[TonyW]

If your lab is professional they should be able to provide you with an ICC profile for the media they are printing on and should advise you to soft proof on your colour managed system and make sure that the file you send to them is embedded.

IF you are working within a correctly colour managed workflow i.e. a calibrated and profiled monitor with the monitor profile actually being used by the OS and you work in an application such as LR or Photoshop and use Soft Proofing you should get a print pretty close to WYSIWYG when returned from the lab.

[Fenwoodian]

If your lab is professional they should be able to provide you with an ICC profile for the media they are printing on and should advise you to soft proof on your colour managed system and make sure that the file you send to them is embedded.

IF you are working within a correctly colour managed workflow i.e. a calibrated and profiled monitor with the monitor profile actually being used by the OS and you work in an application such as LR or Photoshop and use Soft Proofing you should get a print pretty close to WYSIWYG when returned from the lab.

Tony, have you by any chance either written articles on printing, or made a YouTube on the subject? I'd sure be interested in hearing more from you on the subject...

[fehknt]

A sample is useful to see how the medium looks in general but I would assume would be optimized on their end with the optimal resolution. I would want to know how _my_ print will look with the specific resolution I plan to provide. I thought getting a small test print was a common use-case, it's only a $20 print or so. I am not _expecting_ to return anything, it's only if it's not high enough quality that I would complain. To be honest I haven't bothered with this because I've been happy with my lab and haven't done stuff that's suuuper expensive but if I was targeting a couple hundred dollar print like a 40x40 acrylic, I think the lab would prefer me to get a small sample to re-print than have a complaint on the full size. And I don't really care if they say no to a reprint, I'm happy to just order another, but most labs I would bet understand this process and my lab has always offered a reprint with any minor complaint I have (taken them up on it once and found a workaround once).

I'm assuming a fully color managed workflow here, this was about resolution artifacting caused by potential mismatches in the input and output resolutions and bad printer driver interpolation.

[TonyW]

Tony, have you by any chance either written articles on printing, or made a YouTube on the subject? I'd sure be interested in hearing more from you on the subject...

No, I have not done anything like that. TBH what I have said is pretty much well documented and known among those that are old hands at digital printing and can be found in references both on the net and in various books.

A book that explains this briefly but pretty well is The Digital Print by Jeff Schewe. In fact many of Mr Schewe published articles along with the late Bruce Fraser are well worth study. The two of them and a couple of others formed Pixel Genius and are responsible for some of the sharpening methods in PS and LR.
The Digital Print: Preparing Images in Lightroom and Photoshop for Printing: Jeff Schewe: 9780321908452: amazon.com: Books?tag=pentaxforums-20&

Another good book although published in 2013 (old by printer standards) is Fine Art Printing for Photographers by the late Uwe Steinmueller
https://www.amazon.com/s/ref=nb_sb_ss_c_1_25?tag=pentaxforums-20&url=search-...+photographers
Forget the stupid prices here and have a look around for a used copy

[Na Horuk]

I would avoid interpolating, enlarging a photo; especially one that is medium res jpeg. If you had the raw file, post processed it, exported it as 16bit tiff, then you might enlarge. But enlarging usually really enlarges the artefacts and problems, not the amount of detail. I would rather print at lower DPI than enlarge. The above replies are good; try to talk to the people in the back of the shop, the ones that actually do the work. They should be able to tell you which DPI their hardware uses. Use the maximum DPI that you can with their hardware to get an image that is as close to the size you need, or just slightly larger (and then you can cut edges to make it fit perfectly? dunno about that medium, but you can with paper)
If the print shop only tells you 'derp higher DPI is better print!" they probably don't know a lot about printing and you might want to look around for other printers and at least talk to them. There is a lot to printing

OR you can buy a new camera, like a used K-3 or a K-S2 and re-take the photo in RAW, with best settings. Then you won't need to worry about DPI as you will always have more than enough

[Verfallsdatum]

Lots of good contributions in this thread. A lot more than I would have hoped anyway. I think I learned a lot about the difference between input and output printer resolution and so on.
I asked the person in the shop to check with the manager who (supposedly) checked with the print shop (photos are not printed on site), and they now tell me the native resolution they recommend is 800 PPI, which sounds insane.
I figured I might try to process it with On1 to scale it up to 800 and then their printer will scale it back down to its own actual max input resolution.

The shop I go to definitely isn't super professional as they don't print on site, they can't inform you about ideal resolution and they don't provide color profiles, but at least they're fairly cheap compared to other options I have found around here, and the samples they display in the shop look great.

I would definitely buy a smaller sample as a test, were it not for the 4 weeks delay (and the price of course). A 20"x30" print is about 150 CAD so I figured I might as well go for it.

[Miguel]

Lots of good contributions in this thread. A lot more than I would have hoped anyway. I think I learned a lot about the difference between input and output printer resolution and so on.
I asked the person in the shop to check with the manager who (supposedly) checked with the print shop (photos are not printed on site), and they now tell me the native resolution they recommend is 800 PPI, which sounds insane.
I figured I might try to process it with On1 to scale it up to 800 and then their printer will scale it back down to its own actual max input resolution.

The shop I go to definitely isn't super professional as they don't print on site, they can't inform you about ideal resolution and they don't provide color profiles, but at least they're fairly cheap compared to other options I have found around here, and the samples they display in the shop look great.

I would definitely buy a smaller sample as a test, were it not for the 4 weeks delay (and the price of course). A 20"x30" print is about 150 CAD so I figured I might as well go for it.

800 PPI makes me question the digital literacy of your printer. Consider finding another shop where folks may just have a better understanding of their requirements. If you want to test how your image looks printed out at 20x30, see if there is a Costco near you. Their printing is surprisingly good, and you can download a printer/paper profile from the Dry Creek site for soft proofing. Costco charges $10US for a 20x30 poster which should give you an idea.

M

[TonyW]

I agree with Miguel, 800 PPI is not a common printer requirement even for a high res. requirement at least AFAIK. It may be more helpful if the shop could tell you what printer manufacturer.

Common resolutions include 300 / 360 (Canon / Epson normal) and 600 / 720 (Canon / Epson). Fuji and HP systems also seem to use 300 / 600.

By up-sampling to 800 ppi and sending to the printer who will likely let the print driver down sample to the required resolution you are risking IQ losses and even more artefacts than you would get using a more conservative workflow. The proposed route going from 200 ppi (from your first post) up to 800 ppi then back down again to 300 ppi at the shop (my guess on printer requirements) is very far from optimal and is going to be worse IQ wise than just letting the shop upscale.

You would only upsample to the higher PPI 600 / 720 when your native file size greater than 300 / 360. Your quoted PPI of 200 obviously falling below both the high and standard ppi figures would need to be upsampled to the standard 300 / 360 ppi depending on the printer to maintain optimum ppi

[Na Horuk]

In your shoes I would take one of the following options:
a) Send the original image to the shop and let them do their best. If they give bad results, I would demand (partial) refund. I would not do up or down or any scaling. Just the original file with the most data, no new edits. No software can 'add' detail. You can expect mediocre results here, but I think they would be acceptable to the average audience.
b) Find another shop and talk to them. Often it is worth paying a 10% extra and getting better customer support and better product. Problem here is you are pressed for time.

If you are pressed for time and have already wasted some of it, go with a). Good luck, and please post with the outcome

I have seen low res jpegs printed onto large metal plates, like at a tourist attraction. No problem. I recommend you stress out less

[TonyW]

You have no choice as you are already scaling taking an image from either APS or FF sensor whatever the final print size (assuming you want something larger than 1.4" long dims.)

You should expect more than mediocre results here as you are not upsampling by much going from 200 ppi to 300/360ppi

[Verfallsdatum]

800 PPI makes me question the digital literacy of your printer. Consider finding another shop where folks may just have a better understanding of their requirements. If you want to test how your image looks printed out at 20x30, see if there is a Costco near you. Their printing is surprisingly good, and you can download a printer/paper profile from the Dry Creek site for soft proofing. Costco charges $10US for a 20x30 poster which should give you an idea.

M

I know right? I wonder if the manager told me 800 PPI as a way to tell me to leave them alone and stop asking questions. Wouldn't be super nice. The shop is a Deserre (fairly common arts and crafts shop in Québec).

---------- Post added 06-26-17 at 09:18 PM ----------

I agree with Miguel, 800 PPI is not a common printer requirement even for a high res. requirement at least AFAIK. It may be more helpful if the shop could tell you what printer manufacturer.

Common resolutions include 300 / 360 (Canon / Epson normal) and 600 / 720 (Canon / Epson). Fuji and HP systems also seem to use 300 / 600.

By up-sampling to 800 ppi and sending to the printer who will likely let the print driver down sample to the required resolution you are risking IQ losses and even more artefacts than you would get using a more conservative workflow. The proposed route going from 200 ppi (from your first post) up to 800 ppi then back down again to 300 ppi at the shop (my guess on printer requirements) is very far from optimal and is going to be worse IQ wise than just letting the shop upscale.

You would only upsample to the higher PPI 600 / 720 when your native file size greater than 300 / 360. Your quoted PPI of 200 obviously falling below both the high and standard ppi figures would need to be upsampled to the standard 300 / 360 ppi depending on the printer to maintain optimum ppi

That's good info, I wasn't sure whether upsampling more and then letting the printer down sample again was really a good idea. You're probably right though, it's like when you display a photo on your monitor, I noticed it never really looks as good as when you scale it for the exact pixel resolution of the monitor (might not be true for photo manipulation software but I noticed that when using pictures as desktop background).

---------- Post added 06-26-17 at 09:27 PM ----------

In your shoes I would take one of the following options:
a) Send the original image to the shop and let them do their best. If they give bad results, I would demand (partial) refund. I would not do up or down or any scaling. Just the original file with the most data, no new edits. No software can 'add' detail. You can expect mediocre results here, but I think they would be acceptable to the average audience.
b) Find another shop and talk to them. Often it is worth paying a 10% extra and getting better customer support and better product. Problem here is you are pressed for time.

If you are pressed for time and have already wasted some of it, go with a). Good luck, and please post with the outcome

I have seen low res jpegs printed onto large metal plates, like at a tourist attraction. No problem. I recommend you stress out less

Stressing out less sounds like a good idea :-)
It's a vacation picture I'm going to hang in my bathroom to have something nice to look at while pooping, that's probably why I'm being so anal about it (pun intended).
I guess I want to just do it right (or not completely screw it up) and not pay 150 bucks for something that's going to be really ugly.
I'm not really pressed for time, my point was simply that if I do a cheap poster first for testing purposes it might take 4 weeks for that two so I will take two months total...

[Miguel]

I know right? I wonder if the manager told me 800 PPI as a way to tell me to leave them alone and stop asking questions. Wouldn't be super nice. The shop is a Deserre (fairly common arts and crafts shop in Québec).

You know, I think you are onto something there. I will, very rarely, but it happens. . .give an outrageous quote to a potential client who appears to be a massive PITA to work with. Often, that's enough to have them disappear. I didn't follow your earlier posts, but surely there are other printers? Or there are plenty of online resources. For a 20x30 poster you only need a PPI of 180-220 anyway or even less. Smugmug claims a resolution of 1920x1280 works with their EZPrints service.

M

[Verfallsdatum]

You know, I think you are onto something there. I will, very rarely, but it happens. . .give an outrageous quote to a potential client who appears to be a massive PITA to work with. Often, that's enough to have them disappear. I didn't follow your earlier posts, but surely there are other printers? Or there are plenty of online resources. For a 20x30 poster you only need a PPI of 180-220 anyway or even less. Smugmug claims a resolution of 1920x1280 works with their EZPrints service.

M

Would make sense. 20" is the width of my monitor and you have to be pretty close to see the pixels (1920px width). I can't imagine you really have to have 3 times that resolution for a picture on a wall to look good.
I'm definitely going to contact a real small local print shop instead of a chain. I already found one that doesn't look much more expensive and claim to be experts for this kind of prints. I bet they'll be willing to answer a few questions and give me some advice to a customer who might buy a $150 product.
Plus I swear I'm not a PITA, I'm always polite with the clerks and pretend I feel bad for asking questions :-)

[TonyW]

I think there is a danger of overthinking this and coming to incorrect conclusions.

On the other hand do not be afraid to ask questions of the lab because as you have already witnessed sometimes knowledge appears lacking. Any lab worth its salt should be happy to answer your questions. After all it is in their interests to gain a happy customer that will return in the future and supplying you with the correct information for file preperation for their system will help to guarantee that you supply the best data to be interpreted by the print pipeline. This information should ideally include the exact PPI and also an ICC paper profile for your choice of surface - sadly the latter is not always offered and sRGB asked for. Which is a shame as many printer, ink and paper combinations can exceed the gamut of even Adobe RGB!

Would make sense. 20" is the width of my monitor and you have to be pretty close to see the pixels (1920px width). I can't imagine you really have to have 3 times that resolution for a picture on a wall to look good.....

Unfortunately judging sharpness and resolution on the monitor relating to printed output is fraught with issues and again generally misunderstood - assuming that the monitor is a 'standard' resolution of around 100 ppi. On the other hand if you have a 4k or 5k monitor you will notice that your images appear to have better resolution and less noise when compared to a standard monitor and similarly when output to print it is highly likely that you will see better resolution (assuming the image contains detail in the first place!)

On a monitor with 100 ppi if you look at an image at 100% view in PS and your final print destination is to a Canon printer (300 ppi) then you are lookiing at a magnified image 300% final print size - so things may well look crunchy. In fact for sharpening they probably should.

You cannot defeat this either by reducing the size of the image. You reduce the screen image to 33.33% to represent a true to life print size (Canon) and now you have an image that may match in size but contains only 1/3rd of the pixel resolution of the output device thereby not showing a true view of how your print will resolve detail (that detail that you cannot see on screen)

The reason you should send the printer the ppi it demands have been briefly touched upon earlier. To put this into some perspective here are a couple of images showing the difference ppi can make. It should be apparent without me noting which is the 'better' image.

The comparison shows two actual printed images from the same image data that have been scanned to enable on screen comparison. Both are the same print size. The difference is the information sent to the printer one being sent at 150 ppi and the other at 300 ppi. Apart from general softness the 'jaggies' referred to earlier are apparent in the lower ppi version

What you are seeing is an enlarged version of the print (3x) and in the smaller inset actual print size comparison. At a certain distance no benefit will be seen from the 'correct' printer resolution.