A Photo - how to see the file size of a photo?

[frebe]

Again, that is correct, but you (meaning me😂) can’t calculate this easily in the Document Resize dialog box. Being able to view the file size in the dialog makes it quick and easy to reduce the dimensions to fit the higher dpi without calculating.

File size(bytes) is a product of dpi x dimensions, as I’m sure you know, so file size is a good indicator that you are not adding data.

Another option for the Document Resize dialog would be to enable changing the dpi with an option to automatically reduce the dimensions to maintain the same file size, but currently the dialog only allows you to change both separately, they are not linked.

I am crap at calculating but if you explain your formula maybe I could do it that way! 😁
(300dpi is specific to print technology. 360dpi is not, so it has to be 300dpi , or occasionally 400 or 600dpi for highly detailed or colour critical images)

Edited March 28 by frebe

[frebe]

Ok, so I figured I was missing something and found an Affinity video that explains the document resize dialog more clearly. 

It's actually simpler than the photoshop process but not intuitive if you don't realise that you can change the unit type with resample unchecked (because they are greyed out when default unit size is pixels.

So, the process is still 2 step:

1. To increase dpi to 300 - Open document resize dialog, uncheck resample, change dpi to 300, and save. (if you change units to other than pixels, you can see that the dimensions ARE linked to dpi-  ie, dimensions get smaller as you increase dpi - hooray! Pixel dimensions don't change (which also confused me- someone could explain it, but I just need a simple workflow!)

2. To change image dimensions (downsize only) - reopen document resize dialog, check resample, change dimensions, save. Or,  just export in required dimensions. This is actually an easier workflow! 

Sorry, if this is simple and obvious! But anyone else who gets confused like me by the different dialog menu might find it useful.

Here is the Affinity video:

 https://www.youtube.com/watch?v=KTmM8hw2r_M

 

[Alfred]

2 hours ago, frebe said:

Pixel dimensions don't change (which also confused me- someone could explain it, but I just need a simple workflow!)

Pixels dimensions can only change if you allow resampling. Since you’ve unchecked resampling at step one, you’re limited to changing the physical output size.

[frebe]

So I have learned ! - I think I’ve got the hang of it now 😂 Basically, I don’t want to resample until I have to change the image dimensions for printing, so that’s my workflow! 😅

[frebe]

Thanks for your solid input Alfred - helped me to get my brain into gear😂

[Oufti]

On 3/28/2024 at 1:49 AM, frebe said:

File size(bytes) is a product of dpi x dimensions, as I’m sure you know, so file size is a good indicator that you are not adding data.

In fact, file size depends also of compression, metadata (like color profiles, keywords, etc.) Thus it's not such a good indicator of an image quality as one can think first.

Actually the product of dpi and (physical) dimensions is a number of pixels — which is not exactly a "dimension" since pixels don't have intrinsically any physical size, but they are the real data.

I like to compare pixels and letters:
If you ask "How long is that word?", you basically can have two answers: "It's a five letters word" or "It's 25 mm long (or 1 inch or 72 pt)".
  —  In the first case, like with pixels,, it's an abstract number. You have no idea of its physical size, these five letters could be huge on a poster or tiny in an insurance contract. But you know how many significant elements you have.
   — In the second case, you have a physical dimension but no idea about the content (it could as well be a word like "the" or a word like "supercalifragilisticexpialidocious"). 

The link between both answers is the letter size (or for an image, the number of pixels per inch, dpi or ppi, which is equivalent).
— Usually, because it's so small, instead of the size of the pixels, we use the inverse, how many of them are contained in a fixed dimension (e.g. you'll count 300 pixels in an inch), like you can say "each letter is 5 mm broad" or there are 5 letters in 2,5 cm (1"). 

Hope it helps. 

Edited March 30 by Oufti
Punctuation and clarification.

[frebe]

Hey Oufti, that is really very helpful, thanks! Learning a lot on here 😁

[Oufti]

On 3/28/2024 at 1:49 AM, frebe said:

File size(bytes) is a product of dpi x dimensions, as I’m sure you know, so file size is a good indicator that you are not adding data.

In fact, file size depends also of compression, metadata (like color profiles, keywords, etc.) Thus it's not such a good indicator of an image quality as one can think first.

Actually the product of dpi and (physical) dimensions is a number of pixels — which is not exactly a "dimension" since pixels don't have intrinsically any physical size, but [even if] they are the real data.

I like to compare pixels and letters:
If you ask "How long is that word?", you basically can have two answers: "It's a five letters word" or "It's 25 mm long (or 1 inch or 72 pt)".
  —  In the first case, like with pixels,, it's an abstract number. You have no idea of its physical size, these five letters could be huge on a poster or tiny in an insurance contract. But you know how many significant elements you have.
   — In the second case, you have a physical dimension but no idea about the content (it could as well be a word like "the" or a word like "supercalifragilisticexpialidocious"). 

The link between both answers is the letter size (or for an image, the number of pixels per inch, dpi or ppi, which is equivalent).
— Usually, because it's so small, instead of the size of the pixels, we use the inverse, how many of them are contained in a fixed dimension (e.g. you'll count 300 pixels in an inch), like you can say "each letter is 5 mm broad" or there are 5 letters in 2,5 cm (1"). 

Hope it helps.