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Need Some help to prepare a very large printing...


flanoizele

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Hi everyone,

I am a new member of this forum and also pretty new to photoshop. One of my customers requests a photograph to be applied on a wall. The final print will be 20 meters large by 2,5 meters high.

I have done some panorama photographs before but I have no clue how to start on such a huge print.

I know how to stitch the photos in PS.

Can anyone give me some tips on how to prepare for such a large print in Photoshop? What canvas size to use,....

Thanks a lot

Frederic




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Tom Mann

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For prints that large, you can almost always get away with PPI (pixels per inch) numbers for the final print size that are astonishingly less than the 200-300 ppi values normally recommended for photos. The reason for this is that viewers typically don't view images of that size from a foot or two away like they would typically view a print small enough to hold in your hands. Viewers of billboard sized images typically step back far enough so they can view the entire image at one time, and this usually works out to mean that if the photo that you are sending to the printer is more than 4000 to 6000 pixels in the long dimension (NOT ARTIFICIALLY UP-REZ'ED), usually, you will be OK. Obviously, the more pixels the merrier. If your stitching procedure produces an image that is, say, 12k pixels horizontally, don't down rez it to the 4k - 6k range. Leave it where it is. The printer will take care of to adjust the final PPI number to a value that is appropriate for the size and his particular press, and so that viewers don't see individual pixels on the final product.

However, there is one major exception to the above guidelines:

If there is any text or sharp-edged graphics that also need to go on the print, they MUST remain sharp even at the final huge size. This means that the printer can't up-rez them as he would the continuous tone (aka, "contone") / photo-realistic parts of the final product. The only way to ensure this is for you to supply the printer with the graphics and text in vector form. Probably, the most common way to do this is to send the printer your work in a file format that supports both bitmapped and vector graphics. The only way to be sure of what file format he will accept is to ask. Any commercial printer worth his salt will have a FAQ prepared that deals with such issues and will state their requirements. Some might require Adobe Illustrator files, others might want EPS (encapsuated postscript) or PDFs, etc. Some printers will accept a non-flattened PSD file, but many shy away from this because they feel that there is too much room for miscommunication and possible errors with this format. OTOH, pay them more money so that they can spend more time talking to you, and they might accept a PSD. The only way to know is to start talking to the printer before you even start.

HTH,

Tom M
 

flanoizele

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Hi Tom, thanks a lot for your reply. I already tried to contact the printer but am waiting for him to get in touch with me. However, I do think I will have to use a ppi of 240 or higher since this will be a wall print, displayed in a 20 meters long hallway. So people will be walking right beside it. There even isn't enough space to step back and see the print as a whole.


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Tom Mann

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Ahh. I hadn't anticipated that people would be standing that close to your image. That's a whole different ball game. I had PS calculate that your pixel dimensions will be just under 200k pixels wide and 23k px high, or an image size of 12.4 G.

I'm sure you already know this, but a few random thoughts ...

a) Those pixel dimensions are well above the old 30kpx limit (in each direction) for PS, so you better have a fairly new version of PS.

b) You may want to consider having it printed by the folks that Gigapan uses ( http://www.gigapan.com/galleries/10183/gigapans ) including tricks like having it printed out in sections.

c) A 12 Gig image is larger than anything I've seen in the Gigapan gallery. Most of their examples are in the range of a half gig to a few gig. Nothing over 10 G. You may want to hang out on their forums and discuss your project with those folks.

d) Be prepared for every single thing that you do to the image in PS to take much more time than you think. I have a very fast PC (i7, 4 GHz, 64 G of RAM, fast 500G SSD for the OS, two fast 250 G SSDs as scratch /swap drives, etc.), so for yucks, I made a new 8 bpc, single layer image with those dimensions and it immediately filled up 70% of my 64G of RAM, and filled up all but 10% of my scratch/swap SSD (which is normally almost completely empty), etc. I then did a simple USM operation on the image. That one operation took around 4 minutes to complete!

e) I presume your stitching software can handle such large pixel dimensions and you will be able to fill up all those pixels with meaningful (ie, not interpolated) image data.

f) I bet you could go down to 150 ppi (from 240) even with people standing that close and it will still look fabulous and the image / file size will be reduced to ~ 40% of the size at 240 ppi.

Finally, I have to say that I'm jealous, LOL. What a fun project and great opportunity for you! The best of luck with it. If, when it's done, if you can share it with us (at low resolution, PLEASE, LOL) we would love to see it.

All the best,

Tom M
 
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