Ridge

In trying to maintain an ever-expanding and evolving archive of photographs on a relatively small hard drive (HDD), the costs and benefits of the various file types have come into sharp focus.

RAW, TIFF, JPG, PSD et al. all co-exist for the simple reason that they do different things. RAW preserves the original sensor data from the camera to be manipulated later. TIFFs are best at being uncompressed monoliths but are the largest of the file types, taking up to four or five times the space of the RAW file. JPGs compress the file size smaller even than the RAW, but with the inevitable loss of quality each time it is saved.

A complicating factor is JPGs’ and TIFFs’ compatibility with the excellent, non-destructive processing of Abobe Camera Raw (ACR). (Presumably this is also the case with Lightroom and Aperture, but I’ve not tried them).

The first format to fall was JPG, which loses quality at each save – a definite dissuasion for an integrous (integritous? integrious? integral? Just what is that adjectival form?!) archive.

The second also-ran was TIFF, which is redundant given that PSD's lossless compression gives the same quality at half the size. However, storing all my images as PSDs meant that I had to convert them back into TIFFs if I wanted to take advantage of ACR‘s processing, which is all the time.

Here the workflow plateaued, processing RAWs in ACR, saving out as PSDs and then temporarily back to TIFF if necessary.

I’m used to these trade-offs so couldn’t quite believe it when I tested Abobe’s Digital Negative (DNG) and found that any format can be converted into it, including PSDs (via Lightroom). It compresses to marginally over JPG size without any loss, and is ACR compatible. Case closed!

As far as I understand, DNG was devised by Abobe to supplant all proprietary RAW formats such as Canon’s .CR2 and Nikon’s .NEF. These myriad formats live or die with their manufacturers, require their own codecs to be read and inflate the size of any program designed to process them. Being manufactuer-independent, DNG unifies and stabilises the RAW format. All the original metadata such as time-taken and exposes is preserved and it facilitates ACR processing for any image. The only caveat is that layered files have to be PSD, but one could never process them in ACR anyway.