Printing astroimages: size vs. resolution

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zumix

New member
Hello. I am surprised how little information I have been able to find about this topic. After so many hours of processing some of us decide to print some images on photographic paper to decorate our room or to create an exposition... Which is the best way to export the file? After reading and thinking about this I have concluded a few important points, but I really like people to confirm this in case I could be wrong:
1. The size of the image are the pixels it has. No cm, no pixels per inch (ppi). Just the pixels. Unless we resample the image to create new pixels the size is that
2. The resolution depends on the size of the paper we are going to employ: a 3000x3000 pixels image printed into 10x10 inch paper will have 300 ppi, and printed into 30x30 inches will have 100 ppi

Am I right? If so, I need to now the minimum recommended resolution for printing on photographic paper, then depending on the number of pixels of my image I will know how big I can afford my paper to be. I think normal printing machines for big sizes use around 150 ppi, but not sure... Then, there is also the distance at whicj the picture will be seen. One does not expect to watch a 15x 20 inch very close to the paper...

Having fixed this I suppose the format (jpeg, tiff...) might affect the colors... and this is another world to explore...
Finally, taking into account that images in paper will bright less that in the monitor for obviuos reasons, would you recommend to increase brightness in the file to compensate, even if in the screen look a bit clear /burned?
Cheers
 
zumix said:
Hello. I am surprised how little information I have been able to find about this topic. After so many hours of processing some of us decide to print some images on photographic paper to decorate our room or to create an exposition... Which is the best way to export the file? After reading and thinking about this I have concluded a few important points, but I really like people to confirm this in case I could be wrong:
1. The size of the image are the pixels it has. No cm, no pixels per inch (ppi). Just the pixels. Unless we resample the image to create new pixels the size is that
2. The resolution depends on the size of the paper we are going to employ: a 3000x3000 pixels image printed into 10x10 inch paper will have 300 ppi, and printed into 30x30 inches will have 100 ppi

Am I right? If so, I need to now the minimum recommended resolution for printing on photographic paper, then depending on the number of pixels of my image I will know how big I can afford my paper to be. I think normal printing machines for big sizes use around 150 ppi, but not sure... Then, there is also the distance at whicj the picture will be seen. One does not expect to watch a 15x 20 inch very close to the paper...

Having fixed this I suppose the format (jpeg, tiff...) might affect the colors... and this is another world to explore...
Finally, taking into account that images in paper will bright less that in the monitor for obviuos reasons, would you recommend to increase brightness in the file to compensate, even if in the screen look a bit clear /burned?
Cheers
Click to expand...
150 ppi is probably a reasonable number to work with. Different printing services will offer different suggestions, probably ranging from 150-300 ppi.

When I print my images, I resize the source as necessary to hit my intended print resolution. (There are lots of resizing tools these days that can scale an image up and intelligently manage artifacts. I prefer to do it myself as opposed to letting the printing service do it. Some sharpening usually helps... it will look oversharpened on the screen but not on paper.) I have a calibrated monitor, and generally don't need to make any special adjustments for printing. What I get back from the printer looks pretty similar to what I see on the screen. (This applies to paper; I've also had prints on metal, and those I do find need to be overly brightened on the screen to look good printed.)
 
Hi. As Chris says for resolution.

I print at home and use tiff through Photoshop especially at A3. I don't use jpeg to print so can't comment about the quality of a print using it.
Another type you may consider is PNG file format in Pi. I've had very good results with that on A4.
I'm not sure if this is across the board but check with your printer service which type of format they can use.

I use Metallic 260gsm which gives brilliant results but you do need to tweak the brightness, Lustre 300gsm as a great all rounder and Silk Baryta 310gsm with mixed results in both A4 and A3 sizes.

If you do print at home you will need an ICC colour profile for your individual paper and ink which should be available from you paper supplier along with the calibration colour chart you need to print and send back to them to create the ICC profile for each type of paper you intend to use.
Calibrate your monitor as well and your results will be a lot better than the built ins your printer has.
As with everything you may have to do a few test prints to get what your aiming for.
Hope this helps
 
prjcole said:
Hi. As Chris says for resolution.

I print at home and use tiff through Photoshop especially at A3. I don't use jpeg to print so can't comment about the quality of a print using it.
Another type you may consider is PNG file format in Pi. I've had very good results with that on A4.
I'm not sure if this is across the board but check with your printer service which type of format they can use.

I use Metallic 260gsm which gives brilliant results but you do need to tweak the brightness, Lustre 300gsm as a great all rounder and Silk Baryta 310gsm with mixed results in both A4 and A3 sizes.

If you do print at home you will need an ICC colour profile for your individual paper and ink which should be available from you paper supplier along with the calibration colour chart you need to print and send back to them to create the ICC profile for each type of paper you intend to use.
Calibrate your monitor as well and your results will be a lot better than the built ins your printer has.
As with everything you may have to do a few test prints to get what your aiming for.
Hope this helps
Click to expand...
Should also add that for those who don't print at home, it's very easy and inexpensive to create a sort of test image (like an old style contact sheet) with multiple thumbnails of an image, separately tweaked for brightness, contrast, and saturation. The service can print a single copy which can be evaluated, then you know the "recipe" for getting prints that look the way you want.
 
I have two high end printers at home (Epson P800 and HP Z3200ps). I have learned that even though I use color calibration, I still have to raise the brightness of each before printing to them. Having done it for a few years, I know how much to increase it from PS or LightRoom (yup, and there are times I still forget and have to redo it)
 
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