NOTE to the Dev Guys about 72 PPI output

Raw Therapee output - 72ppi.

OK - I’ve trawled the forum enough to have seen this topic raised on a few occasions and I’ve been a little disconcerted by the reactions generated.

I’m personally not that bothered by this crazy, outdated value. And please don’t tell me it doesn’t matter either - I’ve done many a video explaining ppi vs dpi and I understand it better than most.
It’s not hard to take 2 seconds in Ps to change it so no biggy.

However, not everyone is as quick to realise the potential problem - because it IS A PROBLEM!

Try sending full resolution jpegs to Getty, iStock, Adobe(Fotolia) or Shutterstock at 72ppi - and watch every single one get rejected for not being 300ppi.

PoD sites won’t take 'em either, and if you’re into a job destined for web-offset you’ll be in trouble too.

Desktop printer drivers work either in base 300 or base 360 and take their lead from the embedded ppi value - so here again 72ppi causes a load of crap because 300 (the Canon magic number) is not divisible by 72 without some decimal left-overs.
And those left-overs cause print artifacts - yes they do.

So, can the next release of RT please catch up with all the other software out there, even though it might be ultimately unnecessary on a technical basis - pretty please with bells on?

Changing 72ppi to 300ppi to satisfy modern industry standards is, as I said, a 2 second job.

But processing 200 images or more in one go is A LOT OF 2 SECONDS.

Come on chaps - it can’t be hard.

Or have I totally lost the plot and missed something in the current 5.8 release that already allows for changing output resolution?? If I have then pray someone do tell me where it is…

PPI is just metadata, isn’t it?


Where do you see 72 PPI in RT or on the output?

@ChasingShadows - Same place everyone else sees it - nowhere…

But every time I process a raw and export it as a full rez tiff, if I open it in a RIP then there it is - 72ppi resolution.
The simple way around it is to change the ppi to 300 with resample deselected.

But it is a pain in the arse if you are doing a big run of images.

It certainly is Ingo, but I fail to see your point. I’m stating a simple practical set of cast-iron facts about the fault of continuing with this application of a 72ppi tag on exported rasterized images out of RT.
Just change the tag to 300 and have done with it, then folk could export full rez jpegs that CONCUR with todays industry standard - the agency folk that demand it will NOT change it themselves, they’ll just reject the images.
We all know it’s a stupid thing, but that’s where we’re at.

And FYI I know at least 50 people who refuse to try RT because of this - even though I show them how to correct it in Photoshop in a few seconds - why? Because they are big batch processors.

Seriously Ingo, arguing against this is crackers!

Just so you know I know what I’m talking about skip your way through this vid of mine

Seems like something that should be easy to change with exiftool/exiv2.

Why so resistant ?

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I’m not, but I don’t have the skill to change it. I am suggesting a tool that will allow you to fix this problem in bulk, right now, with no changes to RT (which would happen in the next release, whenever that is).

@Andy_Astbury1 If you export a JPEG, IrfanView tells me the DPI is 300. If you export a TIFF or PNG, IrfanView tells me the DPI is not even set.
So, while it would certainly be possible to fix that, just pointing to RawTherapee for being at fault is not the whole story. The other software (maybe plural?) doesn’t handle missing ppi information gracefully and just assumes some value.

@Thanatomanic 72 seems to be the EXIF default value. Search for “dpi” here.

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There has been some effort to support this issue:
Unfortunately it has lost traction.

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Which is strange for PNG because of this:

@floessie - thanks for that.

@Thanatomanic I can’t use IrfanView as it appears to be windows-only, but everything else reports the images at 72ppi - even Macs own system exif viewer.
But just out of curiosity I opened an image in GIMP - and viola, 300.

So, I was assuming that RT literally tagged the output images at 72ppi in the metadata - but do I now understand that it outputs images WITHOUT any ppi tag?


Hmm, interesting indeed. Perhaps this is an issue of IrfanView. GIMP seems to read the ppi information just fine.

EXIF in PNG is an extension, so it could well be that IrfanView isn’t prepared for it.

@Andy_Astbury1 I’ve created this issue as there seems to be at least an inconsistency in the way RT handles the ppi values for different export types:

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@Thanatomanic - ok, though I have just exported a raw file as jpeg, tiff, 8 & 16bit PNG and they all report as 72ppi in Photoshop - which isn’t known for getting this kind of stuff wrong - and also my OS preview exif inspector.
If it’s of any consequence the RT install is the 5.8 Mac release - I’ll give it a try on the Linux dev build to see if there is any difference should I??

Hmm that’s very interesting. The PNG and JPEG are explicitly getting their Exif tags XResolution, YResolution and ResolutionUnit set to conform to 300 dpi.

Can you confirm in another way what the Exif information in your exported files is? Exiftool maybe?

@Thanatomanic - just checked in exiftool, PNG reports X and Y at 300, but TIFF has nothing specified for horizontal or vertical resolution.

I’ve actually learned something - I assumed it was impossible for a rasterised image to exist without a resolution tag!

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Does that mean that there are other ways for Photoshop to determine ppi? (I am not an expert)
It may be good to compare the metadata of a JPEG or PNG file exported from RT and from Photoshop and see which tags are different and could influence the apparent ppi.