Stair Interpolation Action

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Godzilha82

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Does anyone have any tips on writing "Stair Interpolation" actions using Photoshop 6 or 7? I have a Coolpix 5000 digital camera and I've been experimenting with writing an action that will change the RAW Jpegs, which are created to be roughly 24X35" at 72dpi, into printable 300dpi 8X10. I've tried writing an action that incrementally reduces the overall size of the image while increasing the dpi but it doesn't look as good as images that I just change in 1 step using the "Image Size" pull down menu. Supposedly, Fred Miranda has written one that is supposed to be better than the Genuine Fractals program....but I'm not positive that it will work with the kind of Jpegs that the Coolpix produces and no one from that website has returned my e-mail query. So.....anybody have any tips for writing my own? Thanks!!

Trevor
 
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Here is an image I blew up using stair and straight bicubic in Photoshop: http://www.pbase.com/image/2810762 The 20 X 5% increments definitely look sharper than the single step. You will notice the noise is increased as well – which sharpening does also. If you are wondering why there is so much noise, the shot is cropped to only about 3% of the original. A really tiny part of the original.

I guess it is redundant to say I used the % in the pixel dimensions. And to display pixel dimensions you have to check resample. I made and action with 5 X 5% increases and then made actions combining several of the first action.

For what you are doing I would first uncheck “Resample” and size to the new print size. That will give you The same pixels but at a higher PPI. Then if the PPI isn’t high enough you can uncheck “Resample” and try the stair interpolation from there.

I don’t use it much anymore though. A programmer writing other software published a little sharpening utility that is incredible. It doesn’t have a page to view the particulars and I hate to show a link that goes directly to a download but there isn’t much choice here: http://www.dpreview.com/misc/rdr.asp?url=http://www.applied-maths.com/paul/sharpcontrol.zip Here is some discussion on the new version I just linked: http://forums.dpreview.com/forums/read.asp?forum=1021&message=4086845 Almost everyone on the board uses it on occasion.

The Stair interpolation is counterintuitive but it works. Don’t mess with anything though until you resize the page with resample unchecked.
 
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Forgot to mention something:

If you are going to mess with your images at all in Photoshop make sure to set the sharpness to soft or off – whatever Nikon uses for minimum in camera sharpening. Sharpening should be done last. Also save them as TIFF, PNG or PSD. You get more artifacts by saving again as JPG. Sharpened images suffer more from compression than unsharpened ones – another reason to set your Nikon sharpening to off.

Fred Miranda had a free sharpening tool for a while but I lost track of it. Didn’t do any better than the stair action in Photoshop. His edge sharpening action you have to buy is reported to be good, but I haven’t messed with it. SharpControl seems to be more sophisticated than any actions I have loaded for sharpening.
 

Godzilha82

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Jan 8, 2003
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Thanks so much, Slipe...I'll give 'er a rip and see what happens...

Thanks again...

Trevor
 
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My last post wasn’t written very well - I was referring to saving in a loseless format AFTER you open it in Photoshop. If you have reason to use good quality jpg in the camera you just don’t want to degrade it more. Once you sharpen something the jpg artifacts are really noticeable though.
 
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