Strange observation about the straighten tool

Question

I found, that after making adjustments with the straighten tool, other's like exposure or saturation, that usually are quite fast become very sluggish. Disabling the straighten adjustment temporarily makes the other adjustments sliders react fast again.
Now the strange part:
Sometimes making an additional adjustment makes the before sluggish sliders react fast again WITHOUT deactivating the straighten adjustment before.
Example:
making a straighten adjustment -> exposure slider is now very sluggish
now making an additional shadows adjustment -> exposure slider is no more sluggish
So even Aperture now has to do more calculations the GUI is faster. Weird!
I found, that the problem with the straighten tool occurs more often, if it is the first adjustment you apply.
I didn't find a way to make the behavior 100% reproducible. It is somewhat random.
Would be nice, if someone else could investigate into this issue as well.
I suspect, Aperture somewhat mixes up the order in which it applies the adjustments. When the other sliders show the sluggish behavior, Aperture probably recalculates the straightening adjustment from the RAW for each screen refresh, while it uses an already straightened cache file, when the sliders work fast.
If Aperture has an issue with the optimal processing order with other adjustments as well, this may be an explanation for the hugh differences in GUI performance experience, that are reported here for nearly identical hardware.
Peter
Quad G5, GT 7800   Mac OS X (10.4.8)  

Answer 1

David,
it is not just the Shadows/Highlights.
I extended my test a bit. Below you find a list. All effects with a + increase the speed:
Red Eye Correction -
Spot & Patch -
Levels +
Highlights & Shadows +
White Balance -
Color +
Monochrome Mixer -
Color Monochrome -
Sepia Tone -
Noise Reduction +
Sharpen +
Edge Sharpen +
During that test with enabling/disabling each adjustment, it happened occasionally, that after enabling/disabling an additional adjustment, the Brightness slider kept the speed gain (with only Straighten enabled). Disabling and re-enabling Straighten brought back the sluggish behavior.
Your Viewer window must have a minimum size to show the effect . If the actually displayed picture size is below approx. 720x540 px for 4:3 or 724x480 px for 3:2 pictures, enabling the Straighten tool doesn't slow down the Brightness slider (and other adjustments) noticeable and thus there is not speed gain by enabling other adjustments.
I suspect it has something to do with the amount of memory in the graphic card. I disconnected my second monitor to see, whether the cutoff now shifts towards a larger Viewer area (assumed memory for second display would now be available to Aperture). Result: No it didn't change. So there might be an limitation within core image, that is independent from the graphic card memory.
Nevertheless it would be interesting, if others could check, what's the maximum Viewer size they can use, before the speed penalty dials in, when enabling the Straighten tool. I'm especially interested in reports from people with an 128 MB and 512 MB graphic card (mine is 256 MB).
To do this test, choose Basic view (Viewer at top, Browser at bottom), maximize the Browser area by dragging the window separator towards the bottom, rotate a RAW file with the Straighten tool and then drag the Brightness slider. It should move very sluggish (if not you're a lucky guy). Now diminish the Viewer area, until the Brightness slider moves smoothly. Play around with the size of the Viewer window, until you get the exact size, where the behavior changes. Now make a snapshot (cmd-shift 4) of the displayed picture (actual picture area, not whole viewer window), and check for picture dimensions with Get Info. Post your results here.
The above observations make me to over-think my current dual monitor workflow. Instead of using both displays with Aperture, with Projects, Browser and Adjustments on my 24" LCD and the pictures displayed on my carefully profiled high-end CRT, it might be a faster workflow, to drag over the whole Aperture window to the CRT, make sure the Viewer window is not wider than 720 px and do my adjustments there. A bit annoying to have a setup similar to that in these cool, stylish Aperture ads from Apple, but have to work on a single monitor with a tiny Browser window to get acceptable speed when adjusting my pictures.
The fact that an additional adjustment can speed up things, when using a larger Browser window or full-screen mode, shows, there is still something to improve with Aperture's performance. I hope Apple will investigate into this issue.
Btw.: Does anybody know, how I can make Apple aware of my findings? Or do they know already, because they monitor this list?
Peter