STEVE PEARCE PHOTOGRAPHY

One of the things I have noticed over the course of scanning hundreds (or possibly thousands) of slides using my Nikon Coolscan III, is the difficulty the scanner has extracting detail from shadow areas.  What on examination is a well exposed slide, can look very dark when scanned.  A quick search on the internet reveals this to be quite a  normal problem in slide scanning.  Most scanners struggle with the high levels of contrast inherent in slide film.  If you're choosing a scanner, the thing to check seems to be the bit depth capability.  Although manufacturers also quote DMax, which is supposedly a measure of the scanners ability to extract shadow/dark area detail, the measure is not uniformly applied and there seems to be no standard way to measure DMax.  For this reason, DMax figures should be taken with a pinch of salt.  A full discussion of this can be found on Wayne Fulton's scanning tips website which includes lots of good scanning advice.

I have played a lot in order to get the most detail out of shadow areas of slides using Nikon Scan - increase the analogue gain a little, increase brightness and contrast etc.  The problem is, that any further optimisation to bring out shadow detail in Photoshop results in high levels of noise in the shadow areas.  This then also limits the amount of sharpening that I can apply, as this accentuates the problem further.

I have however, found a solution by using Vuescan.  The solution is not fast, but it is quite effective and gets more out of the hardware I have than would otherwise be possible.  The answer lies in multi-scanning - running the scanner more than once over the same slide in order to extract more detail from dark areas.  This is a function that the Coolscan III supposedly does not support - using Nikon scan software that is!  Using Vuescan, it actually works perfectly well however.  It is possible to select from 1 - 16 multiple scans of the same frame and there is an extra option that can also be selected which makes two passes of the frame - one with a low LED brightness and one high, then combining the two passes.
I have had good results with this option switched on, and have found that around six passes of the frame gives a good result. Four passes of the frame seem to limit the amount of work that can be done in Photoshop before seeing noise and ten passes do not seem to improve so much on six, so as to be worth the extra time. The images below show various scans with multiple passes, which have then been heavily lightened in the shadow areas using the photoshop shadow/highlight tool and brightness/contrast.

A couple of other things to note in using Vuescan are the scan bit depth - I select 48 bit, even though my scanner's specification states that only 10 is possible and the second thing of note is the output bit depth.  I select  64 which is problematic for windows to handle and gives a file size just over 70 MB (with a full scan size of around 2500 x 3700 pixels with my LS30).  This is no big issue though and gives a 16 bit file which can be worked on in Photoshop and then converted back to 8 bit after editing, resulting in a file size of around 26MB.

This is all quite time consuming, with multiple scans taking several minutes per frame, but the results are noticeably better.  The only thing I don't like in Vuescan compared with Nikon scan, is that the film strip cannot be previewed.  My workflow in Nikon scan was to preview the whole strip, or select on screen those that I wanted to scan, then tweak the previews before batch scanning.

This is not really an issue in Vuescan, as the editing facilities are minimal.  Without the film strip preview, you need to look at the strip before loading to the scanner, then select the frames to scan and make a cup of tea. Tweaking the previews in Vuescan does not seem to be very effective, so all the editing and colour correction is done post scanning in Photoshop - having a 16 bit file and all that shadow detail there, this is no issue!  I used to find post scanning tweaking in Photoshop was always necessary with Nikon scan anyway to correct colour and sharpen, so this is no increase in work.

I have been working with Nikon scan for a long time, so I guess it's just a case of getting used to a new workflow. Other than the scanning time, this is not drastically increased, as I now only edit once - after scanning, in Photoshop.

Vuescan is well worth $60 or $100 for the pro version, which also allows selection of the output colour space, plus some other colour control features and unlimited upgrades.

Vuescan will allow many people to get more out of their scanner than the scanner manufacturer's software allows.

Words and images copyright Steve Pearce, 2004.