image size and 300 dpi resolution

[ionita_cn]

Hi guys!

Using PH CS4

These are the steps I use for editing the images I then print on my Epson 400 printer, on canvas.

After I chose the images I need, I open them and crop them at 305/403 mm, the resolution setting is 300 dpi , it appears right next to the Height/Width.

I then make small retouches and save the file as JPEG image, using CTRL S command.

After editing all the images, I open Adobe Bridge and print my images from there. Bridge automatically saves images into PDFs and sends them to the printer, after I chose the image size according to the dimensions of my canvas.

My printer got broken few days back and asked one of my friends to print my images. They say they need to redimension the images, as the images don`t have 300 dpi. When I right click on one of them, at Details tab I see:  3602x4760 dimension and only 240 resolution. What happened? Did I do something wrong??

Please help, there are a loooot of images, and .. does he need to re-crop etc all of them  ?

Thank you so much

Cristina

[Dynamic Office]

Resolution and DPI are not the same thing,

May i ask why you need 300 dpi? I think 96 DPI would be fine, unless your intended audience are using magnifier glass to inspect your artwork?

[ionita_cn]

Mm.. I print portraits on canvas. Apart from 30x40 cm size , I also print a

42x57 size. I think the details in the iris or the ones from a curled hair

look nice when there are more pixels. I must agree I am new working in PH.

În mie., 17 apr. 2019 la 19:57, Dynamic Office <forums_noreply@adobe.com> a

scris:

image size and 300 dpi resolution created by Dynamic Office

<https://forums.adobe.com/people/Dynamic+Office> in Photoshop - View

the full discussion <https://forums.adobe.com/message/11033914#11033914>

[JohanElzenga]

PPI (not DPI) is pretty meaningless, even when printing because modern printer drivers will automatically correct for it if you define the print size. The only thing that matters is the dimensions in pixels. 305mm @ 300 ppi = 300 x 305 / 25.4 = 3062 pixels, so your images have the correct size for printing. Your friend should simply ignore that 240 ppi and select the correct dimensions in mm, then the printer driver will automatically use 300 ppi.

[D Fosse]

All you need to worry about is pixel dimensions - so many pixels wide x so many pixels high. That's your file. As long as you don't resample the file, it's the same.

Ppi, pixels per inch, is probably the most misunderstood concept in all of digital photography. It's actually very simple, there's no magic to it. Just read it literally: pixels per inch. Say it out loud to yourself: pixels per inch.

So you have your pixels in the file, a certain number of them. That's your image. Now, how many of them do you want to cram into one inch of paper? Do the math. The denser you print those pixels, the smaller the image is on paper.

To get a good print, a certain pixel density is recommended. It doesn't have to be 300, there's nothing special about that number. It depends entirely on the viewing distance. The bigger it is, the farther away you will stand to take it all in. So ppi requirement drops with increased viewing distance.

[ionita_cn]

So I understand the Resample option is the one that “allows” the file to

modify itself? Sry, but even if I say a stupid question, I have to tell you

I’m pretty new in PH. Thanks

El El mié, 17 abr 2019 a las 20:16, D Fosse <forums_noreply@adobe.com>

escribió:

image size and 300 dpi resolution created by D Fosse

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discussion <https://forums.adobe.com/message/11034045#11034045>

[gener7]

Resampling simply add or subtracts pixels from your file. If it adds or "upsamples", Photoshop has to guess what those pixels will be.

If you are new to this, Automatic is a good choice, until you learn more.

I prefer not to touch the image. If I'm going to print at a certain size, I set my camera for max Megapixels or the scanner to at least 600 ppi.

Scaling is where you uncheck "resample" and decide what size you will print. If the ppi is above 220, I think you will have a decent print. 300 is a holdover from offset presses. 240 ppi would be for a 4 color consumer inkjet. Scaling will not subtract or add pixels, it just decides the size on paper.  And as D. Fosse pointed out, if it's large, then that is reduced as you move away to take in the whole print.

Here's the dialog with resample unchecked. You can adjust print dimensions (inches or cm) and see what the ppi will be.

[Stephen_A_Marsh]

Just adding to this post:

To get a good print, a certain pixel density is recommended. It doesn't have to be 300, there's nothing special about that number.

For those that are wondering why “300 ppi” is often requested… It is due to historical practices in file prep for offset/lithographic printing. A good rule of thumb was always to use a source PPI value at final print size that was roughly x1.5-2 times the value of the halftone screen being used for printing. A 150 lpi (lines per inch) halftone screen was quite common, so 2 x 150 lpi = 300 ppi. It depends on image content though, quite acceptable results could be gained with a 225 ppi (x1.5) file when used for a 150 lpi halftone screen. Having the file at 300 ppi rather than 225 ppi simply allows for a little bit of leeway.

There are of course other “magic numbers” from other historical computer and digital imaging sources that are often repeated and enforced with the fervent of religious mantra: 72 ppi, 96 ppi, 240 ppi, 360 ppi etc.

[D Fosse]

An additional, unfortunate consequence of this is that you get a lot of completely unnecessary upsampling, ultimately resulting in lower quality.

Even assuming 150 lpi screen, you normally get better results printing a 225 ppi image as-is, rather than upsampling it to 300, as many people would do. At least if you prepare it with some care and sharpen optimally.

The 2x lpi number is the point at which there is no way to discern individual image pixels, as a purely theoretical limit. It doesn't necessarily relate to sharpness.

[dottonedan]

For those of us that use Photoshop raster files for other methods, we may see things from a different perspective.

In apparel art, Raster is widely used. Almost as much as vector. Add to that, once a color separation of your raster file is printed to film or a DTS (Direct to Screen) printer, it must be RIPped.  (sent through a Raster Image Processor).  This RIP converts the Digital pixel file into halftones, unlike digital printers to paper.

We might get caught up in the PPI to LPI to DPI discussion, but when you have solid line art painted brush inkings or type with solid edges, The solid art (in addition to that airbrush, Photo illustrated look, you will get horrible image quality results once it is ripped to halftone. Your "type" will be blurred, your paint brush inking will be fuzzy, and you will not get a good clean color separation from a file like that.

You will want a very high file resolution but no higher than your printer will print at. Yes, It's typical (in offset), that most work with will be 300ppi.  It's been the long (go to).  I use 600ppi. Most of you know, as you type out a letter S, This should look solid, not fuzzy or antialiased. With Antialiasing turned off on type, it is created using the individual pixels. When it is solid, you see the stair stepped pixel of the resolution. Compare extreme examples of 72ppi (web) solid type and 600ppi solid type.  The 600 is far cleaner, smoother, with smaller pixels. This translates into a better reproduction of film exposure on the screen mesh stencil, easier washout, and a more accurate image reproduction of a dot onto the shirt. This then represents that color tone (more accurately) and raster type looks like it should and you don't see the jaggies.

[D Fosse]

Yes, the discussion above applies to photographic images. That's where we get most of the questions about resolution.

[dottonedan]

True, and I understand that most designers and photographers out there are more familiar with what they do in their world. But it much of the feedback seemed only towards pixel depth and that resolution didn't matter. It was worth mentioning. Since there may be as many printers out there doing what I'm doing as there are photographers and designers. Well, almost.

For example, Screen printer artist who have only worked in the apparel industry, would never use nor know of Indesign...It's not in our toolbox as it pertains to apparel art.  Once you get outside of apparel art, they may branch into other programs to do other things.

We use Illustrator and/or Photoshop for all raster type images and many shops even use photoshop for solid "vectors type art" as long as you know what you are doing with resolution. I for example, provide a service of color separation to over 300 clients a year using Photoshop alone. There are specific reasons for this that do not pertain to this discussion, but it should open the eyes ti imply that there are more ways and more reasons for certain things. One does not apply to all.  Resolution or pixel depth, do pertain to both printers and photographers since we print to something at some time. So this is more for "others" who come across this. For example, I came across this post due to another resolution question. Just some added info.

[Byron Cortez]

240 dpi is more than enough to print on a printer or a substrate that may not support them.