Photo resolution test

There are many photos on this web site.  Some were taken with a digital camera  - an Olympus Digital Camera, D450Z, and  saved at a resolution of 960x1280.  Others photos were scanned using an Epson 800C canner.    It is pretty easy to spot the scanned photos as they are not as sharp as those taken with the camera.

Below is a test I ran of photo resolution    Clicking here or on the top photo will bring up the original photo from the camera.  WARNING:  That particular image file is 303kb, and takes a while to load.  It will also be far too large to seen all at once in all but the largest monitors.   In order to be of reasonable size for a screen, and small enough in size to load in reasonable length of time, photos for the Internet need to be reduced.  The reductions in size and resolution were done with Paintshop 7.0 by JASC Software.  This is excellent software at and  is sold at an attractive price. It is available for a 30 day trial by download. Go to www.jasc.com if you want to give it a try.

Image 1: The photo above is at a Compression factor of 1, saved from the original at a resolution of  600x800, and then sized for this page at 480x640.  Clicking on this photo will take you to the original 303 kb photo.  Notice this 251 kb photo is very sharp but still pretty large, however the white wall is rendered very clearly.  To see original click on this photo.

Image 2: The photo above is at a Compression factor of 25, saved from the original at a resolution of  600x800, and then sized for this page at 480x640.  It is now shrunk down to 46 kb, a more reasonable size.  A little dithering on the white wall has begun to appear, but the wood still looks fine.

Image 3: The photo above is at a Compression factor of 50, saved from the original at a resolution of 600x800, and then sized for this page at 480x640.  We are now all the way down to 28kb.  If small size was of great importance we could live with this one.

 

Image 4: The photo above is at a Compression factor of 60, saved from the original at a resolution of 600x800, and then sized for this page at 480x640.

Image 5: The photo above is at a Compression factor 75, saved from the original at a resolution of  600x800, and then sized for this page at 480x640.  Only 20 kb in size, but the wall is looking pretty sad. The redwood wainscoting still looks amazingly good.

Image 6: The photo above is at a Compression factor of 85, saved from the original at a resolution of  600x800, and then sized for this page at 480x640.  Now at 15kb. Even the wood is dithered now, and the wall is not very nice.

Image 7  The photo above is at a Compression factor of 90, saved from the original at a resolution of  600x800, and then sized for this page at 480x640.  Just 13 kb,  but dithering at this point is very objectionable.

Image 8: The photo above is at a Compression factor of 82 (which is what Paintshop did as a default optimizer), saved from the original at a resolution of  600x800, and then sized for this page at 480x640.  This is13 kb.
 

PART II:

At the completion of this experiment, I decided to run the entire thing a second time, this time saving the images at the target size for web page.
Baslcally the visual results were the same, except the images are smaller.

Image 1a: The photo above is at a Compression factor of 1, saved  at 480x640.    This is now just 173 kb, about half of the original.  We see, therefore, the advantage of sizing the photo for the page, rather than letting the browser shrink it.

Image 2a: The photo above is at a Compression factor of 25,  and sized at 480x640.  It is now down to 30 kb, a very reasonable size.  

Image 3a: The photo above is at a Compression factor of 50,  and sized for this page at 480x640.  We are now all the way down to 20kb.  

 

Image 4a: The photo above is at a Compression factor of 60 and is 18 kb. We are not getting much compression any longer, but quality is falling off fast.

Image 5a: The photo above is at a Compression factor 75, saved for this page at 480x640.  Only 14  kb.  This photo is reversed.   Where you paying attention?
 

Photo 4: The photo above is at a Compression factor of 85, saved at 480x640.  Now at 13kb. Not much change when you get to this point.

Image 6a:  The photo above is at a Compression factor of 90, saved at 480x640.  Just 9 kb,  but dithering at this point is very objectionable.

Image 7a: The photo above is at a Compression factor of 82 (which is what Paintshop did as an optimizer), saved for this page at 480x640.  This is12 kb, almost the same size at the 600x800 version (13 kb).

OK. So what is optimal. Depends on the subject matter, and the situation.  Because the whole purpose of this photo was to show the quality of the work in this bathroom I did not want to sacrifice too much quality. So I choose a size of 480x640, and a compression of 20. This still gave good quality, and reasonable size (34kb).  That photo is below.  There is some dithering on the wall, but if I had not pointed it out you might not have noticed it.  Remember, you always have the option of starting with a thumbnail, and then providing the option of clicking on it for larger photographs and higher resolution.