Exporting from RT at 300ppi

I’m a newbie here, lets hope I don’t confuse everyone…
I take photos at 24mb, 300dpi, 6000x4000 and use RT to open my raw photos and do minor adjustments before fast exporting to GIMP.
Unfortunately, I have not long ago noticed that all the photos I export from RT into GIMP are arriving at 72dpi - there will be lots of photos in my portfolio that I ‘presumed’ to be 300dpi when they are actually only 72. Very disappointing to say the least!!
Despite reading, searching and praying, I can’t find anywhere in RT that allows me to export a photo at 300dpi.
I would be very grateful if someone could point me in the right direction so I don’t have to remember to resize an image every time I import from RT - which I sometimes forget to do - or having to open every image individually if I do lots at a time.
Thanks everyone - have a wonderful day

Is your printer asking you for the DPI or why do you care about it? It is just metadata used in some DTP programs to import the images in a specific physical size.
In your example it would be imported as an ~50x33cm image if you set it to 300dpi and ~211x141cm if you set it to 72dpi. But even then the Printer will change it to the right size and done.

Ignore it, it is in no way a problem. Digital images don’t have a physical size. Impotent is that the size in pixels don’t change.

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Hi @Glenda, and welcome!

Relax: this is a jungle :slight_smile:

As a start, use the search utility in this forum,
and search for gimp 72 dpi.

Have fun!
Claes in Lund, Sweden

I’m going to quote myself here:

Just keep in mind that the “72 dpi” was for that specific thread.

For screen display, ignore dpi completely.

For printing, check with your print shop; they often don’t need the value set in the file, but dpi is used to relate print size in pixels to “physical” size. For images viewed at ~30cm, optimal dpi would be ~300 (more is overkill, less can give quality loss); for posters to be viewed from 3m, optimal dpi would be ~30…

While the print shop can adjust the pixel size to correspond to the printer requirements, you may want to do the resizing yourself: if there’s a change in aspect ratio, pixels will be dropped in one dimension, if it’s just a resizing, you could get some blurring, which the print shop may or may not correct.

But again, unless and until you print images, dpi is irrelevant.
So if you have to send an image to someone who insists on a given dpi in the metadata, just correct it for that particular image…

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Here is more info about ppi versus dpi:

Have fun!
Claes in Lund, Sweden

Thanks Claes.
I have read the gimp 72 dpi debate and about to crawl under my bed and hide…! Scary stuff. Also confused me even more.
I have also read your link regarding dpi and ppi. That has cleared up one question for me, how many dpi’s = ppi’s!!
So 1 x dpi = 1 x ppi; dpi is dots for printing and ppi is pixels for images. :crossed_fingers:
However - and there is always a but or a however…
If 1 dpi = 1 ppi and my camera is taking 300dpi, I am still at a loss as to why the 6000x4000 300dpi images I export from Rawtherapee into GIMP arrives at 72ppi and not 300ppi.
A 30x20 image printed at 72 ppi is not going to be the same quality as one printed at 300ppi.

Printing this image at a large size would be very poor quality.

I think I must need to change this after importing as the moment I put in 18 x 12 as the width and height, the resolution auto changes from 72ppi to 333.778ppi

I think I have a lot of homework to do before I send any potential client a link to print their image and I will need to recheck a lot of my images.

Thank you everyone. Have a great day.

Morning, @Glenda,

More confusion or revelations (?):

Have fun!
Claes in Lund, Sweden

This depends on how many pixels you have.

If your image has 30*72 x 20*72 = 2160 x 1440, it doesn’t matter if you print it at 300dpi or 1200dpi, you are limited by the number of pixels. Your 6008x4008 image at 30x20 has 200dpi, so printing at 300dpi also doesn’t result any “improvement”.

At 300dpi, you max print size from your 6008x4008 image is 20x13.33.

For a 30x20 print at 300dpi, you would need an image of 9000x6000.

And again, your camera is not “taking” dpi, it is taking 6008x4008, and that’s all there is to it, everything else is logical mapping from pixels to print size.

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That’s where it goes wrong: your camera doesn’t care about dpi, nor does your editor program or even your printer.
What may happen is that the camera maker has to fill out the metadata field, so picks a value close to what they think you want. (if it would be a real ppi, the true value would be closer to 4000 for a full-frame sensor (*) )

True. But if we are talking about 30cm ×20 cm (let’s assume 12’’ × 8"), the 72 ppi version would require 864 × 576 pixels, and the 300 ppi version, 3600 × 2400 pixels.

Your 6008×4008 pixel image would print comfortably at 18"×12", as shown in your screen shot: the calculated ppi (from pixel size and final format) is well over 300.

It’s a simple relation: pixels == length × dpi… Set any two, and you get the third. Once you grasp that, a lot of the confusion disappears.

As for clients, it will depend on who they are (or rather how knowledgable) and what the purpose is. I’m not sure a Walmart or similar printing shop cares about what they get: you give them a file and a final print size, they print…
If they know what size they want to print, you could adapt the pixel size yourself (usually better than trusting the printer). Or you send the 6000×4000 image, knowing that that will give a good print at any size.
Keep in mind that very large print are rarely viewed from 30 cm…

Once again, don’t worry about ppi while editing. And if a client insists on a given ppi value, modify that particular file (ok, not nice if you have to do that for 100s of files).

But we are getting to sizes where you don’t need the 300 ppi anymore, as viewers will be farther away…

And as a pedantic note: strictly speaking, there is be a difference between dpi (dots per inch) and ppi (pixels per inch); a printer can place multiple dots per pixel to allow more graduations in the colours (a form of dithering). But that’s really not a concern when preparing an image for general printing…

(*) if you figure out how I got that 4000ppi value, you understand the concept :wink:

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You still don’t get it.

No, your camera has no clue about the sice you will print the image. The camera manufacture just writes a random number (300) into a metadata field of the image.

Your camera is taking 6000x4000 pixels nothing more nothing less.
(I will only use the wide in this example to make it easier.)

6000 pixels wide is fix, because that’s what your camera provides. If you change that you have quality loss regardless of increasing or decreasing.

Now it is simple mathematics: Pixels / Inches = PPI (PixelPerInch)
6000 pixels / 18 inch = 333,xx PixelsPerInch

In words: Your image is 6000 pixels wide and if you print it on an 18 inch wide paper it has 333ppi by definition. (Regardless of whether 72 or 300 is in the metadata. )

Or if you set the dpi/ppi:
6000 pixels / 300 ppi = 20 inch

In words: Your image is 6000 pixels wide and you define the PPI to 300 your printing will be 20inch wide.

What is not possible is to print the 6000 pixels with 300 ppi in 18 inch.

No, you don’t. You have to learn to ignore the dpi/ppi.

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Okay - I have to forget 72ppi in GIMP and 300dpi in camera and just focus on the 6000x4000 if I want to print large images. If I want to print a smaller image, I can change the dimensions to eg: 8 X 12 and allow the resolution to change automatically - or allow the printer to work it out all by itself.

By God - I think she’s got it!!!

Hard when everything I read says a large print must be at 300ppi or you lose quality. I promise not to look at the resolution when importing… ( :crossed_fingers:)

Many thanks to everyone

It basically says: if you want good print quality (i.e. 300ppi print), please make sure you have enough pixels (image of high enough resolution) for the desired size to really reach that 300ppi.

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And that’s only true when viewing that print from a close distance… Have a close look at e.g. film posters (those 1×2m ones), you’ll be shocked by the quality at close range

But yes, basically what you describe is how to handle it.

For the best possible quality, you’d have to ensure that your image size in pixels matches what the printer wants for the print size (and that’s not always 300 ppi): if you have more pixels than required, the image has to be down-scaled. There are several ways to do that, faster/less precise or slower/more precise. So you can let the printer handle the down-scaling, or do it yourself… (more or less the same reasoning applies when you have less pixels than required, but in that case you wil have a less than optimal quality)

AI-powered super-resolution upscaling to the rescue! Maybe…