Lightroom/Camera Raw: Is raw editing tool by its nature more limited than a pixel editor?

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It is obvious that Photoshop has more advanced editing features that LR and ACR in many areas, including (i) masking/selection, (ii) sharpening, (iii) filters, (iv) geometric adjustments, (v) layers, (vi) local edits and many others.

My question: (a) is this primarily a design choice or (b) are RAW editing tools by their nature more limited than pixel editing tools?

If the former, why was the choice made and why shouldn't we be asking for many/most of Photoshop features that are relevant to photographers to be incorporated into LR and ACR? If the latter, I'd like to know what's possible in a RAW editor and what isn't to know what to ask for!
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Posted 9 years ago

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Rob Cole

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There are some fundamental differences between the two, and some fundamental similarities.

Although its all the same stuff at its deepest level (they both are ultimately doing the same transformations of pixels), there are some very different concerns in the case of a parametric/non-destructive editor, because it does not have the luxury of baking things into the image data and forgetting about it. Instead, it needs to remember everything that needs to be done, so it can replay it all starting with the original image.

So sometimes it comes down to what's possible, but sometimes its just about what's practical - Its a lot easier to design a parametric/non-destructive editor that can do anything, but takes forever, than it is to design one that's fast.

Also, what is practical within one design, may be very different than what is practical within another design...

I'll leave it at that for now.

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PECourtejoie, Champion

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Photoshop is a at its core a pixel editor: its tools edit groups or individual pixels, changing their R, G, B and Alpha values (Or CYMK, LAB, etc.)

While Ligthroom and Camera Raw are parametric editors: the changes applied therein are in fact simple a list of values applied to some algorithms, that are never applied on the actual pixels of the raw files, or the other files that Lr/ACR can edit.
Even the "brush strokes" are recorded as X, Y, radius values, and linked to one or several parameters, and the gradients have an origin, end, and midpoint stored as text values.
Only at export time, new "pixel" files could be created, according to the aforementioned values and algorithms.

(Yes, thanks to layers, adjustment layers, smart object, some parametric changes can be applied in Photoshop, but the main idea is that LR and ACR are almost exclusively parametric. I.E. no pixels are hurt.
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So practically speaking can we get better masking and selection? Better geometric corrections I think are possible. How about filters--why are there none (including unsharp mask, eg)? Why is there no cloning tool?
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Rob Cole

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Answer, in a word: Yep. I would be very surprised if Lr4 does not include a distraction removal brush. I can't predict about the masking/selection.

Note: Despite some performance challenges, Lightroom is one of the best quality *and fastest* raw converter / editors in town. I don't know enough about the internal design of the image rendering software to say what Adobe may or may not do, but just remember: in the land of parametric editing, often what you give up to gain features and flexibility, is speed.

To wrap up on a positive note: Lr10 is going to be awesome! (but there is a limit to how much will be accomplished come Lr4) It really is harder / more time consuming to implement sophisticated, high-quality, *and fast* features parametrically/non-destructively.

Final thoughts:
Although its always going to take a parametric editor that has grand flexibility and massive local adjustments applied a long time to render a photo from scratch, sophisticated intermediate result caching can speed things up considerably when not re-rendering *from scratch*. That's one of the challenges of parametric vs. pixel...
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In principle, everything that can be done with a destructive approach (Photoshop) can also be done in a non-destructive approach (Lightroom).

Just imagine that any interaction you have with Photoshop (all key presses, mouse moves, etc.) is recorded and could be selectively replayed. Lightroom and ACR do pretty much this, however, paying attention to the amount of detail to be recorded being managable.

If the detail to be recorded becomes too large and/or the algorithms fed with the detail are too slow, the parametric approach becomes slow. You'll notice this in prolonged export times but also, worse, during image editing.

Many parametric approaches have a so-called "image pipeline", i.e., image operations are always performed in the same order, no matter what order they were introduced by the user. This means that using an otherwise unproblematic image operation (e.g., exposure adjustment) can be dramatically slowed down by another one that is always performed before it (e.g., noise reduction). If you are interested in possible workarounds, you might want to check out the "Better Develop Module Performance" thread.

Hence the primary technical reason why there is no better distraction removal support in Lightroom yet, is probably performance. This shouldn't be a permanent showstopper, however, as other RAW converters such as Aperture and Bibble 5 demonstrate.