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Thu Jan 1, 2015, 02:00 AM

Question about enlarging digital photographs.

So... I have a couple photos I want to enlarge. Really enlarge. To 30" x 40". Trying to figure out pixels per square inch is making me crazy. Online sources are both helpful and confusing. For instance, one says you can't use photoshop to enlarge pictures but you can use it to downscale photos. It also says 72 ppi will be pixelated if blown up. What I've shot comes up as 72 ppi with an image size of 48" x 32".

My questions are:

If I downsize the image to 30x40 at 72ppi, will it be all pixelated?
or
Can I change the the ppi to 300 and then downsize it to 30x40? Will that be pixelated, too?
and
If both of these lead to gross pixelation, what's a gal to do that wants her own images up in her living room?

I'm using Photoshop Elements, if that has anything to do with anything.

This whole question makes me flash back to doing word problems in math. Please help!!

17 replies, 4028 views

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Arrow 17 replies Author Time Post
Reply Question about enlarging digital photographs. (Original post)
intheflow Jan 2015 OP
CaliforniaPeggy Jan 2015 #1
intheflow Jan 2015 #2
PoliticAverse Jan 2015 #3
intheflow Jan 2015 #5
mnhtnbb Jan 2015 #4
intheflow Jan 2015 #6
jmowreader Jan 2015 #7
intheflow Jan 2015 #12
jmowreader Jan 2015 #14
intheflow Jan 2015 #15
Major Nikon Jan 2015 #8
Silent3 Jan 2015 #9
intheflow Jan 2015 #11
Silent3 Jan 2015 #13
intheflow Jan 2015 #16
Stevenmarc Jan 2015 #10
postatomic Jan 2015 #17

Response to intheflow (Original post)

Thu Jan 1, 2015, 02:03 AM

1. Oh my dear intheflow!

Word problems make me crazy!

I have no idea how you would do this. I'm sorry...

Good Luck!

And a very Happy New Year to you!

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Response to CaliforniaPeggy (Reply #1)

Thu Jan 1, 2015, 02:06 AM

2. One of the brainiacs here will be able to help me.

They always do!

Happy New Year to you, my dear Peggy!

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Response to intheflow (Original post)

Thu Jan 1, 2015, 02:08 AM

3. So basically you are saying you have...

a 3456 x 2304 pixel image ( 48"* 72ppi = 3456 pixels) (32" * 72ppi = 2304 pixels)
that you want to print 30" x 40" (or was it 40" x 30" ?

Who will be doing the printing? You or some print service?


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Response to PoliticAverse (Reply #3)

Thu Jan 1, 2015, 06:22 AM

5. I was thinking about sending it out to Ritz.

I don't have the equipment to print that size at home.

On edit: the 30x40 size is approximate. The print has to be 30" wide by 26" tall to fit the frame. I am planning to hand trim it when I get the larger print since it's much cheaper to buy a standard oversized print than a custom size. I was a picture framer for many years, that part's a piece of cake for me.

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Response to intheflow (Original post)

Thu Jan 1, 2015, 05:39 AM

4. I have a photographer friend who uses this service to upload/sell her photo art.


Might be the easiest way to do what you want.

http://fineartamerica.com/create-art-online.html

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Response to mnhtnbb (Reply #4)

Thu Jan 1, 2015, 06:25 AM

6. Interesting!

I'll look into this. Thanks.

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Response to intheflow (Original post)

Thu Jan 1, 2015, 06:42 AM

7. 72dpi is the normal resolution of a vehicle wrap, and those look okay

Most people aren't going to walk up to a framed 30x40 and stick their nose against the glass. You stand back a ways, right?

Doing a little math gives me a file 3456 px wide x 2304 px high...what is that, 8 megapixels? Never mind, we'll live with it. On a wide-format inkjet printer you can get good "photo quality" images at 150 dpi. 300 gives slightly better results but also gives 4 times larger files.

In your Photoshop Image Size dialog you should have a "resample image" checkbox. Turn that off and change the short dimension to 30" which will give 76.8 dpi resolution. The long dimension will then be 45" which you'll have to reduce to 40" by cropping five inches off the ends.

Make two copies of this file and stick one away as a backup.

Call one of them "version A." Crop it to 11x14 and save.

The other is "version B." Do the following:
Step 1: turn on Resample Image and change the resolution to something really high and really weird...try 783 dpi to start.
Step 2: do a 1.1-pixel Gaussian blur.
Step 3: change the resolution to 150 dpi.
Step 4: save this file, make a copy, crop an 11x14 out of the copy, and save.

A Photoshop file is a grid of dots. Each one has a color value. If you upscale a file by a rational number - from 75 to 150, for instance - Photoshop will just take the color values of two dots, average them to get a "middling" color value and shove a dot of that new value between the two existing dots. Result: the picture looks blocky. By using these weird numbers, and putting just a slight amount of blur on the dots before downsampling, the picture will look better.

Now, take both files to the print house that will do your 30x40s and print the 11x14s on the machine that will print the big posters.

Finally, get a roll of masking tape. Tape off a 30x40 rectangle on the wall and hang the 11x14s in the middle of it. Then step back to where you'd be when you look at your pictures. I think you'll be happy with one of them.

I have the full-blown version of Photoshop. If you'd like me to set up a file for you, send me a PM and I'll see what I can do.

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Response to jmowreader (Reply #7)

Thu Jan 1, 2015, 01:54 PM

12. You lost me a number of places here but I'm really stumped by the 11x14 suggestion.

Why would I tape off a 30x40 grid and put an 11x14 in the middle of it? I have a 30x32 frame I'm trying to fill. Are you saying I crop the photo into a few 11x14s and put them together like a mural?

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Response to intheflow (Reply #12)

Thu Jan 1, 2015, 04:26 PM

14. The 11x14 is a proof print

You tape the 30x40 rectangle off so you know how far back to stand when viewing a full 30x40 print.

11x14s are a lot cheaper than 30x40s, correct? Set up a file so it's ready to print a 30x40, then print an 11x14 chopped out of it and view it at the proper distance for viewing 30x40s, and you'll know fairly cheaply whether the pictures will make good 30x40s.

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Response to jmowreader (Reply #14)

Thu Jan 1, 2015, 04:35 PM

15. Brilliant!

That sounds very smart indeed!

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Response to intheflow (Original post)

Thu Jan 1, 2015, 07:42 AM

8. It will be pretty poor quality regardless of what you do in photoshop

Based on what you said you have it sounds like your uncompressed image is around 10mp which is woefully inadequate for that big of a print. Even 21mp would make a poor quality print at that size.

Printing at anything less than 180 dpi will yield a poor quality print and you are well past that. To print 30x40 @ 180 dpi requires about a 39mp uncompressed image, and 180dpi is not even all that good for prints that will be viewed up close.

If you aren't really looking for photo quality and the print will be viewed from several feet away, it might be acceptable, but for a living room print I wouldn't recommend it.

There is a way to create decent quality prints of this size even with a relatively low resolution camera, assuming the subject is stationary like a landscape shot. Put the camera on a tripod and use a lens that gives you a small portion of your overall subject, then pan and tilt your camera taking multiple photos, which you will later stitch together with software. For instance, you start at the lower left portion of your subject panning along the bottom for 3 shots, then you take 3 in the middle and 3 along the top for 9 shots total. You'll want at least a 30% overlap for each shot. For best results, keep the camera in fully manual exposure and focus mode and don't change your camera settings between shots. You'll need some decent photo stitching software like the full version of photoshop, because you don't want the image to be downsampled. This is the poor man's method of getting an ultra high resolution image with a relatively low resolution camera.

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Response to intheflow (Original post)

Thu Jan 1, 2015, 08:43 AM

9. The quality of the result isn't guaranteed, but of course Photoshop can enlarge pictures.

Any online source that told you that you can't use Photoshop to enlarge pictures wasn't a very good source.

Whether the image looks sharp or fuzzy when you enlarge it is going to be the most common issue, not whether it looks pixelated. You'd either have to start with a very low resolution original, or deliberately go out of your way to use a non-smoothing scaling technique, to see much pixelation.

The important questions here are:

1) What is the original image resolution, in pixel width and pixel height. Don't worry about the original ppi -- what really matters is how many source pixels you have.

2) The distance you'll normally be viewing the image at.

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Response to Silent3 (Reply #9)

Thu Jan 1, 2015, 01:47 PM

11. Original image resolution is

3456W x 2304H in pixels.

It will be viewed from about 3.5 - 5 feet away. We live in a very small space.

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Response to intheflow (Reply #11)

Thu Jan 1, 2015, 02:12 PM

13. You should be fine then.

That will yield an end result with 3456/40 -> 86.4 ppi. While that's not super sharp, it's not bad looking either. With the typical smoothing that's done when scaling, and plenty of target pixels to render the original pixels, you'll get decent results.

It's also unlikely you need to mess around with Photoshop or anything else. Whether you're using your own printer, or having a commercial service create the print, just specify the size you want the end result to be and the printing software will take care of the rest.

Edit: Seeing what Stevenmarc said about Perfect Resize: Yes, you certainly can use software like that to do the scaling before handing the job off to whatever printing process you're going to use, if you want/need to squeeze out every last bit of possible image quality you can get, but you'll probably be pretty happy even with most of the standard default processes.

Please realize that (regardless of the impression TV cop shows might give you) the original resolution of a picture puts a pretty big limit on the real information available in that image. Typical scaling processes (and even this Perfect Resize) can't restore very much image information that wasn't directly visible in the first place. Mostly all you can do is generate various versions of eye-pleasing fakery, either in the direction of gently smoothing out pixelation and/or generating artificial but convincing simulated detail.

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Response to Silent3 (Reply #13)

Thu Jan 1, 2015, 04:45 PM

16. I absolutely get the concept of original resolution size

impacting real available image information. One of the worst mistakes I did when I got my first digital camera in... 2004, I think it was, was to resize my favorite vacation photos down and save them as overwritten original files. The idea being it would save computer space. Had no idea I wouldn't be able to make them big again, and was horribly surprised when I wanted to just blow it up to a 5x7 and it looked like a hooked rug pattern. Haven't had the resources to think about enlargements again until now.

The "frame" I'll be using is an old window, complete with warped glass, possibly from a Victorian-era building. The image quality you're describing should be sufficient for the application. Thank you!

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Response to intheflow (Original post)

Thu Jan 1, 2015, 10:28 AM

10. Two Words

Perfect Resize

I've done quite a bit of work with an iPhone and have made more than a few exhibition prints and while Photoshop can be used to enlarge prints, Perfect Resize has better algorithms than stock Photoshop.

The last show I did I created pieces that were 36"x48" @ 300dpi and they weren't pixilated at all but I also upsized it incrementaly in a couple of steps.

OnOne's Perfect Resize has a 30 day free trial and can be downloaded at their site so you really have nothing to lose in trying it.

http://www.ononesoftware.com/products/resize9/

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Response to intheflow (Original post)

Thu Jan 1, 2015, 04:55 PM

17. For fun I just did an enlargement to 40 x 26 (3:2) at 360dpi

Using two different photo editors. I could see no degradation of the original image. I don't have Elements but you should be able to use it. Look and see if you have a Image Size selection in your menus. I used Bicubic Smooth and regular Bicubic.

When you load the image in Elements do your regular edit and save the image in uncompressed TIFF. You want to keep as much of the original information as you can so using an uncompressed image is the best way to go.

If all else fails send me the original image and I'll make a printable enlargement for you.

In lieu of that you could just print an 8x10 and wear magnifying glasses.

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