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Old Jul 27, 2008, 12:37 PM   #1
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In the 'Landscape Photos' forum we have been discussing the merits and demerits of 'Autostitch' stitching software from UBC (http://www.autostitch.net), at http://forums.steves-digicams.com/fo...907316#p907316. I lke it a lot, though it doesn't always work if one's been a bit careless!

To illustrate how much or how little quality autostitch loses in its operations, here are two 1:1 clips from a large pano I did with my Kodak Z712is superzoom in February. The top one is a clip from one of the original frames, and the bottom one is autostitch's version.

I'm not sure how fair a test this is, as I made huge overlaps of individual frames, and just left autostitch to do its own thing, at 100% size and 90% jpeg quality, and otherwise with its defaults. The light may well have changed a little during the shooting, and this piece appears on several of the originalframes.

A little sharpness and some contrast & saturation has gone. I'll do the same thing on a different part of the image in due course, I hope. I doubt if this would be very noticeable on screen viewing at full height, or a big print at a reasonable viewing distance.

Interestingly, the gate's orientation is a little different, and the field of view in these clips is a little different, presumably because of the projection used in stitching.

The question is, does autostitch work with whole blocks of pixels, or resize & resample them?

Discussion welcome.

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Old Jul 27, 2008, 4:37 PM   #2
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Alan

what is the dpi on the autostitch effort?? when i tried i think it dropped it to 72dpi

just moused over some i did with autostitch and other automated software and sizes average 1 to 2 meg which points to some resampleing going on as my cam shoots at 320dpi

lower dpi means less sharpness when blow up or should i say it wont blow up as big before pixelisation and there is no way back from a downsample

so if u have 5 x 2.5 meg images joined up the file size on original should be10 - 12.5 meg depending on amount of overlap..........yet autosoftware give somewhere between 1-2 meg which isnt right

Gary
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Old Jul 27, 2008, 5:44 PM   #3
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My understanding is thatthe embedded 'dpi' figure is irrelevant unless you're publishing it oncertain types of printing press. The 72 or 320 arejust ameaningless entry in the EXIF file.

When you say your cam "shoots at 320dpi", it has no idea how big you're going to show the image. If you show show a 3000 pixel image on a poster 30 inches wide, it's 100dpi (not enough); if you show it on a monitor or print it 10 inches wide the same thing will be at 300 dpi (plenty for most purposes). It's just the number of pixels that counts.

If I'm doing a big print I resize & resample to 400 pixels per inch on the final print, but usually I'm wasting my time because I'm toldmodern photographic printing machines do just that for themselves before 'writing' the print, regardless of what size image you give them.

Only the number of pixels counts. By "1:1 clip", I mean each pixel in my image corresponds to one pixel on your monitor, in your browser's 'normal' viewing mode. That's why we're generally restricted to 800 or 1000 pixels here in Steve's. Both those clips are 600x700 pixels, and what the dpi is depends on the size of your monitor.

But I expect you know all this.

I agree that the quality can't be as good as you're getting from hand crafting each frame, but it must take you a long time. The point I'm making is that for practical purposes there's not much different when the images are compared even at much greater magnification (1:1) than they'll ever be viewed normally.

Here (in the next 3 replies) is another specimen that I took this evening, consisting of six 3072x2304 images, each about 1800KB, put straight into autostitch set to "Scale 100%". First, the whole pano, trimmed resized to 100 pixels wide, and sharpened in PaintShopPro. Straight from autostitch it was 10016x2575 and 5228KB, so it's about half as many pixels as the six whole frames.
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Old Jul 27, 2008, 5:48 PM   #4
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Next, here is a 1:1, full-size, unaltered, pixel for pixel clip from one of the original frames....
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Old Jul 27, 2008, 5:51 PM   #5
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...and here is roughly the same clip from the trimmed but unsharpened 9990 pixel-wide autostitch version.

This resolution, with the 600 pixel clips 6 inches wide, seen on my 17-inch, 1280x 1024 screen, corresponds to a print100 inches wide at 100dpi, (I prefer ppi) or 333dpi for a 30 inch print. When standing at a reasonable viewing distance for an 8-foot wide print, I'm sure I wouldn't be able to tell the difference.

The end result, with a little sharpening, is 4566KB, 9990x2214 pixels, and I think it'd look quite nice as a 45-inch by 10-inch print at 221 ppi, if I could manage to print and mount it at a reasonable cost. I could do much better with a tripod and lower ISO, and a better camera, but I'm happy enough.

But, as you can see, I'm no perfectionist!
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Old Jul 28, 2008, 1:42 PM   #6
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i got sent a poster to print recently

it was 72dpi and they wanted it 24x36, it was pixelated beyond belief, i passed in through genuine fractles upsizing to 300dpi and the result was still very poor

i emailed them back and asked for fullsize original what came to me as a 300dpi with a rather larger file size but the print was perfect

when you downsize the picture is reduced and there is no way back as the pixels are deleted, just compared a 72dpi and 321dpi at 100% and deffo soft blur and less defined colours.

just opened on of my panos in photoshop and this is the spec if it helps

pixel dimensions 111.8meg, width 10800 pixels height 3618 pixels, width 36 inch and heigth 12.06 inch with 300 pixels per inch, thats the size i work at for my panoramics, they look good from as close as a foot away

re your sizes, biggest print size i can get framed is 44 inch wide, this is dictated by the size of mount board, as largest sheet my supplier can get is 44 inches, its also the biggest his cutter will cut LOL, i have got a 12x44 inch frame and mount her at moments for a special pic. if you ever need any frames and mounts supplying drop me a pm, i can also print that size :-) on my printer

Gary


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Old May 16, 2009, 3:42 AM   #7
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Hi Alan, I see you are having a lot of fun with stitching. I found autistitch very unforgiving, I broke myself in with ulead 360 and asked them to update it with a 'no' reply. I try to chose my subject carefully. usually busy photos so stitching is less apprent, tricky with skies! Dont know if this will upload well, but i like these two. Played with the colours a bit for fun!
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Old May 16, 2009, 3:44 AM   #8
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i have worked the sky since this one but dont have it with me
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Old May 16, 2009, 5:47 AM   #9
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Quote:
Originally Posted by bill43210 View Post
Played with the colours a bit for fun!
Nice pictures, Bill, though your fun on the second one is a bit much for my eyes!

Have you seen my amusing mis-stitch in the 'Biweekly Shootout' at...

http://forums.steves-digicams.com/biweekly-shoot-out/154937-what-went-wrong-another-tay-bridge-disaster.html ?

I've been use the three-stitch in-camera pano facility built in to my Kodak superzooms a lot lately, but on that occasion was too complacent to take the separate shots as well.
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Old May 18, 2009, 12:36 PM   #10
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If you want consistently good stitching, then it's best to use software that enables a degree of manual control to cope when things go wrong, as well as properly handling images taken with the camera in any orientation and with any amount of tilt. I've been using PTGui since 2000 and have found nothing better. It copes with standard lenses and fisheye lenses, and will stitch full 360x180 degree panoramas for viewing in a spherical viewer, as well as partial cylindrical panoramas for printing. This is an example of the latter type, made from 7 portrait images tilted down by 10 degrees, augmented by an additional patching shot of the sea taken with the camera rolled by 30 degrees to accommodate the widest possible view across the diagonal (to avoid discontinuities in the waves rolling in).

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