Best ways to resize an image without losing image quality

TF
Posted By
Tim_Francis
Apr 7, 2004
Views
1947
Replies
15
Status
Closed
Hi all,

I am a scanned image of a poster that you can no longer buy. It is 27cm x 36cm at 72dpi.

Here it is.
< http://www.geocities.com/uploadarea2000/sennatag_original.jp g>

I would like to resize the image to about A3 size so about 29cm in width and what the equal constraint is for the height.

Now Im told that most print is done at 300dpi. With my image sitting on 72dpi, is there anyway I can increase the DPI?. (remembering I dont have an original only the 72dpi image from the web)

I know I can simply resize the 72dpi to 300dpi but what is actually going to happen there?

Or is it just a case of me manually correcting the image once its resized, sharpness, blur etc.

Could someone go over this with me, as I dont FULLY understand print as most of my work is for the web/72dpi. Any tutorials, links, etc for resizing an image while maintaining or increasing image quality would be much appreciated.

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S
Stardancer
Apr 7, 2004
Tim,

I was just coming out to the forum to post a similar question, so I’ll be interested to read responses to your post.

I have digital image I created at 72.ppi. I want it to print as 12 x 12. The file size is 2.14Meg. If I change the resolution to 300 ppi, and leave ‘Resample Image: Bicubic checked and remove the check from ‘Constrain Proportions’, the file is now a 37.1 Meg file. When I press ‘OK’, the image gets *huge*. I’m wondering how this will print. I’m wondering if the image will keep it’s clarity and crispness of the original image.

Will be interested to hear from ‘the experts’ out there.

Stardancer
MM
Mac_McDougald
Apr 7, 2004
I’m wondering if the image will keep it’s clarity and crispness of the original image.

Print it and see, eh?

(hint: no, it won’t)

Mac
BO
Burton_Ogden
Apr 7, 2004
Tim, Stardancer,

For a Digital Photo Interpolation Review, click here: Which image interpolation (photo resizing / resampling) method is the best? < http://www.americaswonderlands.com/digital_photo_interpolati on.htm#Kneson%20(S%20tandard)>

I currently use Genuine Fractals 2.5, but from this review I think I will be purchasing PhotoZoom Pro (formerly S-Spline Pro) from ShortCut Software. I like what it does. To see the whole review, scroll down on the webpage and be sure to click the thumbnails to see the enlarged views. You really can’t make a good comparison with just the thumbnails. These comparison photos will let you decide for yourself which method you like best.

— Burton —
L
LenHewitt
Apr 7, 2004
Tim,

I am a scanned image of a poster <<

Most posts we get are from people not files <g>

Two things to consider:

1) Even though the poster is out of print, chances are it is almost certainly still copyright material and what you propose will be breach of copyright. TAG would NOT be amused!

2) There is absolutely no way that you can take an image 777 x 1043 px and interpolate it up to 3425 x 4598px (a 440% increase) without considerable loss of quality, which unsharp masking is unlikely to fully correct.

You probably would not need 300 ppi anyway, for litho printing at 150 lpi, 210 ppi should be sufficient, and for inkjet printing, 200ppi should suffice.
S
Stardancer
Apr 7, 2004
So would the best way to assure quality of a graphic I wanted to print at 10 x 10 with 300 dpi is to begin with a canvas that size?
BB
Bert_Bigelow
Apr 7, 2004
So would the best way to assure quality of a graphic I wanted to print at 10 x 10 with 300 dpi is to begin with a canvas that size?

Star,
An image of that size contains 9 megapixels. You don’t say what the pixel dimensions are for the original image, but I would guess that it is much smaller. As Len says, you probably don’t need 300 ppi to get an acceptable print, although "acceptable" is in the eye of the beholder. Depends on your intended usage and your personal standards.
You are going to have to upsample the image, and upsampling will inevitably result in a loss of quality. Some people use an incremental approach, doing it in increments of 10% or so to minimize the degradation. Burton’s suggestion that you use Genuine Fractals is another good alternative.
Bert
BB
Bert_Bigelow
Apr 7, 2004
I have digital image I created at 72.ppi. I want it to print as 12 x 12. The file size is 2.14Meg. If I change the resolution to 300 ppi, and leave ‘Resample Image: Bicubic checked and remove the check from ‘Constrain Proportions’, the file is now a 37.1 Meg file. When I press ‘OK’, the image gets *huge

Star,
Another comment on your earlier post: If you uncheck "Constrain Proportions" and change the aspect ratio of the image, you will get distortion. You are "stretching" the pixels in one dimension or the other. Usually, it is not advisable to uncheck that box. The first thing you should do is uncheck the ‘Resample’ box and set the resolution to the value you want (200-300) with the ‘Constrain Proportions’ box checked. When you change the resolution, the new print dimensions of the image will show. Now, you can decide how much upsampling, if any, is required.
Bert
S
Stardancer
Apr 7, 2004
Len / Bert,

Thanks for your comments & thoughts. It’s good news to hear that I probably don’t need 300 ppi. I feel like I’ve been chasing down the proverbial Holy Grail.

Also great info on the "Constrain Proportions" check box. I saw in one of my images that there appear to be wavy lines around some areas of the image. I was wondering why the ‘wave’ images appeared. I’ve manipulated some of these images multiple times, and I’ve lost track of what I’ve done. I wish the ‘history’ option collected all actions during creation.

Anyhow, I’ve made an appointment with a printer for Friday and will take all images – 72 ppi as well as larger ones and see what I’ve got on print. They told me they could probably increase the printed size of the smaller images without losing too much resolution, so I’ll see what I’ve got (fingers crossed).

Stardancer
JM
John_Mensinger
Apr 7, 2004
Further to Len’s post regarding your rights to use the image, for all I know, you have the legal rights to do so, but if you don’t, you’ll be taking a hell of a risk if you reproduce it for commercial purposes.

The gentleman’s countenance used in the ad was that of the late multiple-times World Driving Champion, Ayrton Senna.

I guarantee that if you are working for a living, you don’t stand a snowball’s chance in hell against the type of legal talent that is no doubt employed by his multi-billion $ estate. I could get sued for typing his name here.
BB
Bert_Bigelow
Apr 7, 2004
…but if you don’t, you’ll be taking a hell of a risk if you reproduce it for commercial purposes.

But if you’re just doing it for your own use at home…
BO
Burton_Ogden
Apr 7, 2004
…. who’s to know? Except maybe anyone with Internet access who’s reading this message thread. (grin)
B
benluke
Apr 7, 2004
have been following your post as i posted myself on the same subject and was directed to this post. I also have an image that i need to enlarge. At the moment the origanal image is a jpeg, 216 res, 5" x 4". I need to change to a duotone then inlarge it to A3. whats my best option?

Thank you for eny help

Ben
RW
Rene_Walling
Apr 7, 2004
whats my best option?

the best option is always to rescan at the proper resolution.
B
benluke
Apr 7, 2004
am unable to rescan as i was given the image in disk.
DM
dave_milbut
Apr 7, 2004
ben, to avoid the italics, don’t start a line with a lower case "I" (as in "i am unable…") capitalize it and the forum software won’t italicize your posts…

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