Photo printing

[tims45409183]

I am preparing photos for printing. I want the best quality prints and I have various sizes. The largest sizes that I will be printing are 900mm x 600mm and

1140mm x380mm.

Croping is no issue as the aspect ratios are 3:2 and 3:1 respectively and they are an exact fit for the dimensions.

I have two questions about exporting from Lightroom and I'd greatly appreciate some feedback.

1.  I orinally captured the images on a canon 6D in RAW and I will be providing the files as PDF to the printer. So when I export from Lightroom should I export as TIFF or original image format then convert to PDF through Mac's PDF?

2.  Do I need to even specify image size or just export at 300ppi and tell the print lab I want them printed at the above sizes in mm (900x600)?

Thanks,

Tim

[Per Berntsen]

To print an image 900 mm x 600 mm @300 ppi, you will need 10630 x 7087 pixels.

This is because 900 mm equals 35.43 inches (900:25.4), and 35.43 x 300 = 10630.

The image from your camera is 5472 x 3648 pixels (20 megapixels), and the image you want to print needs to be 75 megapixels. (at 300 ppi)

But if this is inkjet printing, you don't need 300 ppi for such a large print, I use 180 ppi for large prints on my Epson printer.

The number of pixels in your image allows printing at 154 ppi without enlarging (900:25.4 x 154.432 = 5472), and I would make a test print to see if it's good enough.

Your export settings should be something like this:

The image format is set to Tiff here, but I believe most printing services want Jpg files, in which case you should use 100 quality.

Which printing service are you using? Do they want files in pdf format?

As for the 1140 mm wide prints, they will only be printed at 122 ppi without enlarging, which may, or may not be good enough.

And note that all the calculations I'v done here are based on an uncropped original from the camera - i.e. it is 5472 pixels on the long side.

For more information on how pixel dimensions and ppi works, see What is a digital image?

[tims45409183]

Thanks for your response Per.

So if I chose a higher ppi than what my image's pixels support, does this mean interpolation will occur, extra pixels will be created? And in this instance, by choosing a higher ppi my printed image quality will suffer?

As far as image forma, I have gone to a range of different printing services for quotes and they generally tell me they accept JPEG or PDF. I assumed that JPEG was not as good quality as TIFF so I thought I'd export TIFF then convert to PDF. I did notice in Lightroom that there is an option to export as 'original'. So I assume this means the image would export as RAW, and if I'm going to convert to PDF would I be better off skipping the tiff and converting to PDF from an exported RAW post processed image?

My camera is set to shoot in 3:2. Would I need to specify bother long and short side dimensions for my 3:1 images?

Thanks

[tims45409183]

Hi Per,

please pardon don my lame maths brain but what formula do I use to determine the required PPI based on my image size (pixels) and desired print dimensions (eg-900x600mm)?

[Just Shoot Me]

There are formulas in the links I posted for size of print and Dots Per Inch (PPI) they can be printed at.

[Per Berntsen · Accepted solution]

tims45409183 wrote:

So if I chose a higher ppi than what my image's pixels support, does this mean interpolation will occur, extra pixels will be created? And in this instance, by choosing a higher ppi my printed image quality will suffer?

Yes, interpolation will occur, and image quality will suffer, to some extent. I can't really tell you what will work best - printing at the native ppi (154, which is on the low side) or interpolating to a higher ppi. But small increase in the ppi - to 180 - could work well.

180 is a good number, because many inkjet printers (at least Epson) have a resolution of 720 or 1440 dpi (dots per inch), and if printer dpi divided with image ppi results in a whole number, it is supposed to have a good effect on print quality. (720:180 = 4)

As far as image forma, I have gone to a range of different printing services for quotes and they generally tell me they accept JPEG or PDF. I assumed that JPEG was not as good quality as TIFF so I thought I'd export TIFF then convert to PDF. I did notice in Lightroom that there is an option to export as 'original'. So I assume this means the image would export as RAW, and if I'm going to convert to PDF would I be better off skipping the tiff and converting to PDF from an exported RAW post processed image?

If you are going to convert a Tiff to PDF, do not use the native Mac software. I don't use a Mac, but I suspect that there could be compression applied automatically, and that you would have little control over the conversion process.

You would have complete control over the conversion using Photoshop or Acrobat, but there are a number of options in the PDF save dialog, and there's a chance that something could go wrong.

Exporting as jpg is very simple and safe, set quality to 100 and Color space to sRGB.

Although jpg uses lossy compression, you will in most cases not be able to tell the difference between a Tiff and a 100 quality jpg.

But whatever you do, do not edit the exported jpg. Resaving it could lead to a noticeable quality loss.

Exporting as Original is not an option, it will export the unedited raw file.

My camera is set to shoot in 3:2. Would I need to specify bother long and short side dimensions for my 3:1 images?

You only need to specify the long side, since the pixel dimensions are exactly 3:2.

The same goes for the 3:1 prints, if the original has been cropped to 3:1.

what formula do I use to determine the required PPI based on my image size (pixels) and desired print dimensions (eg-900x600mm)?

Pixel dimensions divided by print dimensions in inches results in ppi. (1 inch = 25.4 mm or 2.54 cm)

5472 (pixels) : 35.43 (inches) = 154.445 (ppi)

When making prints this size, only use images that are sharp (unless they are intentionally unsharp of course), and have generally good quality. If you use an underexposed image that needs brightening, there will probably be some visible noise, that might be very noticeable in the print. Proper sharpening is very important, do not oversharpen, and use the Masking slider to prevent sharpening of noise in flat areas. (press the Option key while dragging the slider to see the effect).

Sharpening and noise reduction must always be done at 1:1 view - any other view will be incorrect and misleading because the image has been scaled.

When sharpened properly, the image should look sharp (but not too sharp) at 1:1. If in doubt, sharpen less.

Then use Standard output sharpening for print in the Export dialog.

[tims45409183]

Mate, thanks a bunch! I greatly appreciate your feedback, it certainly is helping make sense of it and gives me a lot to work with.

cheers

[Just Shoot Me]

All as stated above and also take into account the Viewing distance for a large print. The farther away the viewer is the less DPI is needed for the images to look good.

PHOTO VIEWING distance affects perceived sharpness despite resolution |

What print resolution works for what viewing distance?

https://www.photo.net/learn/viewing-distance-the-overlooked-aspect-of-print-size/

[tims45409183]

My printed images are intended for wall hangings in homes and businesse, so they would be viewed from a distance of about a few feet