Scanning Resolutions for APUG

dancqu · Jun 1, 2009

I'm muddling through the process of posting
photos using a Cannon MP520 AIO. I know the
scanner does a terrific job because copying
results are really great.

For posting purposes what ballpark resolution
should I think of using? I can go so far as 2400x
4800 without interpolation. Dan

Marco B · Jun 1, 2009

The maximum image size allowed on APUG is just 850x750 pixels, anything bigger will be rejected, so don't bother with any of these high scanning resolutions unless you intend to use them for other purposes as well. In which case you will need to downsize the image to have them accepted by the APUG server...

A 400 ppi scan of a 35 mm negative should be a good start for APUG, resulting in an about 400x600 pixel image that can easily be uploaded to APUG.

Marco

chriscrawfordphoto · Jun 1, 2009

For the web, resolution doesn't matter. What matters is the absolute pixel dimensions. So, if you have an image that is (for example) 640 pixels by 500 pixels in size, it doesn't matter if it is at 300 dpi or 72 dpi or anything else. This is because web browsers map each pixel in the image to a pixel on the viewer's screen regardless of the size of the screen or the number of pixels per inch you have encoded in the image.

So, your question really is, what size should my images be? Make them between 640 and 800 pixels at the longest side of the photo. This will fit on most modern screens. If you go any bigger than 800, the photo will show too big on most people's monitors. If you go smaller than 640, it starts looking too small on most screens.

Ian Grant · Jun 1, 2009

APUG also has a restriction on file size for uploads of 500kb.

If you shoot panoramic formats (such as 6x17) the 850x750 size is problematic as the images appear too small.

Ian

arigram · Jun 1, 2009

Ian Grant said:
If you shoot panoramic formats (such as 6x17) the 850x750 size is problematic as the images appear too small.

I was wondering if the system can be expanded to cater for panoramics, like with a special option for a long horizontal or vertical like maybe 1024 or 1280 and a short side around 300-400 pixels.

Ian Grant · Jun 1, 2009

It would be good Ari, they don't work very well as thumbnails or images in the Gallery or Portfolio section.

Ian

hoffy · Jun 1, 2009

OK, I'm sure you are going to get plenty of opinions on this, but I will give my 5cents worth as well.

Display sizes online shouldn't matter whether the photos originally were d*****l or analog, but you can unnecessarily waste bandwidth by posting up images that are too big both as a file size and as a physical size.

My personal preference has been to post images no bigger then 800px on the longest side at a maximum resolution of 72dpi. Chris is 100% correct. It doesn't matter if an image is 72dpi, or 1kazillion dpi, you will not get any benefit from a file that is greater then 72. If I use Photoshop to resize the images, I save them off as a JPEG with the quality setting at around 9. This should result in an image that is approximately 150-200kb in size.

For me, personally, anything bigger then that is a waste of bandwidth.

David A. Goldfarb · Jun 1, 2009

I would recommend scanning at the maximum optical resolution of the scanner, so that you'll have as good a scan as you can get for any purpose you may have, and then downsize to the maximum acceptable size for the gallery.

dancqu · Jun 15, 2009

Still Muddling. Questions ???????

Monitor? I've noticed that the angle at which I view
the screen has a marked effect on the brightness
of the image. If I drop my view point the image
on the screen becomes darker. Is that normal?

Screen resolution? My screen has an 85x85 pixel
resolution. I've been scanning at 75. With that
disparity can I expect best reproduction on
the screen?

Print down? Even with a low view point my scans
still present a some what 'washed out' apperance.
Should I print darker for scanning purposes?

Subject? Do some photos simply not scan well?
A photo I've been working with is a mass of
leaves, branches, and other detail. Or is
it the above mentioned mismatched
resolution? Dan

bdial · Jun 15, 2009

As suggested in some of the prievious replies, I scan at a high resolution, and resize in PS down to the target for display. I usually pick 100 dpi which is more or less the top resolution of any monitor, though most are less than that.
Unless I was making a print that would be specifically used for computer display, I print according to what makes the print look best. For the scan I adjust the scan's brightness and contrast according to what looks good on the monitor. I do this in PS rather than the scan software.
The display of an LCD monitor changes radically depending on your viewing angle. You should always make adjustments when looking squarely at the monitor, both up and down and from side to side.
Some photos do scan better than others. Something with a lot of fine detail would be a problem. Fine detail risks getting "pixelated" at monitor resolutions.

Mark Antony · Jun 15, 2009

Dan you are using a cheap laptop? If so getting accurate density is problematic as you are probably working on an un-calibrated system and the off axis display can often be poor.
You can make yourself a step wedge in PS to check all the tonal values are visible I show you how here:
http://unsharp-mask.blogspot.com/2007/06/how-to-make-step-wedge-in-photoshop.html

Scan at the maximum optical resolution your scanner is capable of say 2400-4000ppi (for film) or 300dpi for a 8x10 print then downsize in your image editor to 800 pixels wide, save as jpg the file size will be OK at about 250k or quality 10 - dpi is irrelevant web browsers will take care of display.
If you have a poor monitor check the histogram for ballpark tone values. Also when you scan look at the histogram and try not to clip off too much info-this is setting the black and white points.
Almost any image can be scanned, their are some images that are harder such as Kodachrome slides that have very high d-max but if you set the black and white points in your scan software they should look OK

StorminMatt · Jun 15, 2009

Mark Antony said:
Scan at the maximum optical resolution your scanner is capable of say 2400-4000ppi (for film)

I wouldn't say that it is always best to scan at maximum resolution. First of all, the optical resolution of a scanner is not always usable. This is particularly true of flatbed scanners, which can NEVER produce a good scan of film at maximum resolution. For instance, my Epson 4180 perfection has a maximum optical resolution of 4800dpi - higher than my Nikon Coolscan V, which is only 4000dpi. Does this mean that the Epson will make a sharper scan than the Nikon? NO WAY!!!! Scans on the Epson don't really start to look sharp until you get below around 2000dpi. Then there is the issue of the picture itself. Honestly, I have NEVER seen a slide that can REALLY take advantage of 4000dpi. So I just have to ask myself why I should bother with such a high resolution scan. Of course, if time is not too important, there is nothing wrong with scanning at the highest resolution and dropping it down in post processing.

Mark Antony · Jun 15, 2009

my Epson 4180 perfection has a maximum optical resolution of 4800dpi - higher than my Nikon Coolscan V, which is only 4000dpi. Does this mean that the Epson will make a sharper scan than the Nikon? NO WAY!!!!

Matt
Your Epson may state it has optical 4800 but it actually measures at under 2400, no flatbed will achieve its theoretical resolution because of the way the film is held on the glass, even when wet scanned the focus is approximate. Your Nikon on the other hand can focus on the film itself thus giving a better chance of getting its resolution.
I have seen films that contain detail that can be captured exceeding 4000 ppi but these are rare and exceptional but as a rule of thumb film scanners work well at 2800-4000 then taken down to web size flatbeds are better for MF/LF and flat artwork with 2400 and 300ppi being good starting points.
Much better than scanning at 72 ppi at 800 pixels then uploading to internet.

dancqu · Jun 15, 2009

Ready to Post

Any trick or tricks to it? I'll use the manage
attachments option. A 139KB PNG file from
a 5x7 print. Dan

dancqu · Jun 17, 2009

Now Stymied. Have I the Gear - Software?

I've viewed many APUG Photo posts. In my estimation,
A lot of good looking representations of the actual prints.
And that on my Proview 15 inch monitor.

My scans look harsh with the appearance of increased
contrast. Gradation is rough. I've an Apple running
OS X 10.5. I've used only 10.5's included Image
capture and Preview applications for input
and alterations.

The Canon MP520 provides 16 bit input, 8 bit output
gray gradation. Image capture allows for TIFF, JPEG,
PNG, and PDF image files. No variations of any.

So can any one see where the weak point or points
are with my setup. Perhaps additional software?

BTW, 16 in 8 out? I've looked but not found any
explanation. Assistance appreciated. Dan

Scanning Resolutions for APUG

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