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Scanning size percentage confussion

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  #1  
Old 09-08-2001, 07:35 PM
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Question Scanning size percentage confussion

Here's the question:
Say I'm scanning a 5x7 and because I may want to make larger prints someday, I scan it at a high resolution to avoid resampling. Do I also scan that image at a higher percentage then the actual size? Instead of scanning it at 400dpi at 100% (actual size) would I also make the scan size higher say 200% (twice the size) or higher if I want a poster some day.

My thought is, if I eventually make that 400dpi 5x7 into a 400dpi 8x10, I still wind up resampling don't I? There for if I think I may want a poster eventually shouldn't I scan it at a high percentage as well as high resolution?

It's just a thought I had that has been bugging me lately. Scanning math confuses me sometimes. OK most times.
DJ
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Old 09-08-2001, 07:58 PM
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If you start at a resolution, enlarge, and end up at that same resolution, resampling has to take place.

When you get down to it, "size" doesn't really exist, only the number of pixels. The number of pixels per inch you decide to print determines the size. If that size differs from what you actually have, then you must resample.
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Old 09-08-2001, 08:03 PM
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In that case what do you do for archival purposes? Do you scan the picture to be the biggest dimensions incase someone wants it printed bigger in the future?
DJ
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Old 09-08-2001, 08:05 PM
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Dj, It might be time for you to look closely at the file format plug-in Genuine fractals. What you want to do is exactly what this program excels at. You can make one scan at your usual resolution and by saving it in the Fractals proprietary format, you can then "shrink" or "enlarge" it upon opening to whatever size you desire. Because of the unique math involved in the fractals algorithm you avoid for the most part the usually encountered artifacts, image degradation etc. Tom
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Old 09-08-2001, 08:08 PM
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Do you use that? How easy is it to deal with? Sounds like a good idea if the cost isn't too high. Otherwise I keep scanning larger size and downscale as I have been doing. I will check it out. Thanks Tom.
DJ
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Old 09-08-2001, 08:21 PM
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It's very easy to use and I use it quite a bit. It aint cheap however, around $150 for the regular version and more for the one which has a few more bells and whistles like CMYK support and some other stuff which didnt look really necessary for me at least. Tom
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Old 09-08-2001, 08:27 PM
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I also recently found mention of a product called "S-spline" which looks like it might do a better job than GF - and it's less expensive. Unfortunately, I have no experience with either, so I can't give you any sort of review. But the product looks interesting from the examples shown on the website. Has anyone else heard of this - or even used it?

Jeanie
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Old 09-08-2001, 08:40 PM
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Interesting site. It sort of sounds like a variation of the bicubic algorithm perhaps similar to to the Lanczos type found in Picture Window Pro. Having heard nothing of S-spline until today, I really am in the dark about it but would perhaps be a tiny bit suspicious of the claims. The Fractal algorithm is a well known entity with a proven track record. As to the Lanczos type--it works but not that much better than bicubic, in my experience at least. Tom
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Old 09-08-2001, 08:48 PM
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Oops

I didn't address DJ's original question...

I think this page at scantips.com might be helpful for you. I think the guy tends to repeat himself a lot, but he does have some really good information. (I actually bought his book and am about a third of the way through it. I'll review it when I'm done reading it.)

As far as what I do. I scan as for as large a size as I think I (or a client) might want in the future. That usually means I scan a 4x6 print so that I could make an 8x10 (or 8x12) if I wanted to. But, I don't scan an 8x10 to be able to make a 16x20 (esp. not at 300dpi!)

What I've done in the past is scan at whatever the highest optical resolution of my scanner is (for the smaller prints) - then change the dpi using "image size" in Photoshop to get the size I want. I think I have a little more to learn about the "correct" way to resize though. According to scantips, scaling at the time of scanning (and leaving the resolution at 300dpi or whatever your preferred printing resolution is) produces the exact same results as not scaling the image size, but increasing the dpi. Well, don't know if that makes sense or not - read that page that I mentioned above and hopefully it will make more sense.

I think I've just confused the issue...

Jeanie

Last edited by jeaniesa; 09-08-2001 at 08:51 PM.
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Old 09-08-2001, 09:07 PM
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Thumbs down

Thanks to everyone for your quick responses. I will look into G F and the other one if nothing else than to increase my understanding of things. Not sure that I can afford any new toys yet since I just got PS 6 upgrade.

I also thank you for that site you gave me on scanning tips. I will definately read that one through. I have a feeling I knew the answer but when ever anyone talked about scanning, the only thing they ever mentioned was the pixel res and not the size output so I just had to put it into words. Thanks all for helping clarify things.
DJ
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Old 09-09-2001, 05:12 AM
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The usefullness of GF and other similar programs is controversial. They seem to work great for some types of photos, and not at all (or worse) for others. I know people that say they're a godsend, and others that claim it was a waste of good money.

So, yes, I scan and work at the highest reasonable resolution I think will ever be called for. If someone ever calls up and wants a wall mural of a 5x7 I did for them earlier, I'm screwed, but that hasn't happened yet and I doubt it ever will (not a lot of repeat business so far).

The biggest most people will ever want is 8x10. Every once in awhile someone will ask for 11x14, and I've done about 4 16x20 and 2 20x24 in my entire life (neither of those last two was digital or even recent).

I offer one free print up to 8x10 with every restore, and up to now that's all that's ever been needed for my restoration work. The last job I did, for example, specified 5x7 even though they could have gotten 8x10.
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Old 09-09-2001, 09:13 AM
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Doug,
That's generally what happens with me also. I usually scan high enough to get a good 8x10 if the originals are 4x6 or 5x7. If the original is very small (wallet) chances are they won't blow up to 8x10 anyway so I don't have to worry about scanning real high on that size. But if some one brings in an 8x10 or larger, I do scan big enough to make a larger print eventually. So I guess that is pretty much the way you do things also. My current job is scanning an 8x10 to create a 16x20 so I guess that's why this question came up. I actually scanned it at 400 but made the image 300 percent larger.

I think I now understand this size vs resolution thing much better. To increase print size without resampling you must decrease the resolution and vice versa. So if I want an 8x10 print of a 5x7 scanned at 400dpi and don't want to resample then I will have to lower the resolution to do that which then makes the print size bigger. It does that by making the dots per inch wider apart instead of resampling which adds dots that were never there based on what the values are surrounding it. Does that sound about right?

See guys you are a great help in answering peoples questions. Thanks
DJ
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Old 10-01-2001, 10:37 PM
hawkaye hawkaye is offline
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DJ:

You hit the nail on the head, regarding resampling and resolution. Basically, you've got a given number of pixels/dots both horizontally and vertically.... By spreading them out, or pushing them together, you can change the final image size. For example, a 4x6 image at 600dpi (2400 X 3600 pixel/dots) would make an 8x12 image at 300dpi (still have 2400 x 3600 pixels/dots). You have the same information, just taking up a different area. When it comes time to actually printing the image, I've heard debate as to what benefit there is to higher than 300 dpi images, even on the higher resolution inkjets, like the 2880X720 Epson 1280 printer. Egads, going to quit here before it gets too long :-) Always have enjoyed a good excuse to talk.

Cheers!
Donald
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Old 10-02-2001, 07:44 AM
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Don
I guess they will be debating this subject for years to come. Thanks for your input.
DJ
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