On 4/2/21 6:56 PM, Kevin Parker via cctalk wrote: I'm definitely not an expert. But I have opinions. The thing that smacks me in the face is the difference in -- what I think is called -- the white balance. It may be that the white balance is /so/ /far/ /off/ for the sheet feeder that things can't compensate and you're into the realm of sensors interpreting noise differently between adjacent pixels. It's almost as if the different horizontal pixels have different levels of sensitivity or are being over driven such that they can't compensate. I really notice it on the right hand side of the black canted center window and the blue in the upper left window. It's noticeable in in the text fade out in the lower left window too. When I looked at the flat bed scan first, I didn't see anything wrong. Then I noticed the 2nd link. ;-) The only time that I've ever had anything scan weird, even remotely like your sheet feed example, is when the item to be scanned isn't /close/ /enough/ to the scanning surface. E.g. the middle spine / gutter (?terms?) of a book / magazine that I can't lay completely flat on the scanner. It sounds like the sheet feeder may be part of the lid and that it can be lifted / moved away from the scanning bed. As such, I'll suggest making sure that the lid / sheet feed scanner is properly closed and not gaping in any way. Based on how the flatbed example looks, I don't think that it's a dirt issue. Unless there is another piece of glass that is between the flatbed as part of the body of the sheet feeder that needs to be cleaned. That looks really good to me. Oy vey! Good luck. -- Grant. . . . unix || die

On 04/02/2021 07:56 PM, Kevin Parker via cctalk wrote: When in flatbed mode, there is probably a foam mat that presses the document firmly onto the glass plate, even if the page has a warp or curl to it. To prevent jamming, the sheet feeder probably leaves the page loose, and if warped or stiff, it won't press flat to the glass. There may be something you can adjust to get the page to be closer to the glass, but not so tight that it prevents the page from moving. That might be a delicate balance. But, I can sure see how a page that is several mm away from the glass could get reflections that wash out the details. There may be a damaged stop somewhere that sets the clearance between whatever conveys the page and the glass, or maybe even a missing belt or pad that holds the page close to the glass. The difference is QUITE obvious, almost making the sheet-fed scan worthless. Jon

Hi Kevin, Are you _sure_ the two modes use the same optical sensor? Often sheet feed systems use a different sensor somewhere along the paper path. I suspect they are not, given the odd colour pattering off the top edge of the paper, on the autofeed image. If those two images are definitely produced by the same sensor, through the same glass, then there are a few other possibilities: * A 'mode settings' problem. Scanners always have a bunch of modes, such as photo vs printed, sensitivity adjustment curve, gamma correction, etc. It may be your machine uses different settings for flatbed vs page feeder, and the page feeder settings are _way_off_. * Keeping the paper flat on the glass. Someone else pointed this out - maybe the sheet feed process uses rollers and the paper is bowing away from the glass in those two really bad wide streaks. But there are other problems too, because there are fine streaks as well. * Another thing scanners do, is calibrate the sensor using a standard white/black image bar, usually behind one end of the flatbed bezel. The sensor always has imperfections, but subtracting the observed calibration data results in a clean image. (Ideally, sometimes not.) Maybe your machine uses separate calibration datasets in the two modes, and the one for autofeed is rooted. Download a manual and read. There are defects in your 'good' flatbed image too - for eg the bleed-through of the orange lettering on the other side of the sheet. The way to correct that is to use a black, highly light absorbent backing sheet. Eg black velvet. But you probably can't do that on your scanner. This defect is typical of scans done by people with little discernment for image quality. They don't even notice. Then there are fundamental defects common to both images: * You've used PDF as the end format. As a result the image is stored in lossy JPG coding, and thus has typical JPG edge noise. PDF does not allow any sensible image coding scheme such as PNG. Just a few old ones: JPG (OK for photos, but awful for any image with fine detail and hard edges), TIFF (lossless but very inefficient), the horrible 'Fax mode' (B&W, in which the captured data is stored losslessly, but the capture process is horrifically lossy and destructive of image quality.) Plus another abortion called JBIG2. ( A patch tokenization scheme that is so bad it should be illegal.) * The originals are screened printing, where all tones are created by varying the size of saturated YMCB ink dots laid in a regular grid. To scan this kind of document adequately, you HAVE to scan at high enough resolution to resolve the edges of the tiny dots (the only way to avoid obnoxious moire patterning), then post-process the image to convert (blur) the screen grid dots to smooth colour shading (still at very high resolution) then scale the image to a desired final size. Then lastly change the image encoding to a suitable (lossless) form (eg one of the PNG modes) for sane file size. This is still unavoidably a manual page-by-page process if you want archival quality. And PDF flatly doesn't allow it. Once you realize this is so, you'll become very depressed about all the people who think they are 'saving worthy documents for posterity' by scanning them into PDF. Your images still contain remnants of the screening dots pattern, but messed up by JPG artefacting. Thus the file size is stupidly high due to all the superfluous and messy fine detail. Zoom right in to see it. Sorry to not be very helpfull, Guy At 11:56 AM 3/04/2021 +1100, you wrote: