Import CRAW Files doubling on conversion to DNG

[andrewjp.crisp-btopenworld]

Lightroom Version Number

Lightroom Classic 10.2

Operating System

1. macOS 10.15 Catalina

I have started using CRAW on my Canon EOS R5 but was surprised to see file sizes around 45mb in Lightroom (i.e. similar to raw files). I took two identical photos, one craw and the other raw. On the memory card they are 18.1mb and 43mb respectively but in Lightroom after conversion to DNG they are 41.7mb and 41.4mb respectively so the craw file has ended up bigger than the raw file! Any ideas on what I am doing wrong here?

 

[johnrellis]

What I learned just now by reading up on Canon C-RAW:

The DNG format specifies a standard way to store the array of pixel values in a raw image "losslessly" (without the loss of image quality entailed by lossy compression algorithms such as those used in JPEG). In general, LR/ACR reads the proprietary raw formats and converts them all to this standard representation.

The Canon C-RAW format uses lossy compression to store pixel values (albeit with typically very tiny losses in image quality). So to convert a C-RAW to DNG, LR must uncompress the file and then re-encode it in the DNG standard format (which doesn't use lossy compression), thus greatly increasing the number of bytes used.

 

[andrewjp.crisp-btopenworld]

Thanks - that explains it. So the only way to benefit from the reduced file size the CRAW gives is to keep as a .cr3 and not convert to DNG on import?

 

[johnrellis]

I think so.