Re: filmscanners: What causes this and is there any easy solution ?
Oops! Sorry about the confusing nomenclature. What I meant to express was that at sufficiently small angles, the 'side opposite' leg is effectively the far leg of a 90deg triangle (its an assumption but its pretty darn close). That means that you can apply the basic geometric rule of Side Opposite Tan(theta) = Side Adjacent. So for the average human eye (something like 90% of the population - with folks like Chuck Yeager being the radical exceptions, which largely explains his survival and success in Korea), the limit of resolution occurs when Theta is 1/60 of a degree of arc - which as you correctly pointed out is 1 minute of arc. At 500dpi, the inter-line spacing is 0.002inches. So this means that we can solve for Side Adjacent Side Opposite 0.002inches Side Adjacent = -- = --- = 6.875 Inches. Tan(1/60deg) 0.000291 This is a very well researched formulae - the Society for Information Display has lots more info on the mathematical models of how the eye works - fairly precise models too. So if we go from this equation, we know that if we look at the original film at a big enough enlargement (say 8x10), then we will be able to see any artifacts in the film of the kind being described, if we look more closely than 6.5. Since folks have been doing this in the darkroom for decades - using grain focussers and the like, and these artifacts have not been observered, it is reasonable to conclude that they don't exist except in the opto-electronics of the scanner process - Original Message - From: Arthur Entlich [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Wednesday, May 16, 2001 1:41 PM Subject: Re: filmscanners: What causes this and is there any easy solution ? Karl Schulmeisters wrote: I don't think this is the case. Otherwise you would have seen this phenomenon from enlargements made from transparencies long ago. Consider this, the human eye can resolve about 1 minute of 1 degree of arc (1/60 of a degree) in the horizontal plane (most sensitive - less in the vertical) So take a 35mm slide (which is about 1 tall) and enlarge it full frame to 8x10 that's an enlargement factor of about 8. So a 4000dpi scan of a 35mm slide is about the same as a 500dpi scan of an 8x10. So plugging 1/500th of an inch into the formula X = TanTheta Y where X is the lines/inch and Y is the eye's distance from the 8x10 enlargement, we get ..002 = Tan(1/60deg) Y or Y (max eye resolution) = .002/.000291 = 6.875. If human eyes actually functioned based upon a mathematical formula, you'd have it all solved! ;-) Just so some people unfamiliar with the nomenclature won't get too confused, the symbol [] can be used to both indicate inches as a linear measurement and minutes (1/60th of one degree) of an arc. Your first reference (1) is one inch, your second reference (6.875) is 6.875 minutes of a degree of an arc. The big problem we all face in analyzing the artifacts or other information we see in a scan is that we are looking at the scan in a translated format, either via a monitor (via a software package) or a print (usually inkjet for most people, via a print driver program) each of which add other confounding factors to what is being provided by the scanner. SInce none of these are purely optical in nature, we're in uncharted waters, with no sextant to get us ashore, or is that a-sure? ;-) Art IOW, anyone who has looked at a full frame 8x10 enlargement of a 35mm image, closer than 7 is in essence 'scanning' the 35mm slide at greater than 4000dpi. And since we don't have reports of folks seeing this sort of difference in enlargements at this level (remmember folks use grain focussers to get even higher resolution during focussing of an enlargement) - I don't think there is any 'real information' there.
Re: filmscanners: What causes this and is there any easy solution ?
Karl Schulmeisters wrote: I don't think this is the case. Otherwise you would have seen this phenomenon from enlargements made from transparencies long ago. Consider this, the human eye can resolve about 1 minute of 1 degree of arc (1/60 of a degree) in the horizontal plane (most sensitive - less in the vertical) So take a 35mm slide (which is about 1 tall) and enlarge it full frame to 8x10 that's an enlargement factor of about 8. So a 4000dpi scan of a 35mm slide is about the same as a 500dpi scan of an 8x10. So plugging 1/500th of an inch into the formula X = TanTheta Y where X is the lines/inch and Y is the eye's distance from the 8x10 enlargement, we get ..002 = Tan(1/60deg) Y or Y (max eye resolution) = .002/.000291 = 6.875. If human eyes actually functioned based upon a mathematical formula, you'd have it all solved! ;-) Just so some people unfamiliar with the nomenclature won't get too confused, the symbol [] can be used to both indicate inches as a linear measurement and minutes (1/60th of one degree) of an arc. Your first reference (1) is one inch, your second reference (6.875) is 6.875 minutes of a degree of an arc. The big problem we all face in analyzing the artifacts or other information we see in a scan is that we are looking at the scan in a translated format, either via a monitor (via a software package) or a print (usually inkjet for most people, via a print driver program) each of which add other confounding factors to what is being provided by the scanner. SInce none of these are purely optical in nature, we're in uncharted waters, with no sextant to get us ashore, or is that a-sure? ;-) Art IOW, anyone who has looked at a full frame 8x10 enlargement of a 35mm image, closer than 7 is in essence 'scanning' the 35mm slide at greater than 4000dpi. And since we don't have reports of folks seeing this sort of difference in enlargements at this level (remmember folks use grain focussers to get even higher resolution during focussing of an enlargement) - I don't think there is any 'real information' there.
Re: filmscanners: What causes this and is there any easy solution ?
My experience as well. The lenses Kodak provides for their projectors are very forgiving should we say. My Navitar Gold lenses certainly define what I'm looking at. Art John Matturri wrote: Haven't been following this thread all that closely so this may have been covered. But what lens are you using for your projections? If it is a lens supplied with most projectors the poor quality might be a masking factor. The difference between one of these lenses and a Buhl or similar projection lens is pretty substantial.
Re: filmscanners: What causes this and is there any easy solution ?
The projector you have is typical of many of the time period, but I'm not sure what that time period is. I'm guessing late 1930's to mid 1950's. Some have a metal plate with patent numbers and dates on them if you look carefully. I used to be able to pick them up for $5 at Goodwill. They usually use either a backlight or metal straight line slide tray, or use none and you had to do a left hand right hand manual feeding via the contraption that fed the slides. They usually had no fan, just a black baffle at the top, if that, going to venting holes) so the bulb would heat up the thing to a very high level, making it dangerous to touch. I'm not so sure it was good for the slides either, although some used a heat absorbing glass between the lamp and the condenser lens. I imagine if you keep it long enough it will become a true collectors item, as I'm sure many have now reached the landfill. I finally dismantled several of mine and kept the lenses and condensers and other interesting parts. I just ran out of room for them. I guess with people like me, the value of yours will go up ;-) Those older lenses were, as you mention, often better than the current ones provided with most projectors. Some were even German made. Art Steve Greenbank wrote: As mentioned in a previous message the projector does display the grain, but there is so little in Velvia that at 40x60 you still have to look hard and get within 16 inches to see it. Some slides like early Fujichrome 400 the grain is obvious from 15 feet. The projector is a relic made entirely of steel and cast iron! It's probably worth many times it's original purchase value. It was quite old when it was given to my Dad. He had it for around 20 years before I appropriated it by stealth, as a poor student, 20 years ago. It was made by Aldis. The lens is an Aldis Star Anastigmat 100mm. I have never thought it was stunning, but it was better than the modern alternatives I have seen. The one thing that did worry me was it runs extremely hot (you can only touch the body for a brief moment before burning). But the slide carrier and the lens are on steel rails that allow you to move the slide about an inch from the body and in this position the slides only get slightly warm and I certainly don't see the slide adjust focus as the film bends in the heat- something that I have seen quite often on modern projectors. Steve PS Can anyone date the projector ? It has a gun metal finish. - Original Message - From: Arthur Entlich [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Sunday, May 13, 2001 9:55 AM Subject: Re: filmscanners: What causes this and is there any easy solution ? My experience as well. The lenses Kodak provides for their projectors are very forgiving should we say. My Navitar Gold lenses certainly define what I'm looking at. Art John Matturri wrote: Haven't been following this thread all that closely so this may have been covered. But what lens are you using for your projections? If it is a lens supplied with most projectors the poor quality might be a masking factor. The difference between one of these lenses and a Buhl or similar projection lens is pretty substantial.
Re: filmscanners: What causes this and is there any easy solution ?
- Original Message - From: Laurie Solomon [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Friday, May 11, 2001 5:13 PM Subject: RE: filmscanners: What causes this and is there any easy solution ? As a preface, when you project the slide much of that grain is masked by the surface texture of the screen you are projecting on as well as by the distance you need to use to project to those projection sizes as well as to view the projected image; but the grain is probably still there just as it is in the scanned image ( this can be determined by looking at the transparency under a high powered loupe). When you scan at 4000 dpi, you are probably both picking up the grain as well as any other noise and exaggerating it so as to make it more sharply defined and apparent. So the projection effectively helps mask the grain what a happy coincidence. The point about the distance may be the main reason. In a normal room you switch on the projector (with no slide if you have a relic like me) and suddenly realise that you have dust floating everywhere. Over a longer distance there will be more dust that will effectively randomly filter the smallest details i.e. the grain. I wonder if you used the screen in a chip FAB unit (exceptionally clean environment) whether the grain would be more apparent. Why are you scanning at an optical 4000 dpi? Could you scan at a lower optical resolution if necessary? Lower sampling rates lead to higher noise to signal ratios. Whilst resampling down from 4000dpi will reduce noise to signal ratios. I am pretty certain that it is always best to scan at best optical and then resample down if you require a lower resolution. While for 35mm slides and negatives 4000 dpi optical resolutions may be good if you are going to engage in extreme enlargement and/or cropping, they may not be required ( and even be problematic in the case of some films and images) for prints 8x10 and under. I am hoping to archive the pictures in a form that will allow any one to be selected at random to be output at any size that I may require at that time. Perhaps I'm being a bit over ambitious, but I don't see a lot of point in archiving them digitally if I can still get better prints from the fading original. I have heard that one sometimes can scan materials that generate the sorts of problems that you are experiencing at lower resolutions and save them in Genuine Fractals' lossless mode to a .stn file, which upon opening can be both resized to almost any size as well as upsampled with the added bonus of frequently smoothing out the sharpness of the grain presentation being displayed via its use of fractal and wavelet technologies. I have not tried it for that purpose (e.g., to smooth out the sharp appearance of grain structure displays); but if you are having the problem it might be worth a try. None the less, I would reduce the scan resolutions and see how low you need to go to eliminate the problem versus the minimum resolution you need to output the portion of the image that you want at the size you want. I did try this by resampling a 4000dpi to 2000dpi and 1333dpi and then resizing back (without GF), but you have to reduce the pixel count too much and you are better off blurring the original. GF would have produced marginally better results, but in my experiene GF is slightly better in the 2x-3x range not a miracle worker so I still think a slight blurring would be better. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Steve Greenbank Sent: Friday, May 11, 2001 6:15 AM To: [EMAIL PROTECTED] Subject: filmscanners: What causes this and is there any easy solution ? Today I'm going for the dual prize of most boring picture (see attachment) and most dumb question ever on the list. Mark asked me about a problem in the background of some pictures http://www.grafphoto.com/grain.html The problem is that my sample (a bit of sky) from a slide projects with perfect continuous tones at any size even 40 inch by 60 inch and it still looks reasonably sharp (within reason) but yet when I scan it at 4000dpi I get a grainy effect that will show up in an A3 print and a soft image in general. The problem often gets worse with sharpening . I have found that a unsharp mask threshold 9+ usually avoids sharpening the graininess. Alternatively a gaussian blur removes it but if you do this to the whole image you end up with an even more soft image but on the plus side you can sharpen it more aggressively and use a threshold of 3-4 which means much more gets sharpened. Obviously carefully selecting the sky/problem area and blurring that separately is probably the best option but it takes ages to do this accurately and you still may get noise problems elsewhere. Am I right to assume the noise is grain, CCD noise and chemical faults on the film ? Does every see this noise ? Should I see less with SS4000/A4000 scanner
Re: filmscanners: What causes this and is there any easy solution ?
Lynn said Howcome Polaroid users aren't seeing it? Or are they just not talking about it? Mines an Artixscan 4000T a (I'm told) SS4000 apart from the box and the software. You've seen my section of sky I don't know if its any better or worse than anyone elses, but it is definitely there. Incidentally I tried something suggested by Lynn (off list) involving A channel of LAB mode. A gaussian blur 1.0 followed by unsharp mask 200%,radius 1, threshold 1 and most of it was gone and the sharpness was retained. Later I will look in to this more and check for flaws and try different blurs and unsharp mask. Steve
Re: filmscanners: What causes this and is there any easy solution ?
Be sure that you are using an *optical* mouse or trackball - it will track much more smoothly.. Maris - Original Message - From: Steve Greenbank [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Saturday, May 12, 2001 5:05 AM Subject: Re: filmscanners: What causes this and is there any easy solution ? | I'll try this and see how it compares with gaussian blur. I was hoping | someone would have a solution that didn't involve carefully selecting | sections of a 20Mpixel image. It takes ages to get it right and I wish I had | a bigger monitor there just isn't enough room for the picture on my 17 inch | screen.Sadly there isn't enough room in the house for a significantly bigger | screen. | | Maybe, with practice I will be able to select sections better. Has anyone | tried adjusting their mouse movement settings (slow it down,reduce | accelleration) to make this easier ? | | Steve | | - Original Message - | From: Lynn Allen [EMAIL PROTECTED] | To: [EMAIL PROTECTED] | Sent: Saturday, May 12, 2001 1:00 AM | Subject: RE: filmscanners: What causes this and is there any easy solution ? | | | The solution looks so easy that I probably don't understand the problem | completely. :-) There are two quick ways you can do corrections: | 1) make two scans the same size in Vuescan; one normally, the second with | a | slight positive offset of manual focus (about +1 to +1.5). The second scan | will have corrected much if not all of the g-a, and the subject will be | a | little blurred--but surprisingly little (you might even decide to stay | with | that one, unless you're doing large blow-ups). | 2) load the first scan into Photoshop or your favorite image processor. | Select All and copy it. Then load the second frame in (it's OK to delete | the first one without saving, since you have a copy). Paste the copy over | the second, blurry copy, and Erase the sky from the top layer down to the | blurred layer. | | If you can get a Selector to work, like the Magic Wand for example to | select | just the sky portions (I almost never can--I think the wand is | over-rated), | it's even simpler--select the sky only, and have-at-it with any or all of | the blur filters. :-) | | Another way is to use Channels (if they're available in your programs) | either to select and copy a mask, or--as I'd say in this case--to isolate | the redish pixels in the sky and eliminate them. | | | |
Re: filmscanners: What causes this and is there any easy solution ?
Even better might be a wacom (or other) tablet, which gives the additional benefit of pressure sensitivity. Holding a pen seems much more natural than a mouse for fine movements and raising the pen up and down is much better than clicking the mouse for cloning. Beyond all this I'm not subject to the backaches that used to come from extended photoshop use. With limited space even a 4x5 tablet works well. A better more expensive than a mouse but I think worth it. John M. Maris V. Lidaka, Sr. wrote: Be sure that you are using an *optical* mouse or trackball - it will track much more smoothly.. | Maybe, with practice I will be able to select sections better. Has anyone | tried adjusting their mouse movement settings (slow it down,reduce | accelleration) to make this easier ? | | Steve |
Re: filmscanners: What causes this and is there any easy solution ?
While there maybe some merit to your comments about dust in the air masking flaws in the slide being projected, I had the actual surface texture of the projection screen in mind as well as the actual viewing distance independent of any dust. Laurie Haven't been following this thread all that closely so this may have been covered. But what lens are you using for your projections? If it is a lens supplied with most projectors the poor quality might be a masking factor. The difference between one of these lenses and a Buhl or similar projection lens is pretty substantial.
Re: filmscanners: What causes this and is there any easy solution ?
Anything USB will track better because of the higher sampling rate. Unfortunately the MS USB mouse I bought didn't like the KT133 VIA chipset on the motherboard. This is a common problem with Via chipsets see: http://www.usbman.com . When I first installed the motherboard I couldn't use USB at all with my Epson 1270 and the USB mouse keyboard caused periodic crashes. Eventually I gave up on the mouse and keyboard but I managed to persuade the printer to work. It's not entirely Vias fault though has my Casio camera has had absolute zero problems from day 1. If you have a PS/2 mouse, AT YOUR OWN RISK, you can overclock the sampling rate. Never heard of anyone permanently damaging anything with this procedure but I am sure it can be done (I have tried it before myself). If you did permanently damage the PS/2 port you would have to use a USB or serial port mouse - you have been warned. Steve - Original Message - From: Maris V. Lidaka, Sr. [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Saturday, May 12, 2001 5:22 PM Subject: Re: filmscanners: What causes this and is there any easy solution ? Be sure that you are using an *optical* mouse or trackball - it will track much more smoothly.. Maris - Original Message - From: Steve Greenbank [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Saturday, May 12, 2001 5:05 AM Subject: Re: filmscanners: What causes this and is there any easy solution ? | I'll try this and see how it compares with gaussian blur. I was hoping | someone would have a solution that didn't involve carefully selecting | sections of a 20Mpixel image. It takes ages to get it right and I wish I had | a bigger monitor there just isn't enough room for the picture on my 17 inch | screen.Sadly there isn't enough room in the house for a significantly bigger | screen. | | Maybe, with practice I will be able to select sections better. Has anyone | tried adjusting their mouse movement settings (slow it down,reduce | accelleration) to make this easier ? | | Steve | | - Original Message - | From: Lynn Allen [EMAIL PROTECTED] | To: [EMAIL PROTECTED] | Sent: Saturday, May 12, 2001 1:00 AM | Subject: RE: filmscanners: What causes this and is there any easy solution ? | | | The solution looks so easy that I probably don't understand the problem | completely. :-) There are two quick ways you can do corrections: | 1) make two scans the same size in Vuescan; one normally, the second with | a | slight positive offset of manual focus (about +1 to +1.5). The second scan | will have corrected much if not all of the g-a, and the subject will be | a | little blurred--but surprisingly little (you might even decide to stay | with | that one, unless you're doing large blow-ups). | 2) load the first scan into Photoshop or your favorite image processor. | Select All and copy it. Then load the second frame in (it's OK to delete | the first one without saving, since you have a copy). Paste the copy over | the second, blurry copy, and Erase the sky from the top layer down to the | blurred layer. | | If you can get a Selector to work, like the Magic Wand for example to | select | just the sky portions (I almost never can--I think the wand is | over-rated), | it's even simpler--select the sky only, and have-at-it with any or all of | the blur filters. :-) | | Another way is to use Channels (if they're available in your programs) | either to select and copy a mask, or--as I'd say in this case--to isolate | the redish pixels in the sky and eliminate them. | | | |
Re: filmscanners: What causes this and is there any easy solution ?
So the projection effectively helps mask the grain what a happy coincidence While there maybe some merit to your comments about dust in the air masking flaws in the slide being projected, I had the actual surface texture of the projection screen in mind as well as the actual viewing distance independent of any dust. The further away from the screen you view the image the less likely you are to see things like grain in that like a Surrat painting your eyes tend to blend the individual particles of grain into a single continuous tone structure even though under a loupe or standing up close you will still see theindividual grains. I thought I had covered this with some sort of statement like even when viewed quite close-up, but I must have rephrased this and removed it before I posted the message. Anyway I just tried it 40x60 inch projected onto plain white paper. With Velvia (circa 1990) (I used the slide from which the original sample of blue sky was made). I have to get within 16 inches to see it at all and even then it is so faint you might miss it if you weren't looking for it. Even from 3-4 inches it is minor. I then tried some early Fujichrome 400 (circa 1985) and you can see the grain easily from 15 feet on some slides. I can't wait to try scanning some of these! As for screen texture, most screens have a pebbled or/and rectilinear surface intended to gather and concentrate light so as to make them brighter (they are not smooth surfaces without any texture); this surface texture also tends to break up individual noise and grain patterns so as to mask the grain structure of what is being projected unless it is really very graining so as to have the appearance of an old newspaper 65 line screen halftone. I hadn't considered this and nor did I fetch my screen when I tried the slides tonight. But I can see that how this would work. Lower sampling rates lead to higher noise to signal ratios. I think there is probably a point at which there is NO PERCEIVABLE decrease in the signal to noise rations and further increased optical resolutions are of little practical point except to permit increases in output sizes while still maintaining a reasonably high quality non-interpolated resolution or to permit cropping and enlarging of small portions of the original while maintaining reasonably high quality non-interpolated resolutions. Most monitors cannot use resolutions over 100 dpi and most printers cannot use resolutions over 300 dpi. Since the less noise you have the more apparent the display of grain will be, it may be a good thing to compromise and allow some noise to be introduced in order to tone down the sharp appearance of grain structure. To some extent a little noise may help. Indeed some noise is sometimes added deliberately in some signal processing techniques. My sketchy understanding of digital signal processing tells me that you require 2x (a few experts insist 4x is better[just], but for the rest of this post I'm going to use 2x) the final output sampling rate to achieve an almost totally accurate output. Hence CD's sample at 44KHz to achieve accurate sound up to 22KHz. I think the 300dpi used in the best printers comes from the human eye being unable to see more than 150dpi so you need 2x150 or 300dpi to achieve the desired result. So for a 12x18 you need 3600x5400 which is just short of 4000dpi. I have seen Velvia printed well at 20x30 so I believe a scan of at least 6000x9000 (6000dpi) would be better still. In the case of the Fujichrome 400 you are probably right that 4000dpi and possibly 2000dpi is a waste of time. Something to try on a rainy day and there's plenty of them in the UK :-) Whilst resampling down from 4000dpi will reduce noise to signal ratios. I am pretty certain that it is always best to scan at best optical and then resample down if you require a lower resolution. Although resampling down from 4000 dpi may or may not reduce the appearance of noise but not the actual existence of noise, b it also will result in the loss of informational data that cannot be gained back later and the possible production of other troublesome artifacts. The reduction in resolution that does reduce signal to noise rations is not via the use of resampling but via the actual reduction in optical resolutions being used from 4000 dpi to some optical resolution under that if your scanner has an optical resolution of 4000 dpi. If it has a maximum optical resolution of less than 4000 dpi than any scan over that is an interpolated scan that has been upsampled by the scanner software and not an optical resolution, while any scan less than the maximum optical scan resolution is an optical resolution. Up sampling should generally be avoided if at all possible as it will always lead to some nasty artefacts. I tried it in the hope the artefacts introduced would be less noticeable than the noise removed in the down sampling. While it is true that
RE: filmscanners: What causes this and is there any easy solution ?
As a preface, when you project the slide much of that grain is masked by the surface texture of the screen you are projecting on as well as by the distance you need to use to project to those projection sizes as well as to view the projected image; but the grain is probably still there just as it is in the scanned image ( this can be determined by looking at the transparency under a high powered loupe). When you scan at 4000 dpi, you are probably both picking up the grain as well as any other noise and exaggerating it so as to make it more sharply defined and apparent. Why are you scanning at an optical 4000 dpi? Could you scan at a lower optical resolution if necessary? While for 35mm slides and negatives 4000 dpi optical resolutions may be good if you are going to engage in extreme enlargement and/or cropping, they may not be required ( and even be problematic in the case of some films and images) for prints 8x10 and under. I have heard that one sometimes can scan materials that generate the sorts of problems that you are experiencing at lower resolutions and save them in Genuine Fractals' lossless mode to a .stn file, which upon opening can be both resized to almost any size as well as upsampled with the added bonus of frequently smoothing out the sharpness of the grain presentation being displayed via its use of fractal and wavelet technologies. I have not tried it for that purpose (e.g., to smooth out the sharp appearance of grain structure displays); but if you are having the problem it might be worth a try. None the less, I would reduce the scan resolutions and see how low you need to go to eliminate the problem versus the minimum resolution you need to output the portion of the image that you want at the size you want. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Steve Greenbank Sent: Friday, May 11, 2001 6:15 AM To: [EMAIL PROTECTED] Subject: filmscanners: What causes this and is there any easy solution ? Today I'm going for the dual prize of most boring picture (see attachment) and most dumb question ever on the list. Mark asked me about a problem in the background of some pictures http://www.grafphoto.com/grain.html The problem is that my sample (a bit of sky) from a slide projects with perfect continuous tones at any size even 40 inch by 60 inch and it still looks reasonably sharp (within reason) but yet when I scan it at 4000dpi I get a grainy effect that will show up in an A3 print and a soft image in general. The problem often gets worse with sharpening . I have found that a unsharp mask threshold 9+ usually avoids sharpening the graininess. Alternatively a gaussian blur removes it but if you do this to the whole image you end up with an even more soft image but on the plus side you can sharpen it more aggressively and use a threshold of 3-4 which means much more gets sharpened. Obviously carefully selecting the sky/problem area and blurring that separately is probably the best option but it takes ages to do this accurately and you still may get noise problems elsewhere. Am I right to assume the noise is grain, CCD noise and chemical faults on the film ? Does every see this noise ? Should I see less with SS4000/A4000 scanner (is mine and Mark's a bit duff) ? And what do you do about it ? Steve
Re: filmscanners: What causes this and is there any easy solution ?
Hi Steve, I just took a look at your mottled sky within photoshop. I enlarged it, I sharpened it, I sent it through a spectral analysis, I looked for encrypted messages or codes, I ... ;-) And, you are absolutely right, it is the dullest picture I've ever seen on this list. ;-) OK, enough attempt at humor. I am beginning to develop a theory about these anomalies that appear in scanned images. Is it possible that the CCDs are recording information outside of the realm of human vision? What I mean is could we be seeing artifacts of either IR or UV (or other spectrums) information which are being translated into the visible spectrum? When people speak about these oddities, it is often a whole roll exhibiting the defect where another roll of the same film type doesn't. Could differences in manufacturing, processing or other chemical or structural differences in the film (say even variations in the thickness of some otherwise invisible film layers (remnants of the color filters within the film, gelatin layers, even film base) which for all normal viewing purposes would make no difference at all in the image quality, even at high magnification, be captured via the CCD sensor process, and then translated to visible artifacts? I imagine these things may never be tested for in the manufacturing or developing processes of the film. Does anyone know if CCDs are tested for sensitivity outside of the range of the human perceptible spectrum? I mean, bees see in UV, and their view of the world is vastly different from our own. Flowers with pollen and nectar send beacons to bees which get lost for us in the mix of brilliant colors and fancy shapes... then again, flowers aren't much interested in having me be attracted to their nectar or pollen. Phil Lippencott: does any of your equipment allow for testing CCD sensitivity for the IR or UV spectrum (or even higher or lower than that?)? So, Steve, that's my dumb answer to your exceedingly dumb question... ;-) I think we might all be missing something here, simply because it is outside of our normally responsive reality. Comments, criticisms, supporting or other views? Art Steve Greenbank wrote: Today I'm going for the dual prize of most boring picture (see attachment) and most dumb question ever on the list. Mark asked me about a problem in the background of some pictures http://www.grafphoto.com/grain.html The problem is that my sample (a bit of sky) from a slide projects with perfect continuous tones at any size even 40 inch by 60 inch and it still looks reasonably sharp (within reason) but yet when I scan it at 4000dpi I get a grainy effect that will show up in an A3 print and a soft image in general. The problem often gets worse with sharpening . I have found that a unsharp mask threshold 9+ usually avoids sharpening the graininess. Alternatively a gaussian blur removes it but if you do this to the whole image you end up with an even more soft image but on the plus side you can sharpen it more aggressively and use a threshold of 3-4 which means much more gets sharpened. Obviously carefully selecting the sky/problem area and blurring that separately is probably the best option but it takes ages to do this accurately and you still may get noise problems elsewhere. Am I right to assume the noise is grain, CCD noise and chemical faults on the film ? Does every see this noise ? Should I see less with SS4000/A4000 scanner (is mine and Mark's a bit duff) ? And what do you do about it ? Steve
