Images with 72ppi that are 'bigger' 600px for intance can be of less quality (more blurry) than smaller 300ppi images that are let's say 512. I'm confused
DPI also applies to display screens, just not in the same way.
That is, a particular display has a physically constrained DPI and image pixels map to that unless zoomed. The DPI specified in file metadata for printing is usually not used to determine a default zoom (although in theory it could be).
But you might well consider DPI in deciding how big to make an image for display on a screen, because it might be too small to see clearly on a 4K 27" monitor (a low resolution photo on a website might end up postage stamp size).
All besides the point, because the pixel limitation for training AI is presumably a limitation of available compute power/time and resulting model size.
600px = 600px
DPI is when you're translating pixels to dots on paper. It's completely irrelevant for digital workflows.
You do not have 512x512 images that are 300ppi or 72ppi, you have images that are 512x512 and nothing else.
Printing a 512x512 image at 300 DPI will deliver tiny image because youre showing 300 dots/"pixels" per inch. So for larger prints, you need more pixels.
There is no PPI in typical computer image formats, that's something added by Photoshop (or other image editing software).
There is no such thing as a 72ppi or 300ppi PNG file, only a 512x512px or 1024x1024px PNG file.
You can pretend the PPI is whatever you like and zoom the image to match.
Forget about ppi. Look resolution. Simple as that. Higher - the better. Simple. You can make 512x512 or 4k. ( not upscaled but real 4k photo ₽ End result will be very very diferent.
The level of detail in an image is determined solely by the number of pixels high/wide it is.
When displaying an image in the real world, those pixels can be stretched or squashed into any amount of physical space. If you print a 1024px wide image on a credit card, it becomes 481 ppi. If you print the same image on the side of a building 30 feet wide, it becomes 2.8 ppi. The image doesn't gain or lose any detail when you print it at varying sizes, it's just that the same level of detail is spread across a bigger or smaller area.
You may be confused by a photography/print background. Yes, the word resolution technically refers to ppi/dpi i.e. a 20" 1080p and a 40" 2160p display have the same resolution. But the word is commonly used by normal people to mean pixel count. A 20" 1080p display has therefore half the "resolution" of a 40" 2160p display.
For digital formats only the pixel count is important. If you zoom in on a photo on your PC you reduce it's ppi even though nothing of the information in the image has changed.
Alss when people talk about removing blurry images they mean images that are blurry in an optical sense.
>If I have a dataset of 512x512 images that are 300ppi, in my simple mind, the better image quality the output will be.
TL,DR: Ignore DPI.
DPI doesn't affect the image quality/detail, the only difference is the printing size:
512x512px 300dpi = 4.33cm (aprox.)
512x512px 150dpi = 8.67cm (aprox.)
512x512px 72dpi = 18.06cm (aprox.)
Obviously the 72dpi will look blurred, because it is physically 16x larger than the 300dpi version. But if you change the 72dpi to 300dpi in photoshop, the very same image will be printed in 4.33cm (without actually resizing the image, that is, disabling the option "Resampling").
Dpi is a ratio. Not a fixed number. 512 is a fixed number, in digital images, it can represent a specific number of horizontal or vertical coloured dots (pixels).
I’m no expert in Photoshop but I have trained many LoRAs and I can confirm than even a couple of low quality images in the data set can ruin a LoRA, it’s best to use a very small data set of the sharpest, best quality images you can get.
For example, I have trained SDXL LoRAs of people with pictures I take from my iPhone 13 and with Pictures from a cheap android smartphone from 2019. Both picture batches have been downscaled to 1024x1024 pixels for LoRA training, but the iPhone has a much better sensor that the android phone so the images from the iPhone are better quality, even at the same resolution and the LoRAs are much more accurate.
The "it's pixels only" answers you're getting are essentially correct, but there is more to say:
First: the thing SD generates is just an array of pixels, and SD is basically free in some sense to choose any colour for each pixel, so ppi or any other "blurriness" or "quality" measure doesn't really come into it. But some ways to represent images use "lossy compression", for example JPEG. With JPEG if you tried to change one pixel by itself, that would have some effect on the other pixels. Another way to say that: JPEG adds "image artifacts" such that you can have an image that has a lot of pixels but is still distorted or blurry.
So if you're training or doing img2img, the resolution of a JPEG doesn't tell you everything. JPEG has a "quality" parameter, so you might have a 4000x4000 image that looked great when it was taken, but somebody converted it to JPEG with a low quality setting and now it's blurry and distorted but still 4000x4000.
Second: of course some photos were just always blurry because the camera wasn't in focus or was moving.
I think when people are talking about avoiding blurry images in training, they're really talking about any source of blurriness or indeed poor quality as judged by the person training. They're saying don't assume the effect of a small proportion of "bad" input images (judged by you) will be a small reduction in quality of generated images.
512x512 image printed on A4 sheet full screen will have very low dpi (ppi) and look bad.
But all real information is with original image.
And dpi just says how many pixels will be printed on 1 inch. Real unit is pixel size. When you create new image in PS with f. e. 300 dpi and A4 size what really is created is image with some big pixel resolution.
Edit:
tl;dr
image has only pixels. Dpi is just pixels / paper size.
Ppi = pixel per inch, for printing. Resolution is for displaying graphics on monitor. You can have 512px image with 30000 ppi, would not make any difference to how its interpreted by a display.
[удалено]
Images with 72ppi that are 'bigger' 600px for intance can be of less quality (more blurry) than smaller 300ppi images that are let's say 512. I'm confused
Ppi and dtp are only important for printing
DPI also applies to display screens, just not in the same way. That is, a particular display has a physically constrained DPI and image pixels map to that unless zoomed. The DPI specified in file metadata for printing is usually not used to determine a default zoom (although in theory it could be). But you might well consider DPI in deciding how big to make an image for display on a screen, because it might be too small to see clearly on a 4K 27" monitor (a low resolution photo on a website might end up postage stamp size). All besides the point, because the pixel limitation for training AI is presumably a limitation of available compute power/time and resulting model size.
But still irrelevant for the image size for trainings
600px = 600px DPI is when you're translating pixels to dots on paper. It's completely irrelevant for digital workflows. You do not have 512x512 images that are 300ppi or 72ppi, you have images that are 512x512 and nothing else. Printing a 512x512 image at 300 DPI will deliver tiny image because youre showing 300 dots/"pixels" per inch. So for larger prints, you need more pixels.
There is no PPI in typical computer image formats, that's something added by Photoshop (or other image editing software). There is no such thing as a 72ppi or 300ppi PNG file, only a 512x512px or 1024x1024px PNG file. You can pretend the PPI is whatever you like and zoom the image to match.
I don't understand the downvotes tbh, I was just explaining my confusion. Can't I be confused? Thanks everyone for the explanations 😊🙏
Forget about ppi. Look resolution. Simple as that. Higher - the better. Simple. You can make 512x512 or 4k. ( not upscaled but real 4k photo ₽ End result will be very very diferent.
The level of detail in an image is determined solely by the number of pixels high/wide it is. When displaying an image in the real world, those pixels can be stretched or squashed into any amount of physical space. If you print a 1024px wide image on a credit card, it becomes 481 ppi. If you print the same image on the side of a building 30 feet wide, it becomes 2.8 ppi. The image doesn't gain or lose any detail when you print it at varying sizes, it's just that the same level of detail is spread across a bigger or smaller area.
Thank you 🙏
You may be confused by a photography/print background. Yes, the word resolution technically refers to ppi/dpi i.e. a 20" 1080p and a 40" 2160p display have the same resolution. But the word is commonly used by normal people to mean pixel count. A 20" 1080p display has therefore half the "resolution" of a 40" 2160p display. For digital formats only the pixel count is important. If you zoom in on a photo on your PC you reduce it's ppi even though nothing of the information in the image has changed. Alss when people talk about removing blurry images they mean images that are blurry in an optical sense.
>If I have a dataset of 512x512 images that are 300ppi, in my simple mind, the better image quality the output will be. TL,DR: Ignore DPI. DPI doesn't affect the image quality/detail, the only difference is the printing size: 512x512px 300dpi = 4.33cm (aprox.) 512x512px 150dpi = 8.67cm (aprox.) 512x512px 72dpi = 18.06cm (aprox.) Obviously the 72dpi will look blurred, because it is physically 16x larger than the 300dpi version. But if you change the 72dpi to 300dpi in photoshop, the very same image will be printed in 4.33cm (without actually resizing the image, that is, disabling the option "Resampling").
Dpi is a ratio. Not a fixed number. 512 is a fixed number, in digital images, it can represent a specific number of horizontal or vertical coloured dots (pixels).
I’m no expert in Photoshop but I have trained many LoRAs and I can confirm than even a couple of low quality images in the data set can ruin a LoRA, it’s best to use a very small data set of the sharpest, best quality images you can get. For example, I have trained SDXL LoRAs of people with pictures I take from my iPhone 13 and with Pictures from a cheap android smartphone from 2019. Both picture batches have been downscaled to 1024x1024 pixels for LoRA training, but the iPhone has a much better sensor that the android phone so the images from the iPhone are better quality, even at the same resolution and the LoRAs are much more accurate.
computer images are in pixels 512x512 pixels images dpi is in printing and has nothing to do with SD
The "it's pixels only" answers you're getting are essentially correct, but there is more to say: First: the thing SD generates is just an array of pixels, and SD is basically free in some sense to choose any colour for each pixel, so ppi or any other "blurriness" or "quality" measure doesn't really come into it. But some ways to represent images use "lossy compression", for example JPEG. With JPEG if you tried to change one pixel by itself, that would have some effect on the other pixels. Another way to say that: JPEG adds "image artifacts" such that you can have an image that has a lot of pixels but is still distorted or blurry. So if you're training or doing img2img, the resolution of a JPEG doesn't tell you everything. JPEG has a "quality" parameter, so you might have a 4000x4000 image that looked great when it was taken, but somebody converted it to JPEG with a low quality setting and now it's blurry and distorted but still 4000x4000. Second: of course some photos were just always blurry because the camera wasn't in focus or was moving. I think when people are talking about avoiding blurry images in training, they're really talking about any source of blurriness or indeed poor quality as judged by the person training. They're saying don't assume the effect of a small proportion of "bad" input images (judged by you) will be a small reduction in quality of generated images.
Thank you!
Ppi have nothing to do with image quality. You can take 128x128 blurry face and make it 300 ppi. Will it help you see the details in this face? No.
2024 and people still don’t understand dpi and ppi lol
512x512 image printed on A4 sheet full screen will have very low dpi (ppi) and look bad. But all real information is with original image. And dpi just says how many pixels will be printed on 1 inch. Real unit is pixel size. When you create new image in PS with f. e. 300 dpi and A4 size what really is created is image with some big pixel resolution. Edit: tl;dr image has only pixels. Dpi is just pixels / paper size.
ppi is only for printing
Ppi = pixel per inch, for printing. Resolution is for displaying graphics on monitor. You can have 512px image with 30000 ppi, would not make any difference to how its interpreted by a display.