when I have a large preview window and have 500 or more
files in a single folder CS seems to slow to a crawl as it is "generating previews".

I use a laptop to download and review RAW files when traveling and face these same problems ... one thing I do is keep the number of files in each folder to about half what you have ... I'm guessing you're shooting 2 GB cards since I get about half this many with an 8 Mpix 1D Mark II and your 1D is 4 Mpix?

I'd rather it not generate the previews - I can wait for the preview to be displayed when I select the thumbnail.Can
I turn this off?

Don't use File Browser? (yeah, I know, not practical :) Other than that I don't know how to keep FB from generating the previews.

The thumbnails are generated quick enough and that's great.

They are part of the Canon .tif file, what you see on the camera's LCD when you check images in-camera, so they just get loaded, not generated.

I saw someone mention adding an external hard drive as a scratch disk might help, but USB 2 isn't that fast to be of help, is it? Even a firewire drive is not going to get me EIDE speeds, right?

I tested external drive options for scratch disk on a desktop and got these results ... 100% (fastest) with two internal hard drives (no surprise) ... using C as scratch with 50% RAM allocation slowed to 128% (with more RAM allocated the total times went down but the % went up to 148% so obviously it depends on how much time is spent paging out of RAM) ... I tested two USB 2 drives, one gave 232 % (ie more than twice as long), the other 242 %. Tested a 1394 (Firewire) drive which took 148% with 50% RAM allocation, so about 20% slower than just C drive but much faster than the USB 2 drives.

This was with a desktop with faster internal drives than on a laptop so the % will be different with a laptop and it's possible 1394 might start to approach the speed of just using C drive, though the only way to know is to test it. But basically I'd be surprised if you gain much if anything and wouldn't be stunned to learn that even 1394 is slower than using just C.

I've got 1GB of RAM

How much is allocated to Photoshop, just the default 50%? You can usually bump this up to 75% (I run 86% on my desktops but have more than 1 GB) without problems so long as you aren't running other programs at the same time.

One time I waited 45 minutes for the previews to build and ... it was pretty quick, until I renamed a folder at the top of the tree and then it started rebuilding all the previews all over again

If you export the cache in that folder it won't have to regenerate the previews the next time you open it ... Bruce Fraser's book "Camera Raw with ... CS" has this tip and many others regarding using the File Browser and the RAW converter more efficiently.

Thanks for reading and I appreciate any ideas you have.

To sum it up, I'd recommend having fewer images per folder so you don't hit scratch when generating previews, bumping up the RAM allocation if it's at default 50%, not using a 1394 external as scratch (and definitely not using a USB 2) and periodically running export - cache to save off the previews you generated.

One other suggestion is to look at other converters that might generate previews faster ... I use Capture One for most of my serious desktop RAW conversion work but also have RSE, which is free, and use it on the laptop on the road when I have to look at a lot of images quickly. With the 1D Mark II (8 Mpixels) the RAW files are typically 6-8 MB and each Capture One preview is 2.6 MB or so while each RSE preview is only 846 KB, so using RSE on the road saves on temporary disk space too. Both of these will still take several minutes to generate 500 previews but probably not the 45 minutes you mention for Photoshop. I think it takes about 8-10 minutes to generate 250 or so previews for example (a 2 GB CF card's worth). Worth looking into if this is really bugging you ...

Bill

This Old Man

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CS on a laptop - external USB scratch disk?