Correcting colour and contrast in scanned slides

Question

I am investigating how to scan slides as accurately as possible, with the qualification that sometimes I may accept less than 100% accuracy for a better-looking image. I am in the midst of comparing several scanning methods, and at this stage one particular method stands above all the rest.
My original idea (before I started testing) was that I would not ask the scanner to do much processing of the raw image, that I would edit in Photoshop. The reasoning was: there's no better image-editing program than PS, and if PS (or its plugins) can't improve the image no other software could.
Well, it looks like I was wrong. I have tried to edit several raw scans, and using PS I can't get results that are as good as asking the scanner to edit the slides.
I have uploaded two sample scans to: http://www.mediafire.com/?z1w4ekew39dwa
Each scan has two versions: a "natural" scan out of the scanner (no corrections), and a corrected scan (suffix GB) using various scanner settings.
What intrigues me is that the scanner is able to automatically correct colour casts and improve contrast across a wide variety of slides. i.e. I have tested slides from the 1960s through to 2007 on various stock (Fuji, Anscochrome, Kodachrome, Ilfochrome). In almost all cases, and without changing the scan settings, images come up as good as the two uploaded images. The only setting I sometimes need to alter is what I call the "gamma", for slides that are underexposed or have a lot of dark regions where detail should be visible (and the reverse for overexposed slides).
Maybe I am not using PS to its full potential, so I am hoping that someone can have a go at editing the "natural" scans to see how close they can get to the corrected scans from the scanner – and then explain how they did it.
I am astounded at what the software inside this scanner can do with images. I thought PS was the be-all and end-all for images, but in my hands, PS comes in second and I'd like to know how to improve its performance.
Thanks in advance for any input.
Notes
1. I purposely choose challenging slides for testing. They either have a large contrast range with visible detail in the highlights and shadows; or colour casts; or bright saturated colours.
2. When testing, I compare all scanned images as seen on my computer screen with the original slide on a hand-held light box viewed through a loupe. For example, all colours in the image called Slide Scan 15 GB, even the metallic-looking sheen of the raincoats, appear as a close match to the original slide. The only significant colour variation is in the foreground rocks (which are a grey-brown colour in the slide), and the sky (which is a slightly darker blue in the slide). This slide is, maybe, 1/2 stop underexposed which explains the saturated colours and the dark "natural" scan.
3. The scanner spends a significant amount of time applying corrections. An 18 MB image (2000 dpi) might take 30 seconds to scan, then another minute for the corrections to be applied.

Answer 1

Welcome to the forums elinhjulstrom,
I saw your post about the scan quality issue you are having with your Deskjet F2180 on Mavericks. I would like to share my ideas with you that might help.
Try:
Mac OS X: How to reset the printing system (This will delete all printers)
Repair disk permissions
Re-add the printer (not the AirPrint driver)
Try the scan again
If there is still an issue, check out this link and use another method to scan:
OS X v10.9 Mavericks: Installing and Using the Printer on a Mac
Enjoy your day
R a i n b o w 7000I work on behalf of HP
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