Increase resolution of photos to at least 200dpi

[courtneysc]

Hi all,

I am a novice at photoshop!

I am trying to get a few large (135cm x 90cm) canvases printed but the photos I am submitting are only 97 pixels/inch. I am manually putting in 300dpi (image>image size>resolution), but then my image size shrinks to about 43x29cm. I take my pictures with a Canon 7D, so they should be huge, great quality pictures. I open the page, and save it to my MacBooks 'photos' program, and then import to photoshop from there.

I don't know what I am doing wrong, or how to make my photos "bigger" (more pixels/inch). Any advice would be really appreciated (please use lament terms and/or step by step as I am hopeless!).

Thank you

[gener7 · Accepted solution]

Is Resample checkmarked in the Image Size dialog? If you set the Resolution to 200 ppi it should keep the size.

Use the Preserve Details setting next to Resample.

Gene

[courtneysc]

Hi all,

You are all amazing! Thank you! I hope I will know as much as you all someday.

I checked the 'resample' box.

Thanks again!!

[D Fosse]

courtneysc wrote:

I checked the 'resample' box

As a general rule of thumb, a good, high-resolution file from a current camera will work for virtually anything - no matter what the physical print dimensions are.

The thing is that the bigger it is, the further you will step back to take it all in. IOW it will occupy the same angle of view regardless, and so the optical, perceived resolution is the same.

And even so, there's nothing special about the 300 figure. People are far too hung up on it, to the point where you could call it "the 300 ppi for print-myth".

300 ppi is just the upper limit beyond which no improvement is even theoretically possible, when printed with an 150 lpi screen frequency (which is the standard in book/magazine print). But a lower ppi doesn't necessarily mean less sharp - it just means there is a faint possibility that individual pixels can be made out. You can go a lot lower before it starts to visually deteriorate - even at the same viewing distance.

So, to conclude, checking "resample" won't do anything for basic image quality. However, you can compensate a little - create an illusion - if you carefully sharpen after resampling. This will tighten up edges and transitions, giving the impression of higher sharpness.

If you do choose to resample, anything above 150 ppi will be wasted here. That's as far as I would go.

[Silkrooster]

This is normal, when you size the image at the bottom is resample with a check box in front of it. When it is not marked, it protects the pixel dimensions, therefore the physical size must change due to the formula.

inches x ppi = pixel dimensions

same applies to the metric system

cm x ppcm = pixel dimensions

[Test Screen Name]

It's easy to ask Photoshop to add more pixels, but this will do nothing at all for quality. Probably more important to see what is going wrong and fixing it if we can. What is going wrong could be technical or it could be your expectation. Let's see. A Canon 7D can record up to 5,184 × 3,456 pixels. At 300 ppi that is 5184/300 x 3456/300 inches, which is 17.28 x 11.52 inches.  Multiply each by 2.54 to get cm: that's about 44 x 29 cm.

So, we know that the camera is working on maximum and you are not losing pixels. For 300 dpi detail work your largest canvas is 44 x 29. And if you run at such a large size, well over a metre, 97 ppi is all your camera is capable of. Adding more pixels is basically pointless. But few people will be able to photograph at higher resolution. The fact is you can probably get away with much smaller; a key factor is the expected viewing distance; people view a canvas from further away than a book.

To get the best results you need to work now with your print provider. This will not be a new or surprising problem for them. Ask them what quality you can expect at your chosen size. Ask them if there is any preparation you can do. If they blindly insist on 300 ppi without further explanation, they don't know what they are doing, and run (don't walk) to find someone else.

[Test Screen Name]

Some more info. Canon say on Canon DLC: Article Print: Large-scale Printing Settings  " the Canon EOS 7D has an 18 megapixel (18 million pixels) 5,184 x 3,456 sensor, which contains enough resolution for a 16 x 24-inch print (at 220 dpi) without any loss in quality." So, your wish to print a more than twice that size shows that " they should be huge, great quality pictures" is just a wish. But talk to the print provider as I say. Canvas is quite a coarse material to print on and not like printing on smooth paper.

[gener7]

Just a question, but at such a large size wouldn't viewers be stepping back a few feet to take it in? I'm told resolution does'nt even need to be 300 or even 200 for that purpose.

Gene

[janunderhill]

I just checked into the instructions here to confirm the proper steps for increasing photo resolution for trade show panel graphics. The supplier asked for photos at 100 dpi "effective resolution". Page layout program indicated that the 180 dpi digital photo I'd enlarged to fit my layout had an effective dpi of 76. I checked the resample box in Photoshop and took a guess at the appropriate resolution. After a couple tries, I found that 230 dpi gave me the effective resolution of 101 in my art file.

[Guest]

It's tough to work on Photoshop if you are a novice. I have faced the same issues a few times and in spite of giving too much time in resolving this in photoshop, I tried some other image editing softwares to change the size of my images without compromising the quality. I can't help you in doing the changes in photoshop, but I can definitely suggest you a few better tools that will help you in this particular issue. You can try PhotoViewerPro.

[D Fosse]

IMO this is all psychology, you see what you want to see.

The best results are nearly always achieved by not doing anything - except some careful output sharpening. Other than that, print the file as is. Upsampling breaks up the pixel structure and produces very unpleasant artifacts. Always. No matter what application does it.

Remember one thing: the only reason to ever upsample is to avoid visible pixels - and it takes really low resolution for that to happen. We're talking web files at, say, full page size. If the resolution is that bad, you have much larger problems than upsampling can ever solve.

[gener7]

Have you ever looked the waifu2x project? It's a web based enlarging application that is hosted on a more powerful workstation.

If the enlargement is 1.6 to 2.0, it does a fairly decent job, but it would be interesting to hear your assessment.

The captcha came about because some enterprising app makers were using it to make money by providing apps to access it.

[D Fosse]

You posted while I sent a follow-up to my own post, Gene. It wasn't a direct answer.

To tell you the truth, I'm done with upsampling except in very special circumstances. I think the results are crappy compared to the original in every case. Furthermore, I think that's pretty irrespective of application and algorithm.

But yes, I'll take a look

[gener7]

It does take me a while to get a reply together, so sometimes I find out after I post. Anyway nothing else to add, so I'll leave it at that.

Gene

[D Fosse]

Let me illustrate the realities very specifically.

You have a fairly standard, traditional monitor, and you're sitting at a distance of, what, 60 cm at most? Probably. What you're then looking at is less than 100 ppi at a very close distance. Closer than you likely would be in front of a real print.

Now try to see pixels...

[gener7]

I do understand that, although I'm usually 30 cm from my 13 in laptop screen. I do not use a 27 in monitor where 60 in viewing distance is normal.

When dealing with a 472px H image that would blur if magnified to fill a 800px screen. Proper upsampling does help.

[D Fosse]

I think illustrations and graphics fare better, given proper post-sharpening. Here you have areas of even tone and color, and sharp edges separating them. These edges can be recreated with sharpening.

Photos is a different kettle of fish, with a noise structure that can be quite complex. This is what blows up and ruins the picture. Not to mention jpeg artifacts <shudder> ...

[gener7]

When it's up to me to capture an image, I go as high as my camera will allow or as high as practical for my scanner. I try to avoid upsampling.

If or some reason I need jpeg (space restraints for posting), I keep the highest quality setting. But for flat images, lossless png is best.

Anyway if you do try waifu out, I'd be interested in your evaluation. You're trained in picking up details I may miss and you do have professional grade calibrated equipment.

There is a PC version, "waifu2x caffe" that will get around the limitations of the web version.