Viewing Image DPI in Publisher

[jimjumper]

I copied a number of images from a previous edition of my magazine. I wasn't editor then. When I submitted it to the publisher, he noted that they were low-resolution and had no-bleed. I used Affinity Photo to increase the DPI of the copied image. Will that correct what he is looking at and does the low resolution error appear in pre-flight so I can tell when an image needs correcting?

 

[jimjumper]

Actually I may have found an easier solution. It may be that because I am copying/pasting as a .pdf image that the DPI is different. I pulled the .pdf image, opened it in Finder, then exported it as a .jpeg. The export menu allows you to change or set the DPI. I changed it to 300, repasted it back, and then position and sized it. The pre-flight warning about low DPI went away. But my publisher warned me about 3-4 other images that had low res that aren't showing that in pre-flight as low DPI. Will I need to screen each copied image for DPI to ensure they are not low-res images?

[thomaso]

The Preflight Panel gives you in its Profile's 'burger' menu / dialog window a choice to edit a profile and set min/max values for its image resolution warning or error.

You could create a package of the project or just copy all images via the Resource Manager to a new folder, then upscale/resample the required images, save them (with same file name) and get them updated in APub all together.

[jimjumper]

Great! Just changed that. Does DPI and resolution mean the same thing? The reason I ask is because when I convert the image to get a better DPI the warning goes away but I have 3-4 images that don't show a warning to me but his publishing program does and he informed via email. When I look at the same image in pre-flight I don't see any warning. How do I see what he sees?

[thomaso]

1 hour ago, jimjumper said:

Does DPI and resolution mean the same thing?

Not completely. DPI is a unit for resolution. It is like the relationship between MPH and velocity.

1 hour ago, jimjumper said:

but his publishing program does and he informed via email. When I look at the same image in pre-flight I don't see any warning. How do I see what he sees?

Either by using "his publishing program" or by getting a screenshot from him.

In Affinity you also can check the placed/effective resolution in the Resource Manager (as list view for all resources) or in the Context Toolbar for a single selected image.

 

[Alfred]

45 minutes ago, thomaso said:

DPI is a unit for resolution. It is like the relationship between MPH and velocity.

Strictly speaking, it’s like the relationship between MPH and speed. Speed is just distance per unit time, whereas velocity also has a direction.

[thomaso]

20 minutes ago, Alfred said:

whereas velocity also has a direction.

… like pixels, dots, grids do, mostly horizontal or vertical 😉

[R C-R]

11 hours ago, jimjumper said:

Does DPI and resolution mean the same thing?

I suggest reading https://affinityspotlight.com/article/understanding-dpi/ to get a more complete understanding of when DPI matters & when it does not.

[jimjumper]

All this is interesting information, but since they are interrelated, isn't it a bit moot for editing? When I receive an image from a contributor is there really anything that will improve its visual sharpness besides increasing its physical size and DPI? Since I am limited in physical size  there really isn't much I can do other than use it or not. 

[walt.farrell]

7 minutes ago, jimjumper said:

When I receive an image from a contributor is there really anything that will improve its visual sharpness besides increasing its physical size and DPI?

That seems to be a different question than you started with in this topic, which was about reusing old images from a PDF, not receiving something from a contributor.

For this new question, you need to consider:

1. The pixel dimensions of the image you receive, and the image DPI and original print size.
2. The physical size (dimensions in inches or mm or ...) you are Placing the image in your new document.

Generally:

• If the size in 2 is larger than the size in 1, then you are likely to lose sharpness. You could Edit the image in Photo or in the Photo Persona and Resample it to a higher DPI, which might help, Or you could use some sharpening technique (Unsharp Mask, etc.). But each image may require a slightly different approach.
   
• If the size in 2 is smaller or equal to the size in 1, then the image should be as sharp as the original, assuming the original DPI is no higher than your document DPI.

[thomaso]

3 minutes ago, jimjumper said:

When I receive an image from a contributor is there really anything that will improve its visual sharpness besides increasing its physical size and DPI? Since I am limited in physical size  there really isn't much I can do

If you really (why?) can not upscale/resample the resource to achieve its placed DPI not be lower the document's DPI then you can only use it as is, or reduce its placed size (to increase its placed DPI) … or sharpen the image with one of the various methods. But in particular for images placed with low DPI sharpening can make the visual impression worse than before by an over-sharpened / high-contrast look.

For certain image content it may work to increase its dimensions by adding pixel, e.g. via copy/paste, stretch, inpaint brush etc. I used this method occasionally if I want a certain aspect ration for an image in the layout which the resource does not offer. It's easier with a background texture that doesn't have a certain aspect ratio, like sky, ground, water…