Canvas Size / Image Size

<p>Trying to print a ~8x10 on 8.5x11. (image is actually 8 by 10.353). Not understanding why canvas size and image size are dependent. I set image size then set canvas size to 8.5x11. When I check image size it has changed to canvas size.</p>

<p>ChasB</p>

<p>The canvas size is the size of the whole enchilada including the borders. If you wanted a postage stamp size image on a 16"x20" field, the stamp would be the image size and the very large border would be the canvas size. </p>

<p>Then I expect image size for a postage stamp would read 13/16 inch by 1 inch...instead it reads 8.5x11.</p>

<p>If you reduce the Canvas size, the image will be cropped accordingly. If you increase the size, you will create a border around the image. If you change the Image size, the canvas size will be automatically changed to fit the image. You can also specify the change as "relative" to the image, for a border of fixed dimensions.</p>

<p>The true "size" of the image is always in pixels. The dimensions in inches, centimeters or picas is only valid if the resolution is specified at the same time. If you don't crop or resample, the number of pixels is unchanged, and changes to the dimensions are non-destructive and reversible.</p>

<p>The Canvas size is the working area, like a paste-up page of a few years ago. You can use to for several reasons - to create a border (useful for lab prints which must fit a mat, or must not be cropped), or start a composite or paste-up.</p>

<p>As far as image editors are concerned, the entire field is the canvas and the image, but you can edit the image to have a larger canvas size without affecting the dimensions of the picture it surrounds. When you increase the canvas size but leave the picture unchanged, the canvas/image size changes. "Image" in this case has two meanings.</p>

<p>My document is displayed as my image with a white canvas border. If I set a canvas size to 8.5x11, image size changes to reflect the change. If I set image size to 8x10, canvas size changes to reflect the change. Document size does not change...remains at 126M. I think I may be confused, as many times in the past, with pixel count and dimensions. Can't seem to get it straight. So, I do understand your first and third paragraph response.</p>

<p>ChasB</p>

<p>To begin with, your image is 8x10. If you increase the canvas size to 8.5x11 you're adding pixels and the image size changes in terms of pixels and dimensions. If you then take that enlarged image and reduce its size back to 8x10, the image size (both pixels and dimensions) will change only if you have "resample image" checked in the image size dialog. If you don't have "resample image" checked the document size will remain the same but the image dimensions will change. </p>

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<p>I think I may be confused, as many times in the past, with pixel count and dimensions. Can't seem to get it straight</p>

</blockquote>

<p>Work in pixels! Size is based on how you divide up the pixels you have per unit (inch, mm etc). For example, let us say you have 1000x1000 pixels to keep the math simple. And to simplify this further, let's only consider the horizontal axis. If you have 1000 pixels and divide that by 72, that is, you provide 72 pixels per inch, you could end up with <strong>13.8 inches</strong> using that division (1000/72=13.8). Let's now say you divide up your 1000 pixels using 180 instead. 1000/180=<strong>5.5 inchs</strong>. In both cases, you had 1000 total pixels. The document itself doesn't have a size, other than what space it takes up on your hard drive. The sizes above are examples of what could be produced if you divided up the total number of pixels you have, with some number of which is just a tag within the document. In Photoshop, if you use the Image Size dialog, turn resample OFF (do not allow it to create more or remove pixels), you can enter any value, 72, 180, 1000 into the resolution field and the resulting size is calculated for you. But you haven’t changed the document or the data at all. You just changed a theoretical 'size' if you output your 1000 pixels using that resolution. So again, it's meaningless until you output the data. At that point, lets say you print the image, you can decide how big you wish it to appear and/or how many pixels you want to devote to the output. You have 1000 pixels and someone tells you that you must use 300DPI (which isn't true but that's a different story). 1000/300 would produce a 3.3 inch print. You want a bigger print? Lower the DPI (within reason). You set the DPI for output to use 180 of your pixels to produce 180DPI? You get a 5.5 inch print (1000/180=5.5).<br>

Work with pixels. That's a fixed attribute of the data unless of course you resample that data (add or remove pixels).<br>

</p>

<p>I'm a bit wary of the pixel juggle. If the long side of my image as indicated in Image Size reads 2125 pixels and I want a 10 inch long side print, that gives me 212 resolution. It has been drummed into my head over the years that one should shoot for 240 to 360 ppi. Yes, I understand about viewing a print at such and such feet. I'm looking for better sharpness...usually. Yes, I always leave 'resample' OFF.</p>

<p>Chase</p>

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<p>If the long side of my image as indicated in Image Size reads 2125 pixels and I want a 10 inch long side print, that gives me 212 resolution.</p>

</blockquote>

<p>Correct. Nothing wrong with that value depending on the output device. Be just fine if you were printing an 8x10 on say an Epson ink jet. Set it and forget it. </p>

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<p>It has been drummed into my head over the years that one should shoot for 240 to 360 ppi<br /></p>

</blockquote>

<p>An urban legend. Again, for an Epson driver, if you have 240/360 pixels per inch, use it. Have less than 180PPI for that 8x10, resample to and no more than 180PPI. As long as the resolution tag falls between 180/480, set the '<em>size</em>' you want for the print, even if it's an odd value (239PPI, 186PPI etc), print. Different story going out to a halftone dot. You need to figure out what the linescreen is, then set a quality factor (from 1.5x to 2X). You are printing to a 150LPI screen? 1.5X is fine for that and higher screen output. Lower than that, use 2X quality factor to figure out the PPI you need here. </p>

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<p>Yes, I always leave 'resample' OFF.<br /></p>

</blockquote>

<p>Sometimes it <em>may</em> need to be on. </p>

<p>I will take your suggestions (retrain myself) and give them a go. Using a very dependable 3880 to print.</p>

<p>Best to All,</p>

<p>ChasB</p>

<blockquote>

<p>I will take your suggestions (retrain myself) and give them a go. Using a very dependable 3880 to print.</p>

</blockquote>

<p>I'm using the same printer. Take an image that has the 240/360PPI data, make an 8x10 print. Now resample to 180PPI and make another. See any difference at viewing distance? I can hardly see any difference under a really good loupe. Note that Mac and Windows drivers will handle the resampling differently. On Mac, I see no difference that would warrant resampling. </p>

<p>I'll run this procedure on my Mac tomorrow.</p>

<p>Thanks</p>

<p>ChasB</p>

<p>Make a Document 8X10.353 (Image Size)<br />Go to Canvas Size and make it 8.5X 11" and uncheck Relative.<br />They are dependent in that you start with a image, add canvas border that makes a bigger image.<br />Voila image with tiny border on 8.5x11 page (Canvas Size)<br />Whats the problem with printing it? Am I missing something?<br /> <img src="webkit-fake-url://7cc70b88-db45-4a8f-9501-7fc6b3854719/image.tiff" alt="" /><br /> <img src="webkit-fake-url://c290e377-5a8b-4442-a656-0174f7b62956/image.tiff" alt="" /></p>

<p>Completed the suggested procedure by Andrew Rodney and found I could not, with my aging eyes, detect any difference what so ever between an 8x10 (360 ppi) and an 8x10 (180 pip). I'm startled!</p>

<p>I do have a better grasp of Image Size and Canvas Size after this discussion.</p>

<p>Thank you all!</p>

<p>ChasBOEHM</p>

 

<p>I’ve only recently started to print photos on canvas myself and I’m still working out the details. So thank you for the contributions to this discussion! I’ve had some issues with image size and the size of the canvas as well, so I hope this will help and the next <a href="http://www.smartphoto.co.uk/products/wall-decoration/canvas">photo canvas</a> will come out exactly as planned :)</p>