One Last Argument Against JPG

April 14, 2019 by

I’ve been teaching the benefits of shooting RAW (instead of JPG) for more than a decade. About a year ago, while developing the new display engine for Technical Camera and Kuuvik Capture 4, I did discover another strong reason why you should stop shooting JPG if you care about image quality.

Let me review the usual arguments first.

Limited, 8-bit depth. Digital cameras record at 12 to 16 bits per pixel. Even old ones and your iPhone are 12 bit devices, high-end digital backs are 16. Contemporary DSLR and mirrorless offerings record at 14 bits per pixel. Converting these high bit depth images back to 8 will have serious impact on dynamic range and color range. This is because the 256 possible steps in a JPG aren’t enough to describe a huge range of light and color. And then banding rears up its ugly head. For example, colorwise you are limited to the Adobe RGB color space, while your camera is capable of recording much more.

Fixed white balance. Once a JPG is created, white balance is fixed for good, and cannot be modified later on. You can tweak a little with hard Photoshop work, but it’s quite disastrous.

Lossy compression. The JPG format was designed to compress the hell out of image data. Consequently, you lose some data even on the highest compression quality setting. And digital cameras tend not to use the highest compression quality.

And here’s the last argument:

4:2:2 or 4:2:0 chroma subsampling. If you aren’t familiar with chroma subsampling, read the Wikipedia article first. All Canon and Nikon cameras I’ve seen files from use 4:2:2 subsampling, which means that the color information is halved horizontally. iPhone JPGs are even worse with 4:2:0 subsampling, that is, 3/4 of the color information is missing (you won’t notice it, because the heavy-handed over-processing in these files make them look like crap at actual pixels level anyway). As a comparison, the JPG Quarter HQ image quality setting in Technical Camera uses 4:4:4 chroma subsampling that preserves full color information at every pixel. These HQ files also use higher compression quality setting and are usually quite large.

As you see, JPG files are handicapped at every imaginable level. That’s fine for web display, but make this format totally unsuitable for image capture. Storage is dirt cheap these days, for example a high quality 32GB SanDisk Extreme Pro SD card sells for less than $15, and can store a thousand 26 megapixel images in my EOS RP. In my opinion even lossy RAW compression (such as C-RAW in new Canons) has zero significance in terms of storage. Go with the highest quality, lossless RAW. There will come a time when you’ll be grateful that you did.

Filed Under: Image Processing Tagged With: , ,

Kuuvik Capture 3.2 : JPG Enhancements

September 8, 2017 by

Kuuvik Capture was originally developed to foster a RAW-only workflow. But we received numerous requests for supporting JPG files. At first we introduced a RAW+JPG capture option (where JPG files remained on the memory card), and now in version 3.2 you can shoot as well as download JPG files alone. Capture preferences were changed to reflect this functionality.

Image quality controls whether you shoot RAW, RAW+JPG or a new choice, JPG. JPG files are large/fine ones, since we still want to keep image quality at the highest possible level. When you choose RAW+JPG, an option appears so that you can set whether the JPG files will remain on the card (by default), or downloaded along the RAWs. With the JPG image quality setting files are always downloaded of course.

There’s also a new option to force the native 3:2 image aspect ratio. We’ve added this because aspect ratio control is a complete mess on Canons. You have two settings to cope with, and sometimes get a cropped JPG file and other times a full resolution JPG with metadata to indicate the crop. To make things worse, RAW converters and Photoshop tend to change how they interpret cropping metadata from version to version. We simply don’t want to get involved in this messy situation. So by default Kuuvik Capture forces the camera default 3:2 aspect for all images. You have the option to turn it off, if you really really know what you are doing and need non-3:2 images. But you were warned.

Downloaded RAW+JPG pairs will be handled as a single package, but only the RAW file is used for display. Thumbnails in the Image Browser are marked with a “+” badge to indicate that a JPG is also present, while the file name will show just the RAW.

Deleting the package will delete both the RAW and the JPG.

For RAW+JPG (since the RAW is used for display) the Dual Histogram shows both RAW and processed data. For single JPGs only the processed histogram is available.

A bonus feature

Since a JPG is a JPG, you can use Kuuvik Capture to cull JPG images from any source. For example Agnes went through the majority of our family photo collection during the last few months with the app. This included everything from scanned images through iPhone photos to RAWs. Moreover, JPG previews are displayed from older Canon CR2 files (such as those from the 5D and 1D Mark II), as well as from Nikon NEF and Pentax DNG and PEF files produced by Nikon and Pentax cameras supported by our ShutterCount app. Yes, they share the same image decoder.

IMPORTANT: This is a bonus feature that may work for you, but not officially supported.

Availability

Kuuvik Capture 3.2 is available now on the Mac App Store. It is a free update for users who purchased Kuuvik Capture from the Mac App Store. I’m also working on an update to my free eBook, Kuuvik Capture Inside Out, which will be available shortly.

Filed Under: My Apps, Photo Software Tagged With: , , , , ,