Questions about DPI for Affinity Publisher

[hearhisvoicepoetry]

I am making a book with approximately 200 images or more. I am almost complete. I originally thought that since I chose 300 dpi at my document setup, that when I exported to PDF all my images would convert to 300dpi. I have been told now that resampling down to 300dpi during export only resamples down for images placed that are over 300dpi, and that my images that are under 300dpi need to be changed to 300dpi before placing. So I individually started opening my images in Affinity Photo and resizing. I have changed to 9.25in. height first, then changed to 300dpi, then went back and changed to pixels, then chose bicubic and left resampling checked. This changed the image to 300 dpi. Then I went back to Publisher and opened resource manager and replaced the low resolution image with the new 300dpi one, which exactly replaced it, leaving the crop and filter intact. After replacing, the image is now showing lower than the 300dpi. I assume because of the cropping and filters? So I don't know that any of these steps actually did me any good. I have around 80 or more images that are lower than 300dpi. Is there an easier way to convert all of them to 300 dpi in my document in Publisher? If not, is it okay that after the crop and filter, it is showing less than 300dpi. If that is okay, then is there even any point in me changing any of them to 300dpi? Thanks in advance for your help. It is a 6x9in book plus bleed, Greyscale. 

[Fixx]

Generally there is no gain in resampling up if images are initially low res. Some exotic tools can invent detail to images but that is still more like art than science.

[Joachim_L]

Welcome to the Affinity forums @hearhisvoicepoetry!

Why do you want images to be forced to 300 dpi? Sometimes this does not give you any improvement. You have to judge your material if it is worth the effort. In ancient times working in prepress, we found that 240 dpi were sufficient for offset printing.

Never tested this, but in theory you can resample to higher resolution in the export dialogue. Just set Above DPI to e.g. 72, pick your Resampler and have checked Document Resolution or set your own DPI.

[lacerto]

7 hours ago, Joachim_L said:

Never tested this, but in theory you can resample to higher resolution in the export dialogue.

Thankfully that does not happen. But rasterizing in-place (e.g. right clicking an image and choosing Rasterize) will upscale to document DPI (and I guess always bilinearly), and that is very seldom useful or a desired feature (the RIP software would probably do a better job than applying upscaling uncritically, so e.g. low-res screenshots would normally produce better unhandled than upscaled, unless done separately and qualitatively). 

[hearhisvoicepoetry]

 

Generally there is no gain in resampling up if images are initially low res. Some exotic tools can invent detail to images but that is still more like art than science.

My images are digital images of very old paintings (over 100 years old), so the resolution is low for most. I have found the image with the highest possible resolution that I can. The reason I am trying to convert to 300 dpi is because I am publishing this book with these images on Amazon for print, and every where that I have read says that you need to place your images at 300dpi. Is that not necessary?

 

[Joachim_L]

7 minutes ago, hearhisvoicepoetry said:

I have read says that you need to place your images at 300dpi. Is that not necessary?

You don't need to, but for quality reasons you should. If your images are low resolution and you do not expect any improvements with resampling, leave the resolution as it is. I guess Amazon and others won't be upset about quality / resolution, they print your stuff at whatever quality and sack the money.

[hearhisvoicepoetry]

4 hours ago, Joachim_L said:

Why do you want images to be forced to 300 dpi? Sometimes this does not give you any improvement. You have to judge your material if it is worth the effort. In ancient times working in prepress, we found that 240 dpi were sufficient for offset printing.

Never tested this, but in theory you can resample to higher resolution in the export dialogue. Just set Above DPI to e.g. 72, pick your Resampler and have checked Document Resolution or set your own DPI.

Most of my images are low resolution due to being older pictures from over 100 years ago. The recommended requirements to print is to make your image 300dpi before placing them, is what I understand. I am wondering if there is a for sure way to do this during export, that has been tried and proven to work. When I resample my images through Affinity Photo, then replace it back into my document in the place of the old one through resource manager, it is not showing as 300dpi. Actually, when I at first tried to resize it through AP, without changing the inches, it made my images super large, like 9000x9000 pixels. So that is when I tried the method to put the actual inches with the 300dpi (saw this on an Affinity tutorial), but now it's still showing less than 300dpi.

[hearhisvoicepoetry]

16 minutes ago, Joachim_L said:

You don't need to, but for quality reasons you should. If your images are low resolution and you do not expect any improvements with resampling, leave the resolution as it is. I guess Amazon and others won't be upset about quality / resolution, they print your stuff at whatever quality and sack the money.

I would like to do what is recommended, because I would like the quality to be good. I do not know whether to expect any improvement or not with the resampling. I cannot tell a difference when I am looking at it on the screen, but I guess I was assuming I should do this because it will make a difference once printed. Just want to know the best way to do this and do it correctly. 

[hearhisvoicepoetry]

4 hours ago, Lagarto said:

Thankfully that does not happen. But rasterizing in-place (e.g. right clicking an image and choosing Rasterize) will upscale to document DPI (and I guess always bilinearly), and that is very seldom useful or a desired feature (the RIP software would probably do a better job than applying upscaling uncritically, so e.g. low-res screenshots would normally produce better unhandled than upscaled, unless done separaely and qualitatively). 

Okay, so you recommend each image is done separately, correct? If so, then how do I best resize in Affinity Photo and how come when I resize to 300dpi, it is showing as a different dpi once I replace the image in resource manager? Is that because my crop and filter is still applied after I replace? When I resize to 300dpi and DON'T change the measurements to inches, then my final resized images are like 9000x9000 pixels which is very large, but of course then the dpi is like 600 (which will resample back down to 300dpi in export), but I would rather not have 79 images that large in my document, if there is a way to resize, keep the 300dpi, without having such a huge image.

[hearhisvoicepoetry]

I have been resizing in Affinity Photo as such: Bicubic, 300dpi pixels, resample clicked on. Should I be resizing maybe with the resampling option clicked off? I absolutely do not want to make the quality of my image worse, however. That would defeat the whole purpose.

[hearhisvoicepoetry]

1 minute ago, BofG said:

This is a bit of a muddle, obviously your image files are not over 100 years old, so do you mean the original images that were photographed/scanned are themselves lacking in detail?

Either way, you are not going to get extra detail from out of nowhere (unless you use some kind of AI upscaling, even then results vary). You are probably better off leaving your images as they are and letting the print process deal with things.

Yes, you are correct. The original paintings are over 100 years old, but there has been digital scanning or photographing of those paintings done as some point, which are lower resolutions. For me to look at them on my screen, I am satisfied with how they look. I was just trying to do what is recommended to make sure they print well.

So you are saying you think it is best to just leave them alone? So should they come back close to what I am seeing on the screen in my document when I view at 100%? So resizing up to 300dpi could actually make the quality worse?

 

[hearhisvoicepoetry]

53 minutes ago, BofG said:

Do you have a printer? Run a page off and see, even if your printer doesn't reach the dpi of a press it will still give you a better idea than viewing on screen.

I just printed off one image in the size that it will show in my book, with the original lower resolution. Then I resampled the same image up to 300dpi and replaced it and re-printed. Honestly, I asked both my daughters which was clearer. One chose one, the other daughter chose the other. I honestly could not tell a difference. So I guess maybe I should just not worry about changing any of them. Because of them being images of older paintings, maybe it will be expected to not be crystal clear.

[Old Bruce]

42 minutes ago, hearhisvoicepoetry said:

I asked both my daughters which was clearer. One chose one, the other daughter chose the other.

Be careful, that is how King Lear starts....

[hearhisvoicepoetry]

7 minutes ago, Old Bruce said:

Be careful, that is how King Lear starts....

LOL! Yeah, I will be careful!!

[lacerto]

2 hours ago, BofG said:

Print always makes bad images look worse than on screen.

Not necessarily! The printer's method to produce the "missing" pixels may be far better than some stock bilinear that you would typically get if you resample without clear idea  on what should be done. You might also watch images on screen "unrealistically" close compared to the actual sizes they will be viewed when printed and pay attention to some detail that would not show on paper. It is really difficult to give general instructions...

[hearhisvoicepoetry]

30 minutes ago, BofG said:

Out of curiosity, what is the effective dpi you are getting?

The original image is 91dpi. I could not tell the difference between it and the 300dpi image. 

[John Rostron]

I presume  that you are using Document > Resize document to do your resizing etc. I have sometimes found that the order in which you enter data in the boxes can affect the final size. What units are you using for your image in Photo? If your aim is to occupy a specific, fixed-size space in your Publisher document, then you will be using physical units such as inches. You should ensure that you are using those same units in Photo.

I the resize dialogue, set the dpi first, with Resample ticked. Then enter the target size in the width or height box in (for example) inches. (If you do this the other way round, you may find that the set width changes.)

Now, when you export the resized image it can be placed in your Publisher document, the dpi will not change

John

[hearhisvoicepoetry]

4 minutes ago, John Rostron said:

I presume  that you are using Document > Resize document to do your resizing etc. I have sometimes found that the order in which you enter data in the boxes can affect the final size. What units are you using for your image in Photo? If your aim is to occupy a specific, fixed-size space in your Publisher document, then you will be using physical units such as inches. You should ensure that you are using those same units in Photo.

I the resize dialogue, set the dpi first, with Resample ticked. Then enter the target size in the width or height box in (for example) inches. (If you do this the other way round, you may find that the set width changes.)

Now, when you export the resized image it can be placed in your Publisher document, the dpi will not change

I have tried this and I believe this is gonna work. My end result image size is around 5MB, so I am hoping this will work, since I have so many images. Much better than the previous way ending in 37MB per image. LOL! Thanks for everyones help!