Interpolation: PhotoZoom Pro & PHOTO-PAINT side-by-side

[Sam North]

It took me a few months to get my head around image interpolation for my site (http://www.theimageplane.net/tip2_018.htm). I used two programs to test the process all the way through to the final prints, PhotoZoom Pro and the image-editing program Corel PHOTO-PAINT.

The BIG surprise was how alike the results were! The images below are straight interpolations uploaded as quality JPEGs to the site.

I would have thought Shortcut's PZ Pro would CLEARLY have had the edge.

Any thoughts?

Sam




http://www.theimageplane.net/pp.jpg
http://www.theimageplane.net/pzp.jpg


.

[BigRed450]

The best way I found to interpolate images up is to increase image size in the image size dialoge box by 110% (change pixel setting to percentage). Repeat this as many times as it takes to get the image to the size required. By doing this in the stair step method you only add a little at a time giving a very accurate enlargement with no jaggies.

[Sam North]

Hello Jeff :D

By coincidence I have a magazine article open on my desk here that proves (in words and pictures) that enlarging a digital image in small steps - say 10% - actually degrades the image. One step enlargement produces the best results.

The article shows clearly (to me anyway) that "resizing an image in incremental steps degrades the final result - precisely the opposite of popular belief... Should you have any doubts, it takes only half an hour to prove it for yourself" (Steve Hynes, Professional Photographer magazine, March 2004 edition, ps. 47-50).

Try to get a back issue of the magazine and see what you think - I'm no expert!

I interpolate in one step by setting the software to the actual exact pixel size recommended by my pro lab. I've got very impressive results so far.

From the site:

"The number of pixels contained in a digital image limits the maximum size of the print. For the print to look sharp with good tonal quality and well-defined smooth edges, just as it does on the computer screen, there must be sufficient pixels to every inch.

"A reliable photo lab that uses photo-digital lasers to produce high quality prints on photographic paper will recommend 300ppi (pixels per inch) for the most common print sizes. This means a 6x4 print should be 1800x1200 pixels, a 7x5 should be 2100x1500, a 12x8 should be 3600x2400, and so on. But less than ideal pixels per inch will still deliver reasonable results: a good quality 3000x2000 digital image can be used to produce an acceptable 15x10 print.

"However, if you are using a digital SLR camera that produces 3000x2000 images, and you need 18x12 prints, you will have to make your digital images bigger. Ideally you will need to enlarge your 3000x2000 image to around 4500x3000. This enlargement process is called image interpolation, or resampling.

"Programs like Photoshop and PHOTO-PAINT can easily enlarge a digital image. You can also buy unique interpolation software, like Genuine Fractals and PhotoZoom Pro. Basically, the better methods of image interpolation cleanly smooth out jagged edges and a variety of irregularities by creating new matching pixels to fill the ‘spaces’ produced by enlargement.

"The images below show unsharpened image interpolation results from Corel PHOTO-PAINT and Shortcut PhotoZoom Pro. The original unedited image was captured by an EOS 300D."

The big surprise for me in all of this is that PhotoZoom Pro at £90 doesn't outshine PHOTO-PAINT! Am I missing something?!

Sam

[BigRed450]

Thanks Sam

I will have to try some test patches and try it out.....

[BigRed450]

OK , I did a couple of test patches from images resized to 44.25"X 29.5". You are right Sam. The one step interpolation of the 10D images retain better, smoother detail. However, my Fuji images do not benefit from the one step process. This leads me to believe that different sensors and/or photosite arrangements react differently to resizing.

Thanks again Sam.

[Sam North]

Interesting about the Fuji images... You should write into the mag and query the point. The image used to prove the point in the magazine was shot on a Fuji S2 using the RAW mode and converted to a TIFF.

I've just done an identical test on pxl SmartScale interpolation software, and it's slightly behind PhotoZoom Pro and Corel PHOTO-PAINT. Tried Genuine Fractals demo in Photoshop LE but it wouldn't run, although it's supposed to be compatible - much too expensive anyway!

I also interpolated to the same size with Adobe Elements 2 and it looked identical to PHOTO-PAINT. The 18x12 results I've got from PP look very good indeed.

Good luck with your photography,

Sam

[sdommin]

The big surprise for me in all of this is that PhotoZoom Pro at £90 doesn't outshine PHOTO-PAINT! Am I missing something?!

Yes! :) You're missing the fact that PhotoPaint is a quality program that is every bit as good as PhotoShop (they just have a lousy marketing dept.).

[Sam North]

I agree. In fact I contacted Corel to see if they had any plans to sell PHOTO-PAINT 12 as a stand alone product. I shared my view that the corporation may have shot itself in the foot by packaging a pro image-editing program with CorelDRAW. DSLRs have not yet come close to the number that will be bought up 3-5 years from now, and Corel needs to be ready with PHOTO-PAINT.

Here's the reply I got:

"There is a Standalone version of Photo-Paint 11 available as part of a product
bundle from ACD Systems called Photo Master Suite. It is available from most
software resellers including Amazon.co.uk:
http://www.amazon.co.uk/exec/obidos/ASIN/B0000C4JF4/026-0039995-2494845
This product is not, however, compatible with Draw 11 Standalone."

I've just come back from a major book store where I found a large paperback book on CorelDRAW, but I know there are no plans for one on PHOTO-PAINT.

You're right - they really need to push this excellent software before Photoshop takes over the world!

[sdommin]

You're right - they really need to push this excellent software before Photoshop takes over the world!

I hear ya, Sam. However, I think it's too late. I also think Corel knows this, and they've given up the fight. Too bad!