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Old Oct 17, 2005, 7:25 AM   #1
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I have encountered a strange problem (let me explain.) I have been using an Olympus C-5050 5MP camera for a couple of years, and I absolutely love it. I have been taking aerial photos, and some of my results have been stunning. Often from the air, the camera picks up some haze that isn't visible with the human eye. I set the camera to the highest jpg resolution and then make the correction, using Jasc's Paint Shop Pro. Often the results are great, and the size of the photo gets reduced from about 3.5MB down to maybe just over 2MB. This still leaves plenty of resolution for enlargements. I had an aerial shot of my hometown enlarged to 24" X 36", and the results were very good. Now for the problem:
I recently purchased a Casio Exilim EX-Z110 6.3MP camera. I had a need for a smaller and lighter camera for a project, and this seemed to fit the bill. My preference for batteries are AA, and although I couldn't find a compact camera that uses a CF card, I was able to get a 1GB SD card for the Casio, so I thought it would suffice. When I set the casio up for the highest jpg resolution, in daylight, most of the shots are over 4MB each. And that is OK, BUT: when I use the "one button fix" in Paint Shop Pro, the size of the image gets reduced to about 1MB and often less than that.
I don't understand the disparity between the two mfg.'s. I used the Casio for some ground shots, and haven't even taken an aerial shot yet. I can't imagine how much resolution I will lose if there is any ground or UV haze in the picture.

There is one thing that may or may not be relevent. I purchased an extension ring for the Olympus, and keep a UV haze filter on it just to protect the lens and it's mechanism. I figure that it may play a small role in the amount of lost resolution, since it filters the UV before it ever gets to the camera, and the software doesn't have to remove it. But going from 4+MB down to under 1MB seems excessive. Any thoughts?:?
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Old Oct 17, 2005, 9:00 AM   #2
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When you enhance an image, it sometimes results in loss of detail (even though the photos may look better and appear to have more "pop").

For example, if you have higher contrast in an image, that makes the shadow areas darker and the brighter areas brighter, and can give your images a nicer look. But, you can lose real detail because of it.

Since you're saving in JPEG, less detail compresses more (taking up less space).

The other factor is how much JPEG compression you've got your editor set to save with. If you increase the JPEG quality setting, you'll get larger file sizes with less loss of detail from compression (JPEG is a lossy compression method).

If you click on the "Options" button you'll see when you select the "File, Save As" option in PSP, you'll see a slider for JPEG quality.HIgher Compression = Lower Quality = Smaller File Sizes.


P.S.

Here is a very good article that may help explain it written by Mike Chaney:

JPEG Images: Counting yourLosses



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Old Oct 17, 2005, 11:33 AM   #3
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I don't know about the "one button fix" in PSP (my version is earlier and apparently doesn't have that), but different manufacturers do use different jpeg compression schemes that cause the size to vary widely, even when the number of MP is the same. A good example is the size of files produced at highest JPEG resolution by the Canon Digital Rebel XT and the Olympus e-300 (both 8MP). The Oly files have less compression and are always substantially bigger than the Canon files. This is a deliberate choice on the part of the manufacturers based on their estimation of the balance of value between fidelity left in the image versus the convenience of smaller file size. How that effects PSP's one-button fix, I don't know (or maybe it's irrelevant?). But I personally feel more secure with the larger file sizes of the Olympus.

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Old Oct 17, 2005, 11:53 AM   #4
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Norm in Fujino wrote:
Quote:
I don't know about the "one button fix" in PSP (my version is earlier and apparently doesn't have that), but different manufacturers do use different jpeg compression schemes that cause the size to vary widely, even when the number of MP is the same. A good example is the size of files produced at highest JPEG resolution by the Canon Digital Rebel XT and the Olympus e-300 (both 8MP). The Oly files have less compression and are always substantially bigger than the Canon files.
Larger file sizes shooting in jpeg are not always due to lower compression.

For example, more noise in an image will typically cause larger file sizes if the image is exposed the same.

This is because thedifference in color and brightness in pixels in an area that should be relatively uniform, can result in more detail (the noise) that the algorithms need to compress.

Other factors impact it, too. For example, a different contrast curve or lower settingscan help retain more detail in shadow and highlight areas, resulting in larger jpeg files.

Ditto for sharpening (as sharpening can destroy "real" versus perceived detail when it increasescontrast when it detects edges in an image), and can result in smaller sizes, depending on how the manufacturer implements it.

That's one reason most dSLR models are very conservative in these areas (to retain more realdetail), so sometimes more post processing is needed to bring out their best.

Other manufacturers may do a little more in camera processing, and entry level models (both in non-DSLR and DSLR camera lines), tend to be more aggresive in the way they process (contrast, saturation, sharpening)

Even how models metercan impact file sizes. If one tends toexpose brighter (leaning towards overexposing some of the highlights in high dynamic range scenes), in order to correctly expose most of the image, it may have smaller file sizes (because the detail in those areas is blown so there is less to compress).

This helps to keep photos as printable straight from the camera as possible, so that less post processing is needed.

Most models allow you to adjust these types of things if desired.

Short Version: :-)

Manufacturers tend to make different decisions on how some things are implemented shooting in jpeg (amount of contrast, saturation, sharpness, etc.).

You also have sensor characteristic differences (for example, dynamic range, noise, ISO sensitivtity), as well as metering differences (leaning towards lighter or darker exposures, depending on the scene).

These can all impact file sizes with jpeg
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