I'd just like to remind folks that jb originally asked for suggestions for a
dedicated slide scanner, not flatbed options.
In my experience a dedicated film scanner is going to trump any flatbed scanner; the comparison between the Epson 2450 and the Coolscan IV doesn't change my opinion. The Coolscan sample looks like a "quick and dirty" scan that could be greatly improved with a little tweaking via the scanner software. Heck, it looks like they didn't even use any of the automatic correction options that can greatly simplify scanning slides that are dirty, scratched, faded, grainy or have a wide dynamic range. Using these options in the NikonScan software can save you a lot of time post-processing images in Photoshop or another image editing app:
-Scan Image Enhancer. The Scan Image Enhancer function automatically adjusts brightness and color saturation, producing images with optimal contrast.
- Digital ICE4 Advanced™. Digital ICE4 Advanced™ is an impressive suite of four image correction technologies. Digital ICE™ works with LED illumination to remove surface dust and scratches without altering image composition. Digital ROC™ automatically rebuilds and restores deteriorated color values for faithfully rendered images. Digital GEM™ reduces the effects of film grain, producing sharp, clear images without clumping or graininess. The newly added Digital DEE™ function uses exposure compensation to help reveal details that may be hidden in shadowy or highlighted portions of scenes.
I have been particularly impressed using Digital ICE. Scratches that would be a hassle and time-consuming to remove in Photoshop magically disappear. ICE also eliminates the need to clean up images during post-processing. (VueScan has similar options available in supported scanners with an infared lamp.)
The DMax of the Epson is 3.3 while the Coolscan V is 4.2. A higher density range number is better because it means more data can be captured. This is particularly important when scanning film with detail you want to retain in the shadow areas. On the other hand, scanning manufacturers tend to exaggerate the density range and film has a dynamic range of around 3.4. What does this mean? Take it with a grain of salt, I guess, and assume that the claimed dynamic range of scanners is questionable at best. But if one scanner has a higher number than another, I tend to go for the higher DMax because it is likely to be relatively better.
Scanning a 35mm slide with the Epson at 2400 DPI via USB 2.0 takes 3 minutes; using the Nikon Coolscan V at 4000 DPI takes around 30 seconds. (Using image correction in the scanner software increases the scanning time, but it is still a lot less than three minutes.) If you have a lot of slides to scan the time can quickly add-up.
The Coolscan IV is 2900 DPI resolution scanner. The Coolscan V is a true 4000 DPI scanner. Flatbed scanner resolution numbers have to be interpreted differently for a number of reasons that may be too arcane for some people, but comparing film scanner and flatbed resolutions is like comparing apples and oranges. Relatively easy to understand explanations can be found
here and
here.
The Epson 2450 review ends with this caveat: "However, should you want the best quality output from your transparencies you will get better quality from a dedicated film scanner, like the Nikon Coolscan IV we've mentioned earlier." Flatbed scanners do an admirable job on line art, photographic prints and even medium-format and larger transparencies. But they are not designed for scanning 35mm film with optimum results; the best one can hope for is "pretty good." Whether that is good enough depends on how you plan to use the resulting scans.
