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Hi Gumbo23

You can change the DPI by clicking Document>Resize Document  :)

 

J

This doesn't seem to have made a difference - if I uncheck 'resample' the document is the same size. Should it not be bigger if I've upped the DPI?

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if I uncheck 'resample' the document is the same size. Should it not be bigger if I've upped the DPI?

document: same; image: smaller

 

If you resample you get more pixel but not more quality.

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The video tutorial "Understanding DPI" may help clear up any confusion about what happens when you change the document's DPI.


Affinity Photo 1.8.4, Affinity Designer 1.8.4, Affinity Publisher 1.8.4;  2020 iMac 27"; 3.8GHz i7, Radeon Pro 5700, 40GB RAM; macOS 10.15.6
Affinity Photo 
1.8.4.186 & Affinity Designer 1.8.4.4 for iPad; 6th Generation iPad 32 GB; Apple Pencil; iPadOS 13.3.1

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Hi gumbo23,

 

This doesn't seem to have made a difference - if I uncheck 'resample' the document is the same size. Should it not be bigger if I've upped the DPI?

 

No, if you unchecked Resample. Why do you want to change the DPI? Do you want to print the image at that resolution?

If you only want to increase the number of pixels of the image to increase its size when viewed on a screen, you must keep Resample checked. There's no need to change the dpi.

Simply enter the new dimension in pixels in the width field with the padlock icon closed if you want to keep its proportions and press enter to update the height field and change the Resample to Bicubic or Lanczos to get better results (quality). Then press the Resize button.

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MEB, now I'm really stumped.   In simple, down to earth words, (speak slowly and clearly), Resample checked or not checked, and reasons why.  I always use Lanczos 3 non separable.

 

Cheers,

 

David

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I always use Lanczos 3 non separable.

David, in most cases this is OK. But gumbo23 did not tell us very much about what he has and what he wants.

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That depends on what you want to do:

 

With Resample checked you will change the image pixel dimensions. That means adding or removing pixel to/from the image. This will decrease image quality no matter if you are enlarging or reducing the number of pixels in the image (although enlarging is more problematic).

 

With Resample unchecked, you can only change the physical dimensions of the image when printed without changing the image pixels (the pixels dimensions input fields are greyed out when you uncheck Resample). You can only change the dpi. Assuming that your image has 96 dpi, reducing this value to 72 dpi for example will increase the physical dimensions of the printed image because you are using less dots per inch and thus able to fill a bigger area; increasing it to 300 will decrease the size of the printed image because you are now using more dots per inch and thus only able to fill a smaller area. Note that the pixel image information has not changed in any way - you are simply printing it with different densities (placing the dots closer or farther from each other).

 

[EDITED] You can also change both image pixel dimensions and dpi at the same time for more flexibility when printing, but again since you are adding new pixels to the image you are again sacrificing image quality too as explained above.

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I'm sorry MEB this is the typical reply of someone who works almost exclusively on-screen. Any printshop requires high DPIs, I've noticed myself that when you introduce a low-DPI image (say a logo or something from a third party) into a high-DPI environment AP retains it as a low-DPI layer resulting in loss of sharpness when printing. And I'm sorry Gumbo23 I've tried most of the solutions given above but the only that REALLY works for me so far is upping the DPI in Gravid Converter (under Picture>> Resolution. It does indeed change dimensions then) before introducing the image in AP

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Hi Vala,

When you insert a low dpi image (say 72) into a high dpi document (say 300) Affinity will adjust its physical dimensions (of the image) in relation to the document dimensions to match document's dpi.  

So for example if the image has 800X600 pixels at 72 dpi and is placed on a document to be printed at 72 dpi (just for comparison purposes), the image's width will have 11,11 inches (800 / 72). If you place the same 72 bit image in a 300 dpi document, the image's width will be just 2.66 inches (800 / 300) .

 

 

Regarding Graphic Converter, there's no way to artificially increase the size of an image without sacrifice some quality.

What you are describing and Graphic Converter is doing is changing both image pixel dimensions and dpi at the same time.

You can also do that in Affinity Photo keeping Resample checked and changing the dpi (the image pixel size will increase accordingly) but this also decreases image quality because you are adding (interpolating) new pixels to the image based on existing image information to be able to fill the same physical dimensions at a higher dot density (dpi).

 

Try it yourself: open an image (72dpi) in Graphic Converter and increase the resolution to 300 dpi, then check the dimensions of the image in pixels as you're used to.

Then go to Affinity Photo open the same original image (72 dpi), go to menu Document ▸ Resize Document and change the dpi value to 300 (keep Resample checked) press the Resize button then check the image pixel dimensions. They are the same as the image processed in Graphic Converter.

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I'm struggling with this myself.

 

Having gone through the tutorial(s) and reading threads, here how I think this works:

 

Please correct me if I have anything wrong!

 

Thanks!

 

:)

 

-----------------------------------------

 

 

It is the pixel resolution that determines the quality, clarity and fidelity of a digital image on screen - the higher the pixel resolution, the more information you have to work with, and thus, the better the image.

 

Another setting, which can be confusing, is Dots Per Inch, or DPI.

 

DPI becomes important when you are preparing a document for printing.

 

It is a physical measurement which specifies the number of dots per inch that will be printed.   (Think of it as the print resolution of a digital image)

 

This is referred to as an image’s print density.

 

Affinity Photo’s develop persona works at 96 dpi.

 

When you develop an image in AP it will have a value of 96 dpi.

 

This may seem counter-intuitive, but bringing in and developing an image at 96 dpi does NOT mean that you are working with less resolution or less quality than if you were to bring that same image in at 300 dpi.  (Again, it is the pixel resolution that determines quality in this case).

 

In fact, if you were to uncheck “Resample” and change the dpi of a digital image from 96 to 300 dpi, the image would still have the same pixel resolution that it did at 96 dpi.

 

To put it another way, the quality, clarity and fidelity of your digital image will not be changed by changing its dpi in this manner.

 

Although a digital image currently looks good at 96 dpi on your display screen, a physical print of a digital image usually needs greater print density than that (generally around 200 to 300 dots per inch).

 

Here is the best way to adjust the dpi of a digital image in Affinity Photo:

 

Suppose you need to print an image at 4 by 6 inches with a print density of 300 dpi.

 

To prepare a document for printing at these values follow these steps:

 

Create a new document.

 

In the document setup menu, set the units (for example inches).

 

Set the required page width (4 inches).

 

Set the required page height (6 inches).

 

Set the required DPI (300 dpi).

 

Click OK.

 

Copy and paste your digital image into the new document.

 

Reposition the content to best fit the required size of this new document.

 

Export it when ready.

 

To sum up:

 

Pixel resolution determines the quality of a digital image on screen.

 

Pixel resolution AND print density (dpi) determine the quality of a physical print of a digital image.

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Let’s say I have an image file size of 300 mb’s.   Working with this image file size of 300 mb’s, and keeping 300 mb’s I can increase or decrease the dimensions, top, bottom, left and right.

 

Not dealing with pixels, dpi, ppi.    Physical size IS 300 mb’s.

 

So, what is important to me is to keep the 300 mb’s.   I can then resize the image, smaller or larger and not change the 300 mb’s.

 

What will change is the RESOLUTION.   And this is okay with my workflow.

 

How do I do this in AFFINITY PHOTO?

 

Also, where do I find the mb size of an image in Affinity Photo?   For instance, a 300 mg file, without having to go to export to learn the size.post-26329-0-99964900-1460763659_thumb.pngpost-26329-0-94411300-1460763658_thumb.pngpost-26329-0-57895200-1460763657_thumb.png

 

Using PS CS 5, screen shots show what I am writing about.

 

Cheers,

 

David

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David,

 

An Image document's file size (in KB, MB, whatever) is related to but not the same thing as an image document's physical print size (in inches, cm, whatever).

 

As explained in part in the "File size" section of the Photoshop help document Image size and resolution, the file size is dependent not only on its pixel dimensions but also its file format, any compression applied to the image data (lossless or lossy), image color depth & number of channels, the number of layers or other internal constructs (including multiple resolution versions of the same image included in the file for various reasons), & the amount of embedded metadata (like Exif, IPTC, or XMP) & other data (like an undo history, snapshots, color palettes, etc.) that may also be saved in the file.

 

Note that some of this saved data has nothing to do with image quality but may be useful for other reasons, like cataloging, enabling non-destructive editing, & improving the responsiveness or reducing the memory requirements of some operations.

 

This is why document file size info is not available in AP until you choose which export options to use -- different options (particularly file format) will affect exported file size significantly. Similarly, an image's working memory size may be considerably different from its size when saved to disk (because of caching, buffering, file system differences, etc.), so until a document is actually saved its file size can only be estimated.


Affinity Photo 1.8.4, Affinity Designer 1.8.4, Affinity Publisher 1.8.4;  2020 iMac 27"; 3.8GHz i7, Radeon Pro 5700, 40GB RAM; macOS 10.15.6
Affinity Photo 
1.8.4.186 & Affinity Designer 1.8.4.4 for iPad; 6th Generation iPad 32 GB; Apple Pencil; iPadOS 13.3.1

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R C-R:   Thank you for your explanation.  I appreciate you!   Still, I need to know what steps to take in Affinity Photo, to do the work flow I show in my screen shots.   What you write is good for me!  How do I do what I can do in PS CS5, in Affinity Photo, forgetting the ability to read the mb's of the file?

 

 

Cheers,

 

David

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One thing I find very disturbing in the AP Image Size dialog is the default setting of the "Resample" button.  In my opinion that should never be checked unless you actually want to either add or delete pixels in that image file.  Occasionally I help some of my customers with Photoshop.  The first thing I explain to them is the folly of working on a JPEG file and then saving as a JPEG.  I then show them a sample I did many years ago of a JPEG file that I resaved as a JPEG 10 times and the subsequent deterioration of the image.  The next thing I go to is the Image Size dialog in PS and explain the difference between resizing and resampling and strongly suggest that they leave Resample unchecked unless they have a very good reason to use it.  I cannot count the number of times someone brings in a file they have worked on and then downsized to the print they wanted at that time and had Resample checked.  They then had an 8x10 at 300ppi, but when they next try to upsize it to 16x20 the resolution is 150ppi and they do not understand what has happened.  I then explain to them that by leaving the Resample button checked when simply downsizing the image they are actually throwing pixels away and will never be able to retrieve them.  Oh yes, of course they could resample again when they upsize the image to 16x20, but they are only adding empty pixels, no detail and the image will be inherently lacking in sharpness.  I would like to see the Resample button left unchecked as the default setting, so I suppose I should be posting this in the "Requests" section.

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I am not sure I am following what Garnick is trying to say?

I am no expert.  So please help me out.

 

From my limited knowledge, this is what I perceive:

 

If you resize a document at all, you are either going to add or remove pixels.  You will have to resample in some way.  

 

If you aren't changing the pixel dimensions.  If there is no size change, then I believe the resampling process will do nothing because  there is no change in pixel relationship.  It is a 1 for 1 ratio, and therefore has nothing different to compare, and will therefore do nothing.  So if you don't change the size of the file/document, you don't need to uncheck resample method.  The algorithms will default jump to the end of the program, because there is nothing to resample.

 

Resampling algorithms are specifically designed and in place for analyzing the resizing of a file/document.  The nearest neighbor algorithm being what would be synonymous with the resizing method in Photoshop, and the other resampling methods in line with Photoshop's resampling methods.

 

Resampling has nothing to do with the compression algorithms used within JPG.  So the example of a degraded JPG image seems to be unrelated to the discussion.

 

The only thing I really comprehended from the dialogue was if you were going to resize your document/file for printing, and you are changing the file's original properties/dimensions, don't write over your original file.  Save it as a new file with a different name.  In fact in all conditions I can think of, always save your original file untouched.  Don't ever write over it.

 

I am no expert, so I am probably missing something to this dialogue, or misunderstanding something.  But unchecking the resample method for a file whose dimensions haven't changed, would do nothing from what I have seen.  And if you do resize a document, you will have to resample in some way, except Photoshop calls nearest neighbor resampling, resizing, and the rest resampling.  

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Still, I need to know what steps to take in Affinity Photo, to do the work flow I show in my screen shots.

I don't really understand what you mean by the workflow shown in your screen shots. What the PS resize window shows as "Resolution" is really just ppi, so if you know the required print resolution you can set the dpi in AP to that number & work from there, more or less like O. Chevetaigne suggested.

 

Like the PS help topic explained, there is no point in setting the print resolution to some very large number -- it just increases file size without increasing the quality of the print.


Affinity Photo 1.8.4, Affinity Designer 1.8.4, Affinity Publisher 1.8.4;  2020 iMac 27"; 3.8GHz i7, Radeon Pro 5700, 40GB RAM; macOS 10.15.6
Affinity Photo 
1.8.4.186 & Affinity Designer 1.8.4.4 for iPad; 6th Generation iPad 32 GB; Apple Pencil; iPadOS 13.3.1

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