[filmscanners] Re: Halo Effect
Hello All, I have a Polaroid Sprintscan 4000 (not the Plus version) and am using Vuescan. When I scan a slide (either Kodachrome or Provia/35mm), the white areas (such as a building illuminated by the sun; or pages of an open book) in the scan will exhibit a halo effect. This appears as a kind of a whitish or even greenish glow surrounding the white object in the scan. My questions are: Is anyone else seeing this or getting this effect on their scans? Is this something gone wrong with the scanner? Is it something that different scan settings in Vuescan can correct? Using Knockout 2.0 I can correct most if not all of the halo or after glow. However, if someone can set me straight regarding how to solve the problem before the scan, I would be most appreciative. Thanks Robert DeCandido NYC Unsubscribe by mail to [EMAIL PROTECTED], with 'unsubscribe filmscanners' or 'unsubscribe filmscanners_digest' (as appropriate) in the message title or body
[filmscanners] Re: Halo Effect
How old is the scanner? Dust in scanners will create this effect. I went through a hundred relatively bad scans until I realized that what seemed like slow deterioration in the scan was actually accumulating dust. It can happen so slowly that you don't realize it's getting worse, because you forget how clean the scans originally were. - Original Message - From: Robert DeCandido, PhD [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Saturday, August 17, 2002 12:46 Subject: [filmscanners] Re: Halo Effect Hello All, I have a Polaroid Sprintscan 4000 (not the Plus version) and am using Vuescan. When I scan a slide (either Kodachrome or Provia/35mm), the white areas (such as a building illuminated by the sun; or pages of an open book) in the scan will exhibit a halo effect. This appears as a kind of a whitish or even greenish glow surrounding the white object in the scan. My questions are: Is anyone else seeing this or getting this effect on their scans? Is this something gone wrong with the scanner? Is it something that different scan settings in Vuescan can correct? Using Knockout 2.0 I can correct most if not all of the halo or after glow. However, if someone can set me straight regarding how to solve the problem before the scan, I would be most appreciative. Thanks Robert DeCandido NYC Unsubscribe by mail to [EMAIL PROTECTED], with 'unsubscribe filmscanners' or 'unsubscribe filmscanners_digest' (as appropriate) in the message title or body Unsubscribe by mail to [EMAIL PROTECTED], with 'unsubscribe filmscanners' or 'unsubscribe filmscanners_digest' (as appropriate) in the message title or body
[filmscanners] Re: Halo Effect
Robert DeCandido, PhD wrote: I have a Polaroid Sprintscan 4000 (not the Plus version) and am using Vuescan. When I scan a slide (either Kodachrome or Provia/35mm), the white areas (such as a building illuminated by the sun; or pages of an open book) in the scan will exhibit a halo effect. This appears as a kind of a whitish or even greenish glow surrounding the white object in the scan. My questions are: Is anyone else seeing this or getting this effect on their scans? [Sorry if you get two copies of this. The first one was probably sent from an address not registered and I don't think it went through] Hi, Robert, I have had this effect on three different units: A Nikon LS-30, a Nikon LS-40 and a Minolta Dimage Scan Elite II. IOW, this effect seems inherent in slide scanning and not dependent on the unit in use. I have never seen that effect when scanning negatives, nor have I found these halos to be real ones on the slides in question (checked under a microscope). I have two possible explanations for that: 1. Sensor crosstalk - the brightly lit areas of the CCD may leak some of their light into the shady areas, and there ya go. Slide film has a much higher contrast ratio than negative film which would mean the decrease of light intensity from bright to dark areas on a slide would exceed the respective value for a negative by miles (10 up to 100 times), most likely making the effect much more obvious with a slide than with a neg. 2. Film surface. Slides have a texture on their surface, following the outlines of the subject that is on the slide. I am positive that the thickness of the dye layers in these areas varies with this texture. Jumps in dye layer thickness are likely to cause diffraction of the light coming from the light source to the CCD, diverting light that should hit the bright areas of the CCD to the dark ones. Not sure if, and, if yes, which of those explanations apply. I haven't found anything that would help out, apart from avoiding slides for high contrast situations. Since I have my D60, all problems of that sort are gone anyway ;-) Greetings from Germany - Ralf -- My animal photo page on the WWW: http://schmode.net Best of portfolio: http://www2.fotocommunity.de/pc/pc.php4?mypics=254 Find my PGP keys (RSA and DSS/DH) on PGP key servers (use TrustCenter certified keys only) Unsubscribe by mail to [EMAIL PROTECTED], with 'unsubscribe filmscanners' or 'unsubscribe filmscanners_digest' (as appropriate) in the message title or body
[filmscanners] Re: Halo Effect
1. Sensor crosstalk - the brightly lit areas of the CCD may leak some of their light into the shady areas, and there ya go. Slide film has a much Does the halo only appear along one direction, or evenly in all directions around the highlight? Since film scanners only use one CCD line, this leaking can obviously only take place in on direction. 2. Film surface. Slides have a texture on their surface, following the outlines of the subject that is on the slide. I am positive that the thickness of the dye layers in these areas varies with this texture. Jumps in dye layer thickness are likely to cause diffraction of the The thickness has no more effect that the density variations. As long as the texture is thinner than the features of the picture (which is the case), it has no influence on diffraction. light coming from the light source to the CCD, diverting light that should hit the bright areas of the CCD to the dark ones. Not sure if, and, if yes, which of those explanations apply. I haven't found anything Then, however, you should also see a halo under the microscope or with a (condenser) enlarger, or even with a slide a projector. I think the problem is flare within the scanner. In the case of the Nikons at least, I'm sure it is caused by dust, because their optics are damn good. Andras === Major Andras e-mail: [EMAIL PROTECTED] www:http://andras.webhop.org/ === Unsubscribe by mail to [EMAIL PROTECTED], with 'unsubscribe filmscanners' or 'unsubscribe filmscanners_digest' (as appropriate) in the message title or body
[filmscanners] Re: Halo Effect
Major A wrote: Does the halo only appear along one direction, or evenly in all directions around the highlight? Since film scanners only use one CCD line, this leaking can obviously only take place in on direction. Hi, Major, yes, you're right. I remember the halos to be in each direction, meaning it can't possibly be sensor crosstalk. 2. Film surface. Slides have a texture on their surface, following the outlines of the subject that is on the slide. I am positive that the thickness of the dye layers in these areas varies with this texture. Jumps in dye layer thickness are likely to cause diffraction of the The thickness has no more effect that the density variations. As long as the texture is thinner than the features of the picture (which is the case), it has no influence on diffraction. I have seen Sensia slides which the texture could not only be *seen* but even *felt* on. I am not sure those are in any case thinner than the picture subject's outlines. Then, however, you should also see a halo under the microscope or with a (condenser) enlarger, or even with a slide a projector. Theoretically, I'd agree but I've seen slides under a microscope, scanned and in projection and the optical appearance was different for each type of visualization including features such as scratches, dirt, grain and halos. The method of illumination is different, so is the type of sensor (CCD, eye) being used. I think the problem is flare within the scanner. In the case of the Nikons at least, I'm sure it is caused by dust, because their optics are damn good. I have seen three new Minolta units and two new Nikon units showg only a marginal difference as to this issue. Flare may be a reason (though hard to believe), dust should be almost impossible to be blamed with brand new units. Greets - Ralf -- My animal photo page on the WWW: http://schmode.net Best of portfolio: http://www2.fotocommunity.de/pc/pc.php4?mypics=254 Find my PGP keys (RSA and DSS/DH) on PGP key servers (use TrustCenter certified keys only) Unsubscribe by mail to [EMAIL PROTECTED], with 'unsubscribe filmscanners' or 'unsubscribe filmscanners_digest' (as appropriate) in the message title or body
[filmscanners] Re: Halo Effect
I can think of a few potential causes. One may be just the way you have the software set up in terms of gamma or contrast, however, this can also occur due to a dirty optical path, due to dust, smoke, or other household pollutants coating the lens, and mirrors or other optical surfaces within the scanner. The SS4000/+ is very open to the outside environment, and I keep the one I use under a static free plastic cover when not in use. There are no smokers here, and it is a good distance from any kitchen residue. Unfortunately, film scanners aren't easy to clean oneself in most cases, so if this is the case, you may need to have it professionally cleaned by Polaroid. I don't know what they charge. Art Robert DeCandido, PhD wrote: Hello All, I have a Polaroid Sprintscan 4000 (not the Plus version) and am using Vuescan. When I scan a slide (either Kodachrome or Provia/35mm), the white areas (such as a building illuminated by the sun; or pages of an open book) in the scan will exhibit a halo effect. This appears as a kind of a whitish or even greenish glow surrounding the white object in the scan. My questions are: Is anyone else seeing this or getting this effect on their scans? Is this something gone wrong with the scanner? Is it something that different scan settings in Vuescan can correct? Using Knockout 2.0 I can correct most if not all of the halo or after glow. However, if someone can set me straight regarding how to solve the problem before the scan, I would be most appreciative. Thanks Robert DeCandido NYC Unsubscribe by mail to [EMAIL PROTECTED], with 'unsubscribe filmscanners' or 'unsubscribe filmscanners_digest' (as appropriate) in the message title or body
