how to Resize Document without "resample" image?

[MEB]

Hi PhukAdoubi,
Welcome to Affinity Forums
Yes, this was already fixed and should be working as expected.

@Fixx
This is visible as soon as the dimensions are updated the first time (without resampling) - the dpi field updates to 599. Happens the same in other apps namely Photoshop. With resampling enabled it must keep the dpi value.

[R C-R]

1 hour ago, MEB said:

... the dpi field updates to 599 due to rounding. Happens the same in other apps namely Photoshop.

I think MEB means 299. Anyway, it is easy to see why this happens if you consider that 300 dots per inch is equivalent to ~11.811 dots per mm, so it is impossible to create a document that is exactly 210mm by 297mm (or 148 mm by 210 mm or whatever) at exactly 300 dpi.

So for example, if you create the document using the A4 print preset, the dimensions in the New Document window are displayed as 210mm by 297mm at 300 DPI; but if you have set Preferences > User Interface > Decimal Places for Millimeters to 3 & then open Document > Resize Document, you will see that the size is not really exactly 210mm by 297mm:

BTW, you can't blame this entirely on DPI being specified based on inches. The ISO standard for A series paper sizes specifies that the length divided by the width of the paper is the square root of 2, so the standard sizes are rounded to the nearest integer mm value, even though that results in paper size aspect ratios that are not exactly that value.

[Fixx]

And this is really not a problem as pixel data stays the same all the time.

[skylamar]

Hi. I read through most of this thread and I may not be understanding it completely. But I believe I have at least a similar issue/question. I'm using Affinity Photo version 1.8.3 on a Mac:

I have a photo that is 960X1280 pixels at 72dpi. I opened it in Affinity Photo. I want to turn it into a 300dpi image, but with the same number of pixels. So, basically I want to shrink the picture so it's much smaller in dimensions, but has a greater pixel density. I tried doing that with "Document>Resize Document..." by entering 300 for the DPI and unchecking "Resample," but that didn't seem to work.

I am able to use the Move tool and drag the resize handles of the photo and decrease the photo's size until Affinity Photo's information in the upper-left corner says "300dpi." It's just a little tricky doing that because it requires some trial and error to get the size of the photo so it's exactly 300dpi. 

So, is there a way to resize it the way I want using Resize Document, or is using the Move tool the only way?

Thanks!

[John Rostron]

@skylamarTry my macro Change dpi to 300, one of a set in my macro library. See the link here.

John

[skylamar]

John, thanks. Will try the macro tomorrow.

However, I'm thinking that maybe I'm just confused. When I change the units of my photo to inches and then change the DPI, the inches for width and height do get smaller. And when I hit the Resize button, the rulers show that the photo is now about 3 inches by 4 inches at 300DPI. So Affinity Photo did resize the photo the way I wanted. However, I got confused because the rulers are zoomed in. Is there a way to set the rulers so they are not zoomed in and are showing their exact size?

[skylamar]

Okay, sorry, I realize I was just confused. When I created a 300DPI blank document and dragged the photo into that document, the photo was automatically shown at about 3X4 inches at 300DPI--the same size as when I had resized it from 72DPI to 300DPI. I was confusing myself because I wasn't understanding completely how documents of different DPI are displayed onscreen. 

[FemkeD]

Hi, 

I'm reading this post and don't understand everything but I think I may have the same question. I have a picture in 2:3 format that I know how to change in size without resampling in Affinity. Affinity calculates the right dpi for me. My problem is that I like this picture in a couple of different ratio's (ISO, ,3x4, 11x14, 4x5) and each ratio in different sizes but I do not want to resample. So I need to crop. But when doing that Affinity automatically sets dpi to 300 or I have to calculate and fill it in myself. But since they are  different ratio's I do not know the dpi I need for no resampling. I have to do this for a lot of pictures (selling prints in different ratio's and sizes) so I'm looking for a simple way to change ratio and size without resampling. So that affinity is calculating the right dpi for me.

Using presets would be helpfull. But when I use a preset of ISO A3 for instance it's also resampling. Maybe there's another way for me to set presets with the right dpi's. Does anyone know how to calculate this when changing from ratio? Then I calculate this for all ratio's and sizes for one time and make presets for all the other pictures I like to change in ratio and size in the future.

Or is resampling not so bad as I think and should I go for the easy way and use resample? I'm using sizes form 20x30 cm up to 60 x 90 cm ( 21x29,7 up to 59,4 x 84,1, etc).  I know I will have lower dpi's than 300 for the larger images but it should be fine with the viewing distance.

The original file is 3509 x 5264 pixels at 300 dpi.

Please keep the answers simple since this is higher math for me 🙂

ps I know that not every picture is suitable for all ratio's. But this one is.

 

 

[Wosven]

8 minutes ago, FemkeD said:

My problem is that I like this picture in a couple of different ratio's (ISO, ,3x4, 11x14, 4x5)

Use the ratio in the crop tool, without resampling.

Don't mind the DPI (or PPP) value, it's an old unit used to tell browser how (which size) to display images on screen*. The important values of your images are the width and height in pixels.
You can crop your image at different ratio, and keep the same DPI. It's only a metadata value.
Choose the 3rd option in the menu (± "personnal proportions"), and your ratio:

The DPI value won't change:

 

Now, if you need a A3 (29.7 × 42 cm) picture for print, you would need an image of 3540 × 4956 pixels. (for print at 300 DPI: 1 cm = 118 pixels. 30*118=3540 and 42*118=4956).
If your image don't have enough pixels, it'll print smaller, or you'll have to enlarge (=resample) it. Depending of its original size and quality, it'll be OK or not.

 

* We use it as reference for print (press ready), to know how many minimum pixels we need for an image to use on an area.
For example: to print 1×1 inch image in a magazine need minimum 300 px × 300 px, for a 2×2 inches image you need 600px × 600 px, for 10×10 inches image you need 3000 px × 3000 px, etc.
Your 1 × 1 inch image need minimum 300 × 300 pixels. Its DPI can be 1 or 300 or 1200, it's the same. Modern app can display the "effective" DPI, depending of the size in pixels of your image and the area you put it on in your document. If you enlarge your image in the document, the display PDI value will be less, if your reduce the image, it'll be more.

[FemkeD]

Hi Wosven,

Thank you so much for taking the time to explain it to me so clearly! Only look at the pixels in width en depth and dpi is not important, imaginary value. That makes life a lot easier I think . I will go and try it out tonight. 

You really make my day!!! Thanks!

 

[FemkeD]

Hmm I'm afraid it's not all clear to me though.

These formats are digital prints I offer to customers for printing purposes. I want this files to be print ready, in the sense that customers do not have to make any adjustments. When they print this file (at home or at that local printservice)  it will be in the correct size in good quality. With the size 3509 x 5264 I can make prints in optimal quality up to 29,7 x 44,6 cm (pixels:118) so lets say 30 x 45 cm. But since you see larger images from a bigger distance you do not see see all the pixels and you do not need 300 dpi resolution to have a good quality image I thought. So for the 40x60, 50x75, 60x90 cm prints I thought that a dpi of 222,178, and 148 is sufficient (doubting about the 60x90). (See table in Dutch but the first column is format, then viewing distance and then minimal resolution for a good print, size and megapixels). 

So what I think to understand is that the 20 x 30 and 30 x 45 cm images I make  a 2360x3540 pixel and 3540 x 5310 pixels image and it does not matter which resolution I put it on. (But I will put it on 300 dpi). These pixeldimensions correspondents with the size.

But how do I make these 40x60, 50x75 and 60x90 cm print ready?  Do I keep the 3540 x 5310 pixels and fill in these lower dpi's? Will it than automatically be printed in the correct sizes?  Or will it print at 30x45 cm since the printer only looks at the pixeldimensions? I think because it's print the resolution is important and not imaginary isn't it? And is setting a lower resolution preferable above resampling the image to bigger pixeldimensions?

 

Formaat	Reguliere kijkafstand	Minimale afdrukresolutie  (DPI = Dots Per Inch)	Beeldgrootte	Megapixels
10×15 cm	30 cm	288 DPI	1134×1701	1,9
20×30 cm	60 cm	240 DPI	1708×2835	4,8
40×60 cm	120 cm	180 DPI	2835×4252	12,1
60×90 cm	180 cm	160 DPI	5040×5670	28,6
80×120 cm	240 cm	144 DPI	4536×6804	30,9
180×120 cm	360 cm	120 DPI	8504×5670	48,2

 

 

[Wosven]

9 minutes ago, FemkeD said:

But since you see larger images from a bigger distance you do not see see all the pixels and you do not need 300 dpi resolution to have a good quality image I thought.

In fact (and one detailed explanation is somewhere in this forum in a thread about DPI/PPP terms), depending of the result, you won't use the same machine for printing, and it won't use the same level of details (DPI or LPI) for printing a magazine (usually 300 PPP images, 280 is what we accept as minimal value), or a poster, or a big poster 4×3 m as we used to have in France.

 

16 minutes ago, FemkeD said:

So what I think to understand is that the 20 x 30 and 30 x 45 cm images I make  a 2360x3540 pixel and 3540 x 5310 pixels image and it does not matter which resolution I put it on. (But I will put it on 300 dpi). These pixeldimensions correspondents with the size.

Resolution doesn't matter, you just need enough pixels, or if there is less pixels, the picture should be good and preferably sharp (for example, we can enlarge photo made by photographs, but clients' ones can be so bad that we'd rather use them at 25% size, and defaults would be visible! ). It's not a science, it's also practice.

 

23 minutes ago, FemkeD said:

But how do I make these 40x60, 50x75 and 60x90 cm print ready?  Do I keep the 3540 x 5310 pixels and fill in these lower dpi's? Will it than automatically be printed in the correct sizes?  Or will it print at 30x45 cm since the printer only looks at the pixeldimensions? I think because it's print the resolution is important and not imaginary isn't it? And is setting a lower resolution preferable above resampling the image to bigger pixeldimensions?

The printer doesn't look at anything else that the dimension of your document, and the "effective DPI" of your images. If he ask for a minimal resolution, in fact he asks for a density of pixel by inch.

Now, this table is wrong (values, you take the previous height pixel value but the next format have a different width) and asking for lower DPI is taking the risk to get low resolution files to print and result in unhappy customers.

Keep it simple. Lower formats than A2 need 300 DPI. Higher can be minimum 150 DPI. Don't forget that talking of DPI/PPP to regular people is talking an allien language

 

[FemkeD]

Thank you so much again Wosven for making it simple again, it was getting awfully complicated in my head.

The one thing that still is a bit confusing in my head sometimes is the difference between actual DPI and effective DPI.  I looked it up and found a useful explanation I will share beneath for members who also have difficulties grasping that part.

As I understand it now, the dpi you fill in with scaling doesn't matter at all. It all depends on the dpi of the original file and the effective dpi you get after enlarging or reducing the image.  That's the DPI Affinity calculates for you when you enlarge or reduce the image without resampling. (And the other way around, if you fill in a DPI of 152 without resampling you see the maximum measures of the picture to get a good quality print.) 

Many thanks Wosven!

 

Here's the article:

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PREPRESS TWO CENTS: Actual Resolution vs. Effective Resolution

Understanding the Difference without Using the Nasty Math

OR: My Photos are all 300 dpi; why do some look so bad?

In a perfect world, we would always scan our photos or take our photos at 300 dpi and use our photos at 100%. In the real world, though, we’re often forced to scale our photos once we put them into our page layout program. And that’s where the problems start.

Let’s say you placed a 300 dpi photo at 100% (see Figure A). Now the customer wants the photo twice as big, so you enlarge it to 200% in your page layout program. The actual resolution of this photo is 300 dpi, but now that you’ve scaled it, the effective resolution is 150 dpi, or half the original resolution (see Figure B). Why? Once you enlarged the photo, all the pixels became twice as wide and twice as tall, so now fewer of them will fit “per inch.” Conversely, if you reduce your photo, the pixels become smaller and more of them will fit “per inch.” (By the way, don’t email us complaining that there are 9 dots in Figure B instead of 8-and-a-half; we’re just making a point.)

In a nutshell: reducing the scale increases the effective resolution; enlarging the scale reduces the effective resolution. I know we promised no math, but for those of you who don’t mind it, there’s a simple formula for calculating your effective resolution. Take your native resolution and divide it by the scaling percentage like this:

300 ÷ 200% = 150 (dpi)

or

300 ÷ 50% = 600 (dpi)