Pixel Dimension

[michaeldaggett]

<p>The attached screen captures shows two SOOC files. One from a Rebel, the other from a 5DMKII.</p>

<p>Im trying to figure out the coorelation between pixel dimensions. The Reble file is 28.8 M and the 5DMKII file is 60.2M</p>

<p>How is it that the rebel is half the size as the 5DMKII? What am I missing? Does the document size have anything to do with it? The rebel files is 54inches x 36 inches? But the 5DMKII is 15.X23. If I change the document size of the rebel files to something that closely resembles the size of the 5D file, the Pixel Dimension drops to around 2M. </p>

<p>The Rebel file is from a friend, and says it's SOOC. I can not validate it. The reason this came up is because the rebel file prints "blurry" when printed at 8x10.</p>

<p>Thoughts? Help? I appreciate your time.</p><div></div>

[michaeldaggett]

<p>slight correction, the5DMKII file is direct from LR export after a desaturate.</p>

[Matt Laur]

<p>In case anyone's wondering about the obscure reference, I'm guessing "SOOC" means "straight out of camera."<br /><br />Nothing comes out of the camera in inches. The only thing that matters is the actual number of pixels. You'll see that the image files were stamped, more or less arbitrarily, with a "dpi" value that expresses those pixels in terms of inches. One of those files is randomly expressed at 72dpi, the other at 240dpi. So of course the same number of pixels - if you think of them in terms of inches - are going to look different if you do the math based on those two very different numbers.<br /><br />As for why the 5D's image is actually larger ... look at the actual number of pixels. It's 5615 pixels on the long side, and the Rebel's file is only 3888 pixels on the long side. <br /><br />5D: 5,615 x 3,744 = just over 21 million pixels<br /><br />Rebel: 3,888 x 2,592 = just over 10 million pixels<br /><br />It's that simple. As for "printing blurry" ... printed how, by who? A 10mp image can make a lovely 8x10 print. As long as the image itself is actually sharp, the print can be sharp. If it's blurry, there's somebody handling the process incorrectly.</p>

[michaeldaggett]

Thanks Matt that helps a lot.

 

The 8x10 is being printed by mpix pro - online lab, and they are not coming out as sharp as the 4x6 does. At first I

wanted to say it was the lab, because like you said an 10mp image should make great 8x10's. The original digital file

is sharp and in focus. However the lab is pretty reputable so I want to search for other possible scenarios.

 

From the screen captures posted above, what do the 60.2M and the 28.8M pixel dimensions represent?

[alan_olander1664878205]

<p>The 60.2M and the 28.8 are probably MegaBYTES not pixels. File size (MB) would depend on format (JPEG, TIFF, RAW, etc.) and compression.</p>

[Ed_Ingold]

<p>Adobe's use of "pixel dimensions" appears to be representation of the expanded size of the image. Each raw pixel is split into three pixels representing the three primary additive colors - RGB. However, the units suggest that Adobe uses the binary definition of 1M = 1024 * 1024. The value given is therefore approximately the number of pixels, times 3, divided by (1024)^2.</p>

<p>The calculate value is still somewhat less than the "Pixel Dimensions" value, but I can't explain the difference. Adobe marches to the beat of a different drummer.</p>

[JeffOwen]

<p>As Edward explains; multiply the camera pixel by 3 and you get the approx open file size.<br>

The RAW or Tiff or jpg file will be completely different in size depending on the original pixel count and what level of compression is used.</p>

[michaeldaggett]

<p>Thanks all. Much appreciated.</p>

 

[scott_ferris]

<p>The Rebel print prints blurry because it is set to 72dpi, the 5D MkII is set to a more normal 240dpi. Now some printers will ignore the document size and just rescale to the input DPI, in that case the Rebel print will look blurry with jagged steps to the detail.</p>

<p>To correct that, in your Rebel file, Un-check Resample image, change the resolution box to 240dpi click OK. The print will now be every bit as detailed as the 5D MkII print.</p>

<p>All the time the image is on the computer and screen the DPI is irrelevant, as soon as you go to print it can trip you up.</p>