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08/13/2005 08:30:39 AM · #1 |
I've been considering a stock photo site and in the interest of getting the most bang for the buck (images uploaded within alloted portfolio limit) I noticed some wide variances in image file sizes.
Can anyone shed some light on this for me please?
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Example photo of mine - 
Original out of the camera info:
2272 x 1704, 72 dpi, 2591KB, JPG format
After post-processing in Paint Shop Pro 9, cropped to 2130 x 1704 (for 1.25:1 Aspect ratio) - @150 dpi, file size is 6326KB, JPG format.
After resampling to 3000 x 2400 - @150 dpi, file size is 6590KB, JPG format.
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Looking at some other images on the stock site I'm seeing various sizes.
Examples:
JPEG high resolution image dimensions in pixels: 3000 x 2000
JPEG high resolution file size: 1,445 KB
Calculate Output Size [10.00" x 6.67" @ 300dpi]
JPEG high resolution image dimensions in pixels: 2531 x 3382
JPEG high resolution file size: 3,283 KB
Calculate Output Size [8.44" x 11.27" @ 300dpi]
JPEG high resolution image dimensions in pixels: 3000 x 2400
JPEG high resolution file size: 4,054 KB
Calculate Output Size [10.00" x 8.00" @ 300dpi]
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I realize an image with more image data (colors, details, etc...) is going to be larger - but I don't see how the image I've posted is so much larger in file size than the examples. I'm aware that dpi doesn't impact file size, just print quality & sizing.
Thanks.
Barry
Message edited by author 2005-08-13 12:52:56.
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08/13/2005 12:51:33 PM · #2 |
Does post-processing really add that much to the file size?
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08/13/2005 12:53:24 PM · #3 |
The resultant jpeg size is dependant on the jpeg quality level, which is variable. If your image is larger, it's being saved at a higher jpeg quality than the original, I would imagine.
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08/13/2005 12:56:58 PM · #4 |
Hmmm...well, the camera is set to shoot at the highest quality available, then when I save the Paint Shop Pro (.psp) file as a .JPG, I don't compress at all.
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08/13/2005 12:59:25 PM · #5 |
Originally posted by glad2badad:
Hmmm...well, the camera is set to shoot at the highest quality available |
That may not be the highest the JPEG standard offers, just the value that your the manufacturer decided to called 'High'.
Originally posted by glad2badad:
then when I save the Paint Shop Pro (.psp) file as a .JPG, I don't compress at all. |
Jpeg files are always compressed. In this instance, you probably didn't specify the compression rate. The likelihood is it was set to maxmimum quality, which will be higher than your camera.
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08/13/2005 01:49:41 PM · #6 |
| The size of a JPEG file can also vary markedly with the type of content. For example, I had an entry which was at about 155kb, but after cloning out a small bright spot and lowering the level of Unsharp Mask I applied, it got down to about 110kb at the same JPEG quality setting. |
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08/13/2005 02:25:40 PM · #7 |
Yes, I have noticed that as well. The image I posted as an example has a lot of detail vs an image that has a lot of blue sky...
Originally posted by GeneralE:
The size of a JPEG file can also vary markedly with the type of content. For example, I had an entry which was at about 155kb, but after cloning out a small bright spot and lowering the level of Unsharp Mask I applied, it got down to about 110kb at the same JPEG quality setting. |
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08/13/2005 02:31:55 PM · #8 |
if you really want to see dramatic file sizes out of camera, try shooting a pure white paper, and then a black paper, and compair those to your normal filesizes.
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08/13/2005 02:40:32 PM · #9 |
Some valid points Paul. For a test I just took the original file, made zero modifications to it, did a 'Save Copy As' (to give it a different name), checked the compression (which is set to minimum/best quality of 1 by default), and the file size is now 5272KB. The original file size is 2591KB. It doubled in size.
The main point of interest in my original post was the extreme difference in file size of my example vs the others I mentioned. The comparison photos were substantial in detail also - perhaps a little more negative space (sky, etc...). My example photo is substantially smaller in dimension (pixel width/height) - yet is over 2MB larger in file size.
Another interesting thing is the file size difference from my example photo (cropped and post-processed) vs the resampled image which is larger in dimension but barely larger in file size.
Sorry for the long post - I'm just finding it difficult to get a handle on what basis the file size is factored on. Thanks for the feedback.
Originally posted by PaulMdx:
Originally posted by glad2badad:
Hmmm...well, the camera is set to shoot at the highest quality available |
That may not be the highest the JPEG standard offers, just the value that your the manufacturer decided to called 'High'.
Originally posted by glad2badad:
then when I save the Paint Shop Pro (.psp) file as a .JPG, I don't compress at all. |
Jpeg files are always compressed. In this instance, you probably didn't specify the compression rate. The likelihood is it was set to maxmimum quality, which will be higher than your camera. |
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