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JPEG Save Algorithm for Canon Cameras Changed?

Old 04-25-13, 06:15 AM
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JPEG Save Algorithm for Canon Cameras Changed?

Does anybody here know if Canon changed their algorithm for saving JPEG files in the past few years?

The reason I ask is because I have a Canon S5 IS camera - an 8.0 MP camera - maximum size JPEG is 3264 x 2448 at largest size and finest resolution.

I also have a Canon SX40 HS - a 12.1 MP camera - maximum size is 4000 x 3000 at largest size and finest resolution.

The S5 IS images are nearly all larger (in KB) than the SX 40 HS images. Not just a few of them, but nearly all of them. To me this seems like it should be the other way around!

Examining the metadata views with ACDSee 14, there are no significant differences in what is saved, so a change in what information the camera saves with the file does not account for a difference.

Do I have a defective SX 40 HS? Sometimes it seems like that when I take photos and see the way they come out compared to the S5 IS.

I'm going off on a photo taking trip early tomorrow morning, so I will not be around to answer any questions you have until Monday or Tuesday, sorry.
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Old 04-25-13, 09:02 AM
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Re: JPEG Save Algorithm for Canon Cameras Changed?

That sounds unusual. Have you checked to make sure your camera has the most updated firmware? Has this happened before, or is this a new camera for you?
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Old 04-25-13, 02:05 PM
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Re: JPEG Save Algorithm for Canon Cameras Changed?

I have the latest firmware. I've had this SX40 HS for over a year now and it's been pretty consistent. I've never noticed it when I changed cameras before. I have had a half-dozen digital cameras in the past dozen years and always when I have upgraded, the image size (in KB) has gotten bigger, not smaller
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Old 04-25-13, 09:07 PM
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Re: JPEG Save Algorithm for Canon Cameras Changed?

The S5 uses a Digic 3 processor, while the SX40 uses a Digic 5. I don't know if that explains all of the difference that you see, but I am sure the processor difference affects image compression and noise reduction, and that probably changes file size.
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Old 04-25-13, 10:37 PM
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Re: JPEG Save Algorithm for Canon Cameras Changed?

Originally Posted by kuroiinu View Post
The S5 uses a Digic 3 processor, while the SX40 uses a Digic 5. I don't know if that explains all of the difference that you see, but I am sure the processor difference affects image compression and noise reduction, and that probably changes file size.
This link mentions that both DIGIC 4 and DIGIC 5+ introduced features for reducing image noise.
http://cpn.canon-europe.com/content/..._processing.do

Also, the faster processing allows for problably better compression without compromising quality:
http://www.learn.usa.canon.com/resou...ocessors.htmlp
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Old 04-26-13, 07:50 PM
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Re: JPEG Save Algorithm for Canon Cameras Changed?

More noise reduction = smaller file size. Probably the quality of the images is very much compromised in reducing the file size and also by increasing the compression level (ie, the DCT coefficients). If the processor is *better*, file size should be larger because higher quality will usually result from less JPEG compresion..
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Old 04-27-13, 05:45 AM
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Re: JPEG Save Algorithm for Canon Cameras Changed?

Zyzzle: Okay... Not so very sure that I understand what you are saying. It SEEMS like you may be disagreeing that reducing "noise" would reduce the file size, but on the other hand.....???
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Old 04-27-13, 11:11 AM
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Re: JPEG Save Algorithm for Canon Cameras Changed?

Originally Posted by danwiz
The S5 IS images are nearly all larger (in KB) than the SX 40 HS images. Not just a few of them, but nearly all of them. To me this seems like it should be the other way around!
how big is the file size difference? Like 1.5 MB old cam vs 1.2 MB new cam? Just curious.
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Old 04-27-13, 04:51 PM
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Re: JPEG Save Algorithm for Canon Cameras Changed?

Yes, when you reduce noise by digital means, it usually means you apply some kind of blur to the image. It makes the file more homogenious (that is, the pixels look more similar to each other), and thereby makes the compression larger and file size smaller. The same applies when encoding movies and applying a Digital Noise Reduction algorithm (DNR)... It makes the files smaller, less crisp, and 'easier' to reduce in size.

So, therefore, perhaps you should stick to your old camera.
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Old 04-27-13, 06:11 PM
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Re: JPEG Save Algorithm for Canon Cameras Changed?

Ranger: The average size of about 2,000 photos with the S5 IS is 3,790 KB and the average size of about 2,000 photos with the SX40 HS is 3,213 KB. So - the old camera averages about a 500 KB larger file than the newer camera. But, keep in mind that the newer camera's photos are 4000 x 3000 px and the old camera's photos are 3,264 x 2,448 px. Whew! Took a while to calculate that.

Thanks for your comments here and especially thanks to zyzzle.
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Old 04-27-13, 09:36 PM
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Re: JPEG Save Algorithm for Canon Cameras Changed?

Do check the camera settings. There may be a "JPEG compression level" setting. Set this as low as it can go (ie, apply as little compression as possible) to get a sharper picture and a larger filesize. Or, try looking for an uncompressed option, like TIFF or BMP in the settings. Those files will be huge, however (around 36,000 kb per file at 4000x3000 resolution).
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Old 04-27-13, 10:39 PM
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Re: JPEG Save Algorithm for Canon Cameras Changed?

zyzzle is correct about noise reduction, but only when considering post production. One thing not mentioned yet is that the SX40 may simply have a better sensor, being 4 years newer. Therefore, less noise is in the cpatured image, so less noise to compress without any additional noise reduction, improving the compression ratio without compromising quality.

However, there's also the possibility of improving noise reduction and JPEG encoding algorithms over time that provide better quality to space ratios. I don't know much about noise reduction, but for compression, it's a known fact that codec encoders improve over time. The PDF of the article in this link compares two different JPEG encoders, and finds one clearly superior to another. it also compares different JPEG-2000 encoders and finds differences. So if there's quality differences between different encoders, it stands that any given encoder has room for improvement over time as different versions are released:
http://citeseerx.ist.psu.edu/viewdoc...10.1.1.65.5495


This site has reviews of the cameras with the perfect pics for comparison, the same subject/scene at similar settings on both cameras. The SX40 images do come out smaller despite the higher resolution, but I don't see a compromise in quality.
http://www.dcresource.com/reviews/ca...t_sx40-review/
http://www.dcresource.com/reviews/ca...hot_s5-review/

Comparison images:
http://www.dpreview.com/reviews/cano...s/IMG_0109.JPG
http://www.dcresource.com/reviews/ca...s/IMG_0251.JPG

Originally Posted by zyzzle View Post
Do check the camera settings. There may be a "JPEG compression level" setting.
As the reviews not, the JPEG compression level on these cameras is referred to as a "quality" setting, and can be set to "normal," "fine," and in the case of the S5 IS "superfine." The OP already mentioned that the cameras were set at "their finest resolution, " so he likely already had these set at their finest quality, aka lowest JPEG compression and largest file size.

The cameras don't support RAW or other uncompressed formats, although you'd likely want their RAW format over a TIFF or BMP:
http://www.thephoblographer.com/2011...he-same-thing/
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Old 04-28-13, 04:53 AM
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Re: JPEG Save Algorithm for Canon Cameras Changed?

Jay G: I checked the reviews you mentioned and saved the images. The one shot with the SX40 HS is 2,268 KB and the one shot with the S5 IS is 3,114 KB, assuming that those images were shot under lab conditions then it looks like we have the answer to the question!! So, it appears that the 4 year difference in camera age accounts for the difference in size in the images.

As I stated in the original post - both cameras are set up so as to use HIGHEST (or best) Quality settings and the finest resolution - it's the only way I ever take photos. If I want smaller sizes to e-mail or whatever, then I do that post-production in either Photoshop or ACDSee - depending on what I am using the reduced quality for.

So, it appears that, as I said, we have the answer to the original question, and I will make no further comments unless somebody adds something which blows everything else out of the water.

Thanks so very much to all of you for putting on your thinking caps for this question. I really appreciate your time and trouble. I'll stop worrying about whether my SX40 HS is defective in this regard.

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