Resized Images for Printing – Test Results
charmfoto
Registered Users Posts: 2 Beginner grinner
For a while now, I've been resizing images posted for sale through Smugmug/EZ Prints, because I've always believed that an interpolated, right-sized image will produce the sharpest print.
Furthermore, I did not believe the lab can downsample a larger image and produce a 4x6 print sharper than an image resized specifically for 4x6 printing.
This mindset drove me to create multiple buy galleries, each containing specific resized images. For example, I'd set up a buy gallery for 4x6s, 8x12s and 12x18s. This required much more processing time, upload time and storage space on Smugmug (even though disk space is virtually unlimited for pro accounts).
The 4x6s were resized at 302dpi, 8x12s at 302dpi and 12x18s at 254dpi. Per the information posted here: http://www.smugmug.com/help/print-quality, "Prints up to 10x15 inches are produced on Fuji Frontiers, running at 302 dpi....Prints above 10x15, up to 30 inches on a side, are made on Polielettronica LaserLab printers whose native resolution is 254 dpi."
This is too much work! I don't want to create multiple buy galleries; I want to create just one. So I decided to give the lab downsampling a chance.
Here's my test--interpolated a 12.7MP (Canon 5D) image to four flavors and see which ones will produce the sharpest prints in various print sizes. The assumption is that the 12x18 will go to the Polielettronica LaserLab printers, and the other smaller sizes will go to the Fuji Frontiers. All printed on Lustre paper in True Colors.
The four flavors:
4x6 @ 302dpi, 1812 x 1208, 1.74MB file size
8x12 @ 302dpi, 3624 x 2416, 6.29MB file size
12x18 @ 302dpi, 5436 x 3624, 13.32MB file size
12x18 @ 254dpi, 4572 x 3048, 10.35MB file size
Result--4x6 prints from SHARP to DULL:
12x18 @ 254dpi
12x18 @ 302dpi
8x12 @ 302dpi
4x6 @ 302dpi
Result--8x12 prints from SHARP to DULL:
12x18 @ 254dpi
12x18 @ 302dpi
8x12 @ 302dpi
Result--8x12 prints from SHARP to DULL:
12x18 @ 254dpi
12x18 @ 302dpi
These results are very surprising to me, because the sharpest prints came from the 12x18 @ 254dpi flavor, regardless of printers. I did not expect the sharpest 4x6 print to come from this flavor!
This test is important for me, because I want my customers to experience the convenience, worldwide delivery, incredible packaging, awesome guarantee and great service that Smugmug/EZ Prints offers. Oh yeah, and great print quality—the color is dead on, and the resolution is tack sharp!
Furthermore, I did not believe the lab can downsample a larger image and produce a 4x6 print sharper than an image resized specifically for 4x6 printing.
This mindset drove me to create multiple buy galleries, each containing specific resized images. For example, I'd set up a buy gallery for 4x6s, 8x12s and 12x18s. This required much more processing time, upload time and storage space on Smugmug (even though disk space is virtually unlimited for pro accounts).
The 4x6s were resized at 302dpi, 8x12s at 302dpi and 12x18s at 254dpi. Per the information posted here: http://www.smugmug.com/help/print-quality, "Prints up to 10x15 inches are produced on Fuji Frontiers, running at 302 dpi....Prints above 10x15, up to 30 inches on a side, are made on Polielettronica LaserLab printers whose native resolution is 254 dpi."
This is too much work! I don't want to create multiple buy galleries; I want to create just one. So I decided to give the lab downsampling a chance.
Here's my test--interpolated a 12.7MP (Canon 5D) image to four flavors and see which ones will produce the sharpest prints in various print sizes. The assumption is that the 12x18 will go to the Polielettronica LaserLab printers, and the other smaller sizes will go to the Fuji Frontiers. All printed on Lustre paper in True Colors.
The four flavors:
4x6 @ 302dpi, 1812 x 1208, 1.74MB file size
8x12 @ 302dpi, 3624 x 2416, 6.29MB file size
12x18 @ 302dpi, 5436 x 3624, 13.32MB file size
12x18 @ 254dpi, 4572 x 3048, 10.35MB file size
Result--4x6 prints from SHARP to DULL:
12x18 @ 254dpi
12x18 @ 302dpi
8x12 @ 302dpi
4x6 @ 302dpi
Result--8x12 prints from SHARP to DULL:
12x18 @ 254dpi
12x18 @ 302dpi
8x12 @ 302dpi
Result--8x12 prints from SHARP to DULL:
12x18 @ 254dpi
12x18 @ 302dpi
These results are very surprising to me, because the sharpest prints came from the 12x18 @ 254dpi flavor, regardless of printers. I did not expect the sharpest 4x6 print to come from this flavor!
This test is important for me, because I want my customers to experience the convenience, worldwide delivery, incredible packaging, awesome guarantee and great service that Smugmug/EZ Prints offers. Oh yeah, and great print quality—the color is dead on, and the resolution is tack sharp!
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Comments
Wow, that's an impressive test. In my opinion, there aren't enough really methodical tests like that being performed in our industry.
One thing is changing: the Polis are fabulous printers but the uptime and customer service is a problem. So EZ Prints has purchased Noritsus to replace the Polis and has brought at least one of them online in the last week or two. I'm not sure what resolution they're running, but I will check.
The reason I like to see tests like you performed is there are so many variables and it's hard to get information from makers of lab software on how their systems work.
One variable is the algorithm used for downsampling. We use the Lanczos algorithm at SmugMug, not because it preserves the most sharpness, but because we feel it preserves the most detail. We worry about the softness induced by resizing later. Our goal with unsharp mask is to match the original's sharpness as closely as we can. Here's a really good reference about why we do it like we do:
http://www.cambridgeincolour.com/tutorials/image-resize-for-web.htm
My friend Bill Atkinson swears he gets the best downsampled images by going in steps of 50% each time.
As to the question of what the lab does, I'm afraid I've never been told... What we do know and I think your test shows is that they do it well. Why you get better results starting from 254 dpi as opposed to 302 dpi, I don't know for sure. I have said for a long time, though, that it's my opinion the world has too many pixels. What we need are better pixels. I wouldn't be surprised to find out that ezprints' algorithms were optimized for fewer pixels because that's what we've had until recently.
I will ask them, however, to see if they'll weigh in on this thread.
Thanks,
Baldy