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Hi

I scanned my 1985 slides when I didn't know how to scan properly so some are scanned at 72, 300, or 6400 DPI and many jpgs contain a lot of dust, marks, and mottled skies due to age of slides. As I can't rescan anything right now, I'm editing with AP but have a couple of issues:

  1. Exported jpgs don't appear as sharp as what displays when I'm working in AP.
  2. Don't believe I've changed any settings, but my exported jpgs that were originally 72DPI have started to export as 6400DPI, even though I've set the Quality to 94%. I've watched the AP DPI video but still trying to get my head around it all.)

Am I doing something wrong?

I'd like all my exports as 300DPI as this is what I'll upload to my website for purchasing, then photos go to the print lab.

Any help is appreciated :-)

 

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Your thread title says ‘6400px’ but the body of your OP refers to ‘6400 DPI’. Which is it? :/

15 minutes ago, Nilla's Photography said:

I'd like all my exports as 300DPI as this is what I'll upload to my website

DPI or PPI refers to print resolution. It's irrelevant for websites, since browsers only know about pixels: all that matters is the pixel dimensions of the image.


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Hi @Alfred thanks for your quick response and I understand that for a browser it's not important, but as my images will go to a printer automatically from my Cart, then I need to upload images at 300DPI for a print lab.

 

Sorry for the confusion and I should have been clearer in my title/content. When I open the jpg in Preview>tool inspector, this displays:

"Image DPI: 6400pixels/inch"

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Hi @Nilla's Photography,

As Alfred mentioned, DPI is irrelevant when you're using pixels. DPI is linked with the print size, and not with the pixel size. If all they ask you is a 300dpi image, that's wrong. You need to know the print dimensions to work out the "dpi". 

For example, if your image is 1000x1000px, Printed at 300DPI would only result in a 3x3inch image, regardless of the metadata DPI value of that image. 

Have a look here to understand what's going on: https://www.pixelcalculator.com/index.php?round=&FORM=3&DP=1&FA=&lang=en&pix1=1000&pix2=1000&dpi2=300&sub2=+calculate+#a2

Thanks,

Gabe. 

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Hi Gabe,

Thank you for your response and link.

In the past and regardless of print size, the lab always requested the image to be saved at 300DPI, sometimes I was requested to save the image to exact print dimensions and other times not.

My problem is that I'm setting up my website's Cart so that in the future anyone can order different print sizes from the same image, which will automatically be sent to a print lab. I'm not sure the best way to handle this for optimal quality?

In my old website's Cart when a print size was selected a crop displayed over the image to crop the image accordingly, then this final output was automatically sent to the print lab. I uploaded the photos at their original px size at 300DPI - maybe this was incorrect but I didn't have any issues, perhaps the print lab corrected the image. 

All this aside, is there a way to export a jpg from AP so that it's ready for multiple print sizes?

The other issue is why would my exported image not look as sharp as when I'm working in AP?

 

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16 hours ago, Nilla's Photography said:

is there a way to export a jpg from AP so that it's ready for multiple print sizes?

You can print a jpeg whatever size you wish. The print size is driven by the jpeg resolution and the DPI settings when you print. 

Let's take an image 1000x1000px

@300DPI, you will have 85 × 85 mm

@100DPI, you will have 254 x 254 mm

@72DPI, you will have 353 x 353 mm. 

The lower the DPI value, the higher your print will size will become. 

16 hours ago, Nilla's Photography said:

The other issue is why would my exported image not look as sharp as when I'm working in AP?

Did you resize your document? If so, I suggest you use a different resample method (Bicubic or Lanczos 3):

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18 hours ago, Nilla's Photography said:

In my old website's Cart when a print size was selected a crop displayed over the image to crop the image accordingly, then this final output was automatically sent to the print lab.

From this, it isn't clear to me if you are selling prints that are cropped versions of an image, or the entire image at different pixel resolutions and/or physical dimensions. Can you explain more about that?


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Thanks @GabrielM for the info. No, I didn't resize my document and always export using Bicubic as Lanczos 3 can result in quite an artificial (too contrasty) look.

Sorry @R C-R as my photos are taken with different cameras, the aspect ratio varies. I also have 35mm negs/slide film ratio to contend with - I used PS Elements and also Lightroom to export previously.

What my old site used to do if the aspect ratio didn't match the print dimension ordered, then a crop tool would display over the image so that the customer could position the crop to their liking.

I uploaded the original file (typically 5-20MB) with its original dimensions that came out of the camera and used 300DPI on export. So as an example, an image of 22.9MB with an image size of 5878x3924 pixels at Image DPI: 300 pixels/inch was sent to the print lab for a print size of 24in x 36in, which resulted in a very sharp print.

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1 hour ago, Nilla's Photography said:

So as an example, an image of 22.9MB with an image size of 5878x3924 pixels at Image DPI: 300 pixels/inch was sent to the print lab for a print size of 24in x 36in, which resulted in a very sharp print.

??? An image size of 5878 x 3924 pixels actually printed at 300 DPI would result in a print with dimensions of about 19.6 in x 13 in.


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7 hours ago, Nilla's Photography said:

an image size of 5878x3924 pixels at Image DPI: 300 pixels/inch was sent to the print lab for a print size of 24in x 36in

The DPI would have to be approx 163DPI to get that dimension: http://www.photokaboom.com/photography/learn/printing/1_calculators.htm#Pixels

https://www.scantips.com/calc.html


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Thanks @R C-R and @firstdefence

This is the file that I sent to the lab, but maybe the lab changed settings before printing.

After this discussion, all I'm really after is the best settings to export my files from AP so that whatever a customer choses any print size from my Cart, this image will print result in optimal quality and colour. Is this not achievable? (As mentioned above, I'll eventually automate my Cart so I need to upload optimal image files, which will be sent automatically to the print lab.)

Many thanks for all the information :)

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12 minutes ago, Nilla's Photography said:

After this discussion, all I'm really after is the best settings to export my files from AP so that whatever a customer choses any print size from my Cart, this image will print result in optimal quality and colour.

There is no way to tell you exactly what settings you will need for that without knowing the range of print sizes (dimensions) you offer & what the print will be used for (like for a large poster typically viewed at a distance or an art print in a book or whatever) but you can read about some general guidelines here in another of the scantips.com pages linked to from the second link @firstdefence posted above.

You will also need to take into consideration the effects of cropping to a smaller size if you offer that, but in general the idea is to provide enough pixels in the image that the final print resolution is around 300 pixels per inch for prints viewed up close & somewhat lower ppi for ones viewed at a distance.

It probably would be worth discussing this with your print lab.


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@R C-R

Many thanks for the information and links but also your patience.

Currently I offer these standard print sizes:

8"x12" (20cm x 30cm)

16"x20" (40cm x 50cm)

20"x30" (50cm x 75cm)

24"x32" (60cm x 80cm)

Although, I offer any size the print lab can print to as long as the image goes to that size and across most mediums (canvas, photo, foam, etc.) I know that the above sizes don't cover all aspect ratios, but I can manually adjust these, when this is automated then I'm hoping that my Cart displays a crop tool like my old site. The other thing that my old site used to do is if the image was not compatible with a larger size, a message displayed to the customer to choose another size to suit. (Maybe I should have stuck with my old platform as it really did have a great Cart system and not go to self-hosted.)

Thanks again

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