6D print size/quality PPI confusion.

Okay so I'm trying to make a large print 36x24 I started with a RAW from my 6D and then some lightroom editing saved max quality JPEG. Uploaded print to nations photo lab which is telling me they recommend at least 180 PPI using photoshop it is claiming to be 152 PPI at 36x24 So a print on metallic paper isn't cheap mounted so I'm getting nervous. I have previous printed about this size on my older XSI back in the day and was pretty pleased with the results, like I said I'm going to print on metallic and its a pretty big living room so closest viewing distant will be several feet away. Should I just say to hell with it and print based off the file saved from lightroom or is it a must to go into photoshop and then resize the image first to the print size I want? Ive heard talk about turning off auto resample as it fills in missing pixels but makes the image soft?

attached is the photo
 

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The claim of the photolab means to display the paper near a walking distances, it is recommended 180dpi. If you take seriously this recommendation, its 6D only have good quality prints up to 20 inches long.
Obviously this is not true.

I have made impressions on paper size 28 inches, from a modest Rebel XTi (10 megapixel) with great results.
It would have been sharper with 20 megapixel?
Yes, but that did not stop me from making good use of my XTi at that time.
I'm sure your 6D will make a great print quality in size 36 inches.
Could be more sharper with 5DSr?
Yes, but you know your current camera is capable of better quality (in real world) than the test charts say.
 
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There are 2 issues with printing large - resolution/detail and pixelation. I agree with ajfotofilmagem that a good 6D file is very capable of generating a great 36 inch print (i.e. has enough resolution). However, if their printing process is optimized for 180 dpi or higher then there may be some benefit in up-sizing your image in Photoshop to 180 or 200 dpi to prevent visible pixelation. I'd contact them to see if their processor will up-res for you automatically or if you should do it yourself if that is the case.

Rule of thumb for large prints is that 150 dpi is fine for normal viewing distance, though, so I think you'd be good either way. The old 300 dpi rule is for magazines and small prints viewed up close, but nobody will (or should) be putting their nose on your 36 inch print ;)
 
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20Mp is far more than enough to print that image and look great for that size. Heck, I've seen 15MP images printed 10 feet tall at our local print shop (Bumblejax) standing right next to the print. Looked good to me. I've printed single 5D2 and 6D files at 24x36 and larger and they look awesome. Never had a client even once say anything about details.

The other thing is that you image is a very good image with a strong presence. Interesting shapes and composition. It's not the details that make it have the wow factor.

Smugmug once published a chart showing the reasons people had returned prints from either the photographer or clients buying the prints. Lack of sharpness was at the bottom of the list in terms of number of returns. The main concerns were issues regarding color.

I also personally just let the printers upscale the images instead of doing it myself to match the resolution point for point. They are designed to do a great job at it. I don't know of any modern printer that does upscale the print without resampling the pixels. They all resample it so there is no pixelation.
 
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Curious as to why you exported a single image for print as a JPEG. Even at max quality, it is somewhat lossy vs a lossless TIFF or PNG (or in PSD)--not to mention the greater bit color (which isn't a big deal for this image).

As others have stated, that image in particular isn't so dependent on the absolute maximum sharpness of details so it should scale to that size absolutely fine. I'd send them the best file you can and let them upscale it on their end since they know their equipment's requirements and do this for a living (they may have a better option than Photoshop--which would be just fine anyway). I would also assume that they have the ability to print a sample and adjust if they have any real concerns.
 
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sanfranchristo said:
Curious as to why you exported a single image for print as a JPEG. Even at max quality, it is somewhat lossy vs a lossless TIFF or PNG (or in PSD)--not to mention the greater bit color (which isn't a big deal for this image).

As others have stated, that image in particular isn't so dependent on the absolute maximum sharpness of details so it should scale to that size absolutely fine. I'd send them the best file you can and let them upscale it on their end since they know their equipment's requirements and do this for a living (they may have a better option than Photoshop--which would be just fine anyway). I would also assume that they have the ability to print a sample and adjust if they have any real concerns.

I'm personally really picky about file quality and I can't see any difference between a JPEG set at quality level 12 and a TIFF. As long as the file is not being opened and saved repeatedly or modified in any way, a JPEG works just fine for 8 bit printing. When JPEG is set to 10 or below, it can make a difference, I agree.

It seems like only Adobe offers a setting of 12. DPP doesn't allow anything more than 10 from what I recall.

When sending the print lab a file for a 20,000+ pixel wide print, it can be much easier to upload and handle with the smaller JPEG size.
 
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The quality of the print that is up-sized is more dependent on the capabilities of the RIP software in the printer than minor differences in format submitted or resolution - obviously within reason. You should contact the service again and ask for their recommendation or if they have an upcharge to do it for you. A file from a 6D at maximum resolution should easily produce a quality print at 60"x96".
 
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