Should have mentioned it.
PowerSlide 3650 as scanner.
Using SilverFast scanning software.
Scanning in 48 bit colour to a TIFF file.
Dave S
OK, three immediate options come to mind:
(1) In SilverFast, go to the Selective Color Correction tool, and look at the bottom of the dialog, where you see an "ACR" function (the one with the little butterfly beside it). Check the box and shift the slider rightward. As you do this, the colours should come back. It is essentially a saturation adjustment. If you don't like what it's doing to specific colours, you can amend hue, saturation and lightness to individual colour groups using the controls just above the ACR slider. You click on the colour in the image you want to amend, the tool will auto-select the colour group you should adjust, and you may adjust it preferably using the HSL sliders to the right of the colour wheel.
(2) Don't do any colour adjustment at all in SilverFast. Instead scan the image to your hard drive and open it in Photoshop. Add a Curves Adjustment Layer and change the Blend Mode to Color. Find a point in the image which should be black, select the Black eyedropper and click. This may rescale all the colour, strengthening and balancing. You can do the same thing individually with two of the three colour channels in Curves and that will rebalance and strengthen colour as well.
(3) As above for the scanning and opening in Photoshop, but duplicate the image, (make sure the original scan is saved "as is" because you may wish to revert to it) and convert the duplicate to L*a*b* colour space (Image>Mode). Add a Curves Adjustment Layer. Go into each of the a* and b* channels and drag the linear curves inward at the top and bottom points by equal amounts so that the center of the line always passes through the center of the grid. As you steepen these curves, the colours will emerge - rather forcefully, so be careful not to overdo it. You can also use these curves to rebalance colour by throwing them off-center: a* will adjust between green and magenta, while b* will adjust between Blue and Yellow. When you are happy with the outcome, flatten the image, save it, then convert it back to RGB (Image > Mode). From there, continue working on it in RGB mode. The one downside of this technique is that a conversion to L*a*b* does destroy some image data, but working in 16-bit per channel (the 48-bit mode scan), you most likely won't notice any impact.