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Digital Resizing Methods
April 14, 2003

For the digital photographer, Adobe’s Photoshop image editing application is king of the hill and deservedly so. Most of what a photographer wants to do for editing can be via Photoshop; however, it is sometimes daunting for new users to figure out how to do so. A veritable cottage industry has sprung up to take advantage of Photoshop’s complexity to create Actions, Automations and plug-in filters that automate or simplify the process for popular edits.

One popular edit is resizing an image to produce a print that is larger than what the original scan or digital capture would normally provide. For example, the output from my Nikon D100 is 6 megapixels due to its 3000 x 2000 pixel resolution. Divide these resolution figures by 300 dpi (the standard for photo quality printing resolution, and we end up with but a 6.7 x 10 inch print.

To obtain a larger than 6.7x10 print I can either down-rate the print dpi to 200 and receive a 10x15 inch print. I find that the quality is still quite good, but if I were to push the digital file further and try for a 12x18 inch print by lowering the print resolution to a mere 150 dpi, I need to do some extra work to maintain acutance (the appearance of sharpness – not detail delineation, which is the traditional use of the word “sharp” when using film).

A 12x18 at 150 dpi is passable from an appropriate viewing distance, but is not going to be the last word in quality and to go even larger requires up-sampling of the image data. There are several methods available to up-sample the image file and the most obvious method is found within Photoshop itself, known as Bicubic Interpolation. For Photoshop users, this is also the cheapest way, since it comes included in Photoshop; however, there are other methods and techniques offered by third party programmers or companies, some for a cost varying from affordable to hefty and some for no fee at all.

I purchased one of the best known re-sizing applications a couple of years ago, called Genuine Fractals. It cost a pretty penny at a couple hundred dollars Canadian and when I wrote the original review back in 2001 I felt a bit let down by the performance given its high cost and large hype. Since that time digital photographers have come to understand that Genuine Fractals is a decent re-sizing option for film scans, but may not be necessarily better than Photoshop’s native Bicubic option for original digital captures.

The quality of the algorithms used plays a large role in the quality of the resizing and in recent times more applications have been made available that claim to better Bicubic, including a RAW converter from Adobe, the producers of Photoshop.

Since I happen to have a few of these quality re-sizing applications and since I happened to have received a request from one of the newer third party companies to try out their product, I decided to take another look at re-sizing and see where we are at.

The Contenders

Photoshop Bicubic was chosen as the reference method for resizing. Reference in this regard is merely as a base to compare others to and not as the ultimate that represents the state of the art.

Genuine Fractals 2.0 has been superceded by Version 2.5, which now costs $159 US. I’m not sure how much improvement is offered by version 2.5, but I have little desire to pursue this given the high cost of upgrade. GF is a Photoshop filter that saves files in its proprietary STiNg format (STN). It can take a large file and reduce to it a much smaller file size without any apparent loss of quality and yet be able to resample it upwards with no degradation of the image, or so goes the marketing from Lizardware, the company producing the application.

FSoft Resize Magic is the newest offering (as of April 2003) and the reason why I am writing this piece. It appears that the programmer sent out notices to various photographers with a web presence to inform them of his new product and offering free usage in return for some marketing potential. In a short e-mail exchange with the developer, he indicated that while Genuine Fractals is decent his application still produces more natural looking images and has the added benefit of being able to work with other editing programs besides Photoshop, such as Paintshop Pro. We shall see if the promise pans out.

ProFoto Resize is the cheapest of the third party applications because it just happens to be free from the developer. Although the developer Andy Bell would much prefer that you purchase one of his other offerings, he offers this Resize application as a sweetener. Not only is it free but it is also a standalone product that does not require an image editor to work through like most third party programs. A batch processing feature is also available to make it a decent little image resizer if you use an application other than Photoshop.

Fred Miranda Stairstep Interpolation is actually just Photoshop’s Bicubic interpolation except that this method up-samples the image through a series of 50% increments instead of one global Bicubic interpolation step. Fred Miranda has made a name for himself by offering a number of Photoshop Actions, some custom for specific digital cameras, and some just general for all digital files. He offers his actions for between $9 to $15 US and they do seem interesting. Except that if you’re skilled with Photoshop why would you spend money on edits that you could do yourself? For beginning to intermediate Photoshop users, Miranda’s actions offer a fast and convenient way to obtain some high quality edits without a lot of grunt work and may well be worth the modest cost asked for. The SI version I have is for the Nikon D100.

Adobe Camera Raw is Adobe’s own answer for RAW conversion to supplement their flagship Photoshop program. Thomas Knoll, original developer of Photoshop was less than satisfied with the RAW file converters available either from the original camera brand or from third party developers, so he set out to write his own RAW converter for Photoshop. This is technically not quite a seamless RAW converter because Knoll wrote it as a plug-in filter for Photoshop, but it is suspected (expected?) that Adobe will fully incorporate the RAW converter as a standard function in the next major Photoshop upgrade. As it stands now, interested users need to purchase the plug-in for $99 US. One of the features of the converter is a resizing function that is apparently superior to the Bicubic interpolation found within the standard Photoshop program.

Phase Capture One is a workflow application that is highly regarded by professional photographers using Phase digital backs with medium and large format cameras. Phase made their vaunted Capture One available last year for Canon digital SLRs and recently made Capture One available for Nikon digital SLRs (only D1x and D100 models). It too offers a resizing function and for those that can afford the $600 US purchase price, it offers some pretty slick features that can make life a little easier for digital photographers. Note to Canadian readers, Vistek of Toronto offers Capture One for $800 CAN, which is much superior to purchasing it direct from Phase and getting reamed by the exchange rate. A new "light" LE version of Capture One with most of the fine benefits of full "pro" version is now available for $99 US.

Methodology

I chose a small sampling of images to do this resizing test, four RAW images taken with the Nikon D100 and two scan files done with my Minolta Scan Dual III. The two scan files were from the same session as two of the RAW files in order to do some comparisons of the same subjects taken on film and digital capture.

Scanned images were already in 8 bit TIFF format, so they could be resized quickly as is. For Nikon NEF files (RAW images), I first converted them to 8 bit TIFFs via Photoshop’s Adobe Camera RAW (ACR), I accepted the default settings offered by ACR except for the Sharpening and Smoothness settings for which I set both to zero on the basis that sharpening should be done as the last editing step prior to printing and that I wanted no smoothing over of the image file and risk losing detail.

I used 16x24 inch print size at 300 dpi as the reference size to do the comparisons with. I know that there are many in the world claiming superlative print quality at even larger sizes than this with their 35mm film and 6 MP digital cameras, but I’m not one of them. I think 16x24 is already a big stretch and as such should provide a good point of reference to see how good each resizing method is. Your mileage of course, may vary.

The final review samples were given the same sharpening amounts to keep things constant and to provide a closer example of what the final image would be like before sending the file to the printer.

The methodology may not be perfect, but hey, I try my best as a photographer, not as a lab rat shooting test targets all day.

Results

Photoshop Bicubic
With this method as the point of reference, I offer no comment as to the absolute quality offered by this method except in relation to other applications. It may not be everyone’s favorite method to resize, but there is a strong contingent of Photoshop users who see little need for anything else to resize their images for large prints.

ProFoto Resize
I was a bit skeptical about this freebie offering and wondered how effective such a modest little application would work out. It is quite simple and straightforward in its interface and works with JPEG, PNG, BMP and TIFF image files. For JPEG images, a sliding quality bar is available to select a custom quality/compression ratio. Beyond that you just merely type in the maximum size you want in pixels (it comes with a handy calculator function to compute the size you want) and then hit the Process button.

For resizing the image file upwards to 16x24, ProFoto Resize took on average 30 seconds to up-sample each image, which is better than Genuine Fractals or Resize Magic, but certainly no threat to good old Bicubic.

Results of using this free resizing application indicated no difference compared to Photoshop’s native Bicubic interpolation method; however, since it is a standalone application, it may well be worthwhile to use with other image editors that offer little to no resizing capability. This application uses the Lanczos 3 interpolation method.

FSoft Resize Magic
This application works in a somewhat unconventional manner. You open the image you wish to resize and select the Resize Magic filter from the Filters menu, the filter pops up a small window indicating that the image file has been copied to Resize Magic’s clipboard and that you should now resize your image and then restart the filter.

You resize the image via Photoshop (or whichever editor you use that is compatible with Resize Magic) and in this case I used Bicubic interpolation. After resizing, select the filter again and this time another window pops up to indicate your resizing choice and what kind of sharpening you wish to employ, low, medium, or high. Select your choice then wait for Resize Magic to process the image.

Next to Genuine Fractals, Resize Magic takes the longest of all the resizing applications at around 1.5 minutes per image. Unfortunately, all that extra processing time led to a result that I found no different than Photoshop’s Bicubic or the free ProFoto application. Although not expensive at around $20 US to purchase, I do not see the point for Photoshop users or for those using another editor since the standalone ProFoto is free at this time.

Fred Miranda Stairstep Interpolation
After moving the purchased action into the Actions Palette of Photoshop, it is a simple click of a mouse button to start the process and about 10 seconds later you have a resized image. This method does produce superior results than using Photoshop’s Bicubic interpolation in a one-stop global application with the results being less artifacts and smoother edges.

Genuine Fractals
GF is incredibly demanding of system resources from the computer. It is not much of a memory hog but it will spike your CPU processing to 100% if you were to view the performance feature in the Windows Task Manager. It is such a pig that Photoshop crashed on me when I was reviewing the performance of the CPU while it was processing an up-sample test image. Leave it alone and don’t even think about multi-tasking your computer to do something else. GF also took the longest of any of the resizing applications taking over 2.5 minutes to process an STN file. The workflow is also more onerous as one has to save the image into GF’s proprietary STN file format, then close the file and reopen to input the resizing parameters you desire.

The quality of the GF files was a bit hard to peg down. They seemed slightly more detailed than the images that had been resized by the other applications (except for the Capture One files); however, upon closer examination what I saw were artifacts introduced by the Genuine Fractals resizing method. Halos and jagged edges not apparent in the other files were seen in the GF files.

Although it was not the best interpolation method for original digital captures, it did provide the best quality for the scanned image under review, but this is a pretty subtle conclusion.

Adobe Camera RAW
I had hoped that Adobe’s Camera RAW was going to be a head on competitor especially up against Capture One; however, ACR’s resizing capability maxed out at a mere 5120x3404 pixels, or 11x17 print size at 300 dpi, so it was not a factor in my test. At its maximum output I did not see anything that would challenge Capture One's output.

Phase Capture One
The converted file from Capture One seemed to obtain greater detail than any of the other resizing methods. Highest cost, but resizing is but one of the features and benefits of Capture One and it offers a much more powerful resizing capability than Adobe Camera RAW. The one to beat and so it should be for its onerous purchase price.

Conclusion
Definitely not definitive because there seems to be another new resizing filter, plug-in, or standalone application popping up every month; I just merely sampled a couple of the better known methods and a couple of obscure ones that are low cost.

For film scans Genuine Fractals provided a slightly better up-sampled image than Photoshop’s Bicubic interpolation, but just. One thing to keep in perspective is that the differences I saw were very subtle and not particularly obvious except for the re-sampled image from Capture One. These subtle differences are why I did not feel it worthwhile to post sample images in this review, that and all the naysayers out in cyberland who pooh-pooh the notion of being able to tell anything from small 72 dpi compressed JPEG images (actually, they do have a point).

For film scanning photographers on a budget I would not lost any sleep over not having Genuine Fractals and would utilize a much cheaper alternative such as Fred Miranda’s Stairstep Interpolation for a cheap $15 US, or go through the Bicubic interpolation method manually in 50% increments (hint, create your own action for this step).

For digital captures, Capture One provided the best results with Genuine Fractals and Fred Miranda’s action being a toss up for second and third depending on how one regards the Genuine Fractals output. Coming in third, Bicubic, ProFoto and Resize Magic all tied for last, but I reiterate, the results are subtle.

For a different way of resizing using both stair-stepping and Genuine Fractals, click here.

Update December 10, 2004 - I received a message from a beta tester of Capture 1 about how it was I came to conclude that C1 was better than the other methods of resizing, especially since it just used Bicubic Interpolation, same as Photoshop. He actually answered the question himself by offering that C1 could do better thanks to resizing RAW data immediately rather than having to convert RAW files to TIFF and then resizing. It was an interesting and relevant point that I thought should be shared here.

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