Upsizing for large print

I've had a request for a 24X36 print from a Canon 5D photo. This is a size beyond anything I've printed and have even warned the person that the photo clarity my be slightly disappointing. The photo lab will be doing a Chromira print and the claim to use "ZBE's Resolution Enhancement Technology".

Does it make more sense to res-up the photo in photoshop using the bicubic smoother or to leave it at the native resolution and let the printer res-up things?

I'd sure go with the lab's recommendation. That's what we do. I've compared my own results with those of our lab, and whatever their magic, they won hands down. I'd expect the same from your lab. How big is big? They've produced brilliant 30x40 canvases from D2X files.

That's a tough call Roger. I don't know anything about that particular application, but at least with photoshop you could resize and then print a test print of an 8X10 section to see how it will print at the finished size. I think you should talk to the lab to see if they can print a test strip for you to compare. Possibly one of the RMNP folks would have genuine fractals to try as well.

Mel-

My lab has produced two wonderful 24x36 images from my 30D. Like Hank, I just do it how they tell me to do it because that's what works for them. And what works for them works for me and my client. I would ask your lab what they would prefer. If they add on a small fee for upsizing the file themselves, it will be worth it.

Roger, Shootsmarter.com had a video segment on their web site awhile back where they compared uprezing methods and they stated that their Fuji printer outdid anything they could do in PS or with other software. Having said that, I have no experience with uprezing this way, but my copy of Qimage does a great job of uprezing. Better than PS in my opinion.

Thanks for the help. I did call the lab today (Denver Digital/Slideprinter) and talked with the production manager. Though she stumbled over things enough to make me wonder if she understood my question, she recommended allowing the printer to do the up sizing. I'd welcome other experience, but sounds like that is the most common thought.

If I understand it correctly, the ZBE resolution enhancement feature increases the print resolution on Chromira (from 300PPI to 425PPI) but is not related to resizing the source image. The real answer will depend on whether you feel you can do a better job than the lab technician.
I use Photoshop's bicubic interpolation, though for very large prints from smaller files I often use selective blurring and sharpening to make sure unwanted artifacts are not exaggerated in the process.
Another (expensive) option is to look into software like Genuine Fractals.

Guy

Roger, I have been making 36x24 prints from my Nikon D80 and so far they are remarkably sharp and clear. I see no artifacts at all even from inches away. The original RAW image shows up in photoshop as a 28.8 MB file with a document size of 12.9x8.64 @ 300 pixels/inch. When I increase the size to 36x24 I get a monster file of over 220 MB. Reducing the 300 pixels/inch to 200 pixels/inch gives a more manageable 98 MB file and I even have gone down to 150 pixels/inch with a 58 MB file without seeing any difference no matter how hard I look.

For an unknown reason the workers at the lab tried to convince me that interpolating is not a good idea and they insist the print will look like the actual pixels size in photoshop. That simply isn't true because you judge the outcome by the print size. So far I am getting my way and I am very happy with the results.

Will
Edmonton, Alberta
Canada

Thanks for the help and comments! I checked out the ZBE Enhancement and Guy is certainly right, though I would guess that the Chromira printer also has it's own un-rezing to 300 dpi? I'm not even sure how much improvement the ZBE enhancement from 300 ppi to 425 ppi would be noticable to the eye. With the mixed comments, my current thinking is to rez up to 200 or 240 dpi and see what happens. It would be fun to try a couple of things, but not at the cost to print.