Conversion issue from cr2 to jpg

[RichardZ]

My camera is set up to save files in both cr2 and jpg.  When I look at a picture with brickwork, striations have been added to the jpg.  I downloaded the cr2 and viewed it in Canon Digital Photo Professional and there are no striations.  Exporting to jpg causes the striations to reappear.  Apparently the conversion from cr2 to jpg is failing in both the camera and in DPP. The attached pics are png as saves from screen capture software.  Any ideas on how to fix this? cr2jpg

[rs-eos]

Are you changing the output pixel width and height? i.e, scaling the image when exporting?  I don't use DPP, but perhaps the scaling is not handling this image well.  Are there different options available for scaling?  e.g. Photoshop includes scaling modes such as "Bicubic Sharper" and "Bilinear" and "Nearest Neighbor".  Depending upon the image content, I can see certain scaling algorithms producing lots of moire which is what you JPEG version contains.

[johnrmoyer]

Such moire patterns are common when downsizing an image that has periodic lines like the brick wall. https://www.cambridgeincolour.com/tutorials/image-resize-for-web.htm

I hope some of this might be helpful, but I am just guessing which program might have scaled the image.

If DPP export to JPG scaled the image smaller, you might try turning off that scaling. If the scaling was done by the program displaying the JPG file, then you might try using a different program or use some other program to scale the image before using the problem program to display it.

Some things you might look at in DPP:
1. try turning off sharpness and if that improves the image then select unsharp mask instead of sharpness and try changing the fineness setting and the amount setting.

2. try increasing or decreasing "Digital Lens Optimizer"

[RichardZ]

First my thanks to rs-eos and johnrmoyer.  Here is some additional information.

While busy with other things yesterday my mind was working on this. I have learned a lot about moire and it sort of pertains but not exactly. It appears in Windows Explorer icons, Windows Photo Viewer, and Windows Photos. It does not appear when viewing the jpg file in Gimp, and is dramatically lessened when viewing the jpg in Paint, and somewhat lessened when viewing in Adobe Photoshop Elements So I called the jpg up in Windows Photo viewer, saw the moire, and used the print option to print the picture to my Epson printer. Low and behold, no moire in the print. The image on this post is a screen save png of the jpg (with moire) file opened in Gimp. No moire. So, it doesn't seem that the camera jpg creation process is creating the moire...rather some of the Windows processes, and to a lesser extent other viewers, are creating it when displaying the jpg. This picture was a casual shot so it isn't a big deal with this photo but this will be terribly distracting and confusing on a shot that I want to keep and display. Not sure where to go with this but I want to thank all who provided information. Life is a learning experience!