Conversion of CR3 to JPG using Digital Photo Professional s/w and the resulting file size

[Thiru]

Hi,

I am (new to R7) taking shots using my EOS R7 in both format CR3 and JPG.

Thought of saving some disk space  by deleting the JPG files on my  hard drives thinking that I will be able to convert CR3 to JPG using Canon/Digital Photo Professional/Windows10. 

Converted one file and conversion worked fine and visually I cant see any difference to original JPG file from the camera and the converted JP file. I used Canon/Digital Photo Professional 4.19.10.0 for the conversion and expected the size of the converted JPG file to be roughly the same as that from the camera.

Original JPG file size 12.4 MB

Original CR3   file size 23.2 MB

Converted JPG file size 23.3 MB

Unexpectedly converted JPG file size is roughly the same size as that of the CR3 file.

Can anyone explain why the converted file is so big?

Thanks

Thiru

[p4pictures]

When you do the conversion in DPP, you have a choice of the JPG quality when using the batch conversion or convert and save options. If you maximise the quality the JPG is less compressed than a camera created fine quality JPG, so this is part of the reason. Also if you add contrast and sharpening to the image in DPP, it increases the complexity of the file making it harder to compress, so a larger file.

I think you will soon work out that the way forward is only keep the JPGs that you need, and know you can make fresh ones from the RAW when you choose. Also you'll probably need more external drives to add to your computer.

To use a film camera analogy, I used to have to buy more photo albums to store my 35mm transparencies and prints, then I needed to put up more shelves for the albums. In digital, you will find the need for more hard drives is part of the storage challenge, but at least they are smaller than photo albums

[Thiru]

Thanks Brian.

I know by changing the quality setting I will be a able to reduce the file size. 

I thought with default quality setting I will get the same quality as I get from the camera. Hence I did not change the quality setting and I am getting the same quality as that from the camera. If I reduce the quality in DPP setting then I will not get the same quality picture as that from the camera.

Thanks

Thiru

[p4pictures]

When DPP doesn't change the default output quality since it is processing a RAW and the RAW doesn't contain metadata about what JPG quality was captured at the same time.

So if you previously used quality 9 in DPP, the slider will be quality 9 until you change it.

[johnrmoyer]

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@p4pictures wrote:

When DPP doesn't change the default output quality since it is processing a RAW and the RAW doesn't contain metadata about what JPG quality was captured at the same time.

So if you previously used quality 9 in DPP, the slider will be quality 9 until you change it.

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I so seldom find you providing an incomplete answer, I had to respond 🙂

A CR3 file does contain camera setting metadata for the JPG file size. Most software ignores it. It appears to me that DPP ignores it. The value decoded as "Large" by exiftool in the table below has a variety of numerical values depending upon camera menu settings in the image qualtity menu tab.

MakerNotes:Camera	RecordMode	CR3+JPEG
MakerNotes:Camera	CanonImageSize	Large
MakerNotes:Image	RawJpgSize	Large

[p4pictures]

Thanks John, I guess that must be how DPP knows to keep RAW + JPG images together. I hadn't looked beyond the obvious INFO panel in DPP. Thanks for helping me learn something. 

[stevet1]

Third,

When you do a file Convert and Save, if you look a little further down that page, you can also change the file size. See if that helps. I usually change mine to 1024 X something or other. I think it's 500 or 600 or something. I change it to 1024 and hit the tab key and the program changes the other dimension automatically.

Steve Thomas

[johnrmoyer]

The JPEG standard dates back to 1992. In the standard, quality ranges from 1 to 100. In DPP quality ranges from 1 to 10. DPP quality 10 seems to me to match JPEG standard quality 100, so very little compression. The in camera JPG creation at the best quality seems to me to be similar to JPEG standard quality 90.

DPP can produce a higher qualtity JPG file from the CR3 file than the camera can.

As others have mentioned, the file size will also depend upon image content. A noisy image will compress less than one with out noise. An image blue sky with a gradual color gradient will compress much more than an image with a lot of detail..

More about JPEG and how it works is at: https://en.wikipedia.org/wiki/JPEG

When DPP saves a 16 bit TIF or HIF file, it will contain more information than a JPG file can hold, but will not be viewable on every device, and will still contain much less information than the CR3 file. How much information is useful will vary by how the image is used.