Adjusting document size

[dddeux]

Hello,

 

I must not be understand how the document resize works in Affinity Photo in relation to the dpi. For example if my document is 800 x 600 at 300dpi and I would like to change the dpi to 150 and have the pixel dimension remain and the same so it would now be 1600 x 1200 at 150. If I go to Document / Resize Document the dialogue box opens and unlike PSD if i change the dpi to 150 the document wants to resize to 400 x 300 so it is now half the size and half the dpi density.  What I'm I missing?

[barninga]

i think you have to uncheck the resample checkbox in the resize dialog.

however, i'm not sure i understand your example. if you have a 800x600 px image at 300dpi, and you change the dpi to 150, saying that the PIXEL dimensions have to remain the same and it would be 1600x1200 does not make sense to me. this would mean, if i don't fail, that the print dimensions, not pixel, would remain the same.

[dddeux]

Barninga,

 

Thanks for the reply, but what I was trying to ask about is the pixel dimension remaining the same and the print size increasing. The image isn't resized as much as the quality of the output is decreased size increased, a 1600 x1200 print at 150dpi where the original would be 800 x 600 at 300dpi.

 

I have tried checking and unchecking the resample check box and the only way it seems to work is decrease the dpi and leave the pixel size the same or decrease the dpi and decrease the pixel dimension. It doesn't work the other direction decreasing the dpi and have the pixel adjust upward.

 

This is a simple operation in photoshop the dialog box on resize has two components one for pixel dimension the other document size.

[R C-R]

I am still having trouble understanding what you mean about changing the dpi while keeping the pixel dimensions the same. Pixels can't change size; you can only change the number of them in the document (like by resampling) & how close together they are printed (by changing the dpi).

 

You may find the Understanding DPI video tutorial helpful.

[evtonic3]

decrease the dpi and decrease the pixel dimension. It doesn't work the other direction decreasing the dpi and have the pixel adjust upward.

 

 

Where do you see the setting that allows to decrease pixel dimension?

[MEB]

Hi dddeux,

Welcome to Affinity Forums :)

Affinity Designer/Photo doesn't calculate the physical dimensions for you as Photoshop does.

 

What you are seeing is Affinity raising or decreasing the value proportionately in pixels when changing the dpi with Resample checked: In this situation Affinity is simply translating proportionately the increase in dpi to the pixels value - this is what's leading to the confusion - it doesn't make much sense because when we talk about dpi we are intrinsically talking about physical dimensions and dot density, not about pixels.

 

If you uncheck Resample, then the pixel dimensions are fixed and you can expect an increase in physical dimensions if you reduce the dot density (dpi) and vice-versa. However Affinity doesn't calculate or show this for you and the dimensions in the input box remain the same (even after you change them to a physical dimension). This again doesn't help much. 

 

Here's a small tip that may help (hope it doesn't add to the confusion): If you want to see the physical dimensions your document will have after you change the dpi value (when the units are set to a physical dimension) - check and uncheck again the Resample box - this is only to force Affinity to update the dimensions in the input fields (even when greyed out).

 

Here's a practical example to make this clear (using Affinity Photo here):

- create a document with 800x600 pixels with 72 dpi

- go to menu Document ▸ Resize Document...

- uncheck Resample - this will "freeze" the pixel dimensions, so we will be working with physical dimensions and pixel density only

- change the Units dropdown to Centimetres (or Inches if you prefer) - you will see that the document will have a width of 28 cm if printed at 72dpi

- change the dpi to double (144 dpi) - doing this will increase the density of the dots to double/per inch while reducing print dimensions to half, however Affinity didn't calculate/show the print dimensions in the dialog. It still looks the same.

- check and uncheck the Resample box to force Affinity to update the dialog

You should now see that the document dimensions were updated to half the previous physical size as expected. If you then change the units to Pixels you will see that the document still shows the original 800x600 pixels too. All we have done was changing its physical dimensions in function of the pixel density.

[dddeux]

Hello,

 

I followed your tip I created a document 6 in. x 4.5 in. at 300dpi. I opened the resize dialog window changed the dpi to 150 with resample unchecked, the pixel/inch dimensions where grey and didn't change, I clicked the resize button. Once finished I reopened the resize document window and it now showed a 12 in. x 9 in. document at 150 dpi. This is what I was asking about in the first place.  

 

That what I was expecting to happen, but because it wasn't updated while I was making the initial changes I didn't think/realize it was going to happen. The fact that I could not see the change in the dialog window prior to clicking "resize" is what caused the confusion so I didn't continue. It would be nice to see the change happen in the first window and not have to reopen a second window to know it had resized dimensionally. 

 

I think you can understand my confusion when "However Affinity doesn't calculate or show this for you and the dimensions in the input box remain the same (even after you change them to a physical dimension). This again doesn't help much. " Because I never saw a change in the dialog window I was under the impression nothing was going to happen or change.

 

Maybe this is something that could be dealt with in future updates.