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Author Topic: Uprezing files  (Read 7187 times)

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« on: October 13, 2006, 12:51 »
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This came up on another posting...if the microsites can 'tell' if you uprezed/interpolated an image.
My thoughts are that when you interpolate/uprez a pic, it doesn't 'add' any detail, it only gets rid of the jaggies. If you started with a low rez image and scaled it way up, what you would see is not so much added 'artifact' but rather that an image at the larger scale should have a certain amount of detail...if it's not there, it wouldn't make much sense that the image was taked at that (higher) resolution. IE the output from a c-sized dslr will  always have more detail than un uprezzed 3 megapixel point and shoot. I suppose the only way they can 'tell' is thus just viewing the image closely, for even with a lousy lens,an image at ,say, 30 meg file should have a certain amount of detail.
 Having said that,there is no discernable difference if used selectively.
 For example, I interpolate my Canon 30d images from it's native 240 dpi up to 300 dpi with Photozoom Pro 2. This program offers a very high quality interpolation engine.I usually do the interpolation last and THEN sharpen the image accordingly (with Focalblade).
 Would be great to hear your thoughts ,knowledge and experience on this as I am only really taking a guess here...


« Reply #1 on: October 13, 2006, 13:07 »
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For example, I interpolate my Canon 30d images from it's native 240 dpi up to 300 dpi with Photozoom Pro 2.

FYI: Changing the DPI of an image has nothing to do with the size of the image.

« Reply #2 on: October 13, 2006, 13:29 »
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Well in Photozoom it does...you are changing the dpi but NOT the image dimensions. Would that not therefore increase its size?I think you are talking about in PS where when you change the dpi it chnges the image size accordingly.

« Reply #3 on: October 13, 2006, 16:54 »
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One indisputable fact is that when you uprez an image, information is added to it because pixels are added.

That information has to come from somewhere, and the only place it can come from is the computer program calculating what the colour, brightness, etc. each new pixel should be.

The trouble is (as I see it) ... no computer program can take the place of a lens on a camera, focusing an image from a real scene.

So a number of those new pixels aren't going to be quite the right colour, brightness, etc.


« Reply #4 on: October 13, 2006, 18:26 »
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The neat thing I like about Photozoom is it's elegantly simple interface. You drop an image on it and it shows you the interpolation process as you move about the image....(hard to explain) you should check out the demo. Yes of course it adds artificial detail...but when it comes to digital information there are quite sophisticated algorithms that are quite good at figuring out what those missing pixels are most likely to be (in color and level). A lot of publishers have used it when printing from lower res images...for ex. a lot of photo journalists had to (until recently with higher meg) shoot on quite low rez point and shoots when a SLR or larger camera were not appropriate to use.

« Reply #5 on: October 14, 2006, 04:25 »
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Well in Photozoom it does...you are changing the dpi but NOT the image dimensions. Would that not therefore increase its size?I think you are talking about in PS where when you change the dpi it chnges the image size accordingly.

DPI means dots per inch.  if you have an image which is 1000 pixels (dots) wide by 1000 pixels heigh, and it has a DPI of 1000 that means it would print at 1" wide by 1" tall, change the DPI to 100, and it will print 10" wide X 10" tall

the size of the image has not changed AT ALL, it is still the same 1000 pixel X 1000 pixel image.  DPI just states how many pixels per inch it is going to plop on the paper when you print it.  And yes you can change the DPI in photoshop without changing the size of the photo.

« Reply #6 on: October 14, 2006, 04:29 »
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Well in Photozoom it does...you are changing the dpi but NOT the image dimensions. Would that not therefore increase its size?I think you are talking about in PS where when you change the dpi it chnges the image size accordingly.

oh on reading this again, i think when your program enlarges an image, it figures out that your image is 1000 X 1000 piels at 1000 dpi then it will print at 1", so if you want to double the resolution, it will just make it 2000X2000 pixels and then change the dpi to 2000 DPI so that it will still print at 1"...

same difference, and yes photoshop can do this as well

« Reply #7 on: October 14, 2006, 13:46 »
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I guess all I meant is changing the size.....changing the dpi but leaving the dimensions the same...Of course photoshop can do this but it would then be using it's interpolation...and the interpolation engine in Photozoom (s-spline) is much better than PS's bicubic.
 On another note I see that AlienSkin just anounced a similiar product....blow-up...it sounds promising.Would be nice as it offers blowing up a layered PSD while Photozoom only works on tiffs.

http://www.pdnonline.com/pdn/prodtech/news/article_display.jsp?vnu_content_id=1003252981

« Reply #8 on: October 14, 2006, 14:55 »
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and the interpolation engine in Photozoom (s-spline) is much better than PS's bicubic.


Photozoom's s-spline algorithm is just a slightly weighted version of the bicubic interpolation that CS2 uses. Every unbiased comparison I've seen says they are almost identical.

Genuine Fractal's algorithm has always been considered the best interpolation algorithm available.

Check out this comparison: http://www.ronbigelow.com/articles/interpolation3/interpolation3.htm

« Reply #9 on: October 14, 2006, 17:08 »
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 Thats a matter of opinion...Ive seen other comparisons where s-spline was better. In that article only two of the images he feels are better in Genuine Fractals....and that is probably with the default settings. Also, in Photozoom Pro version 2 they've made the s-spline algorithm even better ..s-splinxe xl it is called now. I guess it's just what program you are used to...I DID just use AlienSkin's blowup....unfortunately it does not seem to have any advanced setting other than sharpen and grain.

« Reply #10 on: October 14, 2006, 17:52 »
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If you actually read the whole article you'll see that the page I linked to was the only one that you could see any difference at all. It was also at 400% which is way beyond what you could get away with if you wanted to upload it to a stock agency. At the lower levels Photozoom and PS are identical.

I hate to tell you this but s-spline "xl" is more hype then improvement. The mathmatics behind it can't be improved much more then they already had. Photozoom uses a nearest neighbor, weighted, low-degree polynomial algorithm. The only thing they can do is tweak the weighting (which is what they did).

You're welcome to believe whatever you want, but you're going to have a hard time proving to me that splining produces better results than fractalization, when they are done correctly. I wrote my master's thesis on use of fractals in image rasterization.

« Reply #11 on: October 14, 2006, 18:00 »
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I wrote my master's thesis on use of fractals in image rasterization.
Well guess you might be a bit biased towards fractals then...hehe. In any event...there is to my eye anyway, having used both Genuine Fractals and Photozoom,not much discernable difference between the two at all. I do like the interface of PhotoZoom Pro 2 however, and I DO definately see an improvement using it over interpolating in PS.

« Reply #12 on: October 14, 2006, 21:39 »
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You do know that you can see a difference though, regardless of which algorithm you use. That was the whole point of the post right? You want to upsize photos for microstock. If you are upsizing more than 20% then I'm willing to bet they get rejected for one of the following: "over filtering", "pixelation", or for the photo being too soft.

« Reply #13 on: October 15, 2006, 03:09 »
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I suppose the only way they can 'tell' is thus just viewing the image closely, for even with a lousy lens,an image at ,say, 30 meg file should have a certain amount of detail.
 

Well aside from the obvious visual clues and there are many, flat pixels, color artifacts, loss of detail, softness etc., the agency can tell very easily if you have interpolated your image. All they have do do is look at the EXIF data for the image which will reveal the Camera make and model with which the image was created. If the image dimensions exceed th known native size of the image produced by your camera then it is obvious that the file was interpolated and would be rejected if it is the agencies policy to not accept upsized images.

« Reply #14 on: October 15, 2006, 04:09 »
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yep i have had a number of images rejected because they saw the image come from a canon 10D and it was too large of a file...... HOWEVER... they didn't take the time to realize that it was a collage of a number of images which is why the size was so large :(

« Reply #15 on: October 15, 2006, 13:41 »
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For a few of my images I somehow lost the Exif data, which is not bad, because I dindn#t care about it. But could it be, if you saved them as PSD and than back at Jpeg that they somehow loose the data? I never had a problem to submit original 3mp images collaged to more than 6 mp. And 6mp to collaged up to 15Mp. Regarding the size, they never complained.

yep i have had a number of images rejected because they saw the image come from a canon 10D and it was too large of a file...... HOWEVER... they didn't take the time to realize that it was a collage of a number of images which is why the size was so large :(

« Reply #16 on: October 15, 2006, 17:43 »
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Well...Photozoom Pro 1 had the problem in that it stripped all exif data...something they fixed in version 2. I believe I can edit whatever exif data I want in Iview media pro...so I could always just take out that info if I wanted too. When you mean a 'collaged' image from 3 to 6...do you mean interpolating?


« Reply #17 on: October 16, 2006, 01:38 »
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When you mean a 'collaged' image from 3 to 6...do you mean interpolating?
Collaged is adding two or more photos together. 

Depending on what and why you collage, you are just giving the buyer twice for the price of 0.25.

« Reply #18 on: October 16, 2006, 11:23 »
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I made collages to make one new image out of a few older images..... not just pasting two images on a white background.

« Reply #19 on: October 27, 2006, 05:08 »
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so you could edit the EXIF data to make it look like the image was shot on a Canon 5D

would this work?

« Reply #20 on: October 27, 2006, 05:22 »
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so you could edit the EXIF data to make it look like the image was shot on a Canon 5D

would this work?
Why stop there - now what was the name of that 100MP camera?

« Reply #21 on: October 27, 2006, 11:34 »
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Why just don't erase the EXIF Data, they do not need it anyway. I never had rejections of my collaged Images. @CJPhoto, I just do not as Leaf described put two images on a white Background. And they sometimes sell by far more better than the single Images together.

« Reply #22 on: October 27, 2006, 17:42 »
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I have upsized a couple of images and they have been approved even at IS.  I also often do small upsizing to fit minimum size requirements.  Not all images upsize well, though.  I had a very good experience with ClearerZoom, but I didn't compare it to other software.

Regards,
Adelaide


 

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