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Karmin Sep 15, 2006 10:21 PM

Hello again friends, after reading some information about the S5200 on a web site, I read that the compression ratio applied to a 5m image is 6:1 when the image is recorded as Fine (F) and 12:1 when recorde as Normal (N). IIt is also observed that this a rather high compression ratio. Is there a big difference to see in the images and what's the importance of the compression applied to a JPEG? Thanks my friends. Germain. [img]/forums/images/emoticons/wink.gif[/img]

jphess Sep 15, 2006 10:56 PM

The more highly compressed an image is, the more likely it will be that there will be JPEG artifacts that will be potentially visible. For images that will be viewed on the computer, or sent via e-mail, or made into small prints, this may not be a problem. But if you are striving for the highest quality, the most detail, and possibly want to print some enlargements, then it would be a good idea to use the "Fine" setting. The best thing for you to do would be to take some images using both settings and compare them. Then, instead of asking for the opinion of others, you will have formed an opinion on your own and you will know what the best choice will be for you.

Karmin Sep 16, 2006 12:04 AM

jphess, thanks for the info. But the lecturing in the last part of the message is out of topic.[img]/forums/images/emoticons/icon_exclaim.gif[/img]

jphess Sep 27, 2006 11:09 AM

I'm sorry I offended you. I certainly didn't mean for that to happen. The only point I was making it is that with digital photography we don't have to really wonder. I often find myself wondering about different settings and forget that the easiest way to find the answer is to just try them. Back in my film days I had a tendency to want every picture taken to be perfect. I didn't want to waste the film. But with digital that is no longer an issue. And I keep forgetting that. Again, I wasn't trying to be rude, only trying to make suggestions.

programmer Sep 28, 2006 6:54 AM

Karmin, a compresion ratio of 6:1 sounds far too high. On the least compression setting my HP 715 produced files that were upto 1.6MB from a 3.3 MP sensor and my S9500 in 9MP Fine setting produces files of around 4.5MB from a 9MP sensor. In both cases this is a pixel to byte compression ratio of approximately 2:1. (It could be that I am misunderstanding the basis for the calculation of the ratios that the website in question states.)

Note that the file sizes depend on the complexity/detail of the image. An image with large areas of very nearly the same colour will produce a smaller JPEG.

What size are the JPEGs produced by your camera? Also do you have the camera set to produce files with the largest number of pixels and the smallest amount of compression?

Karmin Sep 28, 2006 11:18 AM

Hello programmer, thanks for the information and the observations. Here is the address of the website where compression ratio is mentioned My S5200 is set to record 5M images at the finest (F) quality. It gives images in the range of 2.4 -2.6 megapixels. Size is 2592 X 1944. Using the "N" (normal) setting would give 1.2 -.3, images with the same size. This is exactly what is written in the manual. Yep I was a bit surprised when I read on this website the compression ratio but I'm not sure if I must rely on it. well it is not a very important issue but in any case it's always good to have these informations. Where could I find it? Thanks. Germain.jphess: no problem just wanted to say it. Let's have fun.

programmer Sep 28, 2006 12:13 PM


I see why they say that the compression ratio is 6:1. If you have a 5MP sensor this will actually only generate 5 MB of data (since each sensor pixel only handles one colour). However, the camera interpolates the data to give 3 bytes per pixel (red, green and blue) this effectively gives a file size of 15 MB, dividing this by 2.4 gives a ratio of around 6:1.

As you say the main issue is what the images look like to you.


jphess Sep 28, 2006 12:35 PM

As far as the compression ratio is concerned, you have very little control over it. You have two choices; M or F. And you know that using M is going to give you a more highly compressed and potentially lower quality image. You gain more control over that compression in many of the image editing software programs. When you save an image as a JPEG, many of the programs prompt you for the amount of compression or the quality that you want. But I don't get enough information from Photoshop to tell me what the actual compression ratio is.

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