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áòèé÷ :: Filmscanners |
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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: filmscanners: Film Scanner Question Again
Rick, I'm not familiar with your scanner, but I'm going to pretend that I know what I'm talking about. So fasten your seat belt; this may be a bumpy ride. Another post indicated, if I read it correctly, that your scanner has a maximum optical resolution of 3200 ppi in one direction and 1600 ppi in another. As others have stated, it's almost always best to scan at the maximum optical resolution of the scanner. You can always throw away extra pixels later if you don't need them. So, in your case, it looks you should scan at 3200 ppi. The scanner is going to "pad" one scan axis (the one that can only scan at 1600 ppi optically) with some extra pixels by making an educated guess (interpolating) at what they should be, but at least you'll get all of the data out of the 3200 ppi axis. My guess is that, of the 3 scanner parameters you need to set, "DPI" is the one that should be set to 3200. So that leaves the "Source Size" and "Target Size" parameters. I'd set both to the size of the film being scanned, such as 1x1.5 inches for a 35 mm slide. With most scanners I'm familiar with, when you get ready to scan something, you first do a "prescan" and then adjust the sides of a crop box so that it includes only that part that you want to scan. After you've set the crop lines, then you do the actual scan and only that part that you selected with the crop lines gets scanned. In the process of setting the crop lines, I suspect that the "Source Size" will be automatically set for you. You have a fourth parameter you alluded to, that being "Scale." Set it to 100 per cent. I suspect that when you do that, it will cause the "Target Size" to automatically be set the value of the "Source Size." As I said before, I don't know what I'm talking about because I'm not familiar with your scanner, so none of what I'm telling you may be accurate. But a lot of scanners work the way I've explained and there is a lot of interaction between the three or four parameters. If your scanner doesn't allow for a prescan, then you'll have to set "Source Size" yourself. Set it just big enough so that all of your film gets scanned. In this case, you might very well have a larger than normal file because you had to scan in a lot of useless area around the film. It's not a problem. Simply use Photoshop (or whatever equivalent software you are using) to crop off the unnecessary stuff, and the file size will drop to a manageable size. So, in summary, scan at the highest optical resolution of your scanner (3200 ppi), set Source Size and Target Size equal to the film size being scanned, and set Scale to 100 per cent. Then, if you look at the image in Photoshop, you'll see that it is about 1x1.5 inches (for a 35 mm film scan) and has a resolution of 3200 ppi and has a pixel size of about 3200x4800 pixels. Do whatever you want to in Photoshop, then save a copy to your hard drive. Then, use Photoshop to resize the image before printing to, say 8x12 inches, and, at the same time, change the Photoshop resolution to one-eighth (because you increasing the size by a factor of eight) of its original 3200 ppi resolution, or 400 ppi. So now Photoshop has an image that's 8x12 inches, 400 ppi resolution, and still 3200x4800 pixels. (You haven't created, or thrown away, any pixels by resizing, which is usually a Good Thing.) As I mentioned in a previous post, you want to sent the printer at least 300 ppi data, so 400 ppi is more than enough for an 8x12. Boy, I hope I'm guessing correctly as to how your scanner works and that this is going to be of some help to you. Remember, you can always try different combinations of settings and look at the output from your printer to see what works and what doesn't. One final comment. Your scanner has a maximum resolution of 3200 ppi in only one axis. It's half that in the other. So, if you scan at 3200 ppi, one axis of the image is going to be half as sharp as its 3200 ppi resolution implies. We've said that you want at least 300 ppi to send to the printer, but since your image isn't as sharp along one axis as we've been assuming, you might want to send more than 300 ppi to the printer. How much more? Well, it won't be any more than 600 ppi since that's the value we'd use if both axes had optical resolutions of 1600 and we scanned at 3200. So the correct value is between 300 and 600 ppi. I did some fancy math involving root-mean-square and determine that you should send 474 ppi data to the printer when (and only when) you scan at 3200 ppi where one axis has a resolution of half that. This means that, for a 8x12 inch print from a 1x1.5 inch piece of film, the 400 ppi that we have available falls short of the 474 ppi that we would like to have. Don't worry about it. I doubt it'll make all that much difference. But it does indicate that an 8x12 from 35 mm film is a marginal situation for your scanner and you certainly wouldn't want to print anything much larger than that. Let us know if any of this helps. In a message dated 7/7/2001 6:43:09 PM Pacific Daylight Time, rickdecker@hawaii.rr.com writes: I have 3 parameters on my 1640SU scanner - "Source Size" , "Target Size"
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