Resizing JPGs for large prints

[Colin]

What is the best method for resizing a JPG photograph for a large print? Let's say I have a 4:3 aspect ratio JPG out of my camera which is 4592 x 3468 pixels, and I want to print it at the same aspect ratio, but at a size of 40" x 30" for say, a canvas print. Is it best to do that in Photoshop, or just specify that larger size within the RIP? (VW).

If it's acceptable to do it in PS by going to "Image" > "Image Size" and simply punching in the numbers in inches, do I need to lower the Resolution (to about 110 PPI in this case) so that the pixel count doesn't exceed the original, native 4592?

 

[GAC05]

No need to resize (I think)
Set the output size in VW and hit print.
At your production size you are still over 100ppi (about 115) without any resizing of the original bitmap.
Should print fine unless it is a detailed map using 6pt Times Roman for text titles.

wayne k
guam usa

 

[John Butto]

Photoshop / Perfect Resize

 

[Colin]

Perfect Resize

Not sure what you mean there.

 

[John Butto]

http://www.ononesoftware.com/products/perfect-resize/

 

[Colin]

Should print fine unless it is a detailed map using 6pt Times Roman for text titles.

I am referring to a photo, like one would hang on a wall as an art piece, so I want the best possible result.

Here's an example of the settings I'm unclear on (see file). I opened a 4592 x 3468 pixel JPG, punched in the 40" and 30" numbers without altering the resolution (PPI), and the pixels jumped up to 9600. Is that ok, or should I reduce the PPI to achieve a pixel count no more than the original (which would be 110 PPI in this case, resulting in 4400 pixels across).

I'm also wondering about which of the six options at the bottom there would be the correct one for enlargements.

 

[HardbargerSigns]

Don't resize in one big jump, Photoshop automatically adds a sharpen to the image with each resize. So sizing up 25 or so DPI at a time will result in a better image in the end.
Also, saving as a .Tiff will also help your final image quality.

 

[Colin]

Don't resize in one big jump, Photoshop automatically adds a sharpen to the image with each resize. So sizing up 25 or so DPI at a time will result in a better image in the end.
Also, saving as a .Tiff will also help your final image quality.

"at a time"? I'm not sure what you mean by that. As these files are lossy, don't we want to do it just once?

Thanks for mentioning the TIF thing; I've heard conflicting opinions on that too. Is it really better?

 

[GAC05]

Colin is that Photoshop?
I don't think there will be an upside to resizing your photos if you are going to run them out at 40"x30" on canvas.
If you lower the dpi in the resizing dialog so you end up with about the same number of pixels as the original you are not doing anything to the bitmap.
A 40"x30" x 100ppi bitmap would be the same as a 4"x3" x 1000ppi. RIP is going to see the same pixel count in both.

wayne k
guam usa

 

[iprint]

Just uncheck "Resample Image" and put your image to whatever size you want. You will see that the resolution reduces (or increases if you go smaller) automatically and proportionate to the increase in size. As long as you started with a crisp clean pic, you shouldn't have any issues printing onto canvas with an image resolution of 100 or so.
Increasing size while keeping the same resolution will result in degradation of your image.

 

[HardbargerSigns]

.Jpeg is a compressed image type, .Tiff retains more of the pixels and thus provides better results.
When I size an image up in scale, either by inches or DPI, let's say it's 72 DPI, obviously it's going to be a terrible image if it's ALSO only 5 inches wide. If you size it ip to 150 DPI by first resizing to 85 DPI, then 95, and so on, Photoshop adds a sharpen feature, which depending on the image can improve it somewhat.
From your screencap, you should have NO problems printing a good image. If you DO have a bad image to work with, I've often added filters to create the look of a painting, CS6 has an excellent Oil Paint filter that with some tweaking can look AMAZING.

 

[Colin]

Colin is that Photoshop?

Yes. CS6

If you lower the dpi in the resizing dialog so you end up with about the same number of pixels as the original you are not doing anything to the bitmap.
A 40"x30" x 100ppi bitmap would be the same as a 4"x3" x 1000ppi. RIP is going to see the same pixel count in both.

Right, but is it ok (or better) to leave the resolution at 240, and have the pixel count exceed the original? Isn't there a potential negative result with interpolation?

I guess I'd just like a step-by-step process spelled out. Perhaps it is as you said originally - just size it in VW. shrug

 

[Colin]

Just uncheck "Resample Image" and put your image to whatever size you want. You will see that the resolution reduces (or increases if you go smaller) automatically and proportionate to the increase in size. As long as you started with a crisp clean pic, you shouldn't have any issues printing onto canvas with an image resolution of 100 or so.
Increasing size while keeping the same resolution will result in degradation of your image.

Ah, ok, that seems to make sense. I tried that, and the PPI went to 114.8, which is acceptable (I suspect) for a 40" x 30" print.

 

[GAC05]

Yes. CS6




Right, but is it ok (or better) to leave the resolution at 240, and have the pixel count exceed the original? Is there a potential negative result with interpolation?

I guess I'd just like a step-by-step process spelled out. Perhaps it is as you said originally - just size it in VW. shrug

Interpolation when resizing up is always going to degrade the image somewhat. It is adding info(pixels) where none existed before based on some mathematics that only really smart people know. If you are going for extreme resolution changes Photoshop and other dedicated resizing programs come into play to give you the best result.
With what you are doing now you don't need it. A 4k x 3k photo should print very nice on a 40"x30" canvas.

wayne k
guam usa

 

[John Butto]

Don't resize in one big jump, Photoshop automatically adds a sharpen to the image with each resize. So sizing up 25 or so DPI at a time will result in a better image in the end.
Also, saving as a .Tiff will also help your final image quality.

If you don't have the resize software this is the best method in Photoshop to use.

 

[Colin]

When I size an image up in scale, either by inches or DPI, let's say it's 72 DPI, obviously it's going to be a terrible image if it's ALSO only 5 inches wide. If you size it ip to 150 DPI by first resizing to 85 DPI, then 95, and so on, Photoshop adds a sharpen feature, which depending on the image can improve it somewhat.

Um, ok, but bear with me....If I uncheck the "Resample Image" box, as iprint suggested in his post, I'm actually reducing the PPI when I increase the physical size, not increasing, no?

 

[Colin]

.Jpeg is a compressed image type, .Tiff retains more of the pixels and thus provides better results.

Am I correct in thinking that this is only true if one is able to save from a Raw or PSD file? I can't see being able to improve upon a JPG just by saving it as a TIF. (?)

 

[Stefan]

I can't see being able to improve upon a JPG just by saving it as a TIF. (?)

I think it's more about avoiding decreasing quality further by not saving the file as a jpg. Saving as tif won't improve on original jpg image in any way, however, resaving a jpg as a jpg may decrease quality even further.

Here's another program you may want to try for resizing images:

http://www.benvista.com/photozoompro

 

[OldPaint]

4592 x 3468 in my corel is 63" on the long side @ 100 percent....you will need to compress it rather then expand it.

 

[Colin]

4592 x 3468 in my corel is 63" on the long side @ 100 percent....you will need to compress it rather then expand it.

Hi OP. I'm not sure what you mean by "in my Corel", the actual size which shows in Photoshop of a 4592 x 3468 is 19.13" x 14.36" (at 240 PPI).