Image compression for P&S digital camera

YS2003

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Now that I have just received Canon SD700 IS (6 MP) today, I am setting things up with this camera. There are 3 main options for image quality:
L (2816 X 2112)
M1 (2272 X 1704)
M2 (1600 X 1200)
and a few others which I am not interested in (too low resolutions)

And, there are following compression settings:
Superfine (high quality)
Fine
Normal
* "superfine" is double the file size of "fine" setting.

As a P&S digital camera, this camera can only capture data in JPEG format (for a still image). JPEG is a lossy file format to begin with.

I am interested in hearing which setting is recommended. I have 2 2GB SD cards; so, file sizes are not much of a concern to me. But, I don't want to make the files unnecessarily large without noticeable benefit.
 

YS2003

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bousozoku said:
The biggest file probably has JPEG compression of 1:2.7, which isn't bad at all. Compression of 1:8, the medium setting most likely, is noticeably degraded to my eyes.
So, your pick would be "superfine" setting on the JPEG compression?
 

bousozoku

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YS2003 said:
So, your pick would be "superfine" setting on the JPEG compression?
Yes, it would be. The only stronger setting would be a TIFF or RAW file, which would have no compression but since you haven't mentioned that, I'm assuming that it's not available.
 

tech4all

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YS2003, I was reading your other thread about deciding on what P&S to get. I'm in pretty much the same situation you were in. I have a dSLR already, but would like to get a small point and shoot digital camera as a small take-a-long.

Anyways my main reason for this post is I was wondering if you would post a small review of the camera. Somethings you like and somethings you don't like. I've read reviews on dpreview.com but it be nice to hear it from another perspective. About a month ago I was going to get the SD700 and now that Canon has come out with those two new cameras - SD900 and SD800 - I am trying to decide on which to get. And the image stabilization that the SD800 and SD700 have is a big plus for me. I'm wondering, with the introduction of the SD800, if the SD700 has it come down in price at all....if you don't mind me asking how much did you pay for it?

Yea but when you get some spare time, I would really appreciate your feedback on the camera :)
 

sjl

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bousozoku said:
Yes, it would be. The only stronger setting would be a TIFF or RAW file, which would have no compression but since you haven't mentioned that, I'm assuming that it's not available.
<nitpick>
Actually, both TIFF and RAW are compressed. It's just that RAW in particular (and TIFF, depending on how it's used) use a lossless compression algorithm. JPEG, on the other hand, (typically) uses a lossy compression algorithm: it throws away bits of information in order to get a smaller file.

That's why TIFF and RAW files from cameras are so much bigger: they aren't throwing away information (or not as much information as JPEG; I don't know how much of the sensor data is retained in TIFF), so the files can't be compressed as much as JPEG manages. In return for the larger images, you have a greater degree of image fidelity. eg: you can always go from a RAW or TIFF file to a JPEG, but the reverse will not give you the original image back.
</nitpick>

(You can tell I'm a computer geek, can't you? ;) )
 

Abstract

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Dec 27, 2002
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Isn't there such thing as lossless JPEG? I thought this existed more as a way to allow the photo to be opened on essentially any computer (since JPEGs can be opened on any computer, pretty much), but without loss, or "almost" no loss?
 

bousozoku

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sjl said:
<nitpick>
Actually, both TIFF and RAW are compressed. It's just that RAW in particular (and TIFF, depending on how it's used) use a lossless compression algorithm. JPEG, on the other hand, (typically) uses a lossy compression algorithm: it throws away bits of information in order to get a smaller file.

That's why TIFF and RAW files from cameras are so much bigger: they aren't throwing away information (or not as much information as JPEG; I don't know how much of the sensor data is retained in TIFF), so the files can't be compressed as much as JPEG manages. In return for the larger images, you have a greater degree of image fidelity. eg: you can always go from a RAW or TIFF file to a JPEG, but the reverse will not give you the original image back.
</nitpick>

(You can tell I'm a computer geek, can't you? ;) )
TIFF is not necessarily compressed, especially if the developer chose not to pay for Lempel/Ziv/Welch compression. Trust me, they don't give it out for free, just ask CompuServe about the .GIF file format.

RAW files are also not necessarily compressed. It is dependent on the camera manufacturer.
 

ChrisA

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Jan 5, 2006
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Abstract said:
Isn't there such thing as lossless JPEG?
Yes and No. You can set the compression level to almost nothing. But still JPG uses 8-bits per color channel. So if you start with a deep color image that is 12 or 16 bits per channel it will have to compress the dynamic range into 8-bits per channel even if there is no compression of the resolution. If you are starting with an 8-bit image then lossless JPEG i almost losses. There will always be "round off error" when the image in encoded which causes some loss. so "nearly lossless" is as good as it gets

At the highest quality setting the compression in JPG is very minimal and what is tossed out is stuff that the eye can't see. It takes advantage of the fact that the eye sees details using lminance (black and white) and can't see fine details in color. It has to do with the spacing odf the rods vs cone on the back of the eye. So JPG compression does some tricks like cutting down on the number of different shades of red recored in order to preserve fine details in textures, the eye does not notice untill you really crank up the compression settings.
 

YS2003

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tech4all said:
YS2003, I was reading your other thread about deciding on what P&S to get. I'm in pretty much the same situation you were in. I have a dSLR already, but would like to get a small point and shoot digital camera as a small take-a-long.

Anyways my main reason for this post is I was wondering if you would post a small review of the camera. Somethings you like and somethings you don't like. I've read reviews on dpreview.com but it be nice to hear it from another perspective. About a month ago I was going to get the SD700 and now that Canon has come out with those two new cameras - SD900 and SD800 - I am trying to decide on which to get. And the image stabilization that the SD800 and SD700 have is a big plus for me. I'm wondering, with the introduction of the SD800, if the SD700 has it come down in price at all....if you don't mind me asking how much did you pay for it?

Yea but when you get some spare time, I would really appreciate your feedback on the camera :)
Greetings from Idaho. I had a chance to try out this little digital camera (SD700). It was around $330 from Amazon with shipping. It came right on time in one day (so I was able to take this with my trip today) For this trip, I only took my Dell (company-issue, so it has to come with me) and Fujitsu Tablet (because it has the SD reader right on the unit; also, I did not want to risk my Macs through TSA's rough handling at the security).

I agreed with Abstract's comment on P&S camera's MP factor. I just felt there won't be a good benefit for higher MP (over 8 MP) for P&S. Some people have high expectations on their P&S to perform as good as the decent digital SLR camera. I am comfortable with the compromise. I will take this little camera when I am on the go, as I realized it is not practical to take my SLR gears at all times (it's too heavy as I am already carrying 3 laptop almost at all times) I will take my 30 D when I am going to plan taking good pictures.

Here is one of the shots when I was taking a little spin on Rt. 55 with Dodge Magnam this late afternoon.



Canon SD700 IS has various setting for the manual mode. I admit the manual in this camear is not the same as what I can do with 30 D. But, for a P&S digital camera, the available setting is more than enough, I believe.

The camera is very small. The upcoming SD900/800 are also in the simialr size (there is no noticeable size difference pracitcally speaking).
 

tech4all

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YS2003, thanks for the reply. That's a good price you got, $330 with shipping. Over at B&H (who I like btw) it goes for ~$355. I'm not sure how much they are my local camera shop though. Hopefully I get can get close to what you got it for provided the new one's are in stock which would justify a lower price. The SD800 only about 1MP more so I don't think that's a huge improvement and since they use the same size sensor it can have more noise in the pictures.

Yea I'm not all that interested in manual controls in this digi cam - aside from the ISO controls and other manual settings it may have. Just want to point and shoot without thinking too deeply about composition, depth of field, lighting, etc., I can do that with my dSLR when I want to be more conscience of my shots.

And thanks for posting a sample photo. That actually looks really nice.


The only think that caught me off guard when I was looking at the SD700 at Fry's was when I looked into the viewfinder, it was much smaller than I thought it would be. But I guess that has to with the crop factor of the sensor.....Just checked an old Olympus P&S I have and the viewfinder's size seems to be larger (although I don't know how big the sensor is) than the SD700 from what I remember.


Oh yes, one question: How well does the image stabilization work? Do you find that it improves your shots, as far as camera shake is concerned?

Thanks for the information, YS2003 :)
 

YS2003

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tech4all said:
The only think that caught me off guard when I was looking at the SD700 at Fry's was when I looked into the viewfinder, it was much smaller than I thought it would be.

Oh yes, one question: How well does the image stabilization work? Do you find that it improves your shots, as far as camera shake is concerned?
I think IS works very un-intrusively as that is its intent by Canon. I heard there is a gyrating unit inside the camera to counter-act the minor camera shake by the shooter's hands. SD 700 has the 3 settings for IS (always on, right before the shot, and off). IS should be off when you are taking photos from, say, a roller coast ride or from the moving location.

Regarding your comment on what you see on viewfinder, the image should be about 80% to 90% less than the actual pic your camara would capture. I think this is where SLR camera shines (among many other benefits) as you can take the picture as you see in the viewfinder. For P&S camera, viewfinder and lens are not perfectly lined up.
 

tech4all

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Thanks for the info, YS2003. I'll post back if I shall have further questions regarding the camera :)

Hope you're enjoying your new camera! :D ;)