UPSIZING A PHOTO

[bellimages]

Okay, I've read articles on this through the years, but am ready to upsize a photo. Off hand, how much could I increase a photo that's 18" long @ 300 ppi? It's important that I see no visible loss of quality.

And, if this is possible. What is the best method to upsize?

[kpmedia]

Genuine Fractals: http://www.ononesoftware.com/detail.php?prodLine_id=7
I've been using this one for years.
Far superior to basic bicubic/bilinear/etc methods native to Photoshop/etc

You can get up to 200% and have acceptable results. But the less upsizing you do, the better the quality, of course. Depending on image content, it may simply appear slightly grainy, and not have any tell-tale signs up upsize you'd find from other methods.

Here's an example of the method applied to DVD case artwork:
http://www.digitalFAQ.com/guides/video/dvd-storage-photoshop-lowres.htm

It's a fractal method, so pieces are odd-shaped, which leads to the cleanliness of it.

[jbrembat]

Try PhotoResampling.

Jacopo

[Eli Burakian]

If you have Photoshop, try it first.  I think the interpolation algorithms have improved greatly over the years and I use it with much success.

Try before you buy is my philosphy....at least most of the time!

Eli

[jbrembat]

Try before you buy is my philosphy....at least most of the time!

Do you get PhotoShop for free? (LOL)

Jacopo

[PeterAit]

I assume you want to print the photo. Then, 180 ppi is the minimum resolution you need for best quality results. So, you can enlarge the photo to 300/180 x 18 = 30 inches wide. Of course, "best" quality depends on more than just the PPI, like proper sharpening and so on. For larger, you will want to uprez (increase the ppi). Photoshop has some tools for this that other like, but I find Genuine Fractals to work better.

[jbrembat]

180 ppi is the minimum resolution you need for best quality results.

From where is this magic number?

Jacopo

[Bart_van_der_Wolf]

From where is this magic number?

180 PPI equals 7.09 lines/mm or 3.54 linepairs/mm, whereas human vision resolves 5-8 lp/mm at normal reading distance (10-12 inches) under reasonable lighting conditions. So 300-360 PPI seems more in line with physics than the 180 PPI urban legend.

In addition, humans can see much more detail due to "Vernier acuity", so 600-720 PPI is about as good as it gets (which is what the OP was asking for) for reading distances (lower these numbers linearly in proportion to increased viewing distance). This happens to also correspond to the native resolution of many inkjet printer. Of course not all subject matter requires the utmost quality, and the material on which one prints also plays a role.

Cheers,
Bart

[Jack Flesher]

180 PPI equals 7.09 lines/mm or 3.54 linepairs/mm, whereas human vision resolves 5-8 lp/mm at normal reading distance (10-12 inches) under reasonable lighting conditions. So 300-360 PPI seems more in line with physics than the 180 PPI urban legend.

And probably is relevant if your printing a lot of images with small lines organized side-by-side...  But since most of the "P's" in a print are random, I think the 180 value remains "viable" for many larger prints being viewed from more than a few feet distance.  That said, if you closely inspect identical prints that have not been upscaled side-by-side at 180 and 360, there is little doubt the 360 will look "sharper." Whether that's going to be a relevant difference at normal viewing distances remains questionable IMO.  Personally I prefer 240 as a minimum for Photo papers and respect other's opinions will vary...

Cheers,

[jbrembat]

180 may be a good value for Epson (360/720 PPI).
For Canon or HP (600 PPI) is not so good.

Jacopo

[01af]

Off hand, how much could I increase a photo that's 18" long @ 300 ppi? It's important that I see no visible loss of quality.

"How far can I walk before feeling exhausted?"

That's a nonsense question. No serious answer possible ... I mean, short of writing a book.

[Jeff Worsnop]

Do you get PhotoShop for free? (LOL)

Jacopo

Yes - for 30 days.
From the Adobe website.

[edwinb]

I find a good guideline to get acceptable detail on images of maps you need 12 pixels across a the small letter 'e'
also the minimum resolution is approximately 200 ppi for 100% reproduction - using sinar digital system and epson inkjets
Edwin