Request For Information -- Stamp Scanning

Greetings all,

I'm working on some software, and before making a certain design decision, I wanted to ask some other collectors their preference.

Let's say you've scanned a stamp, so now you have this nice, high-resolution photo of your stamp.

Do you:

1. Save the photo as-is;
2. Resize it based on height (ex. 600px high);
3. Resize it based on width (ex. 600px wide);
4. Some combination of 2-3, depending on orientation (ex. tall stamps resized by height, wide stamps by width);
5. Resize it based on a percentage (ex. shrink it 50%);
6. Resize it based on some other method of determining size.

Thanks in advance.

I normally scan at 300 dpi, crop - and leave the image as is. If compressing the image will easily be displayed at unnatural dimensions, so the 'visual size' of otherwise equal stamps don't match up anymore. The images at 300 dpi does not take too much space on my drive and is suitable for the web.

For stamps needing higher resolution for closer study etc I would naturally scan at higher dpi, but I think 300 dpi is sufficient for most uses.

300 DPI was Ok years ago, but I think as time goes on higher resolutions will be standard. I wouldn't scan at less than 600 DPI for an image for an ebay ad, for example (unless I was scanning let's say six or more stamps). I scan a lot of stamps for this forum and other uses, and I typically scan at 800 DPI. To address your other questions, here are my recommendations:

• Place the stamp on the scanner as close to perfectly straight as possible, even if you have to move it several times to get it straight. Realigning the image in an image editor will result in a loss of resolution and color accuracy because the image needs to be re-sampled.


• Scan at the resolution you want in the end. Avoid re-sizing, because this will also result in a loss of resolution and color accuracy.


• If you feel you need to re-size, keep the height and width proportional of course, and keep in mind where you want to use the image when determining which dimension to resize by.

Here is my avatar scanned at 800 DPI:

For quick images that I don't care about...
I scan at 300 dpi and save directly into a compressed format. If I need to resize I usually use PaintShopPro 'smart' resizer.


For images I care about...
For images that I know I want to reuse in the future, I scan at 1200 dpi and save in uncompressed TIFF format. When I reuse them, I resize and/or change them using a high quality app like Photoshop or FastStone Photo resizer. (Resizing or saving in a compressed format like PNG or JPG relies upon the quality of the algorithms. You get what the app developer has paid royalties for, there are many less-than-great bitmap algorithms out there.)
I never go back and resize or resave the same image file twice, each time this happens the image quality deceases. And I never use a scanners app to directly save in a compressed format like JPG, they generally don't use the better (higher dollar royalties) algorithms.
Don

I scan @ 1200 for single stamps. Storage is cheap.

It is not common, despite best intentions, that a scan of a stamp will be completely straight, in my experience.

I then straighten and crop if necessary. (Yes, some loss of resolution, but the original scan was @ 1200! )

For more examples, I have thousands of stamp scans at my blog site.

Scan at the highest resolution possible -- always. It's easier to "resize" or "downsize" than it is to scan again.

I scan pages for the insurance at 600 dpi and save to PDF format. This is handy as a quick reference and is very portable too.

For my own reference copies (to study while I'm overseas and away from my collection, etc.) I scan at 800 dpi and save into TIFF format. I have a relatively old and slow scanner, and I think this is the weak point I'm going to have to address soon because it takes quite some time to get a big new acqusition scanned.

I use Photoshop Pro "Elements" as my editing package, but basically I crop the TIFF file without any extra compression.

Storage is cheap and I don't get hung up on that. Back up frequently if you're paranoid about losing your scans.

I appreciate your interest in creating high-resolution 'archival' scans.

You can always down-sample (resize) or compress later.

1) Determine the optical resolution of your scanner.

Almost every scanner offers to 'scan' at resolutions higher than their optical (think 'physical') resolution, an effect they achieve algorithmically.

If you want (for example) 1200 dpi archival scans, begin with a scanner with "1200 dpi optical resolution".

2) Save those HiRes scans in an uncompressed format; I prefer BMP because that format is sans header (no digital fingerprints), and I am sure that, some day, some piece of software is going to do me/you a favor and change TIFF Uncompressed to its default TIFF Compressed.

3) Save those HiRes scans - or scan a second time - right away, into a suitable LoRes Compressed format.

While storage space is cheap, you time is not. If you are paging thru archived scans for some reason - eg, to find the stamp that bore that piece of a slogan cancel - it is a lot more fun paging thru 150kb files than paging thru 10,000kb files.

4) Get the stamps/covers straight the first time. Levelling software will level the image, but at the cost of detail.

5) If you choose to resize, do so proportionately (divide the pixel count by an integer) and not to some uniform target.

https://goscf.com/t/47496 ... see my excellent (if under-noted & under-praised) advice on resizing

6) If you are preparing a digital album page, you may ignore #5 if you are more interested in uniformity of dimensions than you are interested in uniformity of quality. YMMV.

Cheers,

/s/ ikeyPikey

Ha ha, it seems I am letting most into shock by scanning at 300 dpi "only"... I might have added I do so because I primarily use the scans for my digital albums, holding hundreds of stamps in each file. If using larger size scans, the album-files with several hundred stamps gets too tough on the computer. For the purpose of my digital albums I do not need to see my stamps in jumbo-size presentation anyway, but if required I can still zoom in and enjoy much better details than can be done when looking at stamps in a traditional (paper) album.



(Sample - zoom-in on an ongoing digital album for Spain)



Good idea - Or - save a copy on 'Skydrive' or similar web solution, the images will be safe and available at any time, more or less anywhere. Finally, at an auction or at the dealer, it will be much quicker to browse your scans online at 300 dpi.

edit - IkeyP: You are making some very good points, why not scan the stamps twice - one run for details - the other for 'presentation'. I will start doing that! cheers

51studebaker, PNG is a lossless format. It round-trips from bitmap without a single pixel modified. (See: Wikipedia)

You are right, however, that most of the time JPEG discards information. (Not always; I wrote what turned out to be a fairly popular blog post about that very subject.)

I said that PNG is a compressed format and this makes it subject to the quality of the compression algorithm. This is why some apps ask you for the compression level for the generated PNG. In this case the PNG compression algorithm 'guesses' at the neighboring pixel to save space and does an especially good job with some images. But the tradeoff is that this format is expensive; it moves an extra burden on clock cycles and memory resources. In other words, the higher the PNG compression, the longer it takes a computer to render the image. It is considered lossless but has performance dependencies upon the quality of the algorithm.

My web site currently has over 14,000 images (total of 19,000 files). Although I occasionally use PNG for its transparency capabilities I tend to avoid it for performance reasons.
Don

Sorry, 51studebaker. I thought that you were applying this statement to PNGs as well as JPEGs:

"I never go back and resize or resave the same image file twice, each time this happens the image quality dec[r]eases."

As you obviously know from your last comment, you can save PNGs repeatedly without any degradation.