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Photography Question 
Kathy C. Tugwell
BetterPhoto Member Since: 6/16/2005

enlarging a picture to 18x24

I have someone who wants an 18x24 of one of my pictures. If I have the picture in Raw and need to do a few tweeks, should I save it in Tiff or Jpeg to send out to lab. I know it will depend on if the lab takes a tiff. What size file should I go with to keep a good clear picture.

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2/23/2006 11:21:01 AM

Bob Fately   Kathy, first things first: do you know who you will have print the actual piece? I assume you don't have an Epson 7600 around the house, so you should find out from the lab or service bureau what resolution their printer 'prefers' (different printer manufacturers sometimes work off of different resolutions). Not that your final file must be exactly whatever they tell you, but at least you have a starting point.

Next - the only tweak you absolutely need to make is converting the file from RAW to a generally readable file format. TIFF is better than JPEG in that it is a lossless compression scheme - though JPEG at its highest quality should be fine as well. Again, check with the lab to see what they prefer.

As for what file size to use - well, you want to keep as much data in the file as possible to get the best possible final print, right? So you can resize the image in your image-editing program to 18x24, keeping an eye on the resolution per inch. In other words, when you first open the RAW file in Elements and go to the resize window, you may see the dimensions as 20x30 inches at 72dpi resolution. Well, you may need to go to a 360dpi resolution (some Epson printers like this size, and itmakes the math easier here). So, changing the resolution from 72 to 360 without doing anything else (other than keeping the exact same pixel count) will drop the dimensions by a factor of 5; now you're at 4x6 inches.

But fear not! You can upsize digital images quite a bit before having noticeable decay, so using the scaling function in Elements you can repeatedly upsize the image by 10 or 15% at a time until you hit the magic size you want.

As a final step you may want to sharpen the image (after any further color correction you may want to do) and then save the file (again, as a TIFF).

Finally, if you want to get all fancy about it, and you have your own computer monitor calibrated, you could ask themwhat profile they use for the printer/paper/ink combination they will use. Again, this is a bit above and beyond, but if the lab is high end they may be able to help you.

I hope that helps...

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2/23/2006 1:23:07 PM

Kathy C. Tugwell
BetterPhoto Member Since: 6/16/2005
  Thank you very much,it will help.

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2/23/2006 1:57:04 PM

David Earls   Kathy,

If you're using Photoshop, don't be afraid to use the up-res algorithm in the camera RAW processor. I've printed some pretty spectacular 12x16" prints that started out as 5mp images from a Nikon 5700. Up-res algorithms are pretty effective to sizes as big as 400% of original now; there are service bureaus that have even more powerful enlargement options for digital.

I've even had good luck with jpegs up-res'd using Bicubic Smoother on the Image Size tab in Photoshop.

Obviously, though, you're going to better off doing up-res on a camera RAW image - it has more data in it to start with.

You would up-res the RAW image, then tweek and edit, then sharpen at final print size, just as Bob says -

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2/23/2006 2:58:36 PM

Kathy C. Tugwell
BetterPhoto Member Since: 6/16/2005
  Thanks everyone,
Sorry to say the pictures is an older one and I wasn't using RAW at the time But all is not lost it was taken at 3008x2000 pics. So it was a high res jpeg. I think it will be fine and I am going ahead and sending for one to see how it comes out.
Thanks again for everyones help.
Kathy Tugwell

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2/24/2006 9:07:13 AM

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