It's easy to see real positives in Aperture's announcement of plug-in architecture. Taking advantage of existing third party tools can quickly flesh out its features, while positioning it at the centre of a viable “ecosystem”. Meanwhile third party developers can be working on fully-integrated solutions.

On the other hand, it's a long way short of the original concept of the one ring to rule them all, and might even be seen as defining limits on what's going to appear in the core product.

In any case, even if that fear's untrue, it seems pretty obvious that people don't really want to pay for a range of plug-ins for essential tasks like noise reduction or lens distortion - they will do so, but reluctantly, as a distress purchase. Then there's the hassle each time the host or the plug-in upgrades, or the palaver of tracking down licence numbers when you get a new computer (I'd love to know how many Mac users actually use the automated transfer processes). And when your chosen plug-in developer vanishes? Hopefully the plug-in works in the host's next version, and in cases like noise reduction, there'll always be a replacement, at a price. But will any of your settings transfer? Should you welcome plug-ins so uncritically, forgetting that you have grudgingly accepted you'll always be shelling out for them? Or should you demand the functionality in the box?

It's for reasons like this that I've never been particularly enamoured of plug-ins for Photoshop - only NoiseWare and PTLens have ever made it past an upgrade or change of computer - and I have the same doubts about them in Aperture and Lightroom. Still, it is the accepted wisdom that plug-ins played a seminal role in Photoshop's early history and so they have acquired a semi-mythical status. Questioning their virtue seems as heretical as doubting the Founding Fathers or Good Queen Bess, or Ivan the Terrible if you're Russian.

Just as these personalities can symbolize their nations, and embody certain values, so in the field of digital imaging the term plug-in has a history and a special meaning. It's certainly great PR to announce Aperture has plug-ins, but we're talking about a program whose raison d'etre is non-destructive editing and non-modality. So how can the current crop of external TIF editors in modal windows really be dignified with the term “plug-ins”? Fundamentally that's the question Lightroom product manger Tom Hogarty asks in Plug-in or External Editor? when he explains why we haven't seen image processing plug-ins for Lightroom is because of the:

incredibly powerful link between the raw and rendered workflow, and half measures (my emphasis) with marketing spin labeled as “plug-ins” are not the highest priority for the Lightroom team.

Not surprisingly, that touched a raw nerve, so over at AUPN Micah Walter has a crack at gerrymandering the term plug-in by including batch processing (by which criterion a command line program might qualify as a Lightroom plug-in, let alone Noise Ninja's new standalone) and tries to shift attention to what the plug-in specification allows. Derrick Story makes the same point:

Some of the advantages of the plug-in architecture include: access to metadata, batch processing, Raw processing, and control over Aperture objects.

Surely that's a bit like saying you're already a Latter Day Saint because one day your unborn grandchildren are going to become Mormons? If the host program's essence is as a non-destructive editor, a true plug-in operates within that concept. Until then, all you've got is an external editor strapped on in a modal window.