Pixel Size, Resolution Size & Picture Size

BH
Posted By
Benjamin_Hill
Jun 6, 2004
Views
655
Replies
6
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Closed
Hello All. Admitedly I am not an expert user of Photoshop but I use it to edit images and prepare them for printing. I had a customer come in recently who had an image from her digital camera that had a resolution of 2272 x 1704 and the usual 72 pixels per inch. She wanted this image to be cropped and then resized to a 2 ft x 2 ft image for printing. Considering the 72 pixels per inch when resizing there was a lot of pixelation which was to be expected. Now, here is what I don’t understand. I know that image size can be changed (i.e. taking the 72 pixels per inch and putting it up to a more decent 220). If you do this and STILL want a larger size the image becomes blurry automatically. Hmmm. I guess what I want to know is how do I change image sizes to ANY size that is larger without losing quality, etc. I have been "playing" if you will but still no satisfactory results. Considering that nearly all images from a digital camera will come at 72 pixels and that some of these have been made to print at considerable sizes, I know there is something that can be done. I feel as if I have talked a bit in circles but I would really like any and all advice to image size, ensuring quality from the beginning (i.e. changing at the source which in this case is a digital camera)and any tips you all may have. I really look forward to hearing any advice from anyone.

All the best and take care
Ben
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Don_McCahill
Jun 6, 2004
Re: I guess what I want to know is how do I change image sizes to ANY size that is larger without losing quality

Not much really. Only in TV and the movies can you increase size without loss of resolution. There are some tricks to improve things a bit, like enlarging in smaller increments rather than all at once. But in the long run you are estimating pixels and eventually you will get blurry.
DJ
dennis_johnson
Jun 6, 2004
EDIT: never mind.
J
Jim
Jun 6, 2004
wrote in message
Hello All. Admitedly I am not an expert user of Photoshop but I use it to
edit images and prepare them for printing. I had a customer come in recently who had an image from her digital camera that had a resolution of 2272 x 1704 and the usual 72 pixels per inch. She wanted this image to be cropped and then resized to a 2 ft x 2 ft image for printing. Considering the 72 pixels per inch when resizing there was a lot of pixelation which was to be expected. Now, here is what I don’t understand. I know that image size can be changed (i.e. taking the 72 pixels per inch and putting it up to a more decent 220). If you do this and STILL want a larger size the image becomes blurry automatically. Hmmm. I guess what I want to know is how do I change image sizes to ANY size that is larger without losing quality, etc. I have been "playing" if you will but still no satisfactory results. Considering that nearly all images from a digital camera will come at 72 pixels and that some of these have been made to print at considerable sizes, I know there is something that can be done. I feel as if I have talked a bit in circles but I would really like any and all advice to image size, ensuring quality from the beginning (i.e. changing at the source which in this case is a digital camera)and any tips you all may have. I really look forward to hearing any advice from anyone.
All the best and take care
Ben
First of all, 72 dpi has no bearing on your problem; it is merely a scale factor for viewing on a monitor.. Next, the image must be cropped to print to a square format. Finally, it needs more pixels (how many depends on the desired resolution of the print).

The viewing distance has some influence on the appropriate resolution of the print; 240 dpi is adequate for an 8×10 print which is viewed at a reasonable distance (say 10 feet). Somewhat less than that might be adequate for you 24 x 24 print provided one views it from some greater distance.

If all this sounds vague, it is. There are very few hard and fast rules in digital printing.

Interpolation, which is the only way to add pixels, never improves an image. However, in many instances the degradation is not noticeable. In your example, I would not be optimistic about the end result.

Jim
Jun 7, 2004
resolution of 2272 x 1704 and the usual 72 pixels per inch.

The camera is not taking the images at any particular PPI, only at a particular pixel dimension (in this case 2272 x 1704) but more on that below… Photoshop is reporting 72ppi because it has no other data to go by when it opens the image.

She
wanted this image to be cropped and then resized to a 2 ft x 2 ft image for printing. Considering the 72 pixels per inch when resizing there was a lot of pixelation which was to be expected.

Absolutely. To simplify your grasp of image resolution it is important to note that image resolution is measured by the pixel dimensions ONLY – the PPI of the image only comes into play once you’ve decided upon a specific print size. (There are others who may tell you this is wrong, but trust me on this.)

For example, your 2272px x 1704px image is 72ppi when printed at 31.5" x 23.667"; the exact same file with no modifications is 300ppi when printed at 7.57" x 5.68". The key is to divide the pixel dimensions by the print size (to determine the resolution at a specific print size) or by the resolution (to determine the optimum print size).

Knowing that, it’s time to bust out the calculator. Your customer want this image to print at 24" wide (you can’t print this image at 24" x 24", since the image is a rectangle not a square!); unmodified, this file would be 95ppi when printed at this size. Obviously too low, so upsampling in Photoshop would be required.

Keep in mind that Photoshop *cannot* invent pixels that do not exist in the original, so in all cases printing an image at a larger size than it’s native resolution supports will result in a compromise in quality. Photoshop’s resampling algorithms are quite good (some folks might argue not the best, but that’s another show as Alton Brown would say) but in the end you are asking Photoshop to "make up pixels" and blurriness or pixelization is often the result (more likely the higher you have to resample, and your example is quite a jump).

If this were me and my client I would try to convince them that their image was incapable of being printed that large and suggest that they supply a higher-resolution photo or reconsider the design choice (perhaps redesigning the piece so the photo doesn’t have to be used so large). Alternate ideas include intentionally effecting the image to make the pixelization look intentional – IMO if the end result looks intentional no one ever has to know how you arrived at that point, whereas an image that has been upsampled beyond its reasonable maximum print size just looks poor, period.
BH
Benjamin_Hill
Jun 8, 2004
Thank you to everyone who replied. I have a much better understanding now and I am learning quite a lot. Particular thanks to Brian who gave me some great information and very detailed as well. Nice one. Here is what I did in the end. I scanned the item she wanted to take a picture of and set the pixel size very high and then went to image size, unchecked resample and then changed the image to the desired size, the pixel size amended accordingly and I set it high enough to begin with that after resizing I still had a decent image. I thank you very much Brian for all your advice. All the best to everyone!
Jun 8, 2004
My pleasure. Best of luck!

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