look perfectly fine.

Sorry but you have the misinformation.
Printers have a matrix of dots, such as 4800x2400, based upon the print head and the incremental movement of the paper feed. But printers also have an inherent DPI assumption in software, and Canon uses different DPI assumption in its software than Epson does. The DPI value is mapped by the software into printer instructions which drive the 4800x2400 print head and feed increment. No direct/fixed relationship betweeen [4800x2400 in the print head] with [360 or 300ppi assumed by software] nor [72dpi/ppi vs. 300dpi/ppi vs. 1000dpi/ppi] embedded in the EXIF data!

EOS_JD wrote in post #16771521
1ppi, 10ppi, 72 ppi, 150ppi, 240ppi or 300ppi (pick any number) - is how closely the pixels in the printed image are actually packed together. The higher you set the number, the closer the pixels will., print - and therefore the smaller the print you will get. PPI affects the size of your prints for any given pixel count.

Again, wrong! I can inkjet print three versions of the same JPG, one with '72' , one with '150' and one with '300' embedded in the file versions, and the printed end result -- or the viewed end result on monitor -- will be identical! Try it yourself. I have...using an EXIF editor to alter the values, or using LR parameters in Output to control the creation of JPG files from RAW.

EOS_JD wrote in post #16771521
DPI IS EVERYTHING to do with Print Quality - It has nothing to do with digital Image Quality.

On that point I agree. For the offset press, but NOT at all as a parameter within the EXIF file which affects inkjet printing in any visible way!
Yes, you can affect ink density in the driver software, but not as an input file effect upon quality.

Wilt wrote in post #16772535
Have you EVER noticed that the actual dpi of any printer has NOTHING TO DO with the EXIF value embedded in the photo?!

Isn't that what I said?

Wilt wrote in post #16772535
In spite of that fact, the inherent printer software DPI is meaningless, because I can take a file from a camera which might have '72 dip' embedded within the EXIF information, and I can make a 4x6" print or an 8x10" print on a Canon printer or a 4x6" print or an 8x10" print on the Epson printer, and I have previously done NOTHING to change the embedded EXIF value from the camera default '72 dpi', and even though the Canon claims a different DPI value from Epson in the print driver software that they provide!

You are getting dpi and ppi mixed up.

Images are made of pixels. The size of a print is amended by adjusting the ppi of the image (the dpi is set inthe printer driver)

Your camera does not "embed" any ppi or dpi setting to your images. ppi figures are set at the time you hit print. The dpi is set when you adjust it in the printer driver.

PPI is a variable figure - not embeded.
When you send trhe image to the printer the ppi controls the size of the print. Nothing else and you can freely change that without affecting the digital image in any way.

Wilt wrote in post #16772535
dpi' does have a meaning in OFFSET PRESS printing (brochure, magazine, etc. printed material) but NOT in 'photographic' printing; 'ppi' is meaningful in photographic printing

Actually dpi is a throwover from old printing presses of a year gone by. Nowadays they actually use pixels (anything you see on your screen is pixels) and the printer itself uses dpi but these are unrelated. Perople do use dpi incorrectly but it's so engrained now it's almost impossible to change people's views

Wilt wrote in post #16772535
Printers have values like 9600 or 4800, their software might assume values like 360. Yet these claimed values can be quite meaningless.
https://photography-on-the.net …hp?p=16015048&p​ostcount=3

Yip 9600dpi sounds likje a very high resolution printer! In reality an inkjet printer has to place more than one dot of ink to create the colour of a single pixel so althouygh these numbers sound high the reality is the effective resolution is much lower - Like 300dpi or 360dpi and the like.

the one thing though is that dpi controls the actual quality of the printed image. DPI is known as the quality setting ion ytour printer driver for a reason. Printing at lowest quality (whatever that may be) will result in a pretty useless print. Printing at the highest quality - 9600x24800dpi will result in a high quality print (so long as the image being printed is also decent).

Wilt wrote in post #16772535
Sorry but you have the misinformation.

I'm proving my point Wilt and I'm sure plenty would agree - Your arguments are incorrect.

Wilt wrote in post #16772535
Printers have a matrix of dots, such as 4800x2400, based upon the print head and the incremental movement of the paper feed. But printers also have an inherent DPI assumption in software, and Canon uses different DPI assumption in its software than Epson does.

lol OK Yes printers have a resolution showing something like 4800 x 2400 or 2880x1440 or the like. When you break that down (see above) these are not actually the effective resolution. But we still discussing DPI here - i.e. dots placed on a page pof paper./ The dpi has no effect on the digital image. Only the quality of the print itself.

Wilt wrote in post #16772535
The DPI value is mapped by the software into printer instructions which drive the 4800x2400 print head and feed increment.

You set the dpi in the printer driver (if that is the software you mean)?

Wilt wrote in post #16772535
No direct/fixed relationship betweeen [4800x2400 in the print head] with [360 or 300ppi assumed by software] nor [72dpi/ppi vs. 300dpi/ppi vs. 1000dpi/ppi] embedded in the EXIF data!

The ppi number in the exif data is just a tag and means nothing. It does not affect the image in any way. It can be amended without changing he image in any way - PPI changes the print size.

Wilt wrote in post #16772535
Again, wrong! I can print three versions of the same JPG, one with '72' , one with '150' and one with '300' embedded in the file versions, and the printed end result -- or the viewed end result on monitor -- will be identical! Try it yourself. I have...using an EXIF editor to alter the values, or using LR parameters in Output to control the creation of JPG files from RAW.

Wait a minute here you are still getting all mixed up. The ppi value iteself does not change the digital image so will appear on your MONITOR as the exact same image (because it is).

BUT if you printing the three images they will each have a different physical print size. The 72ppi image will be slightly smaller then half the size of the 150ppi image and that will be half the size of the 300ppi image (no matter the dpi setting)

Very easy to work out too.

Print Size = Pixels/PPI
So lets take your image above. 4000x6000pixel image

@1000ppi
Print size = 4000/1000 = 4"
Print size = 6000/1000 = 6"

@300ppi
4000/300 = 13.333"
6000/300 = 20"

@100ppi
4000/100 = 40"
6000/100 = 60"

So ppi has only changed the PRINT SIZE - Nothing else is changed.


Go to Image size in Photoshop and switch off the resample button.

Now change the ppi setting (to anything). The number of pixels will not change but the print size does.

It's really very simple and you are getting dpi and ppi mixed up Wilt.

Watch that video a few posts back.

Wilt wrote in post #16772535
On that point I agree. For the offset press, but NOT at all as a parameter within the EXIF file which affects inkjet printing in any visible way!

Forget offset press.... That means nothing to what we are discussing here - The same principals apply in ALL cases.
You cannot ember dpi or ppi to an image. You can tag the ppi value but you can easily change that without changing the image - The ppi value is not "embedded". It's meaningless until you actually hit the print button and that assigns the print size of the image

Wilt wrote in post #16772535
Yes, you can affect ink density in the driver software, but not as an input file effect upon quality.

DPI is an OUTPUT value. It's how many dots the printer will place on the paper - that is controlled in the printer driver and yes it changed the densitry of the ink placed on the page.
More ink will equal smoother gradients and a higher quality image (so long as you have a suitable paper).

EOS_JD wrote in post #16772613
Your camera does not "embed" any ppi or dpi setting to your images. ppi figures are set at the time you hit print. The dpi is set when you adjust it in the printer driver.

Here's what you're missing:
There certainly IS a DPI figure embedded in the image metadata. For printing purposes, that embedded data is meaningless - but it's in there.

Much confusion arises from the fact that that many image manipulation programs such as Photoshop and Lightroom allow you to see and change that embedded data, regardless of whether you ever intend to print the image.

In Photoshop's "Image Size" dialog:
http://art.cadmus.com …hop8/win/ps80w_​300dpi.gif

In Lightroom's "Export" dialog:
http://photographylife​.com …Sizing-and-Sharpening.png

Most EXIF viewers will show it; heck, even MSPaint will show it.


Furthermore, many people see that meaningless embedded data tag, and incorrectly try to relate it to "image quality" (whatever that means).

nathancarter wrote in post #16772646
Here's what you're missing:
There certainly IS a DPI figure embedded in the image metadata. For printing purposes, that embedded data is meaningless - but it's in there.

Nathan, the figure is ASSIGNED (not embedded) as such - there HAS to be a number in there and it could be anything. We agree with each other here though., The number itself is irrelevant as it can be amended at any time without changing the file.

nathancarter wrote in post #16772646
Much confusion arises from the fact that that many image manipulation programs such as Photoshop and Lightroom allow you to see and change that embedded data, regardless of whether you ever intend to print the image.

Yes I see what you mean but you can still resample the image there so the Image Size dialogue needs to be set like that as the three variables for printing and resampling are then all in one place.

nathancarter wrote in post #16772646
Most EXIF viewers will show it; heck, even MSPaint will show it.

Yes they show the value assigned but you can easily assign a different value without changing the digital image.

nathancarter wrote in post #16772646
Furthermore, many people see that meaningless embedded data tag, and incorrectly try to relate it to "image quality" (whatever that means).

lol Yes I klnow I should add a bit to my blog about EXIF data

http://www.jbdavies.co​.uk/resolution/ppi-dpi/

EOS_JD wrote in post #16772613
Isn't that what I said?

You are getting dpi and ppi mixed up.

Nope, I clearly understand the difference, but you seem to think I don't know the difference.

• 'dpi' pertains to ink dot density for the offset press, affecting printed IQ, and the dpi value embedded in the EXIF matters.
  
• But 'dpi' pertaining to ink dot density for the inkjet printer, while affecting printed IQ based upon the parameters in the print driver software the user -- the dpi value embedded in the EXIF does NOT matter.
  
• 'ppi' is a derived value

EOS_JD wrote in post #16772613
Images are made of pixels. The size of a print is amended by adjusting the ppi of the image (the dpi is set inthe printer driver)

Your camera does not "embed" any ppi or dpi setting to your images. ppi figures are set at the time you hit print. The dpi is set when you adjust it in the printer driver.

PPI is a variable figure - not embeded.
.

We are in vehement agreement on these points!
Except, the Canon camera does automatically embed the value '72' into the EXIF of every JPG it stores.