Scanning problem

[ronniewillis]

I have a 35mm slide, (let's call it slide A), that appears to be exposed properly when viewed on the light table. However, when I scan the slide, it appears too dark on the screen. Like it's under exposed by a stop or stop 1/2. Looking at the histogram shows no data in the lower 1/4th of the range. (i.e. no white pixels). But when you view the slide on the light table, there is white areas, and they appear as white. They're not muddy, and they're not burned out either. They look correct. There is also some shadow detail. My question - If the scanner is calibrated properly, shouldn't the image on the screen be a fairly close representation of the slide as viewed on the light table?

I'm using Photoshop 6, Silverfast 5.5, and Poloroid Sprintscan 4000. A little history is in order also. I've been using the Sprintscan about a year now, and usually have a problem with the colors. After I scanned another slide, (slide B) out of the same roll of film as above, and it took me about 2 hours to fix the colors, I decided I had enough. I read up on the IT8 calibration, and ran through the calibration procedure. (per Ian's specs on http://www.computer-darkroom.co.uk ). It worked great. I rescanned the slide, and the colors, brightness, and contrast, matched the slide almost perfectly, as viewed on the light table.

I rescanned slide A, and it still looks the same. As if it was under exposed. Slide A is a frontlit scene with both white and shadow detail. Slide B is a backlit, silhouette scene. It doesn't have any white, but it does have a bright reddish orange sun. Brightness and contrast appear correct, as does the histogram. I have data from white all the way to black.

Anyone have any ideas? Can the slide be under exposed, and still look correct on the light table?

[ilyons]

Anyone have any ideas? Can the slide be under exposed, and still look correct on the light table?

Since you have already calibrated the scanner and find another slide to produce a good scan I would question your assumption that Slide A is "correctly exposed". Exposure MAY not be the problem, it might be that the slide simply doesn't have any data in the upper regions of the histogram. I think you'll need to scan lot more slides before deciding if you really have a problem. You might also like to use the button that resembles a lens diaphragm to optimise the range of the scan. The image should then look a lot brighter and if aditional adjustments are required for contrast, color, etc these can also be applied. You should NOT expect ALL images to be full scale unless you use the tone/colour tools provided within SilverFast

<font size=-1>[ This Message was edited by: ilyons on 2001-10-12 09:34 ]</font>

[ianders1]

Ian is very right in saying that you have to use all of the tools in Silverfast to get the optimum image. That is the magic of Silverfast, though.

Just the other day, a client sent me a horrible negative - it was underexposed by about 2 stops, and shot late in the day with an awful yellow cast over the whole picture.

Using Silverfast, though, I was able to eliminate the color cast, and correct the exposure - before I sent it to PhotoShop - saving a great deal of time and work.

Start by clicking on the aperture-looking button Ian Lyons describes - but then play around with the other settings to learn what they do. You can take horrible photos and make them works of art one you learn the ins and outs of Silverfast.

Also, be patient - it takes some time to learn how to use all of Silverfast's sophisticated tools. You'll get it, though and when you do, you'll realize that your investment was worth it.

-Ian A.

<font size=-1>[ This Message was edited by: ianders1 on 2001-10-12 09:45 ]</font>

[ronniewillis]

Thanks guys,
I did play around with the slide last night, while waiting on someone to reply. I found the highlight/shadow locator buttons. When I clicked the highlight locator button it showed me the spot on the slide that had the brightest value. (The picture was a sail boat). It turns out there was a small spot on the mast that was the brightest spot. This spot was apparently brighter that the white areas (the hull of the boat). Silverfast must have made that bright spot the lower end of the histogram scale, and then the hull of the boat, which appeared pure white on the light box, had to fall somewhat further up the histogram scale. I pulled the highlight slider up to make the hull appear as white on the prescan, which I guess caused the bright spot on the mast to burn out. But that's okay, it was only a few pixels. (Clone tool to the rescue). I had already been adjusting the slider to bring the highlight/shadows into range, but I guess I was assuming I shouldn't have to do that, since the slide looked like it was exposed properly. I'm a computer programmer by trade. I, of all people, should know that the computer can't think for us. GIGO - Garbage In, Garbage Out.

[ianders1]

Ronnie,

Glad to hear of your success. I too was frustrated by some of my initial Silverfast scans - but after playing around with the settings, and reading some of Ian Lyons' excellent tutorials, I was able to get some great scans.

Even so - it seems that I keep learning more about using Silverfast each time I use it. Just keep at it.

-Ian A.

[ilyons]

>But that's okay, it was only a few pixels

In the Option>Auto panel you can adjust the value of Auto Threshold Highlight. With the specular highlight being out on its own relative to the remaining bright areas and the setting of 2 (default) even a few pixels can be enough to stop image range being optimised. Try a value of 5 or even 10 with this image and see how it effects the final scan. I think that playing around with this particular image will reach you a LOT about what Auto Threshold does. Also read pages 64 thru 67 of the manual. Even try checking the levels tick box to see how it effects the scan.

You're actually very lucky to have found an image that gives the opportunity to learn about one of SilverFasts MOST powerful tuning tools



<font size=-1>[ This Message was edited by: ilyons on 2001-10-13 00:08 ]</font>

[Guest]

Am I correct in assuming that the scanner always extracts all the data from the slide/negative that it's optically capable of doing, and using the Silverfast tools only affects the interpertation of the bits? That's to say the slider for the highlights sets one end of the scale, and the slider for the shadows sets the other, and moving either slider only serves to parse out part of the scanners total range.

For example, taking my problem slide, if I reset the tools, obviously the sliders start out at 0 and 255. Then I scan my slide, and the first pieces of highlight data appear around 194. (194 is where auto adjust places the highlights with the threshhold set to 2). If I slide the highlight slider to about 194, it obviously makes the scan look better. But that doesn't physically affect the scanner, does it? If I rescan with the highlight slider set at 194, the data on the histogram line still falls along the same points. It appears that I'm only affecting how the data is passed to Photoshop. As far as Photoshop is concerned the 194 point on my Silverfast histogram, is now the 255 point on the Photoshop histogram. Right?

I guess what I'm asking is, "Does Photoshop get passed a more quality image, if you first make adjustments in Silverfast"? I know Photoshop receives a more corrected image. But couldn't the adjustments bave just as easily have been made in Photoshop? Or does making the adjustments in Silverfast, and then scanning, make for a better image? (better meaning more data to work with).

By the way, if I set the highlights threshold to 20, and use auto adjust, it puts the highlight slider at 174. But I have to pull the highlight slider to about 136 to make the whites appear as they do on the light table. There are some specular highlights on the mast and sail. I suppose I'm losing a lot of the data my setting it to 136. Burning out the specular highlights. When I was working on the slide in Photoshop, prior to all the above, I did have to select the hull of the boat, and do a level's adjustment layer, to adjust the white, so I wouldn't burn out the sail. I can achive some of the same results my using the gradation curves in Silverfast.

I guess the slide has a lot more contrast than appears to the eye. I guess my best bet is to use auto adjust to set the highlight point at 194, (or do it manually), and scan into Photoshop at that point. Then I can use a mask to protect the sail, and then brighten up the rest of the image with levels. That way I get the whites without burning out the highlights on the sail and mast.

[ianders1]

Ronnie,

You're both right and wrong. The scanner IS only capable of so much data and dynamic range, and Silverfast does not do anything physically to the scanner. It DOES change how that data is analyzed.

The data from the scanner can be processed in many ways - brightness, contrast, white and black points, color changes, sharpening, etc., etc. If you take the raw scan into PhotoShop, yes, you will be able to achieve the same changes, and possibly with more control. However, unless you are meticulous and using layer masks for every change, you will be losing image data with each change. Silverfast allows you to make all of these adjustments at once to the raw scanner data, so you start out with the purest and cleanest scan possible.

As you use Silverfast, and learn its features, you'll find yourself spending less and less time in PhotoShop. With Epson TWAIN Pro, I found I was spending about an hour carefully cleaning and correcting each scan. Now, I spend about five minutes prescanning, adjusting, and scanning the image, and then about ten minutes cleaning up the image in PhotoShop. This is what makes Silverfast worth it for me.

As for your particular sailboat image, you're right in setting the white point slider to account for the specular highlights. As for the example image I was talking about here it is:

(please forgive the high level of compression - I wanted it to load fast)

<img src="http://www.webdextrous.com/test/hyper1.jpg" width="236" height="296">

This is a raw scan of the print.

<img src="http://www.webdextrous.com/test/hyper2.jpg" width="236" height="296">

Here is the scan from the negative - the only thing I did in PhotoShop was paint out the shadows on his leg. This is the power of Silverfast and NegaFix.

-Ian A.

<font size=-1>[ This Message was edited by: ianders1 on 2001-10-13 10:27 ]</font>

[Tomaz Klinc]

Now here's the sad news: US$ 1 billion deep in the debt hole dug by the digital revolution, Polaroid filed for Chap. 11 bankruptcy protection last Friday. With it's stock almost worthless, the one-time symbol of high tech is not expected to survive.