Hello. I have a question why Rawterapee 5.10 does not process jpg to 300 dpi. I can set it to 5.8 without any problems. The same photo 5.8 4008x6008 pixels, 300dpi, 5.10 only 64dpi. Why?
Where do you set a DPI? Technically you define a number of pixels for each axis, and the resolution is chosen while printing or displaying the final jpg.
Different assumption on print paper size? In raw editing dpi doesn’t matter…
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JPG saving in 5.10 only at 64dpi resolution. It does not matter whether the cropping PPI is set to 300 or 500. Is it possible to change the recording? To print, you need jpg at 300 dpi. In 5.9 with the same settings and the same 300 dpi photo
JPG saving in 5.10 only at 64dpi resolution. It does not matter whether the cropping PPI is set to 300 or 500. Is it possible to change the recording? To print, you need jpg at 300 dpi. In 5.9 with the same settings and the same 300 dpi photo
Are you referring to the XResolution and YResolution tags, EXIF 0X011a and 0X011b?
I’m on RT 5.8 and can confirm that a file with a ppi of 180 that is cropped with a ppi set to 300 does indeed get those tags set to 300 ppi.
Can we just use “ppi”?
“dpi” confuses me with printer terminology.
Having correct DPI set in the export has been important when I have submitted scientific figures to journals for publication. I submitted an image which had resolution set at 72DPI instead of 300DPI. The publisher could have corrected this issue in the blink of the eye, but instead wrote an email which would have taken a longer time to request me to resubmit at required DPI. I reopened the image in GIMP, change DPI setting and reexported imaged. Same number of pixels as what I originally sent but DPI was set different. So even though we may not feel the importance of DPI in editing it may be necessary for end use.
I think all contemporary printer drivers just take the amount of pixels, in your case 4008x6008, and the size of the paper you want to print on and then do the resizing math internally.
Many cameras default this value at 72, others use 300, and all of them can be used to print the images in any size you want to.
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The cropping PPI tells you the width and height of the jpeg in cm or inch with the given pixel count if you print or display the image with the given resolution. The jpeg itself has just a width and a height in pixels and a color for each pixel. Nothing more.
Thank you for your tips. My printing house requires 300 DPI, 72 DPI with photo dimensions of 50x70 cm. In another program, for example Photoshop, you set the width, height and DPI resolution. 72, 150 or 300, etc. Rawtherapee 5.9 developed them at a resolution of 300 dpi, while 5.10 at 96 dpi. Why this limitation and how to change it in the program. You can, of course, export to an external program and increase the DPI to 300, but why if you can prepare photos for printing in RT. I tried different settings and nothing. 5.9 at 300DPI, 5.10 at 96 DPI, the same RAW. I wonder if it can be set in the program. If not, it remains 5.9.
Without changing any settings to this in RT, I cannot reproduce the problem:
export as a tif will show 300 dpi at 6016x4014 pxls
export as a jpg will show 350 dpi at 6016x4014 pxls
(same data are shown in Gimp)
As already explained by others, the DPI is more a theoretical value, which helps to define the size of the print in cm. The value 300 is necessary for good quality print in standard size in standard viewing distance. For posters and bigger, the dpi will be much lower! Poster will go with 60 dpi, at a long viewing distance you can print it with 30 dpi.
The example above: 300 dpi at 6016 pixels the max print-size is about 20 inch. You can print the same file as a poster of 200 inch with 30 dpi.
Means: I dont care about any dpi given by the software, i will define the dpi myself after editing a picture.
The cropping ppi in RT does more than just saying the width and height of the JPEG. On saving, it actually changes the EXIF values to whatever the “cropping ppi” was set to.
Since those values are part of the JPEG, the JPEG does get changed, even if the image data does not.
Please have a serious talk with your printing house.
Or better: just look for a different one.
If they insist on “300dpi” it shows they have no clue whatsoever and are stuck technologically in the mid 70ies of the last century when raster image scanning and processing had to exactly match the raster of the printing machine because otherwise all bets were off.
That technical limitation has been gone from any mainstream print shop for more than 30 years now. Modern professional RIP software (raster image processing) is so good you can throw ANY resolution image at it and it will print an awesome picture even from a thumbnail.
The only usage with setting ppi¹ on files is that they import at predictable sizes into layout software.
¹) there have not been digital files with “dots” in them for a while now, so please refrain from using “dpi” and use pixels per inch or centimeter, pretty please.
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then use it as a help to calculate the required image size:
There are 2.54 centimeters in an inch.
width in inches: 50 cm / 2.54 ≈ 19.69 inches
height in inches: 70 cm / 2.54 ≈ 27.56 inches
multiplying with the required dpi number will give you the required pixel dimensions of the image.
Width in pixels=19.69 inches×300 dpi=5907 pixels
Height in pixels=27.56 inches×300 dpi=8268 pixels
to print an image at 50 cm x 70 cm with a resolution of 300 dpi, the image should have dimensions 5907 by 8268 pixels
just these pixel numbers counts for printing
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Which “it” should be used? 300 “DPI” or 72 “DPI”?
And is Robert’s printing house telling him what size photo he’s going to get?!
hmm … my printer does 9600 dpi in width according to the manual, so 70cm wide = 27.559" and I have to send it 264567 pixels in width … sounds like quite a lot if ppi = dpi …
… unless one “dot” is one squirt from my print head which has nothing to do pixels at all? A bit like my monitor where one pixel equals three stripes. 
As one who doesn’t print, this is all very confusing …
if you don’t print, you’ can ignore dpi requirements given by printing houses 
several printing houses uses these dpi indications to give a hint on the image size needed for a proper result. And yes, thats confusing for those who just see this as a porperty value - so the better printing houses asks for minimum absolute images sizes …
Printer manufacturers on the other side uses dpi as marketing gossip - if your printer can use up to 9600 dpi this doesn’t give any information of the image size you need to get a proper result.
So for one who needs help with this confusing dpi requirement introducing the ppi just add confusion
LOL. Yes, why talk about pixels per inch when ink splodges per inch is so much more … relevant to print size?
Now I have checked the situation. The X and Y resolution are taken from the exif data from the raw file and are not overwritten from that PPI thing on the crop details screen. Of course, the exif data might be overwritten manually.
Here is a screenshot from the exif data in RT.
But at some point in time, I assume while replacing the exif handling, an error has been introduced. The following screenshot shows PP3 details, where the resolution has still been correct:
The next screenshot shows the details where it was wrong:
But as I said earlier, that PPI thing on the crop screen was never involved in the whole thing.
I would recommend that a dev like @Lawrence37 has a look into the whole thing.
Well, RawTherapee or any other raw processor does not “process” the image to a particular physical dimension. “Dimension” doesn’t come into play until the image is rendered to a particular medium.
So, the only cogent purpose I see for such a number in the metadata of an image is to communicate to a printer what resolution to use in printing the image. If the people of a printing service tell you what that number has to be in the image metadata, they’re essentially telling you that is the only resolution their equipment supports…
Now, given all that, you might be compelled to resize your image to produce a JPEG/PNG/TIFF/whatever that prints to certain dimensions. So, if you want a 8x10 inch rendition, if their printing resolution is 300dpi, you could insure your image is somewhere near 2400x3000 pixels, using the resize algorithm YOU want rather than having the printing service use some dodgy resize algorithm in the printer or wherever…
Such fun …
From the Japanese EXIF spec. JEITA CP-3451 v. 3.0.
I guess they hedged their bets, eh?
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