Digital enlargements/Resolution - DPChallenge Forums

Canon 12x IS USM (S3 IS built-in Lens) -- 36-432mm (35mm EQ)

09/20/2002 05:39:59 PM · #1

I took my 7 meg file in to have it printed at 20X30 but they said resolution was too small
I adjusted size and resolution in photoshop but that created a 173MB file..is that normal
what am I doing wrong if anything thanks

GeneralE

Canon PowerShot S3 IS

09/20/2002 05:46:15 PM · #2

You'll probably need something in between (25-30mb). Depending who prints them, you'll need 100-300 ppi (pixels per inch). The quality will also depend on the subject matter.

Where are you having it made, and by what process?

I'm headed for work, so I might not get back to you until this evening. You can email me if you'd prefer...

-Paul

mci

Canon EOS-350D Rebel XT

Canon EF 50mm f/1.4 USM

09/20/2002 05:46:34 PM · #3

Originally posted by rll07:
I took my 7 meg file in to have it printed at 20X30 but they said resolution was too small
I adjusted size and resolution in photoshop but that created a 173MB file..is that normal
what am I doing wrong if anything thanks

What file format are you using to save the file? If you're using something like a PSD or uncompressed TIFF, they could easily get up there in the hundreds of megabytes. Chances are that your digital camera took the photos in a more compressed format, so it probably won't hurt to save it as a top-quality JPEG. It will cut the file size significantly. Also, what resolution (DPI) are you using for the file? Upsampling it to 300dpi or so should be fine for this type of print.

* This message has been edited by the author on 9/20/2002 5:45:29 PM.

Canon EF-S 18-55mm f/3.5-5.6 IS

09/20/2002 07:22:21 PM · #4

I am trying Sony's Image Station site to get a 20x30 poster made. There was no information that I could find that said what file formats they accept or what the maximum size was so I emailed their support and this is what they told me. Tim, still images in JPEG and GIF formats are stored at the same resolution and quality that you upload. Still images in other supported formats (TIFF, BMP, etc.) are converted to JPEG file format in the original resolution and stored at a high quality.Individual picture file can be up to 20MB (in size) and they are saved as .JPEG formats. So I created a file using Genuine Fractals that is 7500 pixels x 5000 pixels at 250 dpi and with moderate jpg compression that file size came to about 15mb. So I was still well under the maximum requirement. I am very anxious to get it back and see how well it looks.

I have a feeling that the site that you are using is looking at the total pixel count and it may be figuring that your image does not have enough pixels to produce what they consider an acceptable image. This is only a guess but I would only upload jpegs with some compression.

I hope this helps.

T

Isaac

Olympus D-490Z

09/20/2002 07:37:36 PM · #5

Here is some print information from Ofoto, a popular online processor owned by Kodak (which I've* used for about 3 years), including a table of minimum resolutions for various print sizes (on their equipment).

Your 250 ppi file should give an adequate result, but I've been in the habit of going up to 300 ppi for years...If you're going to save in JPEG for print, always save in best-quality unless it puts file size over the "legal" limit (like at DPC).

//www.ofoto.com/HelpAboutPrints.jsp?UV=174374337274_82184249503&US=0

*This post brought to you by Paul (GeneralE)

* This message has been edited by the author on 9/20/2002 7:37:39 PM.

Zeissman

Canon EOS-500D Rebel T1i

09/20/2002 08:22:12 PM · #6

you will probably not get an image of resonable quailty for that camera at 20x30. It would put your original image resolution at 69 dpi (200 is recommended minimum for true photo quality).

What dpi does your printer recommend?

Also, if you want to make enlargements, do not save in JPEG format. You lose information every time you save the image.

09/21/2002 01:14:51 AM · #7

you guys are awesome! thanks for all the replies I took it in Raw format on my canon pro90 and then converted to TIFF upped the res to 300 DPI and saved as uncompressed TIFF I guess
maybe I should save as compressed tiff to lower file size... camera is 3 Megapixles so does that mean i can't get clean 20X30???
clueless in colorado

Canon EF-S 18-55mm f/3.5-5.6 IS

09/21/2002 01:17:46 AM · #8

one more Question i changed it to 300 DPI in photoshop but then do I need to save it as 20x30? or save as is and they will increase size? thanks

Zeissman

Canon EOS-500D Rebel T1i

09/21/2002 01:21:51 AM · #9

That will increase the size, but it will "interpolate the data. Which means it will fill in the holes. You will lose some sharpness doing that. You really need to find out what DPI the printer wants. Depending on how they print it, they will need different DPI. There is not point in over interpolating, because once you do, you can't go back.

sanandan

Nikon D300

Nikon AF Nikkor 50mm f/1.8D

09/21/2002 02:56:53 AM · #10

This is what I would do:
Change the DPI in the image size window in Photoshop to 200 dpi, with the resample image window unchecked. This would give me the the exact size for which the camera has given me data at 200 dpi.

Then I would check the resample image box and increase the file size by 5%. Once done, again I would do it by 5% and continue doing it till I get my size. This way when you interpolate, you loose minimum information and sharpness. On the other hand, if you increase the size to the required size straight away, sharpness would suffer much more.
Also there are dedicated softwares available that can help you interpolate to what ever size you want.
Hope this helps.

09/21/2002 02:48:34 PM · #11

I just got my 20x30 poster back and I am very impressed. Genuine Fractals really did the trick. There was nothing wrong with uploading the image as a jpeg, any evidence of compression, if it is there at all, is very minimal. Of course it really helped to have 5 megapixels to work with and no cropping.

T

09/21/2002 09:32:37 PM · #12

Originally posted by Zeissman:
That will increase the size, but it will "interpolate the data. Which means it will fill in the holes. You will lose some sharpness doing that. You really need to find out what DPI the printer wants. Depending on how they print it, they will need different DPI. There is not point in over interpolating, because once you do, you can't go back.

Gotcha never heard of interpolate, but was wondering how it took a file and increased resolution when it was 180 to begin with THANKS a bunch!

Canon 12x IS USM (S3 IS built-in Lens) -- 36-432mm (35mm EQ)

09/21/2002 11:00:43 PM · #13

Originally posted by timj351:
I just got my 20x30 poster back and I am very impressed. Genuine Fractals really did the trick. There was nothing wrong with uploading the image as a jpeg, any evidence of compression, if it is there at all, is very minimal. Of course it really helped to have 5 megapixels to work with and no cropping.

T

what is genuine fractals?

GeneralE

Canon PowerShot S3 IS

09/21/2002 11:12:29 PM · #14

Interpolation and resampling are essentially the same. When you make the image larger at the same resolution, pixels are "moved apart" and new ones created to fill in the spaces. The color value of these newly created pixels is determined by the resampling algorithm (formula) used; in Photoshop you have your choice of three (use Bi-Cubic). The algorithm applies a formula to the pixels surrounding the "space" in the picture, and assigns a color based on the result.

Genuine Fractals is a program which uses fractal mathematics (which I can't explain myself) to allow a much larger "printable area" from less data without loss of quality; for example, I think it will take a 50MB Tiff file down to 2-3MB.

timj351 is using it, and might consider "processing" a fle for you as a test. You might also search for a review at cnet.com or MacWorld. The manufacturer may also have a downloadable demo.

Nikon AF Nikkor 50mm f/1.8D

09/22/2002 05:31:07 AM · #15

I would be very happy to provide a test if someone would like it. Just send me a nice, clean image at the image's current resolution and I will provide a test sample to show what Genuine Fractals can do. It won't create detail where there never was any but you can take an already sharp image at a given size and increase it greatly and still maintain it's relative sharpness.

T

sanandan

Nikon D300

09/22/2002 07:05:18 AM · #16

Sure. I tried doing that using fractals and it gives decent results. The demo download allow 20 saves, and that is good enough for testing. I am thinking of buying it.

Gordon

RIM BlackBerry Curve

Canon EF 85mm f/1.8 USM

09/22/2002 10:23:52 AM · #17

Originally posted by timj351:
I would be very happy to provide a test if someone would like it. Just send me a nice, clean image at the image's current resolution and I will provide a test sample to show what Genuine Fractals can do. It won't create detail where there never was any but you can take an already sharp image at a given size and increase it greatly and still maintain it's relative sharpness.

T

One other (cheaper) option is to use the step interpolation method,
described at Fred Miranda's site

Basic idea is that instead of re-sizing one go, if you do lots of
smaller (say 5% or 10% increments) with bi-cubic resampling, you get
a much better result. Examples show quite favourably against
genuine fractals transforms.

You can either do this yourself, create your own action, or buy
one from the site above. (for about $10 or $20 ) There are also
samples to show it working.

Btw Tim, do you sharpen after you've resized in Genuine Fractals ?

* This message has been edited by the author on 9/22/2002 10:22:49 AM.

09/22/2002 04:13:26 PM · #18

I generally do not sharpen any more after I have resized an image with Fractals. Contrary to what lots of people think I have had great results by applying a small amount of sharpening first. I make sure that I do not oversharpen. I just try to make the original image as good as it can look before I use Fractals on it. I am also one of the few people that sets my camera's sharpening settings to +1 so I am applying a little bit of sharpening before there is any compression applied to the image. On my image that I enlarged to 20x30 I didn't need to apply any more sharpening with Photoshop, I simply color corrected it a little and enlarged it with Genuine Fractals and it was done. It couldn't have been any simpler.

T