Print quality: up-scaling image vs lowering DPI

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#1
Hi all,

For printing large, what yields the best image quality...using Photoshop algorithms to up-scale an image and keep it at 300dpi, or lower the dpi of the print to fit the size you need?

I guess it's a question of resolution vs artifacts, but I'd love to get people's experiences on the matter!

Thanks
 
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Gez
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#2
For making larger prints you can very easily go down to 180 ppi.
Ppi is the input resolution of a photograph or image. (Actual pixels sent to printer.)
Dpi is the output resolution of a printer (dots of ink actually printed on paper)
 
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#5
Hi all,

For printing large, what yields the best image quality...using Photoshop algorithms to up-scale an image and keep it at 300dpi, or lower the dpi of the print to fit the size you need?

I guess it's a question of resolution vs artifacts, but I'd love to get people's experiences on the matter!

Thanks
the standard 300 PPI for printing assuming the print will be hand held. For larger prints that will be viewed from a greater distance, a lower PPI is fine.

If you have arranged for the picture to print at 300 PPI at A4 size, it will print fine at A3 and a lower PPI. It will also print even larger - say A1 - at a much lower PPI as the viewer will be further away from the print.
 
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#6
For printing large, what yields the best image quality
I don't know. I've tended to use PS to interpolate such a resolution upscale, preferring to to do that in-house before sending to print - because I'm of independent mind, and can at least thereby check the result out somewhat on-screen. And I don't think that you've said if it's your desktop printer or a lab. Probably, it hardly matters. Sophisticated algorithms are going to do the job for you, either way.
 
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#8
I would just send the print to the printer and not worry about it, unless you're printing a postage stamp on the side of a bus.
 
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Andy Into The Wild
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#11
Sorry should have given more detail... I use print labs (if it was a desktop printer I'd just do both and see which looks best) but generally speaking I've been up-scaling the image as opposed to lowering the dpi.

So far in what I've seen up-scaling tends to give sharper results, but I'm assuming that would only work so far before it starts looking crappy. I've got a 2ft wide print arriving this week from a 16mp image which was cropped to 16:9, which I upscale at 300dpi so I will see what the quality is like on that
 
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#12
I don't know. I've tended to use PS to interpolate such a resolution upscale, preferring to to do that in-house before sending to print - because I'm of independent mind, and can at least thereby check the result out somewhat on-screen. And I don't think that you've said if it's your desktop printer or a lab. Probably, it hardly matters. Sophisticated algorithms are going to do the job for you, either way.
Is this to say that supplying a file at say 180ppi would just get up-scaled by the print lab anyway? So in that case using print labs it is always better to scale it yourself so you can add additional sharpening etc?
 
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#13
Is this to say that supplying a file at say 180ppi would just get up-scaled by the print lab anyway?
That's what I've always assumed. And also that the more control one has the better. The PS engine has long been pretty damned good. Limits will reveal themselves.
 
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#14
Is this to say that supplying a file at say 180ppi would just get up-scaled by the print lab anyway? So in that case using print labs it is always better to scale it yourself so you can add additional sharpening etc?
It depends on the size in pixels of the image, vs the print size. It's all rather confusing. I see some labs stipulating that images should be 300PPI, which is confusing since you can supply a 2MP image at 300PPI, and it won't print any better than a 2MP image at 72PPI. (The number of pixels is the same, and too low for a reasonable sized print!)

I think it was worth getting bogged down in interpolation when we were trying to print large images from 6MP cameras. Although even then I thought the benefits of using software like GenuineFractals was marginal.

Re sharpening, what looks right on screen might not be right for a print at a given size on a given type of paper. A lot of labs will apply output sharpening themselves at an appropriate level for the print in any case; maybe the way forward is strike up a relationship with a lab who will listen to your requirements and offer advice re the files you hand over to them.
 
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#15
Depending on viewing distance and to some extent paper even 200dpi can be very much acceptable. However I see little problem with using high quality moderate upscale. Photoshop has a new algorithm in the drop down menu (something 2.0) and it is far far better than I've seen anything there before, particularly with lines and clear shapes (no more jagged edges)
 
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#16
A lot of labs will apply output sharpening themselves at an appropriate level for the print size in any case; maybe the way forward is strike up a relationship with a lab who will listen to your requirements and offer advice re the files you hand over to them.
This is certainly true, but they start from a compressed jpeg, and likely not even a 100% jpeg so will upscale any artefacts as well.
 
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#17
maybe the way forward is strike up a relationship with a lab who will listen to your requirements and offer advice re the files you hand over to them
This is a basic, but with many labs getting a meaningful dialogue isn't easy. My policy has been to prepare files properly then have them printed without intervention. A 'good' lab will state this policy, or give it as an option if you ask. No tonal adjustment, no sharpening.
 
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#18
Hi all,

For printing large, what yields the best image quality...using Photoshop algorithms to up-scale an image and keep it at 300dpi, or lower the dpi of the print to fit the size you need?

I guess it's a question of resolution vs artifacts, but I'd love to get people's experiences on the matter!

Thanks
All you do is use the biggest file you have. Forget all this 300 dpi /ppi it is rubbish and from 20 yrs ago.
 
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Andy Into The Wild
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#19
All you do is use the biggest file you have. Forget all this 300 dpi /ppi it is rubbish and from 20 yrs ago.
Not sure what you mean to be honest. If 300dpi is regarded as the maximum level of detail the eye can perceive from up close, and I want to make large prints with a 16MP camera and have the detail as good as possible from closer than 'optimal' viewing distance, either up-scaling or lowering DPI is required. Surely one of them looks better than the other.

Are you saying that they will both look exactly the same?
 
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#21
Only very small pictures get looked at from closer than 2 feet. It really does not matter what the picture looks like close up. What matters is what it looks like at the distance it is going to be looked at from.

Upscaling the number of pixels does not increase or improve detail - that is determined when you press the shutter release. Upscaling will only stop you seeing the square pixels but with the same level of detail.
 
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#23
A wild assertion. You have big cojones? You know everything? You just got back from the pub?
It is a badly expressed assertion but not wrong. With modern sensors, there are enough pixels for you to only worry about the pixel dimensions of the print - you are unlikely to end up with much less than 300 PPI unless you have cropped massively.
 
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#24
Only very small pictures get looked at from closer than 2 feet. It really does not matter what the picture looks like close up. What matters is what it looks like at the distance it is going to be looked at from.

Upscaling the number of pixels does not increase or improve detail - that is determined when you press the shutter release. Upscaling will only stop you seeing the square pixels but with the same level of detail.
I don't understand what you could possibly base the statement "only very small pictures get looked at from closer than 2 feet" on, especially considering my question was specifically about a) printing large and b) viewing from closer than optimal viewing distance with the maximum quality possible. I understand viewing distance is important and you can't magic detail out of thin air, but I have asked for a very specific comparison of 2 englargement techniques from a technical perspective, one of which surely must be better than the other.

It is a badly expressed assertion but not wrong. With modern sensors, there are enough pixels for you to only worry about the pixel dimensions of the print - you are unlikely to end up with much less than 300 PPI unless you have cropped massively.
Again you can't really base that on anything without knowing how large people want to print. An average 24MP camera can print up to roughly 20x13 inches before having to up-scale or lower the DPI...in my case I want to print larger than that and I have 16MP (which allows roughly 16x11 inches at 300DPI).
 
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#25
I've not been happy with either, but if I had to do it, I'd just use a lower native ppi.

I did a print for a friend from a low scan of a 35mm neg and the ppi was really low for 13"x19" - IIRC around 80 ppi - possibly even less? I upscaled it (can't remember what to) and it was "not bad" - my exact words I think.
I recently did an A4 print at 90ppi from a pretty poor low quality jpeg and described that as "ok".
(For both of these, they were fine at distance. Close scrutiny though is what where talking about here)

So for me - it's a choice between "not bad" and "ok". However. My eyes aren't that great. I can print at 200ppi and still see a fab print under close scrutiny. In fact, with 20-20 vision, the eye can resolve around 800ppi at 4" which is the closest focussing distance for your un-aided eyes. 300ppi comes from magazine reading distance (12") hence it's often used by print publishers.

So taking into account my eyesight, and personal taste, I'd choose lower ppi over upscaling. I find upscaling tries to sharpen the image and adds artifacts that I really don't like. Up close, it looks like a badly sharpened image vs a low ppi version which looks blurred up close. Also. Upscaling is adding stuff to the image, which I just 'don't like' the idea of. It's also another software step and I don't really enjoy PP work.

Ultimately, it's going to be down to personal preference. It's easy to replicate. 2 prints. 1 upscaled, the other native ppi. Both the same size. Actually - that sounds like quite a good experiment for a blog post... But at the end of the day - it's your preference that matters.
 
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Andy Into The Wild
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#26
Thanks @Harlequin565 for the response. I think you're right I just need to do both and see which I prefer. I wasn't amazingly happy with the 2ft print I did which I'd up-scaled, like you said it looks quite artifacty up close as opposed to 'blurry' which I think in a way looks more natural.

Next time I order some prints I will post back here and let you know what I think :)
 
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#27
A wild assertion. You have big cojones? You know everything? You just got back from the pub?
It's not a wild assertion.It's a correct assertion. Try addressing the issue intead of the usual attack the singer instead of the song. Pathetic!
 
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#28
It's not a wild assertion.It's a correct assertion. Try addressing the issue intead of the usual attack the singer instead of the song. Pathetic!
I've made a couple of posts since yours explaining why (in my case) it is not a correct assertion, but if you have information to the contrary I'd be happy to hear it.
 
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