Image Size Resolution

[steveg73545872]

Hi, I have a jpeg image photographed that has been supplied at 100% size at 350ppi however I need to tile this up to make a large image size so I need to scale by 10% of final size. I need the image to be 350ppi at 10% size but to retain the pixel data I need to uncheck resample which when scaled to 10% makes the resolution 3500ppi.

Images at 35ppi at final size for a 20m print should look fine however this looks more like 3ppi when I resample and when I don't resample its 3500ppi and 17gb file which does look correct. Please help me understand.

[Per Berntsen]

Please tell us

• The pixel dimensions of the image
• The size of the print you want to make

[steveg73545872]

Hi

• Pixel Dimensions 8200 x 6000

I need to scale this image by 10% so I can artwork at tenth size and enlarge on the RIP by 1000%.

The original image when sized at 10% will be 59.51x43.54mm. If I was creating from scratch I would start at 350ppi at 10% of final size.

• The Print size prior to tiling would be 595.09x435.43mm at 35ppi

Thanks

[Test Screen Name]

Use Image Size

Turn OFF resample (VERY important)

Change ppi from 350 to 35 ppi

Job done!

[JJMack]

fabiennec73545872  wrote

Hi

• Pixel Dimensions 8200 x 6000

I need to scale this image by 10% so I can artwork at tenth size and enlarge on the RIP by 1000%.

The original image when sized at 10% will be 59.51x43.54mm. If I was creating from scratch I would start at 350ppi at 10% of final size.

• The Print size prior to tiling would be 595.09x435.43mm at 35ppi

Thanks

What tiling are you writing about? What is being tiled?

8200 x 6000 is not Pixel Dimensions its the number of pixels you have for your image 49,200,000 Pixels.  350DPI is print pixel size 1/350"x1/350" the print will be 23.4" by  17.1" if you change the Print DPI resolution to 35DPI the print will be 10x  234" x 171"

In the image size dialog all you need do is uncheck RESAMPLE. The in the print size area set the print width or height you want the print to have. Photoshop will calculate what DPI to use set it and it and set the other dimension you do not set height or width.  All the actually changes is the Print resolution setting and the size the print will be. The 49.2MP image is not changed the file size will not change just the Print DPI seting is changed in the file..

[steveg73545872]

Sorry for not being clear enough here.

Basically I have a scan of some gravel and I need to duplicate this image in Photoshop to create a larger background of the image. To do this I need to create a large canvas size but due to the canvas size being 7m long I need to create my whole artwork at 1:10 scale. 350ppi at 1:10 size is suffice for what I need which will make it 35ppi when going to print at finished size. The original image supplied need to be scaled to 1:10 however the image seems to be really pixelated when resizing with resampling off

[steveg73545872]

Hi,

Original is below however I want to scale this image by 10% of this size but retain the resolution at 350ppi so when I enlarge on the RIP at 1000% the actual resolution is 35ppi at final size (100%). Thanks

[JJMack]

There is no image there.   It would be good if you provided some size information and wether the 10% scale is in the up or down direction.  Printing a 350 DPI Print document at a 35 DPI will increase the print size 10x or 1000%  I do not understand you need of interpolating the original image's Pixels up or down 10%  before printing the actual print size you want. Or know what size that is only know it will be printed with a large pixel size a low 35ppi resolution.

In you first append you wrote something about tile. But failed state tile content or how tile will be used????

[steveg73545872]

This is the original image size and resolution. I need to scale down to 10% (1:10) so I can duplicate the image and create a large file over 7m at final size hence the need to scale down to 10% size.

Below shows scaling down to 10% with resample off. However if I select resample and scale down to 10% size and the resolution is left at 350ppi then when I view at 1000% ( Final Size when enlarged) the pixelation is extreme.

when I enlarge the canvas size to the size needed the size is 16GB

[JJMack]

Why are you adding canvas? After the change in print DPI the print canvas size should be the size you set in images size?

[steveg73545872]

Hi,

Initially I am getting the scanned image to the correct size then I need to create a larger canvas so I can duplicate the scanned image to cover the canvas to create one full image of the gravel.

Thanks

[JJMack]

Changing the Print dimension changes the print DPI resolution the print canvas size is changed to what you want it to be.  If you change 350DPI to 35DPI the dimension will change 10X if that is not the size you want instead of changing 350 dpi to 35 dpi change one of the print side dimension Photoshop will set the other values to match your change.

[D Fosse]

You're overcomplicating this.

Just uncheck resample and you'll be fine. Change ppi or print dimensions, whichever you want - the main thing is that as long as resample is unchecked, not a single pixel changes.​ And the file size will also stay exactly the same.

Ppi and print size are inversely connected. As one goes up, the other goes down, and vice versa.

[steveg73545872]

Thanks for the comment.

If I uncheck resample and change the dimensions to 1:10 of the current size then the DPI enlarges from 350ppi to 3500ppi. After this I need to change the Canvas size so I can duplicate the image and make one large background. By doing this I now have a 16GB file that I can't save and/or import in to Illustrator.

Thanks

[JJMack]

No all changing the Print Resolution does is change the size the pixels will be printed. The image Pixels are untouched. You have the same 8200x6000pixels  the file should not change and your file should be nowhere near 16GB in size that would need to be saved as a PSB to be able to be that large..    Your image had nearly 50MP. If edited in 16bit color that would requite 6bytes of color data for each pixel uncompressed that image would only be 3GB of pixel data where are you getting this 16GB figure.

[steveg73545872]

Th 16GB is when I enlarge the Canvas size as the previous pic shows as I need to take the original image and step it up/Duplicate it to create one large backdrop

[JJMack]

If you resample your  350DPI image  to 3500DPI the image files size will be huge and the image quality very poor.  That is 10x 10x10=100  increasing your 49.2MP to 49,200,000pixels becomes 4,920,000,000 5Giga pixels 8bit around 15GB.  That is unrealistic.   Even if you could print at that resolution the human Eye can not resolve down to a 3500dpi pixel size. The image would not look any better even if you had high quality pixels.  Your image will not have high quality pixels interpolating 1 pixel into 100pixels a lot of detail the interpolation needs to come up with and Photoshop performances or any image editor performance will be poor manipulating a 5GP image.

Why do you need a 5GP image?

[steveg73545872]

Thanks again.

When I leave image as is and import image in to Illustrator then create a PDF and view at 1000% (what I need to enlarge by on the RIP) - See below

When I reduce by 1:10 and create the PDF the same way as a above I get this when viewed at 1000%

[steveg73545872]

Sorry not sure why the images are not showing.

I will try again

Images 1

Image 2

[Bojan Živković]

Can you do this:

• Check Resample
• Set measurement unit to Pixels instead of Percent
• Select zero at the end of 8200 and delete it so it will remain 820. You can also retype 820 over 8200. Width should be scaled down automatically to 600
• Please ignore everything else, hit OK and you are good to proceed to the next step whatever it is.

[steveg73545872]

Thank you.

I do understand this however when I place the image in Illustrator and create a PDF then view it at 1000% (what I need to enlarge by on the RIP) it is extremely pixelated.

[Bojan Živković]

Yes it is because it is huge enlargement. I am just trying to help you when scaling down to 10%, you can do that in many ways including to type /  + number in the text field with Height or Width. See screenshot below and Width field. Photoshop will do math for you. The rest is not clear to me so I am not advising anything, only how to scale down to 10%.

[Test Screen Name]

It will be pixellated in a PDF made by Illustrator because by default the resolution is reduced to 300 ppi. So your 3500 ppi comes back down to 300. Turn that off in Export settings.

[steveg73545872]

Thanks

I have turned off all downsampling however I cannot save the 3500ppi file as it will be 16GB

[Test Screen Name]

What says it will be 16GB, exactly?

What size is the PSD (I assume it's a PSD) you place into Photoshop (I assume you do PLACE it, not paste it?)