can't change image resolution in affinity photo

[fdoebbelin]

When I change image resolution with or without rezising, the new value is not stored in the file.

We had created a batch processing, which has so far carried out this change of resolution from 72dpi to 300dpi without any problems.

[Gabe]

Hi @fdoebbelin,

I could not replicate this. Are you definitely running the latest version? 

Thanks,

Gabe. 

[musical-bodger]

I have a similar problem. Using Photo 1.6.7 Mac version.

Changed the resolution and size of a load of images for my web site. Resolution was changed from 300 to 72 and size then adjusted to suit my needs. After exporting as jpegs the resolution is back to 300 but the size remained as I had set it. Annoying!

Any ideas as to what has happened? And how do I stop it happening again.

[MEB]

Hi musical-bodger,
Welcome to Affinity Forums
Click the More button in the Export dialog and untick Embed Metadata for now. This is due to a known issue/conflict with the original image exif data and it's already logged to be looked at.

[musical-bodger]

Hi @MEB

Thanks for the welcome and thanks for the workaround too. Much appreciated.

Pity I didn't know about this issue before I exported 75 images! I was wondering why the website images were taking so long to load. Guess I'll just have to waste another couple of days resizing them all and then redoing the website. Great!

One more question. Are the files I exported as 72 actually 72, or is it just the metadata that is incorrect?

Thanks for the solution.

Steve

Edited November 23, 2018 by musical-bodger
added final question.

[Alfred]

23 minutes ago, musical-bodger said:

I was wondering why the website images were taking so long to load.

If the images are for use on a website, why should it make any difference what DPI value is stored in the file? Web browsers only know about pixel dimensions.

[toltec]

2 minutes ago, αℓƒяє∂ said:

If the images are for use on a website, why should it make any difference what DPI value is stored in the file? Web browsers only know about pixel dimensions.

And how big exactly is a pixel 

[musical-bodger]

3 minutes ago, αℓƒяє∂ said:

If the images are for use on a website, why should it make any difference what DPI value is stored in the file? Web browsers only know about pixel dimensions.

Thanks alfred.

This is something that's always caused me confusion. (I'm a sculptor and musician, not a web designer) So, why is it always stated that resolution needs to be no more than 72 for the web and 300 for printing?

[musical-bodger]

5 minutes ago, toltec said:

And how big exactly is a pixel 

[toltec]

3 minutes ago, musical-bodger said:

Thanks alfred.

This is something that's always caused me confusion. (I'm a sculptor and musician, not a web designer) So, why is it always stated that resolution needs to be no more than 72 for the web and 300 for printing?

I was in the print trade for 30 years and I have never seen that and are you talking about pixels, lines or dots per inch. The trouble is, most people don't seem to understand this.

For what it's worth the imagesetter I used in the print trade was 2540 dots per inch, even although it was normally used to produce  film for 150 lines per inch from 300 pixels-per-inch images. 

And take pixels (the reason for my question) on a 52 inch TV, with an HDMI screen, there are about 36 pixels in an inch. On some iPads there are over 300 pixels in an inch.

So, to repeat myself, how big is a pixel ?

[toltec]

What you need to do is work out how many pixels are required to display on your web page. For half of a 1920 pixel page, you need 960 pixels. That's it, do as Alfred says and ignore PPI, DPI LPI etc.

The only thing that matters is the quantity of pixels in the image.

Because of the different devices and different resolutions, a display of a 920 pixel image will vary in physical size dramatically. So you just can't use physical dimensions for anything.

For litho printing, you need about double the amount of pixels in an inch relative to the lines per inch value of the printer. 

Most colour printing is done with 150 or 175 lines per inch, so 300 or 350 pixels per inch. But as I said, that will be probably be produced on a 2540 dots per inch imagesetter.

You can certainly use higher numbers of pixels per inch but the file sizes will be bigger. That's the only drawback.

[musical-bodger]

@toltec

Thanks so much for taking the time to explain all that. That is really helpful and much appreciated.

I knew the difference between DPI & PPI and my brain has always told me that DPI has no bearing on web images. Great to have it all explained out so simply.

If you want to know anything about wood, just give me a shout! 

[Alfred]

1 hour ago, musical-bodger said:

Thanks alfred.

You’re welcome.

Quote

This is something that's always caused me confusion. (I'm a sculptor and musician, not a web designer) So, why is it always stated that resolution needs to be no more than 72 for the web and 300 for printing?

It’s just the result of copying and pasting of the same myth from one website to another! (The value is usually 72 dpi for Mac and 96 dpi for Windows, but in both cases the inches are ‘logical’ inches rather than physical ones.)

 

[musical-bodger]

40 minutes ago, αℓƒяє∂ said:

It’s just the result of copying and pasting of the same myth from one website to another!

Yeah, I'd sort of twigged that. I guess it's why I was asking on this forum, thought I would get the knowledge here.

I've watched the Affinity video but there's so much info to take in re. building my new website (this is the third, first was in 2001) that I forget as I'm not doing this regularly.

Thanks for your help, Alfred. Much appreciated.