Getting shadow detail

[pmagwene]

Greetings Y'All,

I recently purchased a Polaroid Sprintscan 4000 film scanner. This scanner came with two software packages - Polaroid PolaColor Insight and Silverfast AI (and HDR). The software included in the box was slightly outdate and I've since update the software to the latest versions (Insight v5.0 and Silverfast AI 5.5.0r14).

I'm mostly using Silverfast AI to do scans of chromes (Funi Sensia is the predominant film type I'm scanning). I've calibrated Silverfast using the enclosed ITF-8 transparency and I'm using the default settings suggested on Ian Lyon's excellent website.

For the most part I've been happy with the performace of Silverfast, however when I try to scan images with lots of shadow detail I'm getting miserable results with Silverfast, while PolaColor Insight seems to give me acceptable results right out of the box. I'm hoping some of the forum members can provide me with some guidance in getting better Silverfast scans of images with lots of shadow detail.

To illustrate the problems I'm having I've put up two scans of the same image - a sunset with lots of shadow detail in the foreground rocks. One was created with Silverfast AI v.5.5 and the other with PolaColor Insight v. 5.0. Both were made using the autoexposure settings (the Insight scan also used the automatic "dodge and burn" feature which made the exposure of the sky more even).

The Silverfast scan is here: <A href= "http://pantheon.yale.edu/~pmm34/image/sunset_example_silverscan.jpg"> Silverfast image </A>

The PolaColor Insight scan is here: <A href= "http://pantheon.yale.edu/~pmm34/image/sunset_example_insight.jpg"> PolaColor Insight image </A>

As you can see, the Insight scan manages to pull lots of details out of the rocks in the foreground. With the default autoexposure on Silverfast the rocks are just an indistinct silhouette.

I've tried a variety of things to try and improve the Silverfast images including:
- Changing the automatic threshold
- Manipulating the midtone slider
- Trying to select the lightest and darkest images and midtones using the eyedropper tools

Using the above I'm able to make some marginal improvements in the image, but nothing near as good as the default Insight scan.

I don't doubt that Silverfast can produce comparable, or better, images, but I need some direction as to how to go about obtaining these.

Your comments and suggestions are greatly appreciated.

Thanks,
Paul Magwene

[pmagwene]

In regard to my previous message I should also say I've tried messing with the Lightness settings and contrast settings, also with only marginal improvements to the Silverfast scanned image.

--Paul

[ianders1]

Paul,

You're almost there! You've done well in your experimenting, but what you need to try is the highlight (white point) and shadow (black point) sliders. From the look of your image (nice shot by the way!) it looks like you'll need to move the black point slider down some (in the negative range). Then try adjusting the midtone slider until you get the settings correct. You may want to switch the midtone to "N" instead of logarithmic, because if memory serves me, this works better for an image with a concentration of midtones. I know there not really midtones, but in the overall histogram in your image, they will be. Try this out, and let me know how you make out.

-Ian A.

PS. The reason Silverfast did this to your image is because it's Artificial Intelligence isn't always right. This is a particularly challenging image for it.

<font size=-1>[ This Message was edited by: ianders1 on 2001-10-23 06:45 ]</font>

[ilyons]

Paul,

I pulled your image into SilverFast into HDR here my office (I can't upload the result) but even with your JPEG it is possible to get a LOT more out the SilverFast Image than you are getting.

One thing you might want to try as first step would be to rescan with Limit Gamma Slope unchecked (Option>Special tab).


It won't fix the image, but will give you a tad more shadow data to play with

Ian

<font size=-1>[ This Message was edited by: ilyons on 2001-10-23 16:25 ]</font>

[pmagwene]

Ian and Ian,

Thank you both. All of the suggested tweaks were helpful.

The key adjustment was to uncheck the limit gamma slope checkbox, as suggested by Ian Lyons.

Here's the default autoexposure in Silverfast with the gamma slope unlimited:

<a href="http://pantheon.yale.edu/~pmm34/image/sunset_example_silverscan_no_gamma_limit.jpg"> Silverfast Image, No Gamma Limit </A>

Now we're cookin'!

Thanks a million fellas.

--Paul

[ianders1]

Paul,

My mind at 3am forgot you were using HDR, but that's great you figured it out! The image looks great. That's what Ian and I are always trying to tell people - if you're patient and learn Silverfast, you can get really great results.

-Ian A.

[ilyons]

Paul,

>Here's the default autoexposure in Silverfast with the gamma slope unlimited:


Nice - as "Ian A" has already implied there's more under the hood of SilverFast than most seem to realise and anyone who thinks that they can unearth its secrets in a few days is going to be sorely disappointed.

The SS4000 (I think its MicroTek twin is similar) is one of the few scanners that comes with Limit Gamma Slope (LGS) enabled. If you can live with the side effects - slight increase in shadow noise, but still NOT anywhere near as bad as some theoretically better scanners. With some images leaving LGS active will clip the shadow end VERY tight and hence give the impression of zero noise in shadows. This was at one time the method preferred by most scanner users since it hid the sins, but now we have better harware we might as well see into the shadows.

I think it might be time for LaserSoft to change the default for the SS4000 and your pair of sample images is probably one of the best examples I have ever seen to prove the point.



<font size=-1>[ This Message was edited by: ilyons on 2001-10-23 19:22 ]</font>