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Do you know? Differences in jpg sizes
I have been wondering why jpg file sizes vary so much and how much quality difference this really means?.

Shot with 40D both raw and jpg.

1. Jpg out of the camera: 4,228 kb2. Raw processed with DPP and saved as jpg with 10, 350dpi: 8,676 kb3. Raw processed with LR and saved jpg with 100 quality 240 ppi: 6,192 kb.

What settings do you use to save your converted raw files?..

Comments (6)

Well, first of all, the DPIs are different for those conversions. Have you tried saved with the same DPI on each?.

Second of all, it just comes down to how each company's software works with RAW images. There's differences in quality, and how they interpret any data as well, so of course this would be reflected in file sizes..

Forgot to add: a RAW processed into a JPEG will usually be larger since RAW converters are more complex than in-camera processing, and can extract more detail, even if you can't see it, than in-camera processing...

Comment #1

I have been wondering why jpg file sizes vary so much and how muchquality difference this really means?.

Shot with 40D both raw and jpg.

1. Jpg out of the camera: 4,228 kb2. Raw processed with DPP and saved as jpg with 10, 350dpi: 8,676 kb3. Raw processed with LR and saved jpg with 100 quality 240 ppi:6,192 kb.

What settings do you use to save your converted raw files?.

A couple of points....

1. What is the JPEG setting in your camera? Do you have it on 'highest quality' (or whatever the equivalent is for your camera)? If you have the camera set to a lower setting, the file out of the camera will be more compressed than you would get from a RAW conversion saved with minimum JPEG compression..

2. Also, as the previous poster said, when you have processed a RAW shot you will probably have done it differently from how the camera JPEG conversion software would have done it: you will have carefully optimised WB, saturation, colour casts, sharpness etc. etc. comapred to what your camera would have done. So it's not surprising that the ultimate file size is different; if you have processed the RAW file carefully it will have more information in it. (and JPEG quality 10 may be better than what your camera is set to anyway, see above)..

3. The dpi is irrelevant to the file size; that is only used for viewing / printing. if you are changing this paremeter you are taking the same array of pixels in the same order and simply putting them closer together or further apart on the monitor / print. There is the same number of pixels, and each pixel has exactly the same RGB values, whatever the dpi value..

Best wishesMike..

Comment #2

Three things affect JPEG file size (assuming the pixel dimensions are the same of course):.

- Amount of compression. The essence of JPEG compression is that it allows small inaccuracies at the pixel level in order to compress more effectively. At the highest quality/least compression settings, these inaccuracies are almost impossible to see and by any standards the quality is very high. As the amount of compression increases the inaccuracies increase too, and (to answer the original question) yes, they do have a visible impact on image quality..

- Compression software used. JPEG compression algorithms vary in sophistication and efficiency..

- Amount of detail in the image. This can have a surprisingly large effect - it's a major reason why a collection of in-camera JPEGs varies in file size. But importantly, this applies to both real detail and false detail - just increasing the sharpening will make a jpeg file larger. Similarly, higher ISO speed results in more noise, and the JPEG compression routines are obliged to retain that 'detail' resulting in a bigger file. It follows, therefore, that noise reduction has an impact on file size too...

Comment #3

I'll just add a little to that: different cameras compress a lot more or a lot less. The best give a wide choice and people with those jpg's wonder why others bother with raw and tif's..

In a lot of editing programs you can change how the thing is saved in JPEG's by looking for an "Options" button on the "Save" or "Save As" window. Set it for the highest quality and lowest compression and you'll probably get a bigger jpg than you started with..

It's very easy to experiment with, just "save as" pix 1, pic 2, pic 3 etc and change the compression for each version..

Regards, David..

Comment #4

I recommend reading some of the Technical Articles here:.

Http://www.impulseadventure.com/photo/.

There are some aspects of the broad JPEG standard that affect not only size but quality too...aspects that are vastly under-reported. Things like quantization tables and chroma sub-sampling..

Also recommend downloading Kal's little JPEGsnoop utility. It will show you the differences in the 3 different JPG files and help you understand what is going on. It's quite complicated!.

Kal's latest version of JPEGsnoop also has data on how most cameras and programs save JPG files (their JPEG "signature")...give it a pic from an unknown source and it will identify what camera or software saved it!.

Charlie DavisNikon 5700 & Sony R1HomePage: http://www.1derful.infoBridge Blog: http://www.here-ugo.com/BridgeBlog/..

Comment #5

Glitched wrote:.

Well, first of all, the DPIs are different for those conversions.Have you tried saved with the same DPI on each?.

This has no effect on the file size. The DPI setting is meaningless..

Second of all, it just comes down to how each company's softwareworks with RAW images. There's differences in quality, and how theyinterpret any data as well, so of course this would be reflected infile sizes..

Actually, it has more to do with the different JPEG compression algorithms, then how it is converted. However, different RAW converters will convert the image differently, and that will impact how much a photo CAN be compressed. However, it is the compression algorithm (and the quality setting) that has the biggest influence on the file size..

Forgot to add: a RAW processed into a JPEG will usually be largersince RAW converters are more complex than in-camera processing, andcan extract more detail, even if you can't see it, than in-cameraprocessing..

Actually, the reason is that most cameras use a lower quality compression setting for in camera JPEG - or more accurately, people set the JPEG quality setting higher than is generally needed when they convert from RAW...

Comment #6

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This question was taken from a support group/message board and re-posted here so others can learn from it.

 

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